8.6 Blk reloading info

[45-90]

Have you tried faster powders than H335 with the 160 TTSX?

I tried a few slower powders, but ya can't seat the bullet, because too much powder in the case. Using QL as a guide to keep the pressure at regular magnum levels with hybrid cases...I might get an extra 100 fps, but most aren't using hybrid cases in the 8.6 bolt gun...autoloaders could approach these loads with caution, and an adjustable gas block.
I'm running 65,000 psi loads in my 338 RCM AR 10.
Depending on how long your barrel is, will have great effect on velocities.
H335 is accurate at 2800 fps in my 6.5 twist barrel, with the 160 gr ttsx, which would be plenty for most hunting in the lower 48.
But for elk or bear the 225 at over 2400 fps puts alot of energy on the target, with better down range ballistices and energy retention....but you can not reach those speeds in a 3 twist barrel. They will blow up immediately after leaving the confines of the physical barrel, damaging your barrel devices permanently, and quite dangerous.
The 285 gr lead will not make 50 yds and blow up at 1400 fps, I know I tried without a muzzle brake.
The 3 twist IMO is totally ridiculous, and not needed.
My 6.5 twist gets excellent accuracy with 300 gr Berger or SMK subs and excellent accuracy at high velocity. Making it a real dual purpose cartridge....
So after spending alot of time and effort on the 8.6 Blackout I find it a pretty good cartridge with the 6.5 twist.
But if you like your 3 twist keep it, but mine has been permanently retired, and now part of has become a 338 RCM.

 

[SkyScrapin]

Shot 2 338s today one 8.6 Blackout and one I chambered 338 RCM AR 10.
But this is about the 8.6 Blackout, got some high velocity figures, for those interested in that.
This is the 6.5 twist barrel as many know I have given up on the 3 twist. So I can shoot cheap bullts fast and accurate and shoot 300 gr subs accurately also.
These are hunting bullets most lead but copper too.
The 250 gr were right at 2200 fps tbe 225 gr at slightly over 2400 fps and the 160 gr Barns at 2800 fps.
The 225 and 230 gr would be a nice pick for larger big game, for energy and range...like the elk that hang out in the area.

Those 160s are zipping.

 

[tom12.7]

I think those are 20" barrel velocities, but with a faster powder the 160 TTSX could pick up a little more speed. I'm getting around 2600 in 12" barrels with hybrid brass using faster powders in the H110/1680/CFE BLK range in bolt and gas guns. It's too much pressure for regular brass, but I'm not seeing pressure issues with the hybrid brass and CCI primers.

Edit to add that I have reduced these loads to something not as hot.

 

[SkyScrapin]

I think those are 20" barrel velocities, but with a faster powder the 160 TTSX could pick up a little more speed. I'm getting around 2600 in 12" barrels with hybrid brass using faster powders in the H110/1680/CFE BLK range in bolt and gas guns. It's too much pressure for regular brass, but I'm not seeing pressure issues with the hybrid brass and CCI primers.

Any pointers on where to start with Gorilla Brass, CFE BLK & Hornady CX 185g projectiles out of a 12" bolt gun?

Not expecting anything special, but want to put a couple hundred supers down the pipe before slinging subs.

ETA: Wondering if N110 is a better option for supers. Not much data out there for short bolt guns.

 

[SkyScrapin]

Well got the super sonic test done today for the 8.6 Blackout with a 6.5 twist.
Top velocity for the cheap Speer 200 gr lead bullets was 2604 fps with H335.
AA 2495 =2451 fps
CFE223= 2572 fps
IMR 4198 =2433 fps
2000 MR =2494 fps 4.3 S/D

@45-90

Is this data leveraging a hybrid case?

Posted above this, but venturing a suitable super sonic powder for the 185g CX. Not looking for anything special other than a load to get some supers down the pipe of a 12" 3T.

 

[45-90]

I think those are 20" barrel velocities, but with a faster powder the 160 TTSX could pick up a little more speed. I'm getting around 2600 in 12" barrels with hybrid brass using faster powders in the H110/1680/CFE BLK range in bolt and gas guns. It's too much pressure for regular brass, but I'm not seeing pressure issues with the hybrid brass and CCI primers.

I used QL to help decide which powder, at 65,000 psi not to 80,000 psi for my hybrid cases, to have a safety margin ...and if I relate to others in the autoloader area they may work up to similar velocities.
The new Alpha Munitions 8.6 brass will hande 65,000 psi and so will the AR 10 ...not that every load has to be at maximum.
According to QL you're at 80,000 psi which is a Gustine not knowing the chamber or seating depth etc.
Hybrid cases do not show the case indicators of high pressure...you could be at 90,000 psi...if the gets stiff lift or hard to open thats where you are, stressing the acttion. Heard it said the hybrid cases will handle 100,000 psi but there is noway to test that for the average person.
There is a video of the Ultimate Reloader channel running the new Alpha hard brass cases with a Bat action to over 100,000 psi.
Accuracy went south at 103,000 psi and a slight mark on the Alpha brass.

QL predicted you would gain around 70 fps in 12" by going to H335 at your higher pressures in the short barrel...
And I would loose about 100 fps with the faster powders like H110 and AA 1680, because of barrel lenght.
But I haven't actually shot them.

