8.6 Blk reloading info

[db2000]

Anyone have data for 1680 using 350g Rex from a 12” barrel? I tried to run through this thread and google outside and am striking out. Just got this setup for my Fix.

I am using it in a 10.5” 1:6.5 twist but won’t have data for about a week. I’ll circle back around.

Edit:
Seekins SP10 Mos-Tek 1:6.5 twist 10.5” SS
Garmin Xero C1

2/20/24
48F 42% 30.38”

Maker 350
A1680
Q brass x 2
FGMM 210M
BTO 2.4200
COAL 2.7910
COL 1.6775
16.0 910, 869 fps not stable @ 50
16.5 917, 918, 927 not stable @ 50
17.0 942, 959 stable @ 100 and locks bolt

Barnes 210 GR TSX BT solid copper
A1680
Q brass x 2
FGMM 210M
BTO 2.6100
COAL 2.6670
COL 1.6775
29.5 1762, 1773, 1757 fps
30.0 1837, 1799, 1794
30.5 1920, 1817, 1834 1” @ 100

300 gr SMK HPBT (factory seconds)
BTO 2.1900 (308 comparator used)
17.0 1020, 1023 fps
17.5 1045, 1046, 1048
Q brass x 1
FGMM 210M
BTO 2.1880 (308 comparator used)
COAL 2.790
COL 1.6765
16.5 966, 985, 972, 979, 996 fps
SD 10.3 ES 29.7 0.8” @ 50y
17.0 995, 1013, 1017, 999, 1010
1007, 1010, 997, 1009, 1023
SD 8.5 ES 27.8 1.2” @ 50y
17.3 1033, 1049

 

[Mike6158]

I finally made it to the range. Other than shooting Gorilla ammo out of the 8.6 I haven't had a chance to work up a load until recently. I'm not really a person that likes shooting AR's but I have "a few" (just built 3 AR10's, two were 8.6BLK's). The one saving grace about AR's is if I don't like the barrel/ caliber that I installed, I can change it. Both of the barrels I have are Faxon barrels. Subs were shot through a Dead Air Primal.

I'm not new to reloading. Over the last 25 years I have loaded everything from .338 Edge, to 7mm Rem Mag, down to .223 and .20PPC (love my pea shooter). I'll also say that I am by no means an expert reloader.

I treat everything like it's a precision rifle when I start load development. So when you look at the numbers just remember that I loaded these with an abundance of caution. Too much it seems.

AA1680 is some nasty powder imho. I'll keep it around for the apocalypse or something. Maybe trade it for whiskey or a loose woman That said, here's the subsonic first round test data. I won't continue with this powder.

Velocity came from a new Garmin Chronograph. I have a LabRadar that I brought for a backup but didn't need it. Something is not right about groups 7 and 8. Actually, to me it looks like the last 4 groups are out of order. As I loaded each round I put it in the box. The rounds can't move when the lid is closed due to some foam I put in the lid. <Edit, I think I figured out how some loads got out of order. I loaded the mag in groups of 2. 3 from group 2 first then 3 from group one. Shoot those, record velocity, then reload the magazine the same way. A couple of times during the reload the other guy at the range came over to chat. Loss of focus on my part>

I weighed my charges with a Chargemaster and dumped them to a TRX-925. Trued up to within .01-.02. Then dumped the powder to the case. I seated the bullet to the same COAL within .001". I have "a few" 300SMK's laying around (for the .338 Edge) so I used those. As I said above I may load a second round with N110. It would work (see test below this one), but case fill is in question (for me).

Blue values in the spreadsheet are data entry points. The black values are calculated. All cartridges fit in the magazine with no issues and a little room to spare.

Here's the not-so-supersonic super test. The first two groups were very light and none of them are in the range I was hoping for. I took it easy because I wasn't sure what the Barnes LRX would do. It makes round holes at 100 yards. That's a start. Group 9 is probably sighters. My bench notes say that I loaded 8 not 9 and that explains why the velocity tanked for group 9.

<EDIT> I reviewed what I had scribbled on the load card vs the Garmin and made correct some values.

 

[45-90]

Al ready have the 3 twist in AR 10, looking for something better...
So I trued Rem 700 action and chambered a new 6.5 twist barrel blank for 8.6 Blsckout.
Going for high velocity experiment, making 277 hybrid cases into 8.6 Blackout on a bolt gun. Annealed, formed, annealed, F L die, neck turn...gonna finish one hundered, hybrid 227 fury cases to 8.6 Blk and load the with 300 gr SMK, the goal is 2200 fps QL says its possible. A 1400 yd gun? Just curios as to what can be achieved. I have better calibers for LR, but this will easily reach past 1000 yds, with excellent wind drift numbers...Run the ballistics on big 338 bullets. Plus it can easily sub sonic if needed. Spent a lot of time, effort, & dollars trying to see if this caliber is useful.

 

[Mike6158]

I have a .338 Edge for when I want to shoot out to and past 1,000 yards. The AR platform is not my favorite, but I have a few. I'm "carefully" going to look for a better powder than what I've seen used. I want to see what I can get out of the Barnes 280 gr LRX. My supersonic test spreadsheet posted above has a typo (more than one actually). The SS test bullet wasn't a TTSX, it was the 280gr LRX. Considering that the first two rounds were where I wanted to be for subsonic they shot well. I wasn't shooting "groups" so all I know is that they made round holes at a hundred yards. I was using a thermal for subs and didn't have my aluminum foil target with me. No clue on how they grouped at 100. The 18" barrel only has an 8x scope on it. That's suboptimal for 100 yards and my eyes. Both scopes and rifles work great at 50 yards which is the normal "hog range" for the 8.6 and me. I can't just leave it there.

I have other powders that I can use to try to nail down the velocities that I want to achieve (bumping up to the subsonic limit with a case that isn't nearly empty and 2,200 fps seems like a good goal for the 16" AR). For increased frustration I also built a couple of 300BLK's . The AR is finally tuned. I swapped the barrel (Ruger so it was easy for me to do) for a 1:5 twist from 1:7 twist. I haven't played with that yet.

