Mk12 Setup for High Pressure Loads?

[NHPiper]

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.

 

[Huskydriver]

Only powder I could get close to 2750 mirroring mk262 in my rifles safely was tac.....

 

[nn8734]

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.

Overpressure issues won’t be solved vis an adjustable gas block as that’s for overgassing. Differing length gas systems will also manage gas better but won’t help if the charge weight is too much for the chamber.

Mk262 mod 1 uses non cansiter grade powder that’s not available commercially.

Try AA2520. Gives me 2800 fps in an 18” douglas spr bbl in my mk12 mod 1

 

[NHPiper]

Overpressure issues won’t be solved vis an adjustable gas block as that’s for overgassing. Differing length gas systems will also manage gas better but won’t help if the charge weight is too much for the chamber.

Mk262 mod 1 uses non cansiter grade powder that’s not available commercially.

Try AA2520. Gives me 2800 fps in an 18” douglas spr bbl in my mk12 mod 1

How are you finding it in varying temperatures?

I tried tac and didn't have good luck.

 

[nn8734]

How are you finding it in varying temperatures?

I tried tac and didn't have good luck.

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

All powders do vary a bit, double based moreso than single based but the variability hasnt been a problem for me as I only take the Mk12 to 800m and havent had to make any major adjustment changes from winter to summer. That said, i also don’t have the temp swings that folks see in most other parts of the country…

My load is 25g of 2520, Rem 7-1/2 primer, LC once fired case and 77smk. Basically a clone of mk262 mod 1 and flies just like it, mv and drop wise.

 

[NHPiper]

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

All powders do vary a bit, double based moreso than single based but the variability hasnt been a problem for me as I only take the Mk12 to 800m and havent had to make any major adjustment changes from winter to summer. That said, i also don’t have the temp swings that folks see in most other parts of the country…

My load is 25g of 2520, Rem 7-1/2 primer, LC once fired case and 77smk. Basically a clone of mk262 mod 1 and flies just like it, mv and drop wise.

Thanks for sharing. Are you noticing a shift in velocity or standard deviation once you start firing the case a couple of times? Or do you only get one firing before the primer pocket opens up?

The goal of the post here is to try to find ways to tweak the rifle ideally before heading down the path with more load data.

 

[nn8734]

Thanks for sharing. Are you noticing a shift in velocity or standard deviation once you start firing the case a couple of times? Or do you only get one firing before the primer pocket opens up?

The goal of the post here is to try to find ways to tweak the rifle ideally before heading down the path with more load data.

You’re welcome…Hard to say for sure as i have thousands of once fired 5.56 cases so mostly on just one firing but i did load a small batch of cases four times and shot them and didn’t notice anything unusal. This was a couple years ago in the fall.

That said, don’t worry about standard deviation. Its the most overrated, obsessed-over metric in practical shooting inside of 1000m (at least from what I’ve seen on the Hide and probably everywhere else too). If you were doing bench rest or 1000 yard service rifle then it becomes more important to manage vertical dispersion via MV consistency so your groups are as tight as possible at those distances. It also becomes more relevant at 1000m+/ELR distances for the same reasons.

But outside of that, let your target guide your tweaking.

 

[tnichols]

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

 

[Huskydriver]

How much crimp are you applying?

 

[NHPiper]

How much crimp are you applying?

Very light. My buddy is shooting the same load without crimp and has the same issues.

 

[NHPiper]

You’re welcome…Hard to say for sure as i have thousands of once fired 5.56 cases so mostly on just one firing but i did load a small batch of cases four times and shot them and didn’t notice anything unusal. This was a couple years ago in the fall.

That said, don’t worry about standard deviation. Its the most overrated, obsessed-over metric in practical shooting inside of 1000m (at least from what I’ve seen on the Hide and probably everywhere else too). If you were doing bench rest or 1000 yard service rifle then it becomes more important to manage vertical dispersion via MV consistency so your groups are as tight as possible at those distances. It also becomes more relevant at 1000m+/ELR distances for the same reasons.