 

[45-90]

@45-90

Is this data leveraging a hybrid case?

Posted above this, but venturing a suitable super sonic powder for the 185g CX. Not looking for anything special other than a load to get some supers down the pipe of a 12" 3T.

I use both reformed brass and hybrid cases, have gone to hybrid exclusively now.
I run them at max magnum pressures of 65,000 psi, and no higher according to QL which will give at least some guidance...and AR 10 capable.
You have to know your exact case capacity, brass or hybrid, bullet length, seating depth to get anywhere near an acurate outcome, for the 185s, as copper bullets have double the start pressure spike, it must be taken into account every time.

 

[SkyScrapin]

I use both reformed brass and hybrid cases, have gone to hybrid exclusively now.
I run them at max magnum pressures of 65,000 psi, and no higher according to QL which will give at least some guidance...and AR 10 capable.
You have to know your exact case capacity, brass or hybrid, bullet length, seating depth to get anywhere near an acurate outcome, for the 185s, as copper bullets have double the start pressure spike, it must be taken into account every time.

Agreed.

I had a QL license, but lost the key. Rarely doing any time of load development on wildcats these days. 8.6 being the exception which is new enough that internet searches aren't proving helpful. This thread has more content than most, thanks to you fellas.

Thinking about starting just above Subsonic load data for CFE BLK, working up into super sonic territory. Seems like a reasonably logical way to get started.

Peak pressure & velocity are usually not what works in short barrels. Results in rather ugly ES in my experience. Usually the moderate loads offer best accuracy and consistency even if not a complete burn.

We'll see how things go and make adjustments.

 

[45-90]

For 8.6 Blackout and 185 gr copper bullet and brass cases, AR 10 compatible.
AA1680 33.6 gr
H110 30.2 gr
CFE BLK 37.1 gr
Approximate max loads to "work up to" with common powders used. Final velocities are within 40 fps between them...depending on barrel length, chamber, bullet seating depth which is critical in small volume cases like the 8.6, this was set at 2.700"
For informational purposes

 

[SkyScrapin]

For 8.6 Blackout and 185 gr copper bullet and brass cases, AR 10 compatible.
AA1680 33.6 gr
H110 30.2 gr
CFE BLK 37.1 gr
Approximate max loads to "work up to" with common powders used. Final velocities are within 40 fps between them...depending on barrel length, chamber, bullet seating depth which is critical in small volume cases like the 8.6, this was set at 2.700"
For informational purposes

Thanks for the suggestions. This is a 12” bolt.

 

[LVLAaron]

8.6 Blk. Subsonic Work Up UPDATE:

25 yard indoor range, linear compensator from Tromix.
Measurements taken with a MagnetoSpeed V3 chronograph

FPS = 5 shots averaged

Sierra SMK 300 gr.

Powder: Accurate 1680 16.5 gr 1088 FPS

Powder: TAC 18.0 gr 1084 FPS

Powder: CFE BLK 17.0 gr 1088 FPS

OAL: 2.670”

I have decided to go with TAC. The groups were better and more consistant. Accurate 1680 didn't always lock the bolt back at this powder level. This is a 16" barrel with carbine length full gas. Groups printed about 1/2" lower than supersonic at 25 yards.

I used nickel plated cases that I formed from Federal 6.5 Creedmoor SRP. I annealed them before cutting and sizing, then turned the case neck to fit the 8.6 Sheridan gauge. There was no damage to the fired cases.

USE THIS INFORMATION ONLY AS A GUIDE! Your results may vary.

Thanks for this. Had nearly the exact same results. I was using the faxon/Q data for the 300's and was chasing my tail with only 500-600 fps

 

[DRWilson]

Shot 2 338s today one 8.6 Blackout and one I chambered 338 RCM AR 10.
But this is about the 8.6 Blackout, got some high velocity figures, for those interested in that.
This is the 6.5 twist barrel as many know I have given up on the 3 twist. So I can shoot cheap bullts fast and accurate and shoot 300 gr subs accurately also.
These are hunting bullets most lead but copper too.
The 250 gr were right at 2200 fps tbe 225 gr at slightly over 2400 fps and the 160 gr Barns at 2800 fps.
The 225 and 230 gr would be a nice pick for larger big game, for energy and range...like the elk that hang out in the area.

Just to confirm that these figures are with regular brass?

 

[Floridapanhandle]

Got out this weekend and shot my latest loads.
12" Faxon 1-3 twist
Gorilla brass, 300 gr SMK Rem large rifle primer.

Accurate 1680
5 rounds each
14.8 gr - 947.9 fps
14.9 gr - 958.2 fps
15.0 gr - 973.7 fps
The best standard deviation was the 15.0 gr 5.2 fps

Bolt cycles and locks back on the last round on all loads tested.

Going to load five more each at 15.5 gr and 16.0 gr.

 

[Floridapanhandle]

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

Have you tried shooting any out of a gas gun? Are casting your own bullets or buying them?

 

[45-90]

Just to confirm that these figures are with regular brass?

The 338 RCM is reformed 6.5 PRC brass.
The 8.5 Blackout is now mostly hybrid cases, but they are are held to magnum rifle pressure, according to QL, in order to give a cushion when experiencing with alot of different powders in the 8.6 blackouts.
I am now running a bolt action with a 6.5 twist, where the data is now collected, on the 6.5 twist barrel, where I can run any bullet at max velocity or subs without any fear of blow up, plus excellent accuracy.