 

[Mike6158]

:/ N110 isn't going to get me to 1,900 fps. Supposedly Barnes says that their 280gr LRX will still expand at 1,600 fps. 1,900 fps gets me inside of the 50-200 desired cartridge range

Example 1: MV=1,900 fps. At 300 yards: 1,584 fps / 1,560 fpe. At 200 yards: 1,684 fps / 1,764 fpe. At 100 yards: 1,790 fps / 1,992 fpe.
Example 2: MV=2,000 fps. At 300 yards: 1,671 fps / 1,737 fpe. At 200 yards: 1,776 fps / 1,962 fpe. At 100 yards: 1,886 fps / 2,212 fpe.
Example 3: MV=2,100 fps. At 300 yards: 1,926 fps / 1,560 fpe. At 200 yards: 1,869 fps / 2,172 fpe. At 100 yards: 1,982 fps / 2,444 fpe.
Example 4: MV=2,200 fps. At 300 yards: 1,850 fps / 2,128 fpe. At 200 yards: 1,962 fps / 2,395 fpe. At 100 yards: 2,079 fps / 2,688 fpe.

Load development today came to a screeching, primer blown out of the case halt at 22.0gr of N110. I heard and felt the slight crunch as the LRX seated. Based on the previous two charges having extractor marks (20.5gr and 21.0gr) I figured 22gr was going to be a bit too hot when I heard it crunch.

I'm calling max load for N110 in an 8.6 BLK, 280gr Barnes LRX bullet, and a 16" barrel - 20.5gr of N110 @1,505 fps. That's not good. At 50 yards velocity is (calculated by the Bullet Flight app) is 1,459fps and energy is 1,324fpe. The rule of thumb is 1,000 fpe. Hit it in the right place and that number is much smaller (hogs). I don't know if the LRX will expand at that energy level but it will enter. At 100 yards it's 1,415fps and 1,245fpe. At 200 yards it's 1,332 fps and 1,103fpe. I guess it's not a terrible load but I was hoping for 1,900 - 2,200 fps.

 

[Mike6158]

Just for grits and shiggles I tried Reloder 7 around the max for N110 and I got pressure signs and lower velocity. I tried N130 with similar results. Slower powders, albeit not much slower, don't seem to be better. I'm thinking about trying CFE BLK and Reloader 10x (both are also slower). That'll take care of the slower powders that aren't much slower.

For faster powders, I think I have some AA9. I know I have various pistol powders (like Blue Dot, HS6, etc) but I don't think that's even worth the effort. I'll probably change my mind by tomorrow.

I've got another test loaded with N110. I'll see how the upper end looks in 0.2gr increments. I'll do that at the range so I can shoot a target.

 

[Mike6158]

I've tried a few powders over the last two days. I'm still stuck on using N110 for my AR10 with a 16" Faxon barrel and the 280gr Barnes LRX. I think that if want more velocity I'm going to have to go with a longer barrel. I may do that and, maybe, try to get a 5 twist barrel. Before I go to that trouble I'm going to see if I can talk my son in law into putting me on a hog so I can test the terminal ballistics of this combination.

I've got a burn rate chart from 2023. (I converted it to Excel if anyone is interested in it). This is how the powders I have stack up on the chart. Fastest to slowest.

(51) Blue Dot. I tried 19gr of Blue Dot this evening. 1,498 fps but the case had a very prominent extractor mark on the base, worse than I've seen so far, and it didn't eject (which was odd). 19gr is 3gr less than the hottest N110 charge.
(64) N110. I currently have a 5 group test loaded from 20.0 to 20.8 in .2gr increments. I'm just looking for a node in the 1,500 fps range.
(72) A1680. N110 is cleaner and more stable.
(74) CFE BLK. I haven't tried this one yet. It's next.
(77) Reloader 7. Underwhelming. Not enough velocity for supersonic. Might be a good subsonic powder.
(84) N133. I haven't tried this one yet. Slower hasn't been all that productive.
(87) Reloder 10x. I haven't tried this one yet. Same comment as above.

 

[MSBRPT]

I've tried a few powders over the last two days. I'm still stuck on using N110 for my AR10 with a 16" Faxon barrel and the 280gr Barnes LRX. I think that if want more velocity I'm going to have to go with a longer barrel. I may do that and, maybe, try to get a 5 twist barrel. Before I go to that trouble I'm going to see if I can talk my son in law into putting me on a hog so I can test the terminal ballistics of this combination.

I've got a burn rate chart from 2023. (I converted it to Excel if anyone is interested in it). This is how the powders I have stack up on the chart. Fastest to slowest.

(51) Blue Dot. I tried 19gr of Blue Dot this evening. 1,498 fps but the case had a very prominent extractor mark on the base, worse than I've seen so far, and it didn't eject (which was odd). 19gr is 3gr less than the hottest N110 charge.
(64) N110. I currently have a 5 group test loaded from 20.0 to 20.8 in .2gr increments. I'm just looking for a node in the 1,500 fps range.
(72) A1680. N110 is cleaner and more stable.
(74) CFE BLK. I haven't tried this one yet. It's next.
(77) Reloader 7. Underwhelming. Not enough velocity for supersonic. Might be a good subsonic powder.
(84) N130. I haven't tried this one yet. Slower hasn't been all that productive.
(87) Reloder 10x. I haven't tried this one yet. Same comment as above.

Interested in the excel chart. Have you found anything that groups under or around 1” at 100?

 

[camocorvette]

Been watching since the beginning. I think it's a neat niche gun. With that said I want one haha.

I really like that lower @unclemoak Gorgeous rifle set up.

 

[Mike6158]

Interested in the excel chart. Have you found anything that groups under or around 1” at 100?

I am just shooting for velocity right now. I'll shoot for groups as soon as I can get out to the range. I need to change my scope. 8x and my eyes don't seem to like 100 yards. Either that or I'll call the N110 load I've worked up the 50yd load and shoot that.

Sheet attached, I had to zip it to attach it. It's up to you but I have saved one for each caliber I test. When I try a new powder or bullet I right-click copy the original tab to a new worksheet and rename the tab. It keeps all of the data for the rifle in one place. Blue text is for data entry. entry but no cells are protected (be careful in other words). Powder type is just under the word Number in the top left cell. Charge wt is to the right of that. V1 - V5 are velocity. The Delta row was suggested by an F Class guy on another forum. He said it was helpful for identifying a node. Looking at the .338 Edge load test I ran (the spreadsheet has this info in it), I think he's right. There is a dip in Delta at load 3. If I did another test I would shoot from Load 2 to Load 3 and increment .1 (even though it's a tiny percent change).

 

[archetypefirearms]

I am just shooting for velocity right now. I'll shoot for groups as soon as I can get out to the range. I need to change my scope. 8x and my eyes don't seem to like 100 yards. Either that or I'll call the N110 load I've worked up the 50yd load and shoot that.

