Slower powder for AR10 loads?

[frame12]

I've spent this year shooting F-Class and BR matches (poorly) testing various loads in my 6.5 creed gas gun.

After shooting a large volume of loads, it seems like gas guns simply want 52k psi vs 62k for bolt guns, for both 308 and 6.5 creed even with a "High Pressure BCG".
Some primers will puncture even in that 52k range with a HPBCG. CCI400's in SRP Alpha cases for sure.

Anyhow, I keep dropping the charge on all my loads well below the max for most load data, and there's a lot of empty space in the case. I've been thinking about moving down in speed (4831sc, n165 or n565 instead of 4350.) to get a better case fill.

Anyone have any luck doing this?

 

[Xcount]

Don't kill the messenger here but that's the wrong primer. Use CCI 450 or REM7.5 or equivalent.

 

[simonp]

I think that Xcount is onto something - my loads in my 308 gas gun are all book max or above, no blown / punctured primers here.

 

[M4orturnate]

Definitely the wrong primer. 450s or the mil primers are much harder. Ive also found my gassers like it slow except for 155g 308 but even that is only around 2700fps. Slow and consistent beats speed with flyers

 

[BCP]

Slower powder will give you more port pressure and cause other problems. What loads are popping primers for you?

 

[frame12]

Yeah. Primers are a major factor. I've stopped using 400's for all my gas guns.

So no one is using the magic R26 dust for gas guns?

I've had pretty good luck with Superformance. 2810 fps with 142 SMKs, 450s and 46.5gn.
used that on my first match.
Haven't been able to improve on that. StaBall Match and 140's with Fed AR primers were looking really good, but I'm having ignition issues with StaBall Match in the larger 6.5 cases, regardless of primer.
I loaded up a batch of 223 with StaBall Match and had no ignition issues, using the same primers.
I've only got one SRP left to test, the rem7.5. Going to try with LRP as well.

What LRPs are you using? BR2's and Magtech are puncturing at a similar rate as the 400's... maybe.

Attached pic is the Superformance load. 60 rounds for record @ 500 yards. SD and ES are groups size. For Mean Size, ordered each shot by distance from mean center and then grabbed shot 30 and doubled it for diameter. SD is basically ave distance from mean center x 2. Metrics are for me so I can compare loads.

 

[BCP]

From a 24" barrel using 43gr 6.5 staball and 143 I'm getting 2750fps 2.810". Bolt gun but in a semi auto I'd try the same load. You could check firing pin protrusion it should be ~.040 for a 308 bolt.

 

[isofahunter]

Faster is better in mine.

 

[Jsp556]

REM 7 1/2’s should solve your ignition issues.

 

[Cascade Hemi]

RL26 with 142SMK loaded to 105% fill will get you right to 55kPSI. I have only shot it in a bolt gun and it didn't meet my needs so I didn't load more than a few rounds.

Large rifle primers are more durable than small rifle magnum primers. LRP don't have ignition problems either and if you sticking with lower pressure loads would be a much better fit.

 

[FredHammer]

I've experienced "just noticeable difference" in felt recoil of AR10s between faster & slower powders with same obtained muzzle velocities. For instance, my 708AR with N135 vs N540 (IMR3031 vs Varget spectrum for reference) recoils less and operates the system better. As mentioned already, the port pressure created between the two are very different.

 

[bfoosh006]

What specific brand barrel ?

Could your barrel have a short throat ?

 

[frame12]

REM 7 1/2’s should solve your ignition issues.

Highly unlikely, but I hope so.

What specific brand barrel ?

Could your barrel have a short throat ?