I have scrapped the Faxon 3 twist project as unworkable, after buying into it early, in its development.
The Faxon 3 twist cost me hundreds in damages, a new muzzle brake and a new magnetospeed bayonet.
Using their early load data!..it that took many months to delete, after many of us were bringing it to their attention, ...after many complaints, that their load data was way over pressure and destructive. They finally took that super sonic lead data off their site.
I was skeptical of the 3 twist hype...but was curious enough to give it an honest try.
You must work up to any load data for your rifle and its chamber, seating depth changes pressures quickly in the small capacity 8.6 case.

 

[DRWilson]

Will the bonded bullets come apart in a 1:5 twist. I get mine built any week from Most-tek and need to sort out if I go 6.5 or 5. Paul, from maker suggested I go 5 as bullets are expanding nicely in that twist rate. But he also said either will work. If I play with bonded bullets like you guys are, I just don’t want to blow up a can.

 

[45-90]

Will the bonded bullets come apart in a 1:5 twist. I get mine built any week from Most-tek and need to sort out if I go 6.5 or 5. Paul, from maker suggested I go 5 as bullets are expanding nicely in that twist rate. But he also said either will work. If I play with bonded bullets like you guys are, I just don’t want to blow up a can.

I do not know about the 5 twist.
I don't own that one, but anything with a lead core will blow up in the 3 twist.
Will it do so in a 5 twist?
You'd have to shoot them without a muzzle device to see if they blow up as soon as they leave the confines of the barrel or 40 yds down range, at the velocity you desire to shoot them plus a little extra for insurance.
I do own the 6.5 twist and it shoots everything I've tried, with no failures.
Supers in any lead bullet, bonded or not, as fast as the 8.6 can shoot them, with excellent accuracy.
Cheap lead hunting bullets, so you can afford to shoot it...without worry.
Velocities on the heels of the 338 Federal with lead bullets. Plus excellent accuracy with subs. The 6.5 twist is very versatile.

 

[DRWilson]

What sub loads are people running not using 1680? and not using hybrid brass?

 

[45-90]

What sub loads are people running not using 1680? and not using hybrid brass?

Most 1680 loads have higher S/D in velocity than IMR 4198...my guns.
My favorite load is Berger 300 gr with 15.8 gr of IMR 4198 a S/ D of 9.4 for auto loader, "standard" case.

I use a 6.5 twist, in a bolt gun now, so I don't have to worry about cycling the action.
But at 495 fps I did have to make sure the bullet left the barrel...as I tried a large pistol primer for ignition over a large rifle...it was a powder dependent experiment, with a pistol primer dropping velocity as much as 300 fps.

 

[GregP42]

Have you tried shooting any out of a gas gun? Are casting your own bullets or buying them?

I cast my own out of wheel weights then powder coat and water drop. I have been shooting them in my bolt action, haven't tried them in my AR10 yet, will have to try that next time.

Greg

 

[SigSauerM7]

Is it possible to use hybrid cases in AR's with beefier bolt heads and go to 65-70k psi safely?

Get the 130gr M80A1 up to 3400 FPS and 200gr pills up to 2700 FPS.

6.8 SPC 140gr up to 2700 FPS. Does not seem crazy to me.

 

[45-90]

Is it possible to use hybrid cases in AR's with beefier bolt heads and go to 65-70k psi safely?

Get the 130gr M80A1 up to 3400 FPS and 200gr pills up to 2700 FPS.

6.8 SPC 140gr up to 2700 FPS. Does not seem crazy to me.

I run ARs at a maximum of 65,000 psi which is magnum pressure, with brass or hybrid cases... for 308 bolt heads AR 10.

Going thinner than 5.56 on the bolt face of the AR 15 makes things even worse for those cartridges.
There are no beefier bolts for many AR cartridges with the thinner bolts from the Valkyrie, to 6.8, on to the Grendel, and 6 and 22 , ARCs to the 450 bushmaster. You are out of luck with these Autos in the AR 15 platform by design.
You have to go to a bolt gun with these cartridges, to take advantage of higher pressures.
It's why Hornady limits the pressure on the 6mm ARC, AR 15 bolts, and seperates it from the bolt gun data..it was not the case but the AR 15 was designed around the 5.56 as the mitary cartridge, not intended to be anything but, the 5.56 ... by the orginial designer.

 

[45-90]

I use cast bullets in AR 15 450 bushmaster for a heavy weight bullet try Lee 502 grain a .457" dia sized to .452" this is for 16 twist barrels not 24 twist. Works well and I added a thick recoil pad.
Probably not a viable alternative with a 3 twist, being so fast a twist the lead being soft, it would be hard to grab the rifling and spin the bullet instantly...leaving lead smears and pieces behind in the barrel. Accuracy would be limited number of shots if at all. But try it for yourself and see.
I have a 6.5 twist that would be a better test vehicle...if I had a heavy 338 mould...I'd load up a few...out of curiosity.