But outside of that, let your target guide your tweaking.

You throwing charges with a Chargemaster or similar? Or in a powder drop?

I load everything on a 650 and have two chargemasters going for precision loads. Just curious with that A2520 powder if you can get away with a powder drop like the Dillon uses for blasting ammo if your throw is consistent.

 

[MK20]

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

 

[babyguppy]

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

TAC out of FEDERAL BRASS (1 shot for measurement) 93 degree day
23.1 2660
23.6 2823
23.7 2823
23.8 2777
23.9 - 2804
24 - 2830
24.1 = 2828
24.2 - 2855
24.4 2871

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.

 

[Dogtown]

I went down that road with AA 2520 & 2460 last summer. The burn rate for 2460 is kind of ideal, but I could never get acceptable SD the way I was getting with TAC, which was only a slight bit slower.

 

[nn8734]

You throwing charges with a Chargemaster or similar? Or in a powder drop?

I load everything on a 650 and have two chargemasters going for precision loads. Just curious with that A2520 powder if you can get away with a powder drop like the Dillon uses for blasting ammo if your throw is consistent.

I actually use an RCBS uniflow (have a few of them for ball powders). Ive found them to be very consistent, typically holding +- .1 grain. Only takes about a half hour to charge about 125-150 cases with spot checks done every 10-12 charges or so. You can adapt a Uniflow to work with a dillon though i haven’t gotten around to it for my 750 as it’s plenty fast and I primarily use the 750 for carbine 55g “blasting” ammo and to de-prime and bulk f/l size .223 LC cases.

 

[Pickle Rick]

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.

If you’re blowing primers, there’s no work-around for that. What primer are you using? Try 23.5. 2780 for 18” with 8208 is just too hot. I got mk262 speeds with CFE223 and great accuracy.

 

[Pickle Rick]

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

Holy shit that’s smokin. Love Staball match.

 

[BCP]

Mk262 have a crimped primer? Might be why they don't pop primers like your reloads.

24 TAC, LC brass, 77 nosler, 2.245 was the closest I got to the sort of speeds people talk about with mk262 and it meters very well + is usually easy to find and cheap.

You could also try CFE223/2000MR or one of the other superformance type powders.

 

[NHPiper]

If you’re blowing primers, there’s no work-around for that. What primer are you using? Try 23.5. 2780 for 18” with 8208 is just too hot. I got mk262 speeds with CFE223 and great accuracy.

Using CCI small rifle primers.

The 23.5gr opened up on me for accuracy. The 23.8 seemed to shoot great, so bummer about the pressure. May try the A2520.

 

[ma smith]

OP, I'll pont out the obvious...You're too hot.

 

[scharfschutze762]

Mk262 mod 1 uses non cansiter grade powder that’s not available commercially.

This

 

[NHPiper]

OP, I'll pont out the obvious...You're too hot.

Ya....the reality is if I'm running comfortably at 2700ish in the winter with 8208, I bet that gets to 2750 in the summer

 

[Lightning8]

You throwing charges with a Chargemaster or similar? Or in a powder drop?

I load everything on a 650 and have two chargemasters going for precision loads. Just curious with that A2520 powder if you can get away with a powder drop like the Dillon uses for blasting ammo if your throw is consistent.

I am using a Dillon 550 with Dillon powder drop to load 6BR with AA2520 for practice ammo and I seeing great results on targets but SDs around 10. I use a Dillon 550 with Dillon powder drop to load 223 with TAC and 75ELDMs/80SMKs to AICS mag length again with great results on targets but SDs are 12+. Loaded thousands of the 223 "longs" for my 223 trainer/varmint rifle.

 

[NHPiper]

I am using a Dillon 550 with Dillon powder drop to load 6BR with AA2520 for practice ammo and I seeing great results on targets but SDs around 10. I use a Dillon 550 with Dillon powder drop to load 223 with TAC and 75ELDMs/80SMKs to AICS mag length again with great results on targets but SDs are 12+. Loaded thousands of the 223 "longs" for my 223 trainer/varmint rifle.