Odin Works 22" barrel.
Don't know about the throat. These are my measurement to lands (OAL is only for ref, I only use BTO when loading):

140gn EDLM​	Sticks: OAL 2.87 BTO:2.252​
​	Free: OAL 2.8585 BTO:2.2425​
​	​
142gn SMK​	sticks: OAL 2.85 BTO:2.27​
​	Free: OAL:2.845 BTO:2.2665​
​	​
140gn SMK​	​
​	free: OAL 2.775 BTO:2.265​
​	​
130gn OTM berger​	Sticks OAL:2.842 BTO:2.236​
​	free: OAL 2.8325 BTO:2.226​
​	​
fired H2O case cap​	​
Lapua lrp case capacity​	51.5​
Alpha case​	52​

 

[frame12]

One of the shooters at the F-Class match said he stopped using all ball powders with SRP in 308 because of similar FTF and "hang"/ delayed ignition issues.
IDK, I have no issues with Superformance. On a side note, 46.5 shows no pressure signs with 140 and 142 SMKs, but I got swipes with burrs using 140 ELDMs at that load. Sierra's max is 47.4 and Hornady's is 44.7. That seems to line up with what I'm seeing.

StaBall Match was giving me the smallest groups across the board. Thought it was going My Load. 2.7", 2.74 and 2.4" groups at 300 yards. 5 and 5.4" horizontal groups @ 500 yards, unfortunately 10" tall.
I thought maybe I had compromised the powder canister with excessive humidity. Bought a new tin and have the same problems.

I also initially thought the hang fire was caused by bits of primers in the bolt. That happened when I was loading 308 over pressure.
I cleaned all 3 BCGs and tested them all with the same result.


I have ~15 rounds of the same StaBall Match load in some LRP Lapua cases w/ BR primers and Ficochi primers. Also 20 rounds with the Rem 7.5's.

 

[LRRPF52]

When I tried some slower powders in .260 Rem under a 140gr if I recall, something really weird happened that I’ve never experienced with a gas gun before. Freaking buffer slammed so hard into the back of the RET, rifle recoiled like crazy, and smoke was pouring out of the receiver seams. It was definitely too slow for the action and didn’t get a full conversion in the chamber. Might have been RL17.

I would stick to book data for gas guns and not venture into slower-burners, though the 30˚ Creedmoor case converts propellant better than a .260 Rem.

For .260 Rem and 6.5CM or any of the 6.5-08 class cartridges, I really like how 130gr VLDs and Norma GTs fly from them. Action is right before the edge of optimal performance as well. Once you start messing with pushing 140gr and above trying to go fast, things start to come off the rails. GAP warned me about this tendency back in 2008-2009. George was even a fan of the 130gr VLD in the 6.5 SAUM GAP S bolt gun to reach that 6 mil at 1k drop requirement he was looking for.

 

[frame12]

When I tried some slower powders in .260 Rem under a 140gr if I recall, something really weird happened that I’ve never experienced with a gas gun before. Freaking buffer slammed so hard into the back of the RET, rifle recoiled like crazy, and smoke was pouring out of the receiver seams. It was definitely too slow for the action and didn’t get a full conversion in the chamber. Might have been RL17.

I would stick to book data for gas guns and not venture into slower-burners, though the 30˚ Creedmoor case converts propellant better than a .260 Rem.

For .260 Rem and 6.5CM or any of the 6.5-08 class cartridges, I really like how 130gr VLDs and Norma GTs fly from them. Action is right before the edge of optimal performance as well. Once you start messing with pushing 140gr and above trying to go fast, things start to come off the rails. GAP warned me about this tendency back in 2008-2009. George was even a fan of the 130gr VLD in the 6.5 SAUM GAP S bolt gun to reach that 6 mil at 1k drop requirement he was looking for.

Interesting.
I've only seen load data for gas guns in 223/556, 308 and for 6 ARC.
They all seem to suggest 52k max pressure. I'd guess that's the same for 6.5 creed.
I'm mostly concerned with getting a consistent med small group that doesn't get fliers.

 

[Compadre]

I got a Lyman 1200. Unbelievably easy and accurate. Now, you're going to be stuck with medium rate powders for a 308 Auto. If you try slower powders, you'll end up with extraction trouble and eventual premature part expiration. Varget is an Extreme use powder that is identical to 4064. H4895 was the powder of choice for the Garand, and have some loaded for my M1a to try as soon as the weather settles.

 

[Xcount]

In my opinion you are trying too many components outside the regular 6.5 load window. If you have 4350, LRP brass and primers try the typical 40-41gr load. Maybe start lighter since its an AR10.
Staball match is faster than staball. I don't see many here try staball match in 6.5Cr. mix that in with SRP brass and I can see why you are chasing your tail a bit.

get the known stuff to work first and then change one thing at a time from there.