 

[Mike6158]

I had pretty good sub performance with N133 and the 280gr Barnes LRX BT. Unfortunately I had Chronograph (user) issues. The 12" Faxon barrel is such a pile of crap that I suspended testing until my new barrel comes. AR10 platform with a Dead Air Primal btw. I have other tests beside this one. N133 for subs gives you a wide range of powder charges.

 

[45-90]

I had pretty good sub performance with N133 and the 280gr Barnes LRX BT. Unfortunately I had Chronograph (user) issues. The 12" Faxon barrel is such a pile of crap that I suspended testing until my new barrel comes. AR10 platform with a Dead Air Primal btw. I have other tests beside this one. N133 for subs gives you a wide range of powder charges. View attachment 8404957

I believe you are correct, I did the same thing with my early Faxon barrel ...suspended testing.
I felt I was just wasting components.
I really like my new 6.5 twist barrel, it suits me.
Your new barrel has gotta be much better.

 

[MSBRPT]

What sub loads are people running not using 1680? and not using hybrid brass?

Best results I got so far was with Lil’ Gun and N110 with CCI 450 primers. I have a handful of other powders I’ve been meaning to try. I’ve been using converted SRP 6.5 CM alpha brass and Lapua Scenars (250 and 300gr). SMKs weren’t as consistent for me.

 

[wgranvilleb]

I'm a newbie to 8.6 BO with a recently purchased 12" Fix. I am also a reloader with moderate experience and respect safety over pushing boundaries. I have also read through this entire and very informative thread. Thanks to those who have contributed.

I realize this is a very naive question, but I am wondering if it might be possible to gradually develop some "rules of thumb" relationships for data obtained for the 6.5 vs the 3 twist rate.

Safety remains the primary concern. Would like to use 165 gr and 185 gr Barnes as well as the heavies for subs in the standard Q 12" barrel.

Many thanks.

 

[wgranvilleb]

.

 

[wgranvilleb]

For 8.6 Blackout and 185 gr copper bullet and brass cases, AR 10 compatible.
AA1680 33.6 gr
H110 30.2 gr
CFE BLK 37.1 gr
Approximate max loads to "work up to" with common powders used. Final velocities are within 40 fps between them...depending on barrel length, chamber, bullet seating depth which is critical in small volume cases like the 8.6, this was set at 2.700"
For informational purposes

Sorry, but to verifty . . . are these max load suggestions for a 1:6.5" twist or 1:3" twist?

If 1:6.5", how might these charge weights be adjusted for 1:3"? Suggestions / Thoughts?

Thanks.

 

[45-90]

Sorry, but to verifty . . . are these max load suggestions for a 1:6.5" twist or 1:3" twist?

If 1:6.5", how might these charge weights be adjusted for 1:3"? Suggestions / Thoughts?

Thanks.

I have both 3 twist and 6.5 twist in 8.6 Blackout.
IMO, the 3 twist is ridiculous and not needed.
You can shoot everything in a 6.5 twist at maximum velocities obtainable in a 8.6 Blackout without worrying about bullet blow up, destroying your muzzle devices and chronograph....not to mention some of the fragments could hit the shooter.

All copper bullets, are supposed to be safe at higher velocities in a 3 twist. But I found the 3 twist terribly inaccurate with copper bullets, working up loads, with the expensive copper bullets, was a waste.

For 3 twist lead bullets about 1000 fps max, some keep them at 900 fps with a suppressor.

I have abandoned the 3 twist, as I how no use for it.
It's very limited, inaccurate, and takes high velocity off the table, and expensive to shoot the all copper bullets that should be used with anything above 1000 fps.

Everything I now experiment with and load for is for 6.5 twist. It brings everything to the table that the limited 3 twist leaves behind and covers everything the 3 twist does...with much better accuracy.
Do yourself a favor and get a quality 6.5 twist. You're just wasting time and ammo with the 3 twist.
I have a bunch of test loads worked up for the 6.5 twist for lead bullets close to 338 Federal velocities, not possible with the 3 twist...and they are cheap to shoot. Plus sub and high velocity 300 gr SMK and 300 Berger.

 

[wgranvilleb]

Yes, I understand from your previous posts you have abandoned the 3 twist in favor of the 6.5. Totally understand.

That is why I asked the question in my prior post to clarify that the load data you presented (CFEBLK 37 gr max) is intended for the slower twist barrel. I'm assuming pressures are higher in the faster twist barrels for the same charge weights.

Just looking to clarify for safety.

 

[45-90]

Yes, I understand from your previous posts you have abandoned the 3 twist in favor of the 6.5. Totally understand.

That is why I asked the question in my prior post to clarify that the load data you presented (CFEBLK 37 gr max) is intended for the slower twist barrel. I'm assuming pressures are higher in the faster twist barrels for the same charge weights.

Just looking to clarify for safety.

I'm running the 6.5 twist exclusively now, so any data is for that twist...I chambered a custom, lapped barrel, it has a very nice rifling, and shooting nice groups.

If its an all copper bullet you may get there in a 3 twist but you must work up....with out a muzzle device attached...until you are certain, any bullet you choose at any velocity is going to stay together....there are no guarantees with the 3 twist...as much of the rifling is galled and torn, affecting everything, from shot to shot pressure, accuracy, and all around consistency.

