Mk12 Setup for High Pressure Loads?

[nn8734]

I use the Uniflow III on my Dillon 750 and it's effing amazing, especially compared to the Dillon powder dropper which is a nightmare to set up and use. I spent a lot of time tweaking the Dillon, full-on polishing, the whole nine yards and it's not even close to the RCBS for consistent throws. Highly recommended. I also have the Lee Auto Drum which I haven't run yet, for larger extruded powders like Varget.

I use H335 for .223 loads and will be developing a load for a 12.5" piston and a 16" DI gun, carbine vs. mid gas lengths respectively, 5.56 vs 223 Wylde respectively. Hopefully I can develop one load that works well in both! Thread has definitely given me something to think about.

Your experience mirrors mine with the Dillon powder measures in that I polished the fuck out of them and tried “upgraded” baffles but still not as consistent as the RCBS Uniflow.

You should be able to find a universal 5.56 load that works well in both of your carbines.

 

[NHPiper]

Very temp sensitive lol, which is why I went to something else. Not that I really would care now for my use, but at the time I put way more emphasis on it in general. I don't really play around with loads for the AR's as much as I used to, so I stuck with 8208, but I do still have H335, BLC-2 and CFE223 on hand. I think if you're wanting to get MK262 velocities, you're gonna need one of only a few powders:

TAC
A2520
A2230
CFE223
StaBALL Match
I think PP2000mr is another that can go fast.

No idea which of those are the most temp insensitive. I would imagine Staball or PP2000mr would be the best for that. According to Hodgdon's data center, CFE223 is yielding the fastest but it does not have data for Staball or 2000MR.

Guess I'm gonna stick with the 8208 and low 2700 fps in the winter. In the summer that should be close to 2740ish. Gonna try some 23.6 loads tomorrow which may get me to 2730ish in the winter. 23.5gr had very little if any pressure signs on the 16" gun but didn't seem to like the load.

 

[SERE8541]

.

 

[Thorbeast]

Do you really want to push pressure for velocity? Run a longer barrel or even better, run a different cartridge. The drop/drift you eliminate by picking up an extra 50fps isn't that significant.

 

[NHPiper]

Do you really want to push pressure for velocity? Run a longer barrel or even better, run a different cartridge. The drop/drift you eliminate by picking up an extra 50fps isn't that significant.

Im going to try some different 8208 loads, play around with some A2520 (although that looks to be too temp sensitive for my taste), and the new Staball Match.

 

[towerofpower93]

Guess I'm gonna stick with the 8208 and low 2700 fps in the winter. In the summer that should be close to 2740ish. Gonna try some 23.6 loads tomorrow which may get me to 2730ish in the winter. 23.5gr had very little if any pressure signs on the 16" gun but didn't seem to like the load.

23.6gr of 8208 is my 77gr SMK/TMK load. It gives me ~2,600fps in a chrome lined 18" DD and just under 2,700fps in a PRI Mk 12 Mod 0 with a stainless steel Douglas barrel.

 

[NHPiper]

23.6gr of 8208 is my 77gr SMK/TMK load. It gives me ~2,600fps in a chrome lined 18" DD and just under 2,700fps in a PRI Mk 12 Mod 0 with a stainless steel Douglas barrel.

That seems very very slow. What kind of brass are you using?

The velocity you're getting out of your Daniel defense barrel this slower than I'm getting out of my 16-in barrel with a lighter charge of the same powder. Barrels of different velocities but usually not that different.

My experience has been the Douglas barrels are generally a little bit slower than something like bartlein. 23.3gr in LC brass out of my Mark 12 bartlein is about 2715.

 

[Constructor]

One thing to consider is the specs of the barrel when trying to get maximum performance. A 6 groove barrel with a 50:50 land to groove ratio will create more engraving force than a 3 groove with a low land to groove ratio. That comes on as peak pressure is being developed by the powder. The 3G will also have less resistance in the barrel and more bore area. You should be able to load more powder in the case before seeing pressure signs and get more velocity as a result. Lilja, Blackhole(now Columbia), Pac Nor make 3 groove barrels, Blackstone Arms will handle ARP 3 groove barrels when he gets settled.
4 groove barrels with a low L-G ratio would be better than a 6 groove.