I've had hangfires in 6BR, with Wolf SRM primers with ball powder so small rifle primers, even magnum, are finicky with ball powder.

 

[mettee]

If it was me I'd be using 130 class bullets, with H4350 or RL16. I'm shooting a 260 but I've gotten as far as 2900 fps with a Hornady 130 ELDM with no pressure signs. I hover around 2850 with the rest of the below listed bullets. I recently moved to alpha srp brass, cci 450, and the result was incredibly good... I'm currently bumping the charge to bring the speed up... from 42.7 to 42.9 all shoot/group well(lucky?)

130 Berger AR hybrid
130 SMK CN
136 Lapua scenar
130 TMK
130 ELDM

I feel like a 140 class bullet in a gas gun isn't the most ideal, the platform seems to respond better to the lighter 130s bullet being pushed faster; rather than just trying to make the 140 run at x speed.

This load ^ that data

Alpha 260 srp as shipped!
Cci 450
H4350 42.8 gr
.004" neck tension
.060 off lands

 

[frame12]

In my opinion you are trying too many components outside the regular 6.5 load window. If you have 4350, LRP brass and primers try the typical 40-41gr load. Maybe start lighter since its an AR10.
Staball match is faster than staball. I don't see many here try staball match in 6.5Cr. mix that in with SRP brass and I can see why you are chasing your tail a bit.

get the known stuff to work first and then change one thing at a time from there.

I've had hangfires in 6BR, with Wolf SRM primers with ball powder so small rifle primers, even magnum, are finicky with ball powder.

Interesting on the hangfires.

I've loaded 2 lbs of H4350 behind 4 different projectiles in both LRP and SRP brass with several different primers at least in each configuration.
Just never got small groups with it. IDK. I thought it would work.
I put 10 rounds of 140 SMKs with H4350 40.5gn, and Fed AR match primers on paper at 300 yards and had a 4.5" group.
I put 10 rounds of Hornady's American White Tail next to it and got 4.1"
Earlier in the year I did 15 shots of 140 SMK's with the StaBall Match and got a 2.74" group.
I took that load out to 500 yards and got 40 rounds into a 5.5" x 10.5" group. Felt like I was tossing rounds high and low because every shot was hanging. Didn't collect velocity, unfortunately. Also this match had the most wind so far and I did NOT compensate for it at all.

After that, I spent the next match testing to see if it was my tin of powder or if the primers might be bad.
All of the variations had hanging issues, so I spent that match trying to mitigate 'precoil"

I'm out of H4350 now. Wasn't terribly excited to buy more given the performance so far. Was thinking about getting a stick powder that would fill the case more... hence this thread.

I bought a fresh tin of StaBall Match and it hangs. So I think I ruled out that I ruining the last batch with moisture.

Next match I'll test that load with LRP (Fiochi and CCI BRs) as well as SRP with the Rem7.5.
If those all hang during sighters, I'll move to my Superformance load and see how that does.

I've tested Varget as well, but the case fill is even less than H4350.

 

[Xcount]

I agree with Mettee in trying a 130 or lighter bullet. I run a 123 lapua in my AR10 and my AIAW. I also run a 260R, the only proper 6.5mm cartridge, but I digress.

Staball Match is too fast, especially for 140's. The LRP's should get rid of the hangfire's and that would settle that part of the mystery.

 

[frame12]

If it was me I'd be using 130 class bullets, with H4350 or RL16. I'm shooting a 260 but I've gotten as far as 2900 fps with a Hornady 130 ELDM with no pressure signs. I hover around 2850 with the rest of the below listed bullets. I recently moved to alpha brass, cci 450, and the result was incredibly good... I'm currently bumping the charge to bring the speed up... from 42.7 to 42.9 all shoot/group well(lucky?)

130 Berger AR hybrid
130 SMK CN
136 Lapua scenar
130 TMK
130 ELDM

I feel like a 140 class bullet in a gas gun isn't the most ideal, the platform seems to respond better to the lighter 130s bullet being pushed faster; rather than just trying to make the 140 run at x speed.