Sheet attached, I had to zip it to attach it. It's up to you but I have saved one for each caliber I test. When I try a new powder or bullet I right-click copy the original tab to a new worksheet and rename the tab. It keeps all of the data for the rifle in one place. Blue text is for data entry. entry but no cells are protected (be careful in other words). Powder type is just under the word Number in the top left cell. Charge wt is to the right of that. V1 - V5 are velocity. The Delta row was suggested by an F Class guy on another forum. He said it was helpful for identifying a node. Looking at the .338 Edge load test I ran (the spreadsheet has this info in it), I think he's right. There is a dip in Delta at load 3. If I did another test I would shoot from Load 2 to Load 3 and increment .1 (even though it's a tiny percent change).

Thanks for all the sharing @Mike6158

I hope you don't think I'm stepping on your toes, but awhile ago I had taken the time to update and add from as many burn rate charts as I could find, including some discontinued powders to come up with the following Google Sheet. I believe access is set to anyone with the link, so enjoy and please let me know if any mistakes are found!

Powder Burn Rates

 

[Mike6158]

Thanks for all the sharing @Mike6158

I hope you don't think I'm stepping on your toes, but awhile ago I had taken the time to update and add from as many burn rate charts as I could find, including some discontinued powders to come up with the following Google Sheet. I believe access is set to anyone with the link, so enjoy and please let me know if any mistakes are found!

Powder Burn Rates

I have one that's dated 2023. I didn't make it but I was able to push it out of a PDF into Excel (Mac's are good for things like that). I'll compare it to yours when I get home. If it is or isn't I'll report back.

Man... I wear steel toed boots for work fairly often so it's pretty hard to step on my toes. I believe in sharing info so it's all good.

 

[Mike6158]

@MSBRPT did you mean the 2023 Burn Rate Chart?

 

[JR1200W3]

Al ready have the 3 twist in AR 10, looking for something better...
So I trued Rem 700 action and chambered a new 6.5 twist barrel blank for 8.6 Blsckout.
Going for high velocity experiment, making 277 hybrid cases into 8.6 Blackout on a bolt gun. Annealed, formed, annealed, F L die, neck turn...gonna finish one hundered, hybrid 227 fury cases to 8.6 Blk and load the with 300 gr SMK, the goal is 2200 fps QL says its possible. A 1400 yd gun? Just curios as to what can be achieved. I have better calibers for LR, but this will easily reach past 1000 yds, with excellent wind drift numbers...Run the ballistics on big 338 bullets. Plus it can easily sub sonic if needed. Spent a lot of time, effort, & dollars trying to see if this caliber is useful.

So why not just 375R if you're looking for supersonic speeds?

 

[45-90]

So why not just 375R if you're looking for supersonic speeds?

Because, I don't want one, ...if I did, I'd build one.

 

[JR1200W3]

Because, I don't want one, ...if I did, I'd build one.

I guess that makes sense. I have watched you struggle with this round for over a year. Between the faxon barrel, the super fast twist blowing up bullets, the extensive case prep. I guess you enjoy the process. I'm just watching all these people do this crazy case prep just to struggle to get 2,000 ft per second at supersonic and an AR-10 platform. Seems up there with trying to marry and rescue a stripper.

 

[45-90]

I guess that makes sense. I have watched you struggle with this round for over a year. Between the faxon barrel, the super fast twist blowing up bullets, the extensive case prep. I guess you enjoy the process. I'm just watching all these people do this crazy case prep just to struggle to get 2,000 ft per second at supersonic and an AR-10 platform. Seems up there with trying to marry and rescue a stripper.

Kinda like that...but I enjoy the challenge..and built a whole new rifle with 6.5 Twist barrel, in 8.6 ...but in a bolt gun, this go round.
Guaranteed to get there, ???...soon as the weather cooperates....stay tuned for some fast 8.6,... or one nasty stripper.
.

 

[Mike6158]

Why would I marry a stripper? It's cheaper to just look at em... That way I have more money for bullets, brass, and powder. The way my curiosity works I'm going to need my dinero.

but I enjoy the challenge

That pretty much sums up the why doesn't it.

If the wind lays down I'll shoot the test rounds I've got at 100 today. Otherwise it'll be Saturday, Friday if the prognosticators got the forecast wrong.

I cleaned my my barrel last night for the first time since I started testing. After running a few patches through it and getting carbon but no copper I patched some more IOSSO "triple action oil" and let it sit all night. I pushed that out with a dry patch and now I'm going through the Tactical Advantage accelerator and patchout regimin. Once that's done I'll borescope the barrel to see if it's copper fouling. I'm not seeing it right now.

 

[JR1200W3]

Why would I marry a stripper? It's cheaper to just look at em... That way I have more money for bullets, brass, and powder. The way my curiosity works I'm going to need my dinero.

Exactly. But some people enjoy the fast expensive ride I guess

 

[45-90]

Finnally got out to try out some high velocity 8.6 Blackout loads...in the new 6.5 twist barrel. They weren't as high as predicted...but not too bad either. Much better than the three twist...none came apart in mid flight or damaged the muzzle brake. No primers were blown, either.
Used two powders in ladder tests.

The results were 2480 fps for 200 gr, 2250 fps for 225 gr, 230 gr eldx 2200 fps, 285 gr 1873 fps, 300 gr Berger & Sierra 1808 fps

Powder #2 300 gr Berger 1943 fps, 300 gr Sierra MK , 1934 fps.

 

[MSBRPT]

Finnally got out to try out some high velocity 8.6 Blackout loads...in the new 6.5 twist barrel. They weren't as high as predicted...but not too bad either. Much better than the three twist...none came apart in mid flight or damaged the muzzle brake. No primers were blown, either.
Used two powders in ladder tests.

The results were 2480 fps for 200 gr, 2250 fps for 225 gr, 230 gr eldx 2200 fps, 285 gr 1873 fps, 300 gr Berger & Sierra 1808 fps

Powder #2 300 gr Berger 1943 fps, 300 gr Sierra MK , 1934 fps.

Ran the data for a 2480 fps 200 grain bullet (I assumed this was a Hornady SST) on a calculator. It’s comparable to a 20” .308 shooting 175 grain SMKs at around 2600 fps.

 

[Mike6158]

Nice!

I cleaned my 8.6 (AR) yesterday. I started at 6:30am. I figured that it would be clean and I would be headed to the range by 10. Nope. I finally got the barrel cleaned to almost “borescope satisfaction” by 3:30PM. Carbon buildup (I blame that on shooting so much Gorilla ammo thru it and my A1680 reloads) was pretty bad. I don’t think it’s all out yet but it’s down to specsof carbon now. Once the carbon was mostly removed the copper showed up. That wasn’t too hard to get rid of but it wasn’t light. Then I worked on carbon fouling again. I let the various “remedies” soak an hour or so per instruction. I hit it with everything in my cleaning arsenal.