The pressure is a near max,...So can one use it in a 3 twist?
The answer is maybe and maybe not...because the rough barrels are so inconsistent.
With increasing copper build up and more pressure to get each bullet through the bore, with each shot fired.
What was safe 10 shots ago, may now be over pressure, and dangerous to shoot the next round.

 

[wgranvilleb]

Thanks for your response.

I assumed that was the case but wanted to be sure. There are newbies tracking this thread (myself included) and in an effort to emphasize safety, just wanted to ensure all are aware of the differences with your approach using the 1 : 6.5 twist rate.

Roger all . . . regarding the issues with the 1:3 twist . . . and appreciate you pointing these out.

All of us greatly appreciate your contributions and willingness to push the envelope in another, and likely, safer direction.

Looking forward to the future 45-90 installments.

Thanks again.

 

[MSBRPT]

I'm a newbie to 8.6 BO with a recently purchased 12" Fix. I am also a reloader with moderate experience and respect safety over pushing boundaries. I have also read through this entire and very informative thread. Thanks to those who have contributed.

I realize this is a very naive question, but I am wondering if it might be possible to gradually develop some "rules of thumb" relationships for data obtained for the 6.5 vs the 3 twist rate.

Safety remains the primary concern. Would like to use 165 gr and 185 gr Barnes as well as the heavies for subs in the standard Q 12" barrel.

Many thanks.

In my opinion the inaccuracy issues are most likely due to Faxon’s quality. I’ve personally shot your same rifle configuration out to 600 meters and got consistent hits. It’s accurate enough to hit 6” pie plates at 400 meters as well. All subsonic loads.

 

[tom12.7]

I agree the accuracy issues are more for Faxon barrels than the 1 in 3" twist in general. Q and MOS-Tek 1 in 3" barrels have shot better for me.

 

[Mike6158]

Out of curiosity I rearranged the sonic velocity equation to solve for temperature (deg F) and I got this (last row). I used the average velocity for the calculation so if you're close to or above the temperature shown you'll want a load with a tight ES.

So what does it tell you? It tells you that column 7 is supersonic at 1,144fps at 84 deg F and cooler (I think I have that right?). Nope, it tells you that the velocity of sound at 84 degrees is 1,144 fps. Any velocity at or above that is supersonic at that temperature. If it's hotter, sonic velocity goes up. Then I look up at the 3 shots and see that at least one round was supersonic and one was pretty close. I wish I had all three velocities for column 3 AND the ES was still 0.9.

So when you see a box (or bucket) of ammo labeled supersonic, see if they tell you what the velocity is. Temperature matters.

 

[45-90]

Faxon 3 twist was the only barrel available in 8.6 in the beginning, and I just had to see what the hipe was all about. So I ordered one.
I couldn't see clearly through the barrel.. it was all fuzzy all the way down.
Ran the first patch through and metal and slivers of metal came out. Absolutely the worse barrel I'd ever seen.
Ran the bore scope through it, and the rifling was torn, and galled, with chuncks torn out of the bore, ith reamer marks.
Indicating the clearence was still wrong on the rifling button, while I'm sure enough oil was pumped through cause them make barrels.
It was better toward the muzzle. So I did a bit of lapping to smooth it up and call it the best I can do with a barrel of this quality.
It never shot well, even its best load.
The 6.5 twist on a good barrel, has the versatility of the 300 blackout.
Shoot any bullet as fast as the maximum pressure allows, or shoot subs with better accuracy...no worries of damaged muzzle devices, or bullets not making it to the target.
The 6.5 twist actually over stablizes bullets, so the 3 twist is really ridiculously out there, and why there were so many skeptics, because of ballistics and physics of it.

 

[Mike6158]

Same here. As soon as a barrel was available I bought one, unfortunately. I have a 6 twist for my Ruger American in 300BLK. I haven't shot it yet. Too many projects and not enough time. I'm certain I was switched at birth and should have been wealthy with plenty of free time.

I've got to keep plugging on with the 3 twist and and LRX. But not with the Faxon "thing". Your barrel sounds like mine. Plus it's thin. Really small OD and big ID makes for a barrel that's got thin walls and is going to whip when it's fired. It's evident that it does just that in the target when load testing. I ordered a bull barrel to replace it. Might have to hire me a gun bearer when I get it. It'll be heavy.

 

[wgranvilleb]

Re: Seating depth (percent case fill) versus projectile jump (distance to the lands) - considerations
Equipment: The Fix, 12" 3:1 twist Q barrel ; Magazine length limitation is ~ 2.800" +/- smidge

Previously, in this thread, there was mention of seating depth, pressure, and freebore length considerations. I would like to gather the collective wisdom in this area just a bit more, please.

There seems to be a de facto acceptance that for solid copper projectiles, a .050" jump is considered optimal.
- does this guideline pertain to subs only, or for both subs and supers?
- closer than .050" probably leads to an undesirable increased pressure (spike)
- however, how much bullet jump is too much? At what point are there diminishing returns from too large a gap or other detrimental effects?

45-90 has pointed out the critical nature of the relationship between seating depth and pressure. . . Meaning, that small changes in seating depth (for any given projectile / powder charge weight combination) will likely lead to large changes in pressure. 45-90 has also pointed out that from an overview standpoint, the 8.6 case is not well suited for subsonic loads due to its large case capacity relative to the powder charge weight/volume, leaving a significant residual air volume (percent case fill).