View attachment 8320652

This load ^ that data

Alpha 260 srp as shipped!
Cci 450
H4350 42.8 gr
.004" neck tension
.060 off lands

I bought and loaded 200 rounds of Berger 130 OTMs. Best load I came up with was actually 41.5 of H4350. Didn't see any difference between the BR and 450 primers, so I did the 450's.
I took that to a 500 yard and a 300 yard match and ended up with essentially the same result as the 142 SMK's w/ Superformance. Not as tight of center cluster.
Hard to justify $.60/rnd and $55/lb vs $.39/rnd and $37/lb. Especially, when I got the a slightly better result on paper, and 150fps more speed with the cheaper load.
But...
I have higher hopes than an ES of 2 MOA for 500 rounds @ 500 yards. I'm sure I could shrink those 1/4 with a 40x scope.... but then the open sight guys are shooting nearly the same size groups as me.
(StaBall 6.5 has been the worst performing powder for me so far. Both in 6.5 and 6ARC.)
So....
I moved to the 140 SMK's because they are tangent and seemed like they would be more forgiving.

I'm starting to theorize that the hammer impact is causing "precoil" on all AR rifles. But that's for another thread/topic. I definitely became hyper aware of it while trying to shoot with the delay for 100 rounds.

 

[mettee]

Your game is consistency, so just focus on what brings the best consistency.

I don't experience hang or precoil, maybe I'm just unaware.

I don't know what your rifle set up is or what rest/bipod you use or what approach you use to shoot a gas gun but all that can have a severe effect on your results. I can really F up my groups

Another bullet you should try is the a-tip.

 

[frame12]

Your game is consistency, so just focus on what brings the best consistency.

I don't experience hang or precoil, maybe I'm just unaware.

I don't know what your rifle set up is or what rest/bipod you use or what approach you use to shoot a gas gun but all that can have a severe effect on your results. I can really F up my groups

Another bullet you should try is the a-tip.

You'd only really notice it when dry firing.

If the A Tips shoot amazing in my rifle.......I'd rather not know.

 

[mettee]

I'm really liking the 130 smk cn, it comes pointed from sierra.

I'm also pointing the berger and the 136 scenar...almost convinced in the benefits. Need one more outing to make sure

 

[frame12]

I saw those 130's. Tempting.
Was thinking about 123's if I can't get the 140's to work like they seem to want to. Seems like maybe there's a node hiding @ 2850 or 2950.

When I was exhausting loads for my PSA 308 barrel, I randomly tried 110gn Vmax's with 2015 and they grouped better than even A-Tips.

Seth @ Hornady said something like: "if you can't get 168's and Varget to group, get a new barrel" so I did.
Thinking about revisiting those 110's with a make-shift tuner. There's a benefit in F-Class to shoot 308 with a gas gun. My 6.5 beats the other gas guns with an extreme group size of 2 moa.
However things go, I don't think I'm putting any more money into gas guns till I build up a respectable bolt rifle.

 

[mettee]

I could be wrong but I don't see 140s going much over 2700 fps successfully. 2950 with a 140 in a gas gun....wow!

 

[LRRPF52]

With a 6.5-08 class gasser, I’m happy if 140s are doing 2650-2700fps from a 22” barrel and things are behaving well (no cratered primers, ejector extrusion, weird cycling, etc.).

130gr VLDs just hummed for me in the .260 Rem with less sight picture disturbance, very flat, fun to shoot in rapid TGT-to-TGT strings at medium range, and reach out with to 1200yds with ease. Bartlein barrel spun by GAP, profiled beautifully, matched to the gas block profile at the shoulder, laser. 2.5” groups at 500m, 4.5” groups 3rd at 1000yds.

I should shoot that rifle more, but I don’t.

 

[frame12]

I could be wrong but I don't see 140s going much over 2700 fps successfully. 2950 with a 140 in a gas gun....wow!

I was thinking I could get 2850 or 2950 fps out of the 120's.

I did get 2810fps out of the 142 SMK's with Superformance.

 

[mettee]

I was thinking I could get 2850 or 2950 fps out of the 120's.

I did get 2810fps out of the 142 SMK's with Superformance.

120s maybe.