 

[ma smith]

23.3gr in LC brass out of my Mark 12 bartlein is about 2715.

What is your SD? If running GMM or GMAR primers (and weighing each charge) it should be pretty good.

 

[NHPiper]

What is your SD? If running GMM or GMAR primers (and weighing each charge) it should be pretty good.

12-13 SD out of a Dillon 650, using 2 chargemasters to weigh powder and dump down the 550 style funnel I have on one of the stations. Using CCI 400 small rifle primers.

 

[Constructor]

Rem 6 1/2s, the original Fed 205s and CCI 400s are not the best to use when pushing pressure levels as others have said, they will flatten and pierce before 450s, 41s, 7 1/2s, Fed AR or the Russian primers. Wolf has a slightly smaller flame which lets the powder build pressure more evenly, many have found they will produce lower SD. I understand finding primers is a problem.

 

[ma smith]

12-13 SD out of a Dillon 650, using 2 chargemasters to weigh powder and dump down the 550 style funnel I have on one of the stations. Using CCI 400 small rifle primers.

+1 CCI 400 primers are innapropriate for high pressure .223/5.56 loads due to the thin cup. Suggest you get some 205M (GMM) or GM-AR primers These are are better performing than eg. CCI 450s in 223 REM, although the 450s work and are good for practice ammo. Most people who do A/B testing verify the SDs go down ± 2-3 FPS vs cci 450s with the 205m. Haven't personally used rem 7.5s or CCI-BR-4s so no comments on those.

 

[nn8734]

12-13 SD out of a Dillon 650, using 2 chargemasters to weigh powder and dump down the 550 style funnel I have on one of the stations. Using CCI 400 small rifle primers.

Swap to Fed 205ARs if you can find some, the Remington 7-1/2 or cci41s for the sake of a thicker primer cup.

Beyond that 2700 fps should be fine. How far are you shooting these two platforms, typically?

Trying to understand why you need more velocity that what you’re getting, especially if the load is performing well.

 

[NHPiper]

Swap to Fed 205ARs if you can find some, the Remington 7-1/2 or cci41s for the sake of a thicker primer cup.

Beyond that 2700 fps should be fine. How far are you shooting these two platforms, typically?

Trying to understand why you need more velocity that what you’re getting, especially if the load is performing well.

650 to 700 yd it's pretty normal, sometimes pushing out to 800

Any experience of the Winchester 41 primers?

 

[nn8734]

650 to 700 yd it's pretty normal, sometimes pushing out to 800

Any experience of the Winchester 41 primers?

I never used them but a buddy did for a while and didnt have any issues though i think he used them in a bolt gun. There’s mixed opinions on here about them from what i can recall reading in the past few months.

2,700 fps is fine for 800y and in as the 77smk starts to run out of gas around 750-800m regardless so worst case scenario you’re not any worse off if you can’t go any faster than that safely/reliably. More velocity is great until it starts driving up operating and sustainment (and other) costs.

 

[towerofpower93]

That seems very very slow. What kind of brass are you using?

The velocity you're getting out of your Daniel defense barrel this slower than I'm getting out of my 16-in barrel with a lighter charge of the same powder. Barrels of different velocities but usually not that different.

My experience has been the Douglas barrels are generally a little bit slower than something like bartlein. 23.3gr in LC brass out of my Mark 12 bartlein is about 2715.

Yeah, the DD has always run slow. Most of the brass is once fired LC. When I get my next lot of LC brass in and prepped I'm thinking about going up a couple more tenths to see what those net me, or maybe buy a pound of StaBall Match and give it a run.

The 8208 load has always shot around or below 1MOA, so I've just lived with the little bit of extra elevation I need to dial or hold.

 

[Wormydog1724]

My standard 77gr load is 21.6gr of H322, 20round pmag length COAL, and CCI450 or CCI41. Decent SD's (20's, I mean come on, it's an AR afterall), and good MOA-ish groups. 2740fps or something like it. This is from my KAC 18" LPR Mod 2 (1:7 Kreiger barrel).

