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Thread: 300BLK pistol build not feeding.

  1. #1
    Senior Member L1A1Rocker's Avatar

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    300BLK pistol build not feeding.

    Here's the pistol. Waiting on the SBR form to come back to put the rifle stock on:



    Here's what it's doing to the bullets/brass:









    And this is what it looks like when the jam happens:







    Here's the feed ramp area:












    Specs on the build are:
    Lower is a Sharps, bought 4 years ago when the gun boom went bust. I've build several ARs on these, they work fine.
    Lower kit is PSA
    Pistol tube is PSA
    Magpul ASAP
    Magpul pistol grip
    Magpul ARG (I've got an ATF letter somewhere that says this is OK on pistols so please stay on topic)
    Magpul BAD
    MI first gen carbine free float handguard
    Upper is AR Stoner
    BCG is AR stoner
    Barrel is Alpha Shooting Sports 10.5" Stainless with Pistol gas port
    Gas block is YHM low profile
    Gas tube is Novesky.

    I know, it's a real mutt, but I've been at the mercy of what's available.
    Note: this happened with two different magazines.


    Now I've been told that I need to polish the Bolt carrier's bearing surfaces to take the fresh parkerizing off and will do that, but I don't think that would cause the above issue. I've also been shown that there is no radius on the leading edge of the barrel going into the chamber and that is where the brass is hanging up. Supposedly this is not a problem with the small .223 but can be with the .308.

    Picture showing lack of radius:


    I've looked at my other two 300BLK ARs and sure enough, there is a nice bevel on that leading edge.


    OK, do ya'll concur that this sharp edge is causing my problem? If so how would ya'll suggest fixing it? I was thinking of a precision drill bit chucked up into the lathe to break the edge. Then sandpaper and steel wool.

    Any other ideas? Thanks

  2. #2
    Forum Administrator Schuetzenman's Avatar

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    Before I scrolled down to the barrel photos I was saying, case is hanging up on a sharp edge during chambering. Especially since you have OTHER .300 Blackout chambered barrels as examples and as they have a chamfer, then it seems a no brainer to me, break the edge a bit and it should start to work OK. Do you have a barrel extension removeal / installation socket? If I had one and was faced with your problem I'd take off the barrel extension and break that edge uniformly, then reinstall the extension.

  3. #3
    Senior Member L1A1Rocker's Avatar

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    Quote Originally Posted by Schuetzenman View Post
    Before I scrolled down to the barrel photos I was saying, case is hanging up on a sharp edge during chambering. Especially since you have OTHER .300 Blackout chambered barrels as examples and as they have a chamfer, then it seems a no brainer to me, break the edge a bit and it should start to work OK. Do you have a barrel extension removeal / installation socket? If I had one and was faced with your problem I'd take off the barrel extension and break that edge uniformly, then reinstall the extension.
    Hey thanks for the response Shuetz. I can always count on you. No I don't unfortunately. That makes getting in there with a lathe cutting tool rather problematic. What I was thinking was to chuck the barrel into the headstock of my lathe and a big ass precision drill bit in the tail stock and bump that edge a bit. Then hit it with some sandpaper and steel wool.

  4. #4
    Forum Administrator Schuetzenman's Avatar

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    Quote Originally Posted by L1A1Rocker View Post
    Hey thanks for the response Shuetz. I can always count on you. No I don't unfortunately. That makes getting in there with a lathe cutting tool rather problematic. What I was thinking was to chuck the barrel into the headstock of my lathe and a big ass precision drill bit in the tail stock and bump that edge a bit. Then hit it with some sandpaper and steel wool.
    Well that should work, though a little harder than if you could take that extension off. Brownell's sells those by the way. Good luck with it.

  5. #5
    Senior Member L1A1Rocker's Avatar

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    Update: One thing I did not note on my initial post was the problem with the cast bullets not clambering. In addition to the issue of the jam, if I hand fed the cast bullets in they would not chamber stopping about an inch shy of going into the chamber.

    The update. First I did use the 1/2 in drill bit to take the corner off just a bit. Then using a wooden dowel and polishing compound I cleaned it up a bit.

    Next was to address the chamber. I happened to have a PTG conversion reamer for converting other 300 chambers into Blackout specs. It's easy to use as it does not cut on the shoulder but stops there. I was really amazed at how much material was removed. Here's a couple of pics of the drip pan with all the shavings in it:

    [IMG][/IMG]

    [IMG][/IMG]

    I suspect that the manufacture used a Fireball or Whisper reamer to cut the chamber and not an actual 300BLK reamer.

    Now on to the shooting. It worked. . . kinda. The Factory ammo is still hitting just a bit. Photo of previous hangup and current hit.

    [IMG][/IMG]

    Its not enough to cause a jam, it fed and chambered nicely. In fact, four rounds ran fine with very good ejection and the bolt locked back on the last shot. Problem, the cast bullets jammed up just as before (no photo, sorry). Hand fed they did chamber properly and ejected the case. I think I'll need to take a bit more off the shoulder though. . .

  6. #6
    Guns Network Contributor 04/2013 El Laton Caliente's Avatar

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    That is a lot of work on an AR build...

  7. #7
    Forum Administrator Schuetzenman's Avatar

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    Wow the volume of metal removed really surprised me. I'm thinking if the cast rounds aren't going in the cause is probably the Ogive shape. Can you post a side by side photo of the cast vs. jacketed bullets? You might be able to seat the cast rounds a touch deeper to get them to work.

  8. #8
    that much removed it was probably Fireball it wasn't finished properly.





    Any more info out there yet on loads for this round?
    I'll have my suppressed bolt action .300 Blk hopefully in a few weeks and I'm lookin for sub loads.

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