So, for subsonic loads, for any given projectile (for example the 350 gr Maker) there appears to be a balancing act of percent powder case fill / remaining free air volume versus the bullet seat depth / jump. Meaning, as one seats the projectile deeper to decrease free air volume there is an increase in bullet jump. (Acknowledging a needed compensating decrease in powder charge to prevent over-pressure). At what point is there too much bullet jump?

So, following this line of thinking, it would seem reasonable to seat the projectile as deeply as practically possible to increase the 'relative' percent case fill, while adjusting the powder charge to maintain safe pressure. What else needs to be considered?

Thoughts?

 

[Mike6158]

Once I get the new barrel I'll be retesting to verify powder charge is still good then test the seating depth to see if I can get the groups to tighten up (i.e. tune the load to the barrel harmonics),

The 280gr LRX is long. Somewhere in this group of threads there are some measurements that I made for case fill.

 

[wes1]

Anyone running H110 and 185 gr CX?
Looking for confirmed data.
Thanks!

 

[45-90]

Shooting the 8.6 Blackout 6.5 twist in a bolt gun and more test loads for the AR 10 338 RCM.

But here we are only concerned with the 8.6 Blackout
For subs I tried 10.5 gr of Red Dot, with a 300 gr SMK at 2.750" had a good fill and and consistent velocities around 980 fps.
But a ten shot group was an unacceptable vertical string covering 1.53" straight up...maybe a few tenths more powder to up the velocity would help.
Went back to the 15.8 gr of AA 1680, with 300 gr SMK 2.750" at 1075 fps but 2 went up higher in velocity 1123, 1154...for 14 shots.
But the 100 yd 14 shot group was .950" high and 1.3" wide on a windy day, with no barrel cooling...just shooting all the shots. So this will be my sub load for now, for this
gun...

For supers, in 6.5 twist only...these are lead bullets, and dangerous and not safe to use for 3 twist guns, at these velocities.

225 gr Speer CFE223= 2481 fps. 2.630"
225 gr Speer W 748 = 2330fps
200 gr Speer H335 = 2611 fps 2.608"
200 gr Speer 2000MR = 2549 fps
300 gr SMK IMR 4895 = 1948 fps 2.790"

As one can see the 8.6 can be a nice dual use cartridge with a slower twist, fast supers and accurate subs, and can utilize cheap lead bullets, with good hunting accuracy, and lots of energy in target, if desired.

Can not find any Clays to try on subs as it has good case fill.
I use Red Dot in the 50BMG for case fill subs 5 shot groups running 1" to 1.25" .

 

[wgranvilleb]

Thank you for the excellent and thorough follow-up. Greatly appreciated.

Regarding barrel length. . .
Your 1:6 twist barrel is 16" if I remember correctly.

After poking around on some old school cast bullet reloading forums, there were many comments regarding older pistol and shotgun powders functioning well in downloaded situations with low percentage case fills. Your interest with Red Dot and Clays sounds spot on. As much as I wanted H110 or CFEBLK in the 'go to' role, they tend to prefer full case fills.

Regarding the vertical stringing. . . What are some common conditions that induce that? If it's 'positional', then I guess that gets tricky quickly too. I'm wondering if Universal Clays (Unique equivalent) might be worth considering. Acknowledge your results with AA1680.

Many thanks for your excellent data and insights.

 

[45-90]

The barrel blank came in as a McGowen 6.5 twist 24" Rem Varmit contour. I was going to cut it to 20" after chambering ...but left it a full 24" on the Rem 700 SA.
I can always cut it shorter.
This was to see how close to the 338 Federal published data I could get which is all 24" test barrels, in high velocity loads.
This is for test purposes to see what the 8.6 Blackout is capable of.
I believe 20" for a bolt and 16" to 18" for an AR are probably good practical lengths for this cartridge, especially unsuppressed.
The vertical stringing may be that the velocity is a bit low for this barrel length, and it's harmonics.
These fluffy, high case fill shotgun powders have a 100 % burn rate in sub loads, which helps keep velocities more consistent, and a lot of powders do not, longer barrels and higher pressures contribute to burn rate consistency.
If the barrel gets too long like 30" in a 308 test sub, the bullet actually needs a couple tenths more powder to keep the velocity up to a shorter 22".

 

[wgranvilleb]

Re: 8.6 subsonic load development
Barrel: 12" 1:3" twist Q barrel for The Fix

Please pardon this simplistic approach, but as I get started into the process of load development for the 8.6 subsonic, I need to be able to visualize the percent case fill for different representative powders. I realize that the density charts provide the same information, but sometimes seeing is believing. My apologies to the more sophisticated reloaders with greater experience, but this exercise has helped me better understand some of these initial issues. I also thought this information might help others just starting out as well.

I envy @45- 90's ability to make what he wants with proper machine tools. I'm limited to hand tools and a drill press. Please give me a pass on the rough fabrication. The ID of the acrylic rod is very nearly (within a few percent) the same ID as the .338 case. The length of the acrylic rod represents the 'trim to' length of the 8.6 case. The two dimes are super-glued together and very closely represent the thickness of the shell base (after a little sanding to remove a few thousandths). The projectile is the Maker 350 gr and the 'O' ring maintains the OAL of 2.780" (chosen due to the magazine capacity is 2.800" and @45-90's data which has fixed OAL to the same length). As there is a dynamic relationship between seating depth and powder charge, I was thinking of starting out by 'fixing' as many variables as possible and just change one at a time.