Borescoping the barrel let’s just say Faxon deserves all of the criticism it gets. The “substantial” gas port split a land about 2/3 land 1/3 groove.

Does anyone make a slower twist rate AR10 barrel?

 

[Mike6158]

8.6 BLK, SAMMI, Hornady, etc. News LINK

 

[archetypefirearms]

8.6 BLK, SAMMI, Hornady, etc. News LINK

disappointing overall if you ask me

 

[45-90]

Nice!

I cleaned my 8.6 (AR) yesterday. I started at 6:30am. I figured that it would be clean and I would be headed to the range by 10. Nope. I finally got the barrel cleaned to almost “borescope satisfaction” by 3:30PM. Carbon buildup (I blame that on shooting so much Gorilla ammo thru it and my A1680 reloads) was pretty bad. I don’t think it’s all out yet but it’s down to specsof carbon now. Once the carbon was mostly removed the copper showed up. That wasn’t too hard to get rid of but it wasn’t light. Then I worked on carbon fouling again. I let the various “remedies” soak an hour or so per instruction. I hit it with everything in my cleaning arsenal.

Borescoping the barrel let’s just say Faxon deserves all of the criticism it gets. The “substantial” gas port split a land about 2/3 land 1/3 groove.

Does anyone make a slower twist rate AR10 barrel?

Mos-Tek makes 3, 5, & 6.5 twist AR 10 barrels.
I ordered a 6.5 twist blank from McGowen and chambered it myself. It took 3 months to get a 6.5 twist barrel and a .510 10 twist barrel.
They have a nice interior, like a barrel should. Not like the Faxon 3 twist barrel with rough torn rifling.
And high velocity bullets do not come apart to damage your muzzle devices or magneto speed chronograph.
Doing the high speed tests and tried just two powders with a variety of bullets.
The accuracy with the first powder looked excellent, for me, I have Macular Degeneration in the shooting eye so it's hard to see with bright sunlight...on overcast days just shoot the center of a distorted paper plate. Get eye injections to try to preserve the eyesight. My left eye has good sight, but shooting lefthand is awkward.
But, yesterday was able to put 3 or 4 in the same hole then move the impact up as powder increased.
IMO the 6.5 twist is a much better option for the 8.6 blackout and I already have a 3 twist, which is very limiting, in bullet choice and velocity it can run,...plus Faxon has bad rifling, on mine, and others. So far I can run any 338 lead bullet as fast as I can with no fear of bullet blow-ups. Which gets you into real killing power with much less cost. I shot some 2 liter jugs yesterday and the difference on impact was drastically different. Punch a hole or rip the jug to pieces in an explosive mist.

 

[archetypefirearms]

I just got started on my load development yesterday with CFE BLK powder. When I set up my chronograph I started off with my "commercial" cartridges from Gorilla. Has anyone else run these suckers through a chrono? Mine are the Barnes 210 gn TSX loads and according to the Q chart you are looking for 2086 fps out of a 16 inch barrel.. My 5 rounds of the Gorillas put them at an average of 3099 fps or let's call it a rough 50% extra velocity.. this seem excessive to anyone else given the Q load chart?

I am still working my own charge weights up nice and slow. Given the load chart I am going to try for 2100 fps average in the supers.
Word to the wise though, for being a powder that is very close on burn rate to the accurate 1680 that I can't find in stock the CFE BLK has some pretty hefty charge weights. I will share my numbers once I finish dialing in, but let's just say my supers were super slow at -10% and my Subs at PLUS 10% came out at 500ish fps...I have a LOT more tinkering to do.. lol.. to be honest very soon I will be starting on twice fired casings.

I know this post is quite old now, but I was also initially worried about the Gorilla 210 gr TSX ammo as I was seeing some significant extractor marks on my 8" gas gun back around the summer of 2022. Fast forward until today and I finally have a 16" barrel bolt gun that I shot through my Primal suppressor and measured the velocity for 7 shots with my Garmin Xero C1 as follows:

Shot	Velocity
1	2149.7	2140.80	average
2	2136.8	14.81	std dev
3	2166.4
4	2118.5
5	2133.2
6	2138.2
7	2142.8

I had called Gorilla in advance to see what the powder charge should be in these rounds and they told me 29.30 grains of whatever they were using. I pulled one just to confirm based on what I was seeing initially to double check and it was at 29.60 grains. Temp here in eastern PA today was probably around 45 F and elevation around 450', but the velocity was definitely nowhere near the 3100 you were initially seeing and I was worried about also seeing.

I also had loaded up some of my own 210 gr TSX rounds with 29.5 of AA1680 from the Q data and it gave me the following:

Shot	Velocity
1	2005.8	2031.96	average
2	2023.4	12.46	std dev
3	2034.7
4	2044.2
5	2032.1
6	2043.7
7	2034.6
8	2037.2

The first shot was the first round every out of that gun and without the suppressor, so that's what I'm chalking up to the lower velocity. COAL for both rounds were at 2.650".

 

[Mike6158]

disappointing overall if you ask me

It is. Hornady possibly coming out with an 8.6 ARC, on one hand, it smells, and on the other, it'll add yet another cartridge to the mix.

 

[Mike6158]

Aside from not sleeping last night (allergies), a front passing, the wind howling, and my brain being all jacked up from not sleeping and allergy medicine, range day sucked

I'm giving up on the 280 gr LRX Barnes bullet in a 16" Faxon burr grinder... I mean barrel. I may still try it subsonic. I don't think the terminal ballistics will be very good at subsonic velocities. I guess I'll test the LRX's in my .338 Edge.

If I was going to load any I'd load between 20.4 and 20.6 (note my sighter loads at the bottom). It's the same place I got to the last time I did a load test.

Here's the data. No targets, just velocities. The Garmin dropped 1 and I forgot to enable one. One of the things I liked about the LabRadar is that I could arm the LR from an app on my iPad and read the results. Garmin's interface sucks imho. But... it's small and easy to use.

I'm going to run a borescope through the uncleaned barrel and see what's in there. When I bore scoped the rifle yesterday I noticed that there was a lot of copper in the first 6-8" of barrel then it faded to nothing. If the lands are cutting copper doesn't that mean that as the bullet travels down the barrel gas can bypass the bullet in the grooves that the lands cut into the bullet and give me lower velocities?

 

[45-90]

It is. Hornady possibly coming out with an 8.6 ARC, one one hand, it smells, and on the other, after today, it'll add yet another cartridge to the mix.