I find that loading with the powder drop on the 650 is all about the stroke and making sure you dont rush it when the powder is dropping.

 

[xciapup]

If only adjustable gas blocks and heavier buffers erased the physics of excess pressure. If only......

 

[Tx_Aggie]

Using CCI small rifle primers.

The 23.5gr opened up on me for accuracy. The 23.8 seemed to shoot great, so bummer about the pressure. May try the A2520.

If by small rifle primers you mean CCI 400s, you might try a primer with a thicker cup. In my experience CCI standard SRP don't like high pressure loads. I'd suggest trying CCI BR4, CCI 450, or Federal 205MAR primers.

A great thread about primers here on the hide:

Small Rifle Standard

CCI 400 -thin .020" cup, not recommended for AR15 use by CCI/Speer. Good for .22 Hornet, .30 Carbine. See Note 1 at the bottom of the page
CCI BR4 - match primer with a thicker .025" cup.
Federal 205 - Mil-Spec cup thickness according to Federal - okay for 5.56mm. .0225" cup thickness.
Federal 205M - same as the 205 but the match version.
Magtech PR-SR - .025" cup thickness (not much feedback yet on this new primer as to AR15 suitability but with the same cup thickness as the Rem 7 1/2 it looks good so far)
Remington 6 ½ - thin .020" cup, intended for older, lower pressure rounds Remington says do not use for the .223 Rem or other similar pressure rounds. Good for .22 Hornet, .30 Carbine.
Remington 7 ½ BR - A match or "bench rest" primer. Lyman & Nosler classify this primer as a Standard. Remington says the compound is the same as the 6 1/2 but with a thicker .025" cup.
RWS 4033
Winchester WSR - some piercing issues noted when changed from silver to brass cup. Cup thickness is a bit thinner at .021". Most say they are good to go for the AR15 despite that, probably because of the hardness of the cup. Some feel they are less resistant to higher pressures.
Wolf/Tula Small Rifle SR #KVB-223 - soft, sensitive copper cup, not recommended for AR15/military rifle use or high pressure rounds.

Small Rifle Magnum

CCI 450 - same thicker .025" cup as the BR4 and #41.
CCI #41 - commercial version of the fully-qualified DOD primer for use in U.S. military ammo. With this primer there is more 'distance' between the tip of the anvil and the bottom of the cup than with other CCI SR primers. .025" thick cup. Same primer mix as CCI 450.
Remington 7 ½ BR - A match or "bench rest" primer. Hornady, Handloads.com, and Chuck Hawks classify this primer as a Magnum, differing from other sources that classify it as a Standard. .025" cup thickness.
Wolf/Tula Small Rifle Magnum SRM - hard, less sensitive brass cup intended for AR15/military rifle and high pressure rounds - #KVВ-5,56M.
Wolf/Tula Small Rifle 223 SR223 - #KVB-223M "This is the newest primer available in the Wolf line. It is ever so slightly hotter than the small rifle magnum primer and it comes with a brass colored thick cup. This primer can be used in place of the SRM primer or used when a different powder is used that is hard to ignite."

A PRIMER ON PRIMERS

While searching around for some info I stumbled on to this thread and its too good not to share. Taken from the following and posted by Frisco Pete http://www.sksboards.com/smf/index.php?topic=56422.0 CHOOSING THE RIGHT PRIMER - A PRIMER ON PRIMERS Based on an article by John Barsness - GUNS...

www.snipershide.com

 

[Gustav7]

Using CCI small rifle primers.

The 23.5gr opened up on me for accuracy. The 23.8 seemed to shoot great, so bummer about the pressure. May try the A2520.

Deffff need to use thicker primers. I settled on 23.5 with 77TMK's and CCI 450's in my 18" Lothar Walther barrel. No issues up to 90*.