I'm running low on H322 so I've been trying AA2230-C (same load data as AA2460). At 23.8gr I'm at 2720fps and 20-ish SD's. I'm going to sprinkle some voodo sauce on them to cut those SD's in half, just haven't been back to the range to confirm. I'm also loading these longer since I now have some good 20 round ASC mags that have more room. I'm at 2.277 COAL. 24.0gr was also good as was 23.7gr. I like even numbers so I went 23.8gr. I know.

Where's everyone getting this speed from CFE223? I tried CFE223 and it gave great groups, acceptable SD's again, but holy moly it was slow. 24.5gr was .63MOA but only 2591fps from my 18". I gave up on it and focused on AA2230-C. If I could get the speed up to 2700fps, sub-moa, and keep my face, I'd really like to give CFE223 another try.

 

[Wormydog1724]

have you tried AA 2460? I started to play with that, stuff is FINE.. I mean WATER fine. you even thing of breathing and this stuff goes everywhere.
I used federal Brass and 1 shot for FPS..
20"semi auto ar15 used

AA 2460 93 degree day
24.5 - 2855
24.6 - 2844
24.7 2877
24.8 2877
All these AA 2460 loads were above book max, so be careful. I started to show signs of pressure and stopped.

After seeing this, maybe I need to keep going up with my AA2460 loading. I stopped at 24.0gr and settled on 23.8gr. If I could get closer to 2800fps from an 18" barrel AND keep my groups MOA, that would be a winner for me. Easier said than done I suppose. Something to try tho, thanks.

 

[Molon]

Decent SD's (20's, I mean come on, it's an AR afterall),

Despite having an extra hole in the barrel and mammoth chambers, AR-15s can produce good standard deviations. The 10-shot string pictured in the print-out below was fired from a 20" Colt AR-15 with one of my hand-loads for 77 grain OTMs. The 10-shot string has a standard deviation of 4 FPS.

....

 

[Wormydog1724]

Despite having an extra hole in the barrel and mammoth chambers, AR-15s can produce good standard deviations. The 10-shot string pictured in the print-out below was fired from a 20" Colt AR-15 with one of my hand-loads for 77 grain OTMs. The 10-shot string has a standard deviation of 4 FPS.





....

Cool. i've gotten SD's in the single digits with my AR's too.

 

[264pr]

Don’t be afraid to try Viht N540. It’s my go to powder to clone the Mk262. Its trueing at 2740ish in my son’s 20” RRA at 655 yards. Accuracy is 0.75 moa or better.

Shooting buddy uses it as well and it was his initial testing that led me to it. YMMV

Can you expound on that N540 load a little further?

I'm working up a 556 load using N540, 77gr SMK's and Starline 556 brass and am finding that at 24.3g N540 its already a compressed load and vendor shows max charge for this projectile to be a full grain higher (25.3g)

They are being seated to max length for magazine, 2.260

 

[ma smith]

Can you expound on that N540 load a little further?

I'm working up a 556 load using N540, 77gr SMK's and Starline 556 brass and am finding that at 24.3g N540 its already a compressed load and vendor shows max charge for this projectile to be a full grain higher (25.3g)

They are being seated to max length for magazine, 2.260

maybe that starline has lower internal case volume than reference brass

 

[264pr]

maybe that starline has lower internal case volume than reference brass

Maybe but I see same results with LC 19 brass and didnt see a specific brass manufacturer listed in VV's load data

 

[264pr]

I guess I shouldnt be too surprised its a compressed load.

Just stumbled across this vid that mentions compressed load at end using factory load data I;m working off

.223 Rem - 77gr Sierra Match King with VihtaVuori N540 - The Reloaders Network

The 13th installment of our Mk 262 Mod 1 clone series. VihtaVuori N540 is the primary test powder but we also shoot some groups with Accurate 2520, IMR 8208 XBR, and AR-Comp. Test bullet is the 77gr Sierra Match King with Cannelure.

www.thereloadersnetwork.com

EDIT: VV load data does mention bras used....lapua

Anyone ever compared volume of lapua and LC brass?