I checked out the video ...if true, in the AR 15 platform?
There is no room with a 300 gr Berger, the bullet is down on the ogive for crimping.
So shorten the case back to where you can crimp it...the results is a tiny powder capacity for limited use, ... a sub load only option. But a better option than the current 8.6 for subs only, as the 8.6 Blackout has too much case capacity for subs.
But then, add the tiny capacity to weak bolts of the Grendel and a few tenths difference in powder charge or slight change in seating depth, will spike pressures beyond the bolt strength...and that could be a problem for handloaders. Hornady would most likely supply load data in the future, that would be strictly adhered to, so it may be a win for the sub only crowd.

They already have the 338 Spectre for the AR 15 platform...for subs
But it would be more successful if Hornady marketed it, as they hype the hell out of everything.

 

[Huckleberry75]

FYI Gorilla dropped 8.6ammo today

 

[Mike6158]

I was a bit premature with the "giving up post" I've got one more 100 yard test that I want to do. After that I will look for a bullet with a little less weight.

On another note, Shawn Carlock came out with his .338 Edge +P after my .338 Edge was delivered. If I remember right I could have a gunsmith use a +P reamer on it and make it a +P but it shoots fine and there is a barrel life cost associated with it. Here's Shawn's explanation for the stepped design that they are using and some history about +P chambering.

What if someone made a reamer with the +P stepped chambering for the 8.6BLK? It's supposed to reduce the initial, brass eating, pressure spike. I'm no gunsmith but physics is physics.

 

[45-90]

I was a bit premature with the "giving up post" I've got one more 100 yard test that I want to do. After that I will look for a bullet with a little less weight.

On another note, Shawn Carlock came out with his .338 Edge +P after my .338 Edge was delivered. If I remember right I could have a gunsmith use a +P reamer on it and make it a +P but it shoots fine and there is a barrel life cost associated with it. Here's Shawn's explanation for the stepped design that they are using and some history about +P chambering.

What if someone made a reamer with the +P stepped chambering for the 8.6BLK? It's supposed to reduce the initial, brass eating, pressure spike. I'm no gunsmith but physics is physics.

Nothing new....Weatherby has long Freebore in their rifles since about 1950...to get the high velocity without the initial pressure spike...but there is still a pressure spike, delayed or slightly spread out for a fraction of a milli second.
That's how Weatherby obtained its velocity records over the years.

 

[45-90]

Not to concerned about 8.6 blackout pressure spikes...I'm running 80,000 psi hybrid cases. But do not take them to that pressure.
Can not find the bullet ya want ...make your own, or modify existing bullets to fit your chamber. The all copper bullets are easy, to modify from weight to boattail, even the ogive for putting the bullet down the bore farther so you can add more powder.
It could be possible to reach 3000 fps in a 8.6 blackout...inquiring minds want to know...or...it gives retired machinist something to do.
I got 3760 fps in an AR 10 16" barrel with 50 gr copper 9mm hollow points, they grouped good but fade shed velocity very fast...a fun but ridiculous experiment of little value.
This will be more practical...and improve the 8.6 blk ...maybe?

 

[Mike6158]

Nothing new....Weatherby has long Freebore in their rifles since about 1950...to get the high velocity without the initial pressure spike...but there is still a pressure spike, delayed or slightly spread out for a fraction of a milli second.
That's how Weatherby obtained its velocity records over the years.

Yeah... he says that in his article.

WE KNEW THAT WE COULD GAIN 100 FPS BY SIMPLY ADDING A GROSS AMOUNT OF “FREEBORE” THEREBY REDUCING THE PEAK CHAMBER PRESSURE AND ALLOWING THE ADDITION OF MORE POWDER TO COME BACK TO MAX PRESSURE. THIS TECHNIQUE WAS WELL EXPLORED BY ROY WEATHERBY OF COURSE. THE DOWNSIDE OF THIS IS THAT INITIAL ACCURACY AND LONG TERM ACCURACY WERE AFFECTED IN THIS PROCESS, AND IT WAS NOT THE SUBSTANTIAL VELOCITY INCREASE WE WERE LOOKING FOR.​

What he also says:

OF THE BUCKET FULL OF IDEAS WE KICKED AROUND, THE ONE WE KEPT COMING BACK TO WAS THE CURRENT VERSION OF THE +P WE NOW USE ON THE 338 EDGE +P. THIS WAS AN IDEA OF A STEPPED THROAT, INSTEAD OF THE BULLET HAVING TO INITIATE TWIST AND TAKE THE ENGRAVING OF THE FULL DEPTH OF RIFLING ALL AT THE SAME TIME WE THOUGHT THAT REMOVING A PORTION OF THE RIFLING FOR A GIVEN DISTANCE WOULD ALLOW THE SPIN INITIATION AND INITIAL ENGRAVING PROCESS WITH MUCH LESS PRESSURE BEFORE COMING INTO FULL RIFLING CONTACT.​

That's a bit different than long freebore.

During this short experiment I've blown a primer out and and had ejector marks so bad the case wouldn't slide into the shell holder even after I filed the marks off. That't well outside of my normal comfort level.

I wish there was an easy, cheap, and accurate way to measure pressure for every round fired in whatever rifle I was testing. For some reason, easy, cheap, and accurate never seem to fit together very well.

And... oh to have chosen the path of machinist long ago...

 

[Mike6158]

The resolution on the borescope photos below isn't great. The first image was take AFTER a few hours of cleaning. I didn't borescope before I started so I don't know if carbon covered up the copper but I think it probably did. The first three are of the progression for clearing out the copper fouling.

The borescope does better with the right angle mirror installed. I have a replacement for the cracked mirror. I guess I should use it

1. Lots of carbon and copper

2. Better but still a lot of carbon

3. I went back to working on the carbon fouling after this one. It's not perfect but it is much better

4. I put the (broken) mirror on for these. The proper location for a gas port. I reckon not. Much cleaner but not clean by any means.

5. Stubborn carbon. This is after I threw everything at it, including IOSSO paste, CLR, Tactical Advantage Patchout and Accelerator, Boretech, MP5, etc. I run an alcohol patch through after every chemical followed by a dry patch.

These are from this morning. No cleaning has been done. I fired 20-ish rounds. The copper fouling started later in the barrel than what I saw yesterday. I'm not sure what the blob is in the first one.