I did successfully hit MK262 and a little more, but like others have said, TAC was the only way I could do it. It was not very temp stable, but I think I hit around 2800-2825fps with the 77TMK. Would have been a fun load, but I bought a keg of 8208 and just rolled with that.

 

[VegasKyle]

Only powder I could get close to 2750 mirroring mk262 in my rifles safely was tac.....

I went through this years ago before CFE223 or XBR were around and TAC is also what I landed on for cloning Mk262

Mk262 have a crimped primer? Might be why they don't pop primers like your reloads.

24 TAC, LC brass, 77 nosler, 2.245 was the closest I got to the sort of speeds people talk about with mk262 and it meters very well + is usually easy to find and cheap.

You could also try CFE223/2000MR or one of the other superformance type powders.

Crimped primers are key. The only way I was able to replicate the velocity of Mk262 was to use brass from pulled down m855. LC brass with a factory crimped in CCI 41, TAC and a 77gr SMK or Nosler CC was indistinguishable from the Black Hills load.

 

[MK20]

Once again, try Staball Match

 

[nn8734]

I went through this years ago before CFE223 or XBR were around and TAC is also what I landed on for cloning Mk262


Crimped primers are key. The only way I was able to replicate the velocity of Mk262 was to use brass from pulled down m855. LC brass with a factory crimped in CCI 41, TAC and a 77gr SMK or Nosler CC was indistinguishable from the Black Hills load.

If you run out of pull down powder, try AA2520. 24.7-25.3g will get you mk262 mv and performance with those two bullets. 2520 has a slower burn rate than TAC and isnt quite as temp sensitive (though its moreso than Varget or XBR from what ive seen). You can run that exact same load across all 5.56 or .223 Wylde chambered rifles you own.

 

[Mike_in_FL]

Somewhere on one of the iterations on this site was a multi-page thread on the same subject. The conclusion at the time was unless you could buy LC brass with the primers crimped, it would be impossible to equal Mk 262 in an 18". Maybe Staball Match is the answer now

 

[Doc68]

Running 24.4gr of TAC with a 75gr BTHP and avg is 2765 out of 16" barrel. Gotta Chrono new 18" barrel tomorrow and see what it's spitting out at.

Doc

 

[nn8734]

Somewhere on one of the iterations on this site was a multi-page thread on the same subject. The conclusion at the time was unless you could buy LC brass with the primers crimped, it would be impossible to equal Mk 262 in an 18". Maybe Staball Match is the answer now

You don’t need to run crimped primers nor do you need to crimp the case mouth to match the Mk262 mod 1 mv. Douglas mk12 SPR bbls from either PRI or CLE will get you there provided correct components are used with the correct development process. I use Rem 7-1/2 primers which is what I believe mk262 mod 1 uses but I could be wrong about that (the primers look identical to the Remington primer).

 

[TheGerman]

I ran into the same problem with 8208 while chasing Mk262 velocity. It shot, but the brass was dirty as shit and had all sorts of primer issues and ejector marks.

McCourt did some voodoo magic and made a round for me that was more accurate and also 100fps faster than the 8202 load with zero pressure signs. I don't know what powder he uses or if you can get it.

As far as the gas settings fixing your problem; that isnt a thing.

 

[babyguppy]

I went down that road with AA 2520 & 2460 last summer. The burn rate for 2460 is kind of ideal, but I could never get acceptable SD the way I was getting with TAC, which was only a slight bit slower.

what did you settle on for your charge of TAC.. Enquiring minds want to know

 

[Dogtown]

24gr of TAC w/ 77gr bullets @ 2.26ish seems to be a very common load. I have an old PRI SPR Mod 0 clone that's my service rifle nostalgia item and it loves that combo with SMKs.

On a side note, 24.1gr of N140 is my other precision 77gr load that my 16" build much prefers.