 

[tnichols]

Can you expound on that N540 load a little further?

I'm working up a 556 load using N540, 77gr SMK's and Starline 556 brass and am finding that at 24.3g N540 its already a compressed load and vendor shows max charge for this projectile to be a full grain higher (25.3g)

They are being seated to max length for magazine, 2.260

Right off the recipe card:
77 gr SMK over 24.7 gr of N540 in new Lake City 09 brass with Fed GM205M.
Base to ogive 1.864 OAL 2.257-2.263
Trued at 2735 FPS at 655 yards

 

[Molon]

Anyone ever compared volume of lapua and LC brass?

....

 

[357Max]

Staball match, 2520, & Lever 77SMK loads below. 18” 223W 8T

Not sure why Lever is Often overlooked for these MK262 loads.

I’ve settled on the 2520 load for MK262 clone.

Changed OAL from 2.255 to 2.265. Still using all virgin 223 IVI Ruag primed brass.
77 SMK Staball Match
25.2 2737 / 16.4 / .535" Locked back on last round. Brass GTG. Still faster than the Black Hills 77.

Also Confirmed my gun just plain likes Accurate 2520 better with these MK262 loads.
77 SMK @ 2.255 Acc 2520
25.3 2758 / 10.3 / .368" Lock back & brass GTG.

 

[264pr]

Right off the recipe card:
77 gr SMK over 24.7 gr of N540 in new Lake City 09 brass with Fed GM205M.
Base to ogive 1.864 OAL 2.257-2.263
Trued at 2735 FPS at 655 yards

Did you happen to track your SD's with that recipe?

 

[tnichols]

Did you happen to track your SD's with that recipe?

I did not. However, I look at what the waterline tells me. If it’s holding the waterline based on the platform it’s being used in (RRA 20” run by a 17 year old kid), that’s my data.

 

[towerofpower93]

Staball match, 2520, & Lever 77SMK loads below. 18” 223W 8T

Not sure why Lever is Often overlooked for these MK262 loads.

I’ve settled on the 2520 load for MK262 clone.

Damn, those Lever loads are moving.

Isn't Lever pretty temp sensitive? Thought I've read that's its Achilles heel in 6.5G/6ARC.

 

[357Max]

Damn, those Lever loads are moving.

Isn't Lever pretty temp sensitive? Thought I've read that's its Achilles heel in 6.5G/6ARC.

I run Lever in Valk & ARC. Tested my 77RDF & several other 224 loads @ mid 40’s & mid 90’s. Only saw about 10fps difference.
Case size & load efficiency has a bearing on temp sensativity.

The Staball match gets me good velocity, but so far in my barrel, Lever and 2520 win for precision.


That 223 Lever load wasn’t even top end. The 2520 load just shoots so well I’m going to roll with it for now.

 

[264pr]

Working on N540 load under 77gr SMK with GMM AR primers.

Working my way up from 24.3 starting load.

No signs of pressure so far, rounded edges on primer still and no cratering of firing pin dent

Out of an 18" barrel I was seeing velocity of 2800-2808 for 24.7gr

24.5 was a good node for SD/accuracy

Curious to see what 24.9 and 25.1gr produces/looks like wrt pressure

Factory load data shows 25.3 is max load

 

[Jason S]

Shooter's World Match powder
77gr TMK
Rem benchrest primers
Nosler match brass

I'm in the mid 2,800s without issues out of a 20" WOA. I use PRI mags so that I can load to an OAL of 2.3". The extra 40 thou seems to help avoid pressure issues. I am over the manual max of 25.8gr after careful work up.

I've stretched it out to 928yds at matches with good results. Someone borrowed it last weekend and took 1st in the gas gun division.

 

[Csteven]

A little late to the party but I just chronographed some loads with tac. Will attach a pic with my scribble. I am hoping I don't wind up with some holes in primers once the temp gets up to 95. This is from my AR set up for xtc service rifle matches. Krieger barrel 1-7.7 twist 20". The pic of the brass is attached afterwards as well. Left side is the 77gr smk right is berger 80.5 center is one shot at 24.7 gr with a 80.5 berger. The primers are a little flattened but I dont really see any ejector marks so i loaded 50 of each up. What do you guys think am I pushing my luck here?