Or the "worm tracks" in this one and the one that follows it

Copper started around the gas port

 

[45-90]

Before I even shot it, I lapped the 3 twist bore with silicon carbide valve grinding paste, available at automotive supply houses. In the Bridgeport, I milled a large V groove in home built aluminum vise jaw, over the Kurt hard jaw, and bolt it down.
A piece of leather belt over the face of the movable jaw.
Insert the new barrel and clamp it down.
Then machined a thick aluminum cup with a hole that slips over the cleaning rod and the cup is a snug fit on the barrel extension.
Tape the area where the rod stops before exiting the barrel with electrical tape.
slide the cup down to the tape.
Load the tight patch ...(it must be very tight) with the silicon carbide grinding compound. Tap in the bore with the leather glove on the hand.
Work it through the bore back and forth.
More at the chamber, and little at the muzzle. At to have a slight bore taper.
It will give your arms a workout, adjust the mill table to suit, your workout height.
Clean bore, check with bore scope, all lines parallel to bore, then a finish polish with Iosso paste, clean and done.
Helps the nasty Faxon 3 twist.
Just finished chambering a bolt gun on a 6.5 twist for the 8.6 Blk, with a nice barrel blank.
I also machine AR barrels from barrel blanks, that are not readily available from quality barrel suppliers.

 

[Mike6158]

I did a "fine powder" test today. as expected, 20.7gr ruined the bottom of the three cases that I shot. I can take a photo if anyone wants to see what ruined means. Targets, load data, velocities, etc are in the attached PDF. I almost got under 1MOA. Group 1 and Group 6 but 6 is unusable because it destroys the brass. Group 2 had better stats than Group 1.

I changed the seating depth. I don't recall the exact number I measured on the magazine, it was something like 2.839. I loaded everything at 2.825. The previous load test was in .2gr increments and 2.800. Having less bullet in the case seemed to help a little. 10 degree warmer temps might helped a little with that as well.

I have one more little thing to try before I call 20.1 or 20.5 good enough.

 

[45-90]

I did a "fine powder" test today. as expected, 20.7gr ruined the bottom of the three cases that I shot. I can take a photo if anyone wants to see what ruined means. Targets, load data, velocities, etc are in the attached PDF. I almost got under 1MOA. Group 1 and Group 6 but 6 is unusable because it destroys the brass. Group 2 had better stats than Group 1.

I changed the seating depth. I don't recall the exact number I measured on the magazine, it was something like 2.839. I loaded everything at 2.825. The previous load test was in .2gr increments and 2.800. Having less bullet in the case seemed to help a little. 10 degree warmer temps might helped a little with that as well.

I have one more little thing to try before I call 20.1 or 20.5 good enough.

For higher velocities ya need to go to slower powders.
W748, H335, & RL 17.
With copper bullets ya need .050" jump according to most manufacturers.
RL 17 33.7 gr max should get around 1700 fps at max pressure...all are a compressed load
W748 1680 fps 30.7 max
H335 1665 fps. At 29.7 grs max
WITH ONLY...2.825" COAL , 280 gr copper LRX bullet 1.864" length.
Nothing can be changed with out reworking up a load when you strive for max velocity, with heavy bullets, and small case capacities, as pressures Really spike.
Do not change seating depth as pressures spike tremendously with just .020" deeper into the small case...makes 4000 to 5000 psi difference. And all of the sudden you're way over max...weigh all charges .2 increase will get you into trouble...unless you're way down in the safely zone and can take a 5000 or more psi hit to the case, where most sub loads will be at.
The reason primers are blown and cases torn up, you're over pressure,.. Stop.
Those are informational loads and to be worked up to slowly...if used at all.
The 3 twist looses slightly more velocity because there is more energy expanded to the bullet's rotation and a bit less left for forward velicity.
The reason I went to the 6.5 twist and a bolt gun, to utilize the hybrid 80,000 psi cases incase of a 5000 psi pressure spike will not cause any damage, if I seat one .030" too deep or get .2 grain powder extra in the case. And can run all the loads to magnum pressures of 65,000 psi or slightly more...in a bolt gun with 6.5 twist, you can use cheap lead bullets, 200 grs at 2480 fps on the first powders tried...more experiments needed, I think it will reach much higher velocities.
Can not do lead bullets very fast in a 3 twist max 1400 to 1600 fps most will blow up soon as they leave the barrel, some less.
Also maching some hornady GMX copper bullets to 152 gr to see what they will do, they are machined to fit my chamber with .050" jump.
Yeah, a bit extreme...but in the end I will know what the 8.6 Blackout is capable of... even if its not available from manufacturers, I will make it myself...to find out.

 

[Mike6158]

Since we are discussing this on a forum I'm going to start with this first- I'm not arguing with you. You make some very good points and one has to be careful about what info they put on a forum. I don't disagree with anything you wrote. Some of it was new, some of it is reloading 101, but it has to be said. You've obviously been chasing a good load longer than I have. I hope we can continue the conversation.

"The reason primers are blown and cases torn up, you're over pressure,.. Stop." I know... I worked up to it in .1g increments on purpose. It literally went from hot but not terrible to f-that in 0.1g. I was pretty sure that it was going to be hot because it was hot the last two times I loaded it. Just not that hot. Most of the cases are trashed because the &%@($ bolt smashed the case mouth. Yes I know... that means the gas system needed to be tuned. I've had a love hate relationship with the AR platform for about 8 or 9 years now. Mostly hate. Ironically that's why I have "a few". They test me...

I'll take a good bolt gun over an AR any day. I had this AR's gas system tuned but I think that when I cleaned the barrel up that changed. The barrel was nasty. I wish I had borescoped it before I spent hours cleaning it. Yesterday, the rifle was very undergassed down at the lower charges and slightly undergassed at the top end. I have a Superlative Arms adjustable gas block. I like it. It does a nice job when it's set right. I just need to clean the rifle and set it. But first I need to find a charge that I like or at least hate less.

The last load had some raised ejector marks on it that lead me to toss the brass. It's Gorilla brass and has been fired at least 4 times. Primers were not cratered or flattened. The load before the load that I tossed the brass might have an ejector swipe mark on it but it's very faint.

"With copper bullets ya need .050" jump according to most manufacturers."
This is one place I'm delinquent. I went for maximum mag length on the last test. The few times I've tried to find jam (and then back it up 0.XXX") I ended up with round that wouldn't load in the magazine (not the 8.6BLK). I assumed that would be the case with the 8.6BLK. In short, I don't know how far from the lands the bullet is. I do know that I picked up some velocity by moving it out .025", 2.800" to 2.825". I have a little bit of room to go a little longer. I think I'll see where the lands are and see where .050 come out. I have a feeling it'll be too long for the mag but we'll see.