 

[Laseredge]

PP 2000 MR

Alliant Power Pro 2000 MR

Alliant 2000 MR Review

www.natoreloading.com

 

[TxWelder35]

Once again, try Staball Match

Picked up a jug of it yesterday from PV with the free hazmat shipping. Excited to try it out. Been running 2520 and 8208. Had good results with both, will be good to add another temp stable powder to the mix.

 

[VegasKyle]

If you run out of pull down powder, try AA2520. 24.7-25.3g will get you mk262 mv and performance with those two bullets. 2520 has a slower burn rate than TAC and isnt quite as temp sensitive (though its moreso than Varget or XBR from what ive seen). You can run that exact same load across all 5.56 or .223 Wylde chambered rifles you own.

I think I have a couple lbs of 2520 floating around, I’ll have to give it a shot. I love TAC, cheap, easy to meter, great velocity but it does get pretty spicy when it’s hot out.

 

[nn8734]

I think I have a couple lbs of 2520 floating around, I’ll have to give it a shot. I love TAC, cheap, easy to meter, great velocity but it does get pretty spicy when it’s hot out.

Yep, that’s why I switched over from TAC to 2520.

 

[NHPiper]

Deffff need to use thicker primers. I settled on 23.5 with 77TMK's and CCI 450's in my 18" Lothar Walther barrel. No issues up to 90*.

I did successfully hit MK262 and a little more, but like others have said, TAC was the only way I could do it. It was not very temp stable, but I think I hit around 2800-2825fps with the 77TMK. Would have been a fun load, but I bought a keg of 8208 and just rolled with that.

Thicker primers could help with piercing, but I blew a few out entirely. How are the primers gonna solve that? Tighter in the cup?

 

[FUNCTIONAL]

Working up AR-Comp now and getting 2750 and night have a little room left.

Mr2000 gave me over 2800 but it was on the edge for NY summers. Think it was 25.5gr in a Douglass mk12 barrel with Wolf primers. Was no joke getting consistent 1/2" or better groups with 77smk and a light crimp. Best shooting AR I ever had.

Your chamber will make a bigger difference. Rem match will have more pressure signs than Wylde and wylde will have more pressure than 5.56 nato. Has to do with the lead angle which is why 5.56 can handle more pressure.

 

[Huskydriver]

24gr of TAC w/ 77gr bullets @ 2.26ish seems to be a very common load. I have an old PRI SPR Mod 0 clone that's my service rifle nostalgia item and it loves that combo with SMKs.

On a side note, 24.1gr of N140 is my other precision 77gr load that my 16" build much prefers.

That's my load as well

 

[ma smith]

Thicker primers could help with piercing, but I blew a few out entirely. How are the primers gonna solve that? Tighter in the cup?

AFAIK you can equal (if not outperform) 2750 fps Mk262 at distance by using a lower SD handload in the 2700-2730 range. Notice the SDs ...12-19 fps...in the JRLB field test of mk 262....So if you are tring to shoot 600+, just get something with the 2700-2730 speed range with single digit SD, and you are good. No need to chase the last 30-50 fps.

 

[LRRPF52]

None of this will really address the main problem though, which is really anemic performance at even relatively close distances from 5.56.

When you spot and listen for 5.56 hitting steel even at 400yds, it looks like someone barely took a small pain brush and dabbed the steel. You may or may not hear it, depending on wind.

Pull the barrel/bolt, install something with more impact.

SPRs are really cool when you pull out the gutless 1.8L and drop something with more retained energy at distance.

6.5 Grendel and 6mm AR or 6mm ARC work demonstrably better for that, at lower chamber pressures that don’t have you chasing primer-popping conditions trying to match Mk.262.

It is so much more rewarding to hear and see the impact on steel with these types of cartridges. That’s really the practical difference that can be immediately felt by the layman.