 

[357Max]

A little late to the party but I just chronographed some loads with tac. Will attach a pic with my scribble. I am hoping I don't wind up with some holes in primers once the temp gets up to 95. This is from my AR set up for xtc service rifle matches. Krieger barrel 1-7.7 twist 20". The pic of the brass is attached afterwards as well. Left side is the 77gr smk right is berger 80.5 center is one shot at 24.7 gr with a 80.5 berger. The primers are a little flattened but I dont really see any ejector marks so i loaded 50 of each up. What do you guys think am I pushing my luck here?

So you're single loading @2.480??? I'd think it'd be ok at that length, but every barrel has it's own personality. Might get spicy in the heat.

I've run 25.0 Tac with 77smk @ 2.255 oal = 2801 from a 18" proof.
24.8 Tac with 80.5 Berger's @ 2.280 oal was 2766 from same 18" proof. No pressure issues on those in my barrel.

Also the rumor is that Starline 5.56 brass is a little harder on the bottom end so primer pockets hold up better with hot loads.

 

[ma smith]

What do you guys think am I pushing my luck here?

Pic says:

COAL 2.26, 77SMK, 2,850fps,with temp sensitive powder, small capacity brass, and cci 400 primers only rated for rem .222...etc?

IMHO that is asking for trouble with a +30˚F temp swing, but YMMV


What was your ambient test-date-temperature?

 

[357Max]

Pic says:

IMHO that is asking for trouble with a +30˚F temp swing, but YMMV


What was your ambient test-date-temperature?

Looks like 2.480" to me on pic of Green ammo box??

 

[ma smith]

Looks like 2.480" to me on pic of Green ammo box??

Just taking the notes "mag length" at face value.

 

[Alaska]

I am trying to run 23.8gr of 8208 behind 77gr SMKs in two different guns. The 16" gun gives me more substantial pressure signs, including several blown primers. Pressure signs are primarily ejector marks on the brass (substantial on the 16"). However, after shooting Mk262 through both guns, I get similar speed as the 23.8gr load with no pressure issues. Both guns are run suppressed with a Surefire RC2 (waiting on an OCM-5).

I am wondering if adjustable gas blocks or restricted gas tubes would solve the issue. I would love the extra speed. My 23.3gr loads shoot at 2610fps 12SD and 2705 13SD in the 16" and 18" barrels, which is about 75fps slower in NH winters than the 23.8gr load or Mk262.

GUN 1
16" Douglas SPR Barrel from PRI
Mid length gas system
Geiselle 42 carbine buffer spring
H3 buffer
23.8gr Velocity 2700ish

GUN 2
18" Bartlein SPR barrel from CLE
Rifle length gas system
Sprinco Green Rifle Spring
Noveske 5.2oz A2 rifle buffer
23.8gr Velocity 2780ish

Any thoughts on ways to modify the gas or recoil systems to reduce pressure? Or am I just going to have to stick with the 23.3gr loads.

Same here the same load ADI uses for their MK 262 Mod 1 load …….23.8 of 8208 but like you use 23.3 for best accuracy.

 

[357Max]

Just taking the notes "mag length" at face value.
View attachment 8107446

@Csteven - Please clarify oal is mag length?

I have run this high with TAC @ 50 degree temp without issue, but I'm betting it will need to be backed down for summer temps.

My barrel likes AA2520 the best without pushing it hard @2750. TAC is my backup load for now. Staball match is showing promise. Speed is there, & temp stability looks outstanding for ball. I'm going to do a few more load ladders for seating depth with the Match. Just pushing OAL +.010 to 2.265 shrunk the Staball Match load nicely. Need to see if it repeats.

 

[Csteven]

@Csteven - Please clarify oal is mag length?


View attachment 8107462
I have run this high with TAC @ 50 degree temp without issue, but I'm betting it will need to be backed down for summer temps.

