Powder for heavy(200+gr) supers in AR

[MinimalistNutter]

It's definitely the bolt speed, recoil is extremely snappy with the loads on the milder end of the malfunctioning loads it was simply just the bolt moving too fast to feed, on the upper end the extractor not being able to hold it's grip the whole way to the ejector. With Lil Gun it did the weird fake hold open thing(not sure what to call it) where when you take the empty mag out the bolt returns home.
tested with both the steel 20rd and Daniel defense 32rd so it's not a magazine issue

Too much gas, not enough weight. Feels a lot like shooting +p+ and 45 super when my USP had a well worn 12lb spring, just beating itself up violent and loud. The USP had the same extraction issues with 45 super too where the brass was still expanded and the slide was moving too fast the extractor would just slip off the rim, a fresh spring fixed that up along with softening the abuse.

The CFE loads I think will be great once the pistol is ironed out for it, even the brass was landing in nice tight groups with the lower loads that reliably extracted and ejected.

I will put my buffer on a scale tomorrow to make sure it's not even lighter than 3oz. It came from one of the generic receiver extension kits so there's no telling. I'll investigate the DIY options.

For the sake of adding information:
My barrel is a US Arms pistol gas, 1-8 HBAR 10.5" out of MN. My gas port I think is .091 but calipers and drill shanks are not accurate measuring tools.

[dellet]

It's definitely the bolt speed, recoil is extremely snappy with the loads on the milder end of the malfunctioning loads it was simply just the bolt moving too fast to feed, on the upper end the extractor not being able to hold it's grip the whole way to the ejector. With Lil Gun it did the weird fake hold open thing(not sure what to call it) where when you take the empty mag out the bolt returns home.
tested with both the steel 20rd and Daniel defense 32rd so it's not a magazine issue

Too much gas, not enough weight. Feels a lot like shooting +p+ and 45 super when my USP had a well worn 12lb spring, just beating itself up violent and loud. The USP had the same extraction issues with 45 super too where the brass was still expanded and the slide was moving too fast the extractor would just slip off the rim, a fresh spring fixed that up along with softening the abuse.

The CFE loads I think will be great once the pistol is ironed out for it, even the brass was landing in nice tight groups with the lower loads that reliably extracted and ejected.

I will put my buffer on a scale tomorrow to make sure it's not even lighter than 3oz. It came from one of the generic receiver extension kits so there's no telling. I'll investigate the DIY options.

For the sake of adding information:
My barrel is a US Arms pistol gas, 1-8 HBAR 10.5" out of MN. My gas port I think is .091 but calipers and drill shanks are not accurate measuring tools.

A couple of things stand out and this is a long shot;
Buffer might be light, but you’ll know soon enough.
Port size maybe on the smaller side, it’s probably no bigger than .095” and that’s close enough, that’s not huge for subs but for hotter supers it more than needed.

The bolt releasing when you drop the magazine is an indication the bolt did not travel back far enough to catch on the bolt face, it caught on the carrier. It could have been speed, could have short stroked. Since you had trouble feeding with the CFE I’m leaning towards short stroking.

Short stroking does not explain the heavy recoil.

What might make sense is the wrong spring, or a short buffer tube. Either would have the buffer banging on the tube even with light loads. There is probably an actual spec for this, but I’ve never looked. Check to make sure that when you pull the charging handle all the way back, you should have about 1/4” between the bolt face and catch.

I had similar problem with a tube that the index channel was cut too deep. When you pulled the bolt back there was barely enough room for the catch to come up. I ended up backing it off one turn. It’s a long shot since factory and other loads worked fine, but it’s worth a look.

[MinimalistNutter]

I have approximately .180-190" travel from resting on the catch to as far back as I can pull it it without compressing the buffer. Not the easiest thing to measure even with a dial gauge. Another .120 for the bolt face depth, so right around 300-310"

The buffer was in spec for a C buffer at 3.0oz So I took it apart and put a lead mystery alloy weight in, now it's a hair heavier than an H1 buffer, 4.0oz with room for the lead to move freely. I'll head out again today and try some CFE supers (12.5gr at 100% fill) again as well as a round or two of 120gr UMC.
Thinking back the 120gr UMC brass does get flung into the next county, as did my other super handloads that did cycle reliably.


Update, with the 4oz it felt better but didn't cycle much if any better. The first round was a failure to fully extract trying to feed the second round under the spent case, 2nd round failure to fully extract and failure to lock bolt back(This time was a magazine issue, wouldn't lock back when I pulled the CH), 3rd good ejection 6' at 4:00 and locked back.
Forgot to shoot any UMC factory supers.
Also did one round of unique at 6.4gr, a little hotter than expected but I didn't blow my face off. My understanding is Unique shouldn't even be able to unlock the bolt at all, well it did entirely disengage the bolt from the locking lugs. I missed catching it on camera but I suspect it didn't cycle any further than that.
My scrap brass bucket is almost full and that's some money dedicated to gun stuff.