2810 with the 142 and super but you said that didn't perform well? That's got to be a hot load.

 

[LRRPF52]

Hornady technical data on Superformance loads and gas port locations/port pressure...

 

[frame12]

120s maybe.

2810 with the 142 and super but you said that didn't perform well? That's got to be a hot load.

46.5. It's a grain below Sierra's max of 47.4. No pressure signs.

Hornady has max at 44.7 and that seems correct for their 140gn ELDm projectile. I tried 5 rounds at 46.5 and my brass had burrs. 44gn had no pressure signs.

 

[bfoosh006]

Sorry I should have also asked about the gas system length... just for a more thorough idea of the parts involved.
And Adj. GB ?

 

[natdscott]

Slower powder will give you more port pressure and cause other problems.

I feel like this got glossed over a little bit, so I'm going to re-emphasize that statement.

You need to FULLY understand your gas system and how load changes will interact with it, or you will continue to break things.

 

[frame12]

Sorry I should have also asked about the gas system length... just for a more thorough idea of the parts involved.
And Adj. GB ?

It's listed as Extended Rifle.
adjustable GB, yeah. Barrel shipped with the gas system.

 

[frame12]

I feel like this got glossed over a little bit, so I'm going to re-emphasize that statement.

You need to FULLY understand your gas system and how load changes will interact with it, or you will continue to break things.

You mean: "Start to break"? I haven't broken anything yet.
I've punctured CCI400 primers with standard 6.5 creed powders.

Slowest powders I've used are Superformance and StaBall 6.5. H4350 is right there in burn rate.
4831 is slower, but still on both Sierra's and Hornady's data.


The thesis of this thread was supposed to be:

Given that Gas Guns are limited 52k psi (generally) and full cases are desirable, shouldn't Gas Guns be fed a slower powder that peaks at 52k AND fills the case, across all bullet weights?


Seems like, no.
And it seems like people are getting better results with faster powders, including myself.

 

[natdscott]

You mean: "Start to break"? I haven't broken anything yet.
I've punctured CCI400 primers with standard 6.5 creed powders.

Look at your FP tip, bolt face, and annular clearance of the FP. Might take some gages, but if you blew primers, you did damage.

 

[GIXXER2000]

I run Fed 210's with IMR 4064 SHOOTING 175 Custom Comp Nosler in my Sig 716 without issue.
Update: I also use the same primer powder combo in my Scar 17s and M1A

 

[frame12]

3471, 3466 and 3467 are the original PSA BCG and pin. The darker looking (lighting) is the Odin bolt and darker pin is Odin. It's the narrower type HP bolt.
I've treated the PSA bolt poorly for sure. I've had to replace the fp retaining pin a few times. There's not excessive wear on the lugs The visible dark ring is inset/embossed. No idea if it came that way. I haven't cleaned the PSA pin.
I also have PSA dual extractor BCG. Bolt face looks smooth and flat. Lugs are the most worn of the three. Worn on just one side.
But the pin is toast! Tip's broken off. Glad you made me inspect.
Thx!

 

[Shoots 700's]

To me it sounds like you’re expecting way too much speed out of a gas gun with certain bullet weight.

 

[frame12]

To me it sounds like you’re expecting way too much speed out of a gas gun with certain bullet weight.

IDK, I expect to get ~ 100-150 fps slower than the published max load data. 50-100 fps slower because gas gun's max pressure is lower, and 50 fps slower because I have a 22" barrel instead of the usual 24".
example: Sierra has max load of Superformance for 140's at 47.4 with a velocity of 2900+. I used 46.5 which should net me 2850, minus 50fps for barrel and I'm seeing 2800 fps. This is what I chrono'd
example 2: Hornady has 41.5 for their max load of H4350 behind their 140's and that gets 2700 fps. I drop the charge to 40.5 (2650 fps per Hornady) and minus the 2" off the barrel and I'm at 2600 fps. This is what I chrono'd

I'm meeting my expectations.


Maybe I'm confused. I believe slower powder is less energy, so more case fill with slower powder is the same energy as less case fill with faster powder.

The end result I believe I would get, would be the same velocity but with more case fill.