My barrel likes AA2520 the best without pushing it hard @2750. TAC is my backup load for now. Staball match is showing promise. Speed is there, & temp stability looks outstanding for ball. I'm going to do a few more load ladders for seating depth with the Match. Just pushing OAL +.010 to 2.265 shrunk the Staball Match load nicely. Need to see if it repeats.
View attachment 8107487

the 77 Gr is mag length but the 80.5gr is 2.480

 

[Csteven]

Pic says:

IMHO that is asking for trouble with a +30˚F temp swing, but YMMV


What was your ambient test-date-temperature?

It was about 75 degrees on test day

 

[Csteven]

@Csteven - Please clarify oal is mag length?


View attachment 8107462
I have run this high with TAC @ 50 degree temp without issue, but I'm betting it will need to be backed down for summer temps.

My barrel likes AA2520 the best without pushing it hard @2750. TAC is my backup load for now. Staball match is showing promise. Speed is there, & temp stability looks outstanding for ball. I'm going to do a few more load ladders for seating depth with the Match. Just pushing OAL +.010 to 2.265 shrunk the Staball Match load nicely. Need to see if it repeats.
View attachment 8107487

So you're single loading @2.480??? I'd think it'd be ok at that length, but every barrel has it's own personality. Might get spicy in the heat.

I've run 25.0 Tac with 77smk @ 2.255 oal = 2801 from a 18" proof.
24.8 Tac with 80.5 Berger's @ 2.280 oal was 2766 from same 18" proof. No pressure issues on those in my barrel.

Also the rumor is that Starline 5.56 brass is a little harder on the bottom end so primer pockets hold up better with hot loads.

Yes single loading the 80.5 I use them for 600 yard slow fire prone that has to be loaded single anyway. I just double checked my Jam it is at 2.5. This barrel was cut to take the long 80 gr. That is good news about the starline brass. Reading what another commenter said I really wish I would of used the gm205m primers I have now.

 

[FredHammer]

TAC is more temp sensitive than 2520 in my experience and likes to be ran on the ragged edge of pressure.

That is the TAC we all know & love. LOL. In everything I've load developed with TAC, it performs the best right at that cusp of over pressure, if not in it a little already!

 

[nn8734]

That is the TAC we all know & love. LOL. In everything I've load developed with TAC, it performs the best right at that cusp of over pressure, if not in it a little already!

That's one of the reasons I've moved away from TAC and completely over to AA2520 (I also have a bunch of 8208 but there hasn't been a need to trial any 5.56 loads w/it). Plus I got about 40 fps more MV out of my 77smks with less overall pressure, gas volume and a bit lighter recoil (though it'd be a stretch to call any sort of recoil from a 5.56 gun hard to manage. Ejection pattern moved from 1-2 oclock w/TAC to between 2-3 w/AA2520 across all my AR pattern platforms. Even brass seems marginally cleaner but could be my imagination.

 

[LRRPF52]

The biggest question you have to answer for yourself is whether or not primer-piercing velocities do anything of merit for you down range.

For example, does 2750fps vs 2670fps mean much shooting 77gr?

2750fps 77gr SMK Doppler Radar data, 2.7” optic height over bore, sea level 59˚F
400yds 2 mils drop 1.2 mils drift 1829fps 572 ft-lbs
500yds 3.2 mils 1.5 drift 1635fps 457ft-lbs
600yds 4.6 mils 1.9 drift 1456fps 362ft-lbs
700yds 6.2 mils 2.4 drift 1289fps 284ft-lbs
800yds 8.2 mils 2.9 drift 1138fps 221ft-lbs
goes subsonic between 800yds and 825yds

2670fps 77gr SMK Doppler same conditions
400yds 2.2 mils drop 1.2 drift 1768fps 534ft-lbs
500yds 3.4 mils 1.6 drift 1579fps 426ft-lbs
600yds 4.9 mils 2 mils drift 1403fps 336ft-lbs
700yds 6.7 mils 2.5 drift 1240fps 263ft-lbs
775yds 8.2 mils 2.8 drift 1130fps 218ft-lbs
goes subsonic before hitting 800yds

Both are really anemic already at 500yds, you won’t see or hear any different on impact at 400yds, so it really doesn’t matter. I would find a happy load that doesn’t trash your brass, that behaves well, groups around an inch at 100yds, and go blast with it unless you’re just chasing paper groups at 100yds, which doesn’t matter what you do velocity-wise at that point. Just chase groups.