The 350 gr projectile is likely the largest to be fired in this application, and thus represents a 'best case design' for case fill. The 300 gr and 250 gr projectiles get progressively shorter, if the OAL distance remains fixed. By the way, the distance for touching/seating at the lands for the Maker 350 gr and 300 gr projectiles measures ~ 2.880" (~.110" jump), and the SMK 300 gr touches/seats at around 2.820" (~.040" jump). For these heavy subsonics, several sources suggest a bullet jump of ~ 0.050" +/-, noting the SMK is pushing the suggested limit just a bit, but is commonly used and likely ok.

All powder charges are 14 gr. This is NOT a recommended charge weight, but only a way to compare the different powders, on a relative basis, for the percent case fill with the same projectile and same OAL.

The first images / powders, H110 and CFEBLK show quite a bit of air gap (or lower percent case fill).
- from prior experience, I have learned that H110 and CFEBLK performed better with filled / mildly compressed charges.
The third image is for Clays and is quite compressed.
- I have used Clays extensively in SASS shooting with low percentage case fills, and it has worked fine.
The fourth image is for Univeral Clays (slower than Clays), and has only a minimal air gap.
- I will be using a 12" 1:3 twist Q barrel and that barrel length might be enough for the majority of the powder to burn, but needs to be confirmed.

Next steps:
I will likely start with the Maker 350 gr and Clays powder. Previously in this thread, @45-90 jumped in with the fast pistol powder and suggested Clays as another reasonable consideration. Does anyone have any ballpark ideas for powder charge weights for the 350 gr projectile and Clays powder?

Thanks.

 

[45-90]

Alot of work, but the visual gives one the idea of case fill, for hopefully more consistent velocities needed with subs, as the distance to the target increases.

When actual testing begins, I'd take a cleaning rod, to clean the barrel often...see if the interior of the barrel is causing problems, loading up with copper.
Clean, fire one or two fouling shots, then shoot for group size while checking velocity. There may be a cutoff point where velocity fluctuates more...stop and clean.
See if velocity is fairly stable for a certain number of shots. That will be noted when hunting...up close it won't matter but as the distance increases it will.

 

[wgranvilleb]

Thank you. All excellent suggestions, and appreciate your input.

I'm thinking of starting with Universal Clays, which is a little slower than Clays, and a 1:1 substitute for old school Unique powder.

Now, I need to figure out a couple of starting charge weights that will bracket the velocity range of interest.

 

[MSBRPT]

Re: 8.6 subsonic load development
Barrel: 12" 1:3" twist Q barrel for The Fix

Please pardon this simplistic approach, but as I get started into the process of load development for the 8.6 subsonic, I need to be able to visualize the percent case fill for different representative powders. I realize that the density charts provide the same information, but sometimes seeing is believing. My apologies to the more sophisticated reloaders with greater experience, but this exercise has helped me better understand some of these initial issues. I also thought this information might help others just starting out as well.

I envy @45- 90's ability to make what he wants with proper machine tools. I'm limited to hand tools and a drill press. Please give me a pass on the rough fabrication. The ID of the acrylic rod is very nearly (within a few percent) the same ID as the .338 case. The length of the acrylic rod represents the 'trim to' length of the 8.6 case. The two dimes are super-glued together and very closely represent the thickness of the shell base (after a little sanding to remove a few thousandths). The projectile is the Maker 350 gr and the 'O' ring maintains the OAL of 2.780" (chosen due to the magazine capacity is 2.800" and @45-90's data which has fixed OAL to the same length). As there is a dynamic relationship between seating depth and powder charge, I was thinking of starting out by 'fixing' as many variables as possible and just change one at a time.

The 350 gr projectile is likely the largest to be fired in this application, and thus represents a 'best case design' for case fill. The 300 gr and 250 gr projectiles get progressively shorter, if the OAL distance remains fixed. By the way, the distance for touching/seating at the lands for the Maker 350 gr and 300 gr projectiles measures ~ 2.880" (~.110" jump), and the SMK 300 gr touches/seats at around 2.820" (~.040" jump). For these heavy subsonics, several sources suggest a bullet jump of ~ 0.050" +/-, noting the SMK is pushing the suggested limit just a bit, but is commonly used and likely ok.

All powder charges are 14 gr. This is NOT a recommended charge weight, but only a way to compare the different powders, on a relative basis, for the percent case fill with the same projectile and same OAL.

The first images / powders, H110 and CFEBLK show quite a bit of air gap (or lower percent case fill).
- from prior experience, I have learned that H110 and CFEBLK performed better with filled / mildly compressed charges.
The third image is for Clays and is quite compressed.
- I have used Clays extensively in SASS shooting with low percentage case fills, and it has worked fine.
The fourth image is for Univeral Clays (slower than Clays), and has only a minimal air gap.
- I will be using a 12" 1:3 twist Q barrel and that barrel length might be enough for the majority of the powder to burn, but needs to be confirmed.