 

[Dogtown]

Just to add, and this might go without saying, but I’ve done tests of both of my 77gr loads swapping out LC brass for Lapua brass, and CCI #41 mil primers for GM2015MAR primers, and it resulted in an improvement in group size and consistency of about 20%. Is it worth it? Depends. No one wants to run and gun with .223 Lapua brass and GM205MAR unless you’re on someone else’s dime. So when I make batches of each, one gets labeled “use wisely at distance.”

 

[Gustav7]

None of this will really address the main problem though, which is really anemic performance at even relatively close distances from 5.56.

When you spot and listen for 5.56 hitting steel even at 400yds, it looks like someone barely took a small pain brush and dabbed the steel. You may or may not hear it, depending on wind.

Pull the barrel/bolt, install something with more impact.

SPRs are really cool when you pull out the gutless 1.8L and drop something with more retained energy at distance.

6.5 Grendel and 6mm AR or 6mm ARC work demonstrably better for that, at lower chamber pressures that don’t have you chasing primer-popping conditions trying to match Mk.262.

It is so much more rewarding to hear and see the impact on steel with these types of cartridges. That’s really the practical difference that can be immediately felt by the layman.

Ya I don't think anyones arguing that, but that's only one metric of many for choosing what cartridge you want to shoot.

Everything about any of those 6mm is more expensive, less available, and with less diversity in every aspect. Barrels, Bolts, Brass, Bullets, more powder, less data, less options, etc etc.

Agreed, it gets harder to spot misses and hits past 400ish, but thats not gonna be enough to deter me from shooting the most popular rifle caliber of all time. 223/556 is fun, easy, cheap.

Thicker primers could help with piercing, but I blew a few out entirely. How are the primers gonna solve that? Tighter in the cup?

Well that I'm not sure of, but obviously you'll have to work up the load using thicker primers and see what happens. I've always ran 450's in any AR load that is getting close to max: 8208, TAC, H335, and CFE223 in SPR and 223AI precision loads.
8208 is a great powder, but I'd scrap any MK262 dreams with it.

I did look back in my book and I was lower than I thought. 18" Lothar Walther barrel, I was running 24.5gr TAC with 77TMK's getting 2750ish. 24.8gr is NATO max with TAC.

 

[NHPiper]

Ya I don't think anyones arguing that, but that's only one metric of many for choosing what cartridge you want to shoot.

Everything about any of those 6mm is more expensive, less available, and with less diversity in every aspect. Barrels, Bolts, Brass, Bullets, more powder, less data, less options, etc etc.

Agreed, it gets harder to spot misses and hits past 400ish, but thats not gonna be enough to deter me from shooting the most popular rifle caliber of all time. 223/556 is fun, easy, cheap.



Well that I'm not sure of, but obviously you'll have to work up the load using thicker primers and see what happens. I've always ran 450's in any AR load that is getting close to max: 8208, TAC, H335, and CFE223 in SPR and 223AI precision loads.
8208 is a great powder, but I'd scrap any MK262 dreams with it.

I did look back in my book and I was lower than I thought. 18" Lothar Walther barrel, I was running 24.5gr TAC with 77TMK's getting 2750ish. 24.8gr is NATO max with TAC.

How temp sensitive did you find the tac? I have seen that A2520 is about 2fps per 1'F. Which is a lot in NH between winter and summer, could easily be 2780fps in the summer at 90'F and then drop to 2640fps at 20'F.

 

[Gustav7]

How temp sensitive did you find the tac? I have seen that A2520 is about 2fps per 1'F. Which is a lot in NH between winter and summer, could easily be 2780fps in the summer at 90'F and then drop to 2640fps at 20'F.

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.

 

[Ape_Factory]

I actually use an RCBS uniflow (have a few of them for ball powders). Ive found them to be very consistent, typically holding +- .1 grain. Only takes about a half hour to charge about 125-150 cases with spot checks done every 10-12 charges or so. You can adapt a Uniflow to work with a dillon though i haven’t gotten around to it for my 750 as it’s plenty fast and I primarily use the 750 for carbine 55g “blasting” ammo and to de-prime and bulk f/l size .223 LC cases.

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.