I'm not looking for more velocity. Maybe I'm putting too much emphasis on case fill, but that's one of major factors in cartridge design.

Seems like instead of just simply dropping the charge weight to accommodate the lower pressures, you'd pick a more optimum powder for the job.

 

[Shoots 700's]

Have you looked in the 6.5 gas gun only in the reloading section? Gasser will run different than a bolt gun and needs a powder burn rate that runs the gun optimally without beating the crap out of it.

Not that it matters because all guns are different, I was running 140 class bullets out of a 22” gun and getting 2700 fps. Nothing wrong with that speed and does anything needed.

 

[powerspc]

Not sure if this adds anything to the conversation or not, but when I couldn't find any other bullets I came across some 129gr Spire Points. They shot phenomenal out an LMT with a 20" / 6.5CM barrel.

Powder: H4350
Load: 41.5gr
Primer: F205M
Trim: 1.910"
CBTO: 2.1785"
COl: 2.7120
FPS: 2791
ES: 5
Sd: 1.96

 

[frame12]

Have you looked in the 6.5 gas gun only in the reloading section? Gasser will run different than a bolt gun and needs a powder burn rate that runs the gun optimally without beating the crap out of it.

Not that it matters because all guns are different, I was running 140 class bullets out of a 22” gun and getting 2700 fps. Nothing wrong with that speed and does anything needed.

I'll look for it.

I'm seeing ~2600 on my 140gn projectiles with StaBall match and H4350
2700+ with StaBall 6.5
2500 with Varget.
Factory ELDm 2600
Factory ELDx 2640.
Factory Berger 130's were 2800
Factory Berger 144's were 2700.

 

[frame12]

Not sure if this adds anything to the conversation or not, but when I couldn't find any other bullets I came across some 129gr Spire Points. They shot phenomenal out an LMT with a 20" / 6.5CM barrel.

Powder: H4350
Load: 41.5gr
Primer: F205M
Trim: 1.910"
CBTO: 2.1785"
COl: 2.7120
FPS: 2791
ES: 5
Sd: 1.96

I shot a 6 shot group of the factory American White tail, and it was 4.25" @ 300 yards. Pretty impressive for being nearly the cheapest 6.5 factory ammo on the market. It uses those 129's.

 

[natdscott]

IDK, I expect to get ~ 100-150 fps slower than the published max load data. 50-100 fps slower because gas gun's max pressure is lower, and 50 fps slower because I have a 22" barrel instead of the usual 24".
example: Sierra has max load of Superformance for 140's at 47.4 with a velocity of 2900+. I used 46.5 which should net me 2850, minus 50fps for barrel and I'm seeing 2800 fps. This is what I chrono'd
example 2: Hornady has 41.5 for their max load of H4350 behind their 140's and that gets 2700 fps. I drop the charge to 40.5 (2650 fps per Hornady) and minus the 2" off the barrel and I'm at 2600 fps. This is what I chrono'd

I'm meeting my expectations.


Maybe I'm confused. I believe slower powder is less energy, so more case fill with slower powder is the same energy as less case fill with faster powder.

The end result I believe I would get, would be the same velocity but with more case fill.

I'm not looking for more velocity. Maybe I'm putting too much emphasis on case fill, but that's one of major factors in cartridge design.

Seems like instead of just simply dropping the charge weight to accommodate the lower pressures, you'd pick a more optimum powder for the job.

You aren't confused, just ignorant.

Slower powder doesn't necessarily mean lower energy. The slowest powders in common use are for .50 BMG, and similar, for example.

Slower means that it takes a longer burn time to reach peak pressure.

Think about this.

Whereas, gas port is in an immovable location,

and Whereas the gas pressure at the port will be determined largely by powder, bullet, and charge weight,

and Whereas, for these arguments, bullet weight and bearing surface shall remain same,

and Whereas the pressure curve of a faster powder's pressure curve will have significantly eroded by the time the bullet crosses the port and pressurizes the gas system

and Whereas a slower powder's pressure curve will be peaking or only slightly eroded, at the same distance from the point of ignition,

THEN, by these facts, it is hereby presented that a slower powder will often pressurize the gas system at a much higher residual pressure than woupd have the faster powder, all else equal.