Next steps:
I will likely start with the Maker 350 gr and Clays powder. Previously in this thread, @45-90 jumped in with the fast pistol powder and suggested Clays as another reasonable consideration. Does anyone have any ballpark ideas for powder charge weights for the 350 gr projectile and Clays powder?

Thanks.




View attachment 8416539

I tested Alliant Unique up to 10.6. I think 10 grains gave small SDs, within 1 fps. I should’ve taken better notes, I think the bullet was a 300gr Lapua Scenar. I remember it being really quiet but not accurate. I didn’t play with seating depth at all to see if tuning it would improve accuracy. I ran a similar load on GRT, 14 grains of Unique with a 350 maker seated to where there wasn’t a lot of space and I think it said the load was dangerous.

 

[MSBRPT]

Re: 8.6 subsonic load development
Barrel: 12" 1:3" twist Q barrel for The Fix

Please pardon this simplistic approach, but as I get started into the process of load development for the 8.6 subsonic, I need to be able to visualize the percent case fill for different representative powders. I realize that the density charts provide the same information, but sometimes seeing is believing. My apologies to the more sophisticated reloaders with greater experience, but this exercise has helped me better understand some of these initial issues. I also thought this information might help others just starting out as well.

I envy @45- 90's ability to make what he wants with proper machine tools. I'm limited to hand tools and a drill press. Please give me a pass on the rough fabrication. The ID of the acrylic rod is very nearly (within a few percent) the same ID as the .338 case. The length of the acrylic rod represents the 'trim to' length of the 8.6 case. The two dimes are super-glued together and very closely represent the thickness of the shell base (after a little sanding to remove a few thousandths). The projectile is the Maker 350 gr and the 'O' ring maintains the OAL of 2.780" (chosen due to the magazine capacity is 2.800" and @45-90's data which has fixed OAL to the same length). As there is a dynamic relationship between seating depth and powder charge, I was thinking of starting out by 'fixing' as many variables as possible and just change one at a time.

The 350 gr projectile is likely the largest to be fired in this application, and thus represents a 'best case design' for case fill. The 300 gr and 250 gr projectiles get progressively shorter, if the OAL distance remains fixed. By the way, the distance for touching/seating at the lands for the Maker 350 gr and 300 gr projectiles measures ~ 2.880" (~.110" jump), and the SMK 300 gr touches/seats at around 2.820" (~.040" jump). For these heavy subsonics, several sources suggest a bullet jump of ~ 0.050" +/-, noting the SMK is pushing the suggested limit just a bit, but is commonly used and likely ok.

All powder charges are 14 gr. This is NOT a recommended charge weight, but only a way to compare the different powders, on a relative basis, for the percent case fill with the same projectile and same OAL.

The first images / powders, H110 and CFEBLK show quite a bit of air gap (or lower percent case fill).
- from prior experience, I have learned that H110 and CFEBLK performed better with filled / mildly compressed charges.
The third image is for Clays and is quite compressed.
- I have used Clays extensively in SASS shooting with low percentage case fills, and it has worked fine.
The fourth image is for Univeral Clays (slower than Clays), and has only a minimal air gap.
- I will be using a 12" 1:3 twist Q barrel and that barrel length might be enough for the majority of the powder to burn, but needs to be confirmed.

Next steps:
I will likely start with the Maker 350 gr and Clays powder. Previously in this thread, @45-90 jumped in with the fast pistol powder and suggested Clays as another reasonable consideration. Does anyone have any ballpark ideas for powder charge weights for the 350 gr projectile and Clays powder?

Thanks.




View attachment 8416539

I tested Alliant Unique up to 10.6. I think 10 grains gave small SDs, within 1 fps. I should’ve taken better notes, I think the bullet was a 300gr Lapua Scenar. I remember it being really quiet but not accurate. I didn’t play with seating depth at all to see if tuning it would improve accuracy. I ran a similar load on GRT, 14 grains of Unique with a 350 maker seated to where there wasn’t a lot of space and I think it said the load was over pressured.

 

[45-90]

A .338 dia Maker 350 gr bullet 2.020" long.
A Winchester converted 6.5 CM cases 45.7 gr of H2O
Cartridge overall length 2.780" very important. Can not jam 10,000 psi pressure spike. Copper has double the start pressure over cup and core bullets, without jamming.

Do Not Exceed 1050 fps according to Maker, and for the 3 twist according to Maker.

12" barrel 8.6 Blackout
Clays
Start 8.1= 955 fps * danger do not go below 8.0 grs start pressure too high.

8.6 gr = 986 fps
9.0 gr =1010 fps here looks good IF velocity is correct, and approaching max load, and max velocity.
9.1 gr 1016 fps
9.2 gr 1022 fps definitely max for pressure for the case and bullet recommended maximum velocity.
This powder has good fill percentage, 100% burn, and good efficiency.
Will it get more consistent velocities?... Don't know, but the potential is there.

WARNING: I have Not fired this in my rifle, I do not have any Clays powder or Maker 350 gr bullets to try. This is for informational purposes only.
As always, test without muzzle devices attached to the 3 twist barrels, to make sure bullets will stay together and not damage muzzle devices or your face...and that the bullet actually exit the muzzle.