"RL 17 33.7 gr max should get around 1700 fps at max pressure...all are a compressed load"
I don't have any RL17. I wish I did. I'm on the list at Powder Valley but I'm not the only one. RL17 is gone right after the email that it's in stock arrives. I have IMR4350 (next to RL17 on the burn rate chart) and RL19 (quite a bit slower). I can get about 30-31g of IMR4350 in a case but, as you say, it's a compressed load. I haven't been willing to play in the realm of compressed loads with this round. I might have some H335. If I do what I always do, and look sideways at max, and slowly work up to what my rifles max is, maybe I'll find something I like. Or I can move to a lighter bullet. Idk...

"WITH ONLY...2.825" COAL , 280 gr copper LRX bullet 1.864" length." I'm assuming 1.864" is calculated base to ogive? I haven't found a Barnes bullet yet that has good base to ogive consistency. I load to fit the magazine. I have to. "Only 2.825" is the limitation of the magazine. I might be able to go to 2.835. I need to back up and find the distance to the lands.

"weigh all charges .2 increase will get you into trouble." The fact is, I double weigh. I let the RCBS Chargemaster do the initial drop, then dump that into a TRX-925 and adjust that to the nearest 0.01g. Then dump it in the case. For the record, .1 grain was the difference between warm and too hot. BTW- the scale I use reads at .01 grain, but it's accuracy is to the first decimal place. It took a lot of loads to condition myself to allow 0.01 grains and not correct it. I still don't allow -.01g

All of the following info is in the PDF that I attached in the other post. The best group was load 2 and it also had the best SD. For the record I don't put much, if any, stock in SD values for 3 rounds. It's a statistically insignificant number of samples.

Average velocity for test two was 1,502.2 fps and the group was 1.094 MOA. Group one had the best MOA (0.980) but the difference could have been on the shooter (me).

Strictly from a short range hunting perspective- Calculated velocity and energy looks like this- 1,500fps mv gives us:
1,329 fps at 200 yards with 1,099 fpe.
1,412 fps at 100 yards with 1,240 fpe.
1,456 fps at 50 yards with 1,319 fpe.

I don't know if the LRX will expand at the velocity / energy that is listed above. That's the $2.00 question.

One thing I see in the targets is the effect of barrel harmonics. That little skinny-assed barrel must be whipping pretty good.

 

[Mike6158]

Mos-Tek makes 3, 5, & 6.5 twist AR 10 barrels.

<Edit> 18" barrel makes no sense with this round. If I change barrels I'd think about 1:5 or 1:6.5 twist, and the heavy, Xray, barrel. But I do like the 3 twist, just not the limited bullet selection. 6 months or better lead time

Also... looking at the Berger stability calculator, the LRX is stable at subsonic speeds at 8 twist. I guess the lower rotation speed would take away some of the effect of the bullets impact. And... same old problem, I don't know if the LRX will expand at subsonic impact velocities. Spinning fast like what I get with a 3 twist barrel is probably going to give good terminal ballistics performance.

 

[Mike6158]

Adding a data point. 2.825" COAL / 1.928 CBTO in my rifle is .036 jump so I could come back another .013" to get .050' jump. I just need to use my comparator to set seating depth instead of COAL. I was kind of surprised that the throat was that short.

 

[45-90]

<Edit> 18" barrel makes no sense with this round. If I change barrels I'd think about 1:5 or 1:6.5 twist, and the heavy, Xray, barrel. But I do like the 3 twist, just not the limited bullet selection. 6 months or better lead time

Also... looking at the Berger stability calculator, the LRX is stable at subsonic speeds at 8 twist. I guess the lower rotation speed would take away some of the effect of the bullets impact. And... same old problem, I don't know if the LRX will expand at subsonic impact velocities. Spinning fast like what I get with a 3 twist barrel is probably going to give good terminal ballistics performance.

There is no scientific evidence that a fast twist develops more killing power. A bullet spins only once in 3 inches or once in 10 inches, makes little difference.
But bullet high velocity along with bullet mushroom, and fragmentation, make big wounds, hitting bone and blowing it into tiny pieces, cause the bone to become a projectile.
Every wound channel and wound in flesh and bone is different, no two are alike. It ain't consistent like ballistics gel.. ya can't poke your finger into the side of a deer, elk, or bear.
A bullet stops spinning, or begins to tumble, curves off path, resulting in different wounding properties or lack there of.
An 8 twist will stablize most of the bullets, for this caliber. I went with the 6.5 because there is no downside. I can run cheap lead bullets, at high velocities.
My AR has a 16" barrel. My bolt gun is 24" barrel for high velocity with all bullets.
I'm machining my own copper bullets to fit my chamber, and expect to get to 2900 fps...maybe. This bolt gun will shoot subs but is primarily a high velocity endevor. I shot a 2 liter jug with 300 gr match bullets at 1943 fps...it just punched a .338 hole through and water slowly leaked out.
Did the same with a cheap lead 200 gr Speer at 2500 fps and the 2 liter just exploded.
IMO bolt guns with good 20" barrels really improve the high velocity killing power, and accuracy of the cartridge using conventional lead bullets in 6.5 twist, and have ya covered when using subs...very versatile. Your gun build it your way. Just sharing what I've learned messing with making this 8.6 work for me.

 

[45-90]

"WITH ONLY...2.825" COAL , 280 gr copper LRX bullet 1.864" length." I'm assuming 1.864" is calculated base to ogive? I haven't found a Barnes bullet yet that has good base to ogive consistency. I load to fit the magazine. I have to. "Only 2.825" is the limitation of the magazine. I might be able to go to 2.835. I need to back up and find the distance

The 1.864" IS the actual length of the bullet listed.
Not the cartridge.
Seating bullets to jam can cause huge pressure spikes like 10,000 psi especially with copper.
Should always know where the lands are with relationships to your cartridge overall length.
SA have been good adjustable gas blocks, for me.
Eample, count the clicks down from standard or sub velocity to high pressure loads..on 308 its 7 clicks down to run 200 gr SMK at 2674 fps in an 18" barreled AR 10, run the same pressure as the bolt gun. Then 7 clicks open for standard 168 gr ammo.
ARs are capable of excellent accuracy with good barrels .5" 5 shot groups are common.
Add a sticky backed fiber strip, available at craft stores, to the shell deflector of the AR to eliminate dented cases and case mouths.

 

[Mike6158]

Post 1 after my last post - not a single argument against any of what you wrote. Especially the first sentence. Mathematically 1,600 fps works out to .00015s for 3" of travel and .00052s for 10" of travel. It takes longer to blink... Until I shoot a hog with whatever load I end up with, I see it die, and I see the wound, the load is suspect with the bullet I'm playing with.

Post 2 (face-palm) of course.... I didn't even think about bullet length. Even though I misunderstood you, it worked out. It made me check the distance to the lands (I'd never intentionally load to jam btw. It's not a pretty face... but I've come to like my face. No sense in blowing it off this late in the game).

