224 Valkyrie AR-15 Bolt carrier is not staying open on last shot

[Iron Worker]

I was shooting my 224 Val yesterday, testing loads with Alliant Power Pro 2000-MR Ended at 28grs behind 80.5 gr Berger Full Bore average velocity 2947 FPS out of a 23" Krieger bbl. But the action wouldn't lock open upon the last round fired. BUT loads with 25grs of Re#15.5 pushing 75gr ELD did lock open upon the previous shot?

 

[Kamerad]

Magazine related?

 

[Doom]

The most likely issue is insufficient gas pressure to force the bolt all the way back to catch the bolt catch. Where is your brass ejecting to with the 2000MR ( 12 o'clock is towards muzzle, 6 o'clock is towards stock)?

 

[Iron Worker]

It's 90 degrees. Shooting off a bench with a brass-catching screen clamped to the bench. The load with 25grs of Re#15.5 behind a 75gr bullet bolt stayed open, and 25grs of Re#15 behind a 60gr bullet stayed open. But 28grs of 2000MR behind an 80.5 gr bullet didn't lock back. Also, I was getting higher velocity with the 80.5 gr bullet than the 75. Now, with the Re#15.5, the primer was flatter but didn't open or expand the primer pocket. (These two powders are next to each other on the powder burn rate chart) The 2000MR average velocity was 2,947 out of ten shots, and the SD was 20.6. I think I have room to increase the powder charge.

 

[Doom]

You might have some room to up the powder but I would be careful. If you have an adjustable gas block I think I would try that first. I tried using Gordon's Reloading Tool but I don't have faith in the powder model so I won't say what the results were. The 2000MR is known for giving higher velocities, I got 80-100 fps easily in my 308 over the 4064 velocity.

 

[Nobody of Consequence]

13th months later, did you figure it out? I have a White Oak upper that doesn't like to feed right with a duramag, feeds a little better with a PRI but won't lock bolt back on last shot and after a while starts to show the same symptoms of the duramag (bolt rides on top of round that it's supposed to be loading). It appears to be slightly undergassed but not horribly, has a +1 rifle length tube I think, and non-adjustable gas block. Recently I watched some couple year old video from some youtube reloading guy who said he had best luck with AR-Stoner magazines in his 224 Valk. I bought a couple and only taken them out twice, only been loading 5 rounds at a time. But so far these AR-Stoner 10-round magazines seem to lock the bolt back and stripping rounds fine for 80-90 rounds (then starts to have issues, assumedly because the rifle is dirty, but haven't played around enough yet). It doesn't appear that Wolff makes extra power 10-round magazine springs, so I might try to cut down a 15-round spring for the duramag and PRI to see if that helps. The body of the duramag has much better looking spot welds, and the PRI just seems like a better magazine, I'm just getting feeding issues and bolt hold back issues with them. I haven't tried any of the higher capacity magazines I bought years ago when I first put the rifle together and let it collect dust for 3 years.

I should also say I also shot some really hot loads, up to 0.2 over list, but it didn't help and ejector marks stopped me short of continuing. The last rounds I fired were launching the 88gr ELD-M's at 2850. That brass went in the trash.

 

[Iron Worker]

13th months later, did you figure it out? I have a White Oak upper that doesn't like to feed right with a duramag, feeds a little better with a PRI but won't lock bolt back on last shot and after a while starts to show the same symptoms of the duramag (bolt rides on top of round that it's supposed to be loading). It appears to be slightly undergassed but not horribly, has a +1 rifle length tube I think, and non-adjustable gas block. Recently I watched some couple year old video from some youtube reloading guy who said he had best luck with AR-Stoner magazines in his 224 Valk. I bought a couple and only taken them out twice, only been loading 5 rounds at a time. But so far these AR-Stoner 10-round magazines seem to lock the bolt back and stripping rounds fine for 80-90 rounds (then starts to have issues, assumedly because the rifle is dirty, but haven't played around enough yet). It doesn't appear that Wolff makes extra power 10-round magazine springs, so I might try to cut down a 15-round spring for the duramag and PRI to see if that helps. The body of the duramag has much better looking spot welds, and the PRI just seems like a better magazine, I'm just getting feeding issues and bolt hold back issues with them. I haven't tried any of the higher capacity magazines I bought years ago when I first put the rifle together and let it collect dust for 3 years.

I should also say I also shot some really hot loads, up to 0.2 over list, but it didn't help and ejector marks stopped me short of continuing. The last rounds I fired were launching the 88gr ELD-M's at 2850. That brass went in the trash.

The magazine locked open on all my loads and factory, but not with Alliant 2000MR powder. It sounded different when using that powder as if it was overpowered. Regardless, I sold that rifle. I regret ever buying it.