These carbines were meant to extend the reach of the AR-15 within dismounted small units without having to lug around an SR-25 or Mk.11 Mod O, while maintaining magazine/ammo compatibility between Assaulters and Sniper Support elements, who could also maneuver as a contingency if things went south. SOCOM drifted away from that with the SPR, making it more of a belly-rider blaster and less of something that worked well for CQB like the original 723 JSOC Mod Sniper Carbines.

Once SOPMOD Block II caught up to that more or less, the SPRs got put out to pasture.

 

[MontanaMan]

Quote from Constructor

"One thing to consider is the specs of the barrel when trying to get maximum performance. A 6 groove barrel with a 50:50 land to groove ratio will create more engraving force than a 3 groove with a low land to groove ratio. That comes on as peak pressure is being developed by the powder. The 3G will also have less resistance in the barrel and more bore area. You should be able to load more powder in the case before seeing pressure signs and get more velocity as a result. Lilja, Blackhole(now Columbia), Pac Nor make 3 groove barrels, Blackstone Arms will handle ARP 3 groove barrels when he gets settled. 4 groove barrels with a low L-G ratio would be better than a 6 groove."

This is a hugely overlooked factor, from a guy who's worked around barrels long enough to have a lot of experience.

To the OP, lose the CCI-400's & your primer piercing issues will go away. Might also want to verify FP protrusion as well. Been a while since I check that on a bolt & FP, but going from memory, I think the spec is from .026 - .034".

Rem 7 1/2's are pretty available now as are CCI-41's & they never don't work; I've had a stash of Wolf Match Mag primers that I've been working off of & am down to 1,000 or so & they are excellent but not available anymore. Also have a few thousand Fed AR's but haven't wrung them out yet but all reports are positive.

If you want velocity (& hopefully good enough accuracy in your guns), look to VV-N540 & Alliant 2000-MR, however at the expense of using a little more powder. I'm using 24.7 gr of 540 & 26.5 gr of 2000-MR & both are about the same accuracy as what I get from the same barrels with 8208 or AR-Comp. Neither are as temp stable as 8208, but they are not bad in temps from 20 -90F, IME.

Great test series & write up in your follow-up thread on Staball Match & that's a powder I'd like to try. May be the best of the bunch due to it's temp stability if that's a must have characteristic. I've also not tried Lever either, as I have enough of the 540, 2000-MR & 8208 for quite a few more thousand rounds to use up.

MM

 

[MontanaMan]

I am getting 2820 with the max book load of Staball Match in my 18 inch.

Below is what Hogdon (Winchester) "book" shows; so are you saying that you are getting 2820 FPS with 24 gr in an 18" barrel?

And brass is OK?

What am I missing when everyone else mentioning velocities with the same combination are not close to that?

MM

Twist: 1:12.000"
Barrel Length: 24.000"
Trim Length: 1.750"

BULLET WEIGHT
77 GR. SIE HPBT
CASE
WINCHESTER
PRIMER
WINCHESTER SR, SMALL RIFLE

	Starting Load		Maximum Loads
	Manufacturer	Powder		Bullet Diam.	C.O.L		Grs.	Vel. (ft/s)	Pressure		Grs.	Vel. (ft/s)	Pressure
	Winchester	StaBALL Match	OUT OF STOCK	0.224"	2.260"		22.0	2,497	41,200 PSI		24.0	2,754	54,700 PSI

 

[ma smith]

Wait wut. 1x12 twist for 77SMK... ?

Twist: 1:12.000"
Barrel Length: 24.000"
Trim Length: 1.750"

BULLET WEIGHT
77 GR. SIE HPBT
CASE
WINCHESTER
PRIMER
WINCHESTER SR, SMALL RIFLE

 

[MK20]

I don't have my load data available as I am at work, but I used the online hodgdon load data and a Hornady 75 gr and at mag length in a 18" white oak battel I got 2820.