I tried 30.0 grains of IMR4350 and got 1,287.6 fps. I've got 5 rounds, starting at 31.6g, increasing in 0.3g increments loaded, but it's 6pm on Sunday, even though my neighbors have been known to test a bump stock or sight a rifle in every now and then, I'm going to wait to shoot those rounds tomorrow or later in the week. I live out of town and even then the closest town is 1,100 people so I'm not too concerned with shooting... I just have to watch for the guy that owns the section next to me's cows. I wish I could shoot targets here but that's not a good idea. I drive about 70 miles to get to the range I shoot at.

Should always know where the lands are with relationships to your cartridge overall length. Yup... I assumed... I'd have measured and documented a bolt gun before I ever put powder in the case. No sense in treating an AR any different.

It'll make the AR heavy but I think I'm going with the Mostek 18" bull barrel, 6.5 twist for the AR. I think the Faxon pencil is slinging bullets all over the place, Going with a Mostek barrel will get rid of the squirrely, hard to find suppressor adaptor weirdness on the end of the Faxon barrel too. I've shot supers through the Dead Air Primal with the AR I'm working on now so I'm not too worried about a 18" 6.5 twist barrel beating up my can like I am with the current setup.

I don't know if you've ever used a barrel tuner or not. I have three tuner brakes and the targets I posted above show the signs of the effect barrel harmonics. The groups rotate around a center for each velocity node. That's related to the timing of the bullet exiting the barrel vs the position of the barrel when it exits. Seating depth is how that's mitigated most of the time. The tuner gives the shooter a way to dial it in if there's a change in how the rifle is shooting. I got my 7 Rem Mag dialed in to 1/4" at 100 yards. You can see the rotation in each of the groups below, then it stopped stringing and shrank. The black circle is 1/2" in diameter. I need to do a followup test to make sure it repeats, just not right now.

 

[45-90]

Keep working on it... imr4350, is a bit too slow.
Some that "might" get 1500 fps with some accuracy...try
Max loads work up with 280 gr at 2.825"
H322 28 GR
H335 29.7 GR
BC-L2 32 GR
H 4895 29.7 GR
IMR 4198 24.8 GR
8208 XBR 29.1 GR
IMR 3031 29.1 GR
AA 2495 30.8 GR
AA 2520 31.1 GR
W 748 30.8 GR
Information to carefully observe, study, and play with, at your own risk..work up carefully...
Something in this group should improve your end results.
Have fun.

 

[Mike6158]

Man, you aren't kidding... you've been working hard on getting this thing to shoot.

 

[towerofpower93]

I checked out the video ...if true, in the AR 15 platform?
There is no room with a 300 gr Berger, the bullet is down on the ogive for crimping.
So shorten the case back to where you can crimp it...the results is a tiny powder capacity for limited use, ... a sub load only option. But a better option than the current 8.6 for subs only, as the 8.6 Blackout has too much case capacity for subs.
But then, add the tiny capacity to weak bolts of the Grendel and a few tenths difference in powder charge or slight change in seating depth, will spike pressures beyond the bolt strength...and that could be a problem for handloaders. Hornady would most likely supply load data in the future, that would be strictly adhered to, so it may be a win for the sub only crowd.

They already have the 338 Spectre for the AR 15 platform...for subs
But it would be more successful if Hornady marketed it, as they hype the hell out of everything.

If Hornady is going to make 8.6 ARC on the Grendel case it'll basically be 338 Spectre/338 Razorback with the 6.5 vs 6.8 bolt face, no? Could be cool for the guys who are trying to collect the whole set of ARC cartridges, haha.

And I definitely think you're right that it'll be subs only at AR15 mag length. I think Hornady has seen the disadvantages of the 1:3 twist and is divorcing themselves from it. The market wants to shoot .338 projectiles out of a gun, but 8.6BO in its current form just seems to have too many warts.

 

[unclemoak]

Been watching since the beginning. I think it's a neat niche gun. With that said I want one haha.

View attachment 8353404

I really like that lower @unclemoak Gorgeous rifle set up.

It's done a hurting on stacks of pigs.

 

[GregP42]

Can not do lead bullets very fast in a 3 twist max 1400 to 1600 fps most will blow up soon as they leave the barrel, some less.
Also maching some hornady GMX copper bullets to 152 gr to see what they will do, they are machined to fit my chamber with .050" jump.
Yeah, a bit extreme...but in the end I will know what the 8.6 Blackout is capable of... even if its not available from manufacturers, I will make it myself...to find out.

Now I really need to find a lighter cast bullet, the 315gr cast I have been shooting have been flying straight and not exploding at up to 1200fps out of my bolt action. If I had some of those steel headed cases I would try to push them harder. So where did you get them from?

Greg

 

[45-90]

Now I really need to find a lighter cast bullet, the 315gr cast I have been shooting have been flying straight and not exploding at up to 1200fps out of my bolt action. If I had some of those steel headed cases I would try to push them harder. So where did you get them from?

Greg

I bought the last 300 hybrid cases in stock...they will arrive in a few days. I already converted 100 of them. They were on sale! And sold out, quickly. Don't know if any will come back in stock, this was at American Reloading.
The military is supposed to be using them, if the war effort subsides they should be plentiful and cheap everywhere.
They require some work, like neck turning, and annealing. But give you a safety margin if ya don't over do it. And have a bit more case capacity.
I pushed the cheap jacked Speer bullet to 1600 fps in my 3 twist AR 10,16" ..but that depends on how rough your 3 twist is..if from Faxon...I had to lapp mine with silicon carbide lapping compound.
I used 19.7 gr 1680 2.570" OAL 200 gr lead jacketed Speer hot core...really cheap. And they didn't explode, plus fairly accurate. Fired in AR 10 3 twist.
I shoot this bullet to 2480 fps in the 6.5 twist bolt gun, hybrid cases and a different powder.
This might be the best bullet for this cartridge in supersonic endeavors, especially the 6.5 twist where you can go all out. I have machined some copper bullets about 153 grs, expecting some good velocities on these, as they are machined to fit my chamber giving maximum powder capacity. I can make them very light incase I want to go to 3000 fps in the 8.6 bolt gun... more fun than serious. Stay tunned...been sickly and the weather is nasty.
Here is a picture of the two bullets seated the machined 153 gr copper longer then 2500 fps 200 gr Speer, for 6.5 twist barrels. There is 45.9 grs of powder under the copper 153 hybrid case. That is about max for that powder... load more and chronograph in a few days. Kind of a mad scientist on this high velocity tour for the 8. 6 Blackout.