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Old December 4, 2019, 02:01 PM   #1
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needa little advice

having trouble getting a new 10mm build to feed live cartridges. Feeds snap caps just fine. using sellierr and bellot in genuine Glock magazines. The bolt strips the round but the round doesn't orient straight. seems to be getting hung up in the chamber though I cannot see any obvious obstruction. I've polished all the contact surfaces excluding the chamber. The bullet and about 10% of the casing make it into the chamber then it fails to slip onto the bolt face. I'd upload pictures but for some reason a "security tag" is missing from the files and the site won't let me upload them.
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Old December 4, 2019, 04:33 PM   #2
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Sounds like the mag feed lips aren't letting go of it early enough. Is it FMJ or one of their hollow point bullet designs?
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Old December 4, 2019, 06:49 PM   #3
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You have to determine what is stopping it.

If I read you right, the bullet is going up the feed almost sounds like the issue is happening at the rear of the case. After the bullet starts up the feed ramp, the mag should release the case head. The release should be able to power its way under the extractor. Sometimes magazines hold on too long(out of spec) or the extractor is too tight.

I’m not sure what 10mm build means. Are you building an 80% Glock type frame and attaching to a Glock type slide?
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Old December 5, 2019, 12:03 AM   #4
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Assuming that it's a 80% build-out, is everything aligned and squared?
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Old December 5, 2019, 12:25 AM   #5
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Is the extractor preventing the case head from sliding up the boltface?
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Old December 5, 2019, 12:57 AM   #6
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Is this an:

AR pistol caliber carbine with a real "bolt"?

Polymer 80% pistol? - in which case we're referring to the breech face of the slide as being the bolt?

If this is a pistol, is there a chance that you've used a wrong upper parts kit and installed an extractor for a smaller caliber? - or perhaps an aftermarket extractor that's not to spec? It could also be the milling of the slide affecting how the extractor sits in the slide and what angle it presents itself. I once had a Spinta Precision slide that wasn't milled out completely near the breech face so I filed the corner of the barrel down to fit.

You could try a new factory extractor if that's the problem.

It might be helpful to know which parts are Glock factory parts, and which are aftermarket. Upper parts kit, barrel, slide, frame....
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Old December 5, 2019, 03:34 AM   #7
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TO begin with, verify that the snap caps that feed are dimensionally the same as the ammo (which doesn't).

Snap caps are close to live ammo size but not guaranteed to be the same exact size, as they are snap caps, and not dummy rounds.

Also consider this, the WEIGHT of a snap cap is not the same as a live round.

I ran across a 1911 that would feed snap caps, hollow points and ball ammo. It would eject fired cases, snap caps and loaded hollow points but would NOT eject loaded ball ammo. Hollow points ejected ok because they were shorter than loaded ball ammo. I found it interesting that snap caps, the same size as ball ammo would eject just fine, but ACTUAL ball ammo would not eject and would jam in the gun requiring about 3 hands and a screwdriver to clear the round as the slide could not be locked back or barely moved at all once jammed.

It was the weight of the loaded round that when ejection was attempted, gave it a very slightly different angle of travel than the snap cap, and that angle was enough different that the round did not clear the slide and jammed the gun,

Turned out the gun had the wrong ejector installed. Not your issue but I mention it to make the point that sometimes snap caps will show proper function when live ammo won't.
All else being equal (and it almost never is) bigger bullets tend to work better.
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Old December 5, 2019, 12:22 PM   #8
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Are you racking or are you easing the slide forward?
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Old December 5, 2019, 09:16 PM   #9
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As above, snap caps are just that...snap caps. They're useless for trouble shooting.
For purposes of trouble shooting problems you need Action Proving Dummies.

These are the exact size, weight, and even balance of live ammo.

Buy these from Brownell's.
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Old December 13, 2019, 03:36 AM   #10
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Follow up, after fiddling with with it a bit more gave the top of the upper receiver a proper thump. The bolt closed. After this i sanded the cartridge pushing bit at the 6 o’clock position on the bolt face. Took off about half a millimeter, then polished to a mirror shine. I also put two 0.0010 shims between the upper and the barrel. Thing runs like a champ now.
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Old December 14, 2019, 02:07 PM   #11
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"...round doesn't orient straight..." That sounds like the back of the chamber might need chamfering. You extend the feed ramp about half way up the sides of the chamber with a fine file. Happened a lot with .45's trying to feed SWC's before they got popular. Most pistols come that way now. A new 10mm barrel may not have it already though.
Have a look at the extractor too. It clean and moving freely?
And look at the mag lips. If the mag is brand new, the lips may have gotten squeezed in a tick. Fixed with needle nosed pliers. A slight tweak to open the lips a wee bit is all you need do.
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