That's why shit breaks when you run too much of too slow a powder.

 

[mettee]

^ solid as Sears dude.

 

[frame12]

Shot 10 rounds of StaBall Match and Rem 7.5 primers Friday. Some hung, some didn't. Didn't group that well, but the LRP Lapua cases w/ BR2's and Fiocci grouped ok and didn't hang. So I decided to use the LRP brass loads for the Saturday BR match.
Didn't have enough LRP Laupa brass loads left to shoot the match Saturday, so I loaded up some Hornady cases I had already prepped and used the Fiocci primers. StaBall powder. SMK 140's

Shot the 1st and 2nd relay with those (140 SMKs w/ 38.1 StaBall Match and Fiocci LRP and Hornady brass). First round wasn't good. Three shots were outside 2moa. For the second round, the sighters seemed to be responding in a more predictable way, so I shot those for record. 2nd relay was better than the first round. Everything inside 2moa.
I had 16 rounds in Lapua cases left (1/2 BR2 and half Fiocci primers) so I ran those for the third relay and shot new sighters when I switched primers. That round shot the same as #2.
Depleted of the Laupa loads, I went back to the Hornady brass for the last relay and that shot under 1.5 moa.
No hang fires.
The final relay felt pretty good. Predictable impacts. Not great but certainly a step closer to my expectation.
Not sure why the same loads shot so much better at the end. Temps were up from the first rounds maybe 7 degrees @ ~40.
First round might have been neck tension, cold weather or who knows.

I lost 3 cases due to loose primer pockets. So I'm thinking 38.1 is still too hot. FPS is in the 2575 range.
My SRP Alpha cases show no signs of abuse. Primer pockets are still tight after 7 firings.
Lapua and Hornady cases were on their 3rd or 4th.
Might knock .2 off and load the rest of my SMK's into the Lapua cases for next month and see if stands up.

After that, IDK... 120 grainers?
or maybe buy a Savage 110? Dude next to me shots .6 moa max all year long with his factory 110 Precision (the one that ships in an MDT chasis) and a Shilen pre fit barrel. Pretty much any load he puts in it.

 

[Yondering]

One of the shooters at the F-Class match said he stopped using all ball powders with SRP in 308 because of similar FTF and "hang"/ delayed ignition issues.

This comes from an inadequate primers in the cold (if there's just not enough spark to light it off consistently) or inadequate primer strike; either a lightened hammer spring in a tuned trigger, or maybe too much or wrong lube in the firing pin channel in cold weather, etc. A similar thing can be seen in magnum revolver cartridges when the hammer spring is lightened too much; velocity variations go way up because ignition is inconsistent.

I may have missed it, but don't think you said - do you fully understand tuning the gas system, and have you tuned it for the max loads you're using? Doesn't count if you tuned it for some other load, or just "have an AGB", especially if you're using Superformance - you've gotta tune that gas system specifically for Superformance if you're using it as intended for high velocity loads.

IME when people talk about ARs having to run milder loads, most of the time its because they didn't tune the gas system very well, if at all. I'll also point out that tuning is a lot more important than what gas system length you have, but unfortunately most people just focus on that length instead of setting up the rifle right.

 

[Yondering]

When I tried some slower powders in .260 Rem under a 140gr if I recall, something really weird happened that I’ve never experienced with a gas gun before. Freaking buffer slammed so hard into the back of the RET, rifle recoiled like crazy, and smoke was pouring out of the receiver seams. It was definitely too slow for the action and didn’t get a full conversion in the chamber. Might have been RL17.

Not really anything weird about that; you used a slower powder, which put more gas flow back into the bolt carrier and made it cycle harder. If the gas system were tuned for that powder, function could have been the same as normal. (Other than perhaps a small difference in recoil due to more powder mass, same as you'd feel in a bolt gun.)

This is very much the same thing as using something like Leverevolution in the Grendel; if your rifle isn't tuned for it, it'll cycle really hard, and you'll get false pressure signs due to early unlocking, which will make some people back off the load when really they just needed to restrict gas flow more. The OP's Superformance and Lever have similar behaviors in that regard for AR platforms, in my experience.