[SJ 40]

Unique is a no go.


Shooters World Blackout, 1680 and CFE BLK are probably the best choices.

This is one combination that I would expect CFE BLK to be the best choice. It will be the lowest pressure load of the three powders. The powder likes compression, but watch out for damaging the bullet when seating.


As for your buffer, pistol gas really should have an H2 buffer and a Full auto carrier.

I would concur,Unique is fine if you want single shot loads,I've never been able to get Unique to cycle at any safe charge with a couple of differing bullet weights.
CFE Blk would also be my choice and does the trick for me for subs and supers.

[dellet]

I have approximately .180-190" travel from resting on the catch to as far back as I can pull it it without compressing the buffer. Not the easiest thing to measure even with a dial gauge. Another .120 for the bolt face depth, so right around 300-310"

The buffer was in spec for a C buffer at 3.0oz So I took it apart and put a lead mystery alloy weight in, now it's a hair heavier than an H1 buffer, 4.0oz with room for the lead to move freely. I'll head out again today and try some CFE supers (12.5gr at 100% fill) again as well as a round or two of 120gr UMC.
Thinking back the 120gr UMC brass does get flung into the next county, as did my other super handloads that did cycle reliably.


Update, with the 4oz it felt better but didn't cycle much if any better. The first round was a failure to fully extract trying to feed the second round under the spent case, 2nd round failure to fully extract and failure to lock bolt back(This time was a magazine issue, wouldn't lock back when I pulled the CH), 3rd good ejection 6' at 4:00 and locked back.
Forgot to shoot any UMC factory supers.
Also did one round of unique at 6.4gr, a little hotter than expected but I didn't blow my face off. My understanding is Unique shouldn't even be able to unlock the bolt at all, well it did entirely disengage the bolt from the locking lugs. I missed catching it on camera but I suspect it didn't cycle any further than that.
My scrap brass bucket is almost full and that's some money dedicated to gun stuff.

There is one other issue completely unrelated to ammo that you need to check. I had this problem (as did some others ) with Gen 3 Pmags. The follower in the magazine sucked. It would slip in front of the bolt catch and not lift it.

You may have a second mechanical issue. The other being a week extractor spring. Any chance of another bolt to try?

[MinimalistNutter]

I should be able to borrow a gen 1 M&P15 sport BCG. I had wondered about that As I can easily actuate the full travel of the extractor with my pinky nail. That could very well be part of the issue, then the light buffer cause the bolt to hypercycle(more-so with lil'gun) makes sense to me so the only thing to do is test.
I think I should note my PSA bolt did have poor QC, first thing I noticed out of the gate was an oversized firing pin hole, so it really wouldn't shock me at all if the extractor spring wasn't right either.

I will be using the 32DD mags for testing from this point foward because just like you said with the Pmag, the steel 20rd did that same thing, it wasn't touching the catch at all.
I did load up a couple almost powderpuff level subs before leaving town again, 9.6gr CFE under the 230-5r just to see how they would cycle. Not particularly interested in a load that soft but the more I experiment the more I learn about this AR and I figure there's not much risk but a potential squib.

[dellet]

I should be able to borrow a gen 1 M&P15 sport BCG. I had wondered about that As I can easily actuate the full travel of the extractor with my pinky nail. That could very well be part of the issue, then the light buffer cause the bolt to hypercycle(more-so with lil'gun) makes sense to me so the only thing to do is test.
I think I should note my PSA bolt did have poor QC, first thing I noticed out of the gate was an oversized firing pin hole, so it really wouldn't shock me at all if the extractor spring wasn't right either.

I will be using the 32DD mags for testing from this point foward because just like you said with the Pmag, the steel 20rd did that same thing, it wasn't touching the catch at all.
I did load up a couple almost powderpuff level subs before leaving town again, 9.6gr CFE under the 230-5r just to see how they would cycle. Not particularly interested in a load that soft but the more I experiment the more I learn about this AR and I figure there's not much risk but a potential squib.

I ran some incredibly light loads with that powder. I think down below 800 fps and they still cycled. the problem was velocity swings.

The mechanical issues make more sense than load issues, especially with using CFE. just keep at it and eliminate the known issues like the mags. Since it's doing it with multiple brands, might be worth a closer look at the catch or even slop in the lower.

[MinimalistNutter]

Just stripped the bolt and actually took a look at what was inside: 4 coil extractor spring with no insert or O-ring. Now I have to track down one of the BCM upgrade kits locally, my LGS probably has it but I am not wasting 5 gallons of fuel for a $5 part, evil big box sporting goods stores and one decent LGS are on the route of my errands Monday.