Sub-X COAL for AR-style auto loader

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Ape Factory
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Sub-X COAL for AR-style auto loader

Post by Ape Factory »

Ran into an issue hand loading the Hornady Sub-X rounds, specifically bullet set-back when dropping the bolt from a locked back position.

I've fired the factory loaded Sub-X rounds and found they weren't very accurate. The S&B 200 gr. subs were sub-MOA at 100 yards but they don't expand. So...I loaded up on the Sub-X bullets wherever I could find them and figured I could tweak the load enough to make it more accurate.

I discovered the bullet setback while experimenting with neck tension tonight. Seems the round is being pushed into the chamber at such a steep angle that the nose is hitting the barrel extension instead of the inside top of the barrel extension, leaving a nasty gash on the bullet and seating the bullet further into the case. I did a huge over crimp and got the same results despite the massive increase in neck tension.

I pulled the pin on the bolt and loaded a factory Hornady round. Got the same issue. Loaded up an S&B, no issue. That's why the Hornady's weren't accurate!

I just ran my first test, seating the bullet more shallow, pre-cannelure and they fed without bullet setback! Success! I will polish the feed ramps (it's a Faxon Match grade stainless nitrided 10.5") just as a precaution.

So have others run into this issue and have you found a certain COAL that seems to work well? I'd measure to the ogive but the Hornady's seem to vary quite a bit.

Factory is around 2.065 give or take and my first experimental was at 2.172. See photo below.
Image

Here's the factory loaded round after having the bolt dropped on it. Normally you can see a bit of the cannelure.
Image
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Bob the nailer
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Re: Sub-X COAL for AR-style auto loader

Post by Bob the nailer »

One ragged hole! The quest for accuracy continues...

Bob the nailer
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Ape Factory
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Joined: Wed Sep 08, 2021 8:31 pm

Re: Sub-X COAL for AR-style auto loader

Post by Ape Factory »

Fack. Long reply somehow lost it. Appreciate the link Bob but it did not address my question directly. Still, a good read so greatly appreciated.

Ran through a bunch of tests tonight to try to determine the issue and Faxon is going to send me a new barrel under warranty so great customer service there. I've also ordered a Rainier match barrel, just in case, but with the Faxon, the rifle just functions no matter what I feed it, suppressed, unsuppressed, subs or supers. Bullet setback with the sub-x notwithstanding, the barrel shoots and is a great value.

I'll report back once I have a solution.
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