function problem

Discussion about rifles in 300 AAC BLACKOUT (7.62x35mm), hosted by the creator of the cartridge.

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Hubert
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function problem

Post by Hubert »

1. The problem: failure to extract, top round in magazine typically jams very hard as it's stripped. Difficult to clear (round half in/half out of the mag, jamming it in place). Problem typically appears after 4 to 6 rounds are fired (fire a few, jam. Clear, fire a few, jam). Ammo used primarily Remington 130gr Barnes "hog hunter". A few rounds with Hornady subsonic, same problem.
2. The upper: 16" bbl, carbine length gas system. Bought the upper complete. Receiver has Cerro Forge marking, nothing else. Barrel manufacturer is unknown.
3. Lower built by me on a Bushmaster receiver, and functions perfectly with standard 5.56/.223 upper.
I'm thinking it's under gassed, but I really don't know how to check that. I suppose it is also possible that the buffer/spring might be the problem, but as it functions perfectly with 5.56,???? I suppose it could be the extractor, but it is new, with less that 100 rounds through it, and looks ok visually.
Would appreciate some ideas.
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themonk
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Re: function problem

Post by themonk »

What buffer weight are you running?
tallburnedmidget
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Re: function problem

Post by tallburnedmidget »

Hubert wrote:1. The problem: failure to extract, top round in magazine typically jams very hard as it's stripped. Difficult to clear (round half in/half out of the mag, jamming it in place). Problem typically appears after 4 to 6 rounds are fired (fire a few, jam. Clear, fire a few, jam). Ammo used primarily Remington 130gr Barnes "hog hunter". A few rounds with Hornady subsonic, same problem.
2. The upper: 16" bbl, carbine length gas system. Bought the upper complete. Receiver has Cerro Forge marking, nothing else. Barrel manufacturer is unknown.
3. Lower built by me on a Bushmaster receiver, and functions perfectly with standard 5.56/.223 upper.
I'm thinking it's under gassed, but I really don't know how to check that. I suppose it is also possible that the buffer/spring might be the problem, but as it functions perfectly with 5.56,???? I suppose it could be the extractor, but it is new, with less that 100 rounds through it, and looks ok visually.
Would appreciate some ideas.
Hi and welcome.

First thing to try is a few different mags and then continue on from there.

Also the following info about your rifle would help:

Buffer weight and is the spring mil spec or something different?
The standard configuration for a 300BLK 16" carbine gas upper would be the milspec carbine buffer and spring
Hubert
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Re: function problem

Post by Hubert »

The buffer and spring are milspec for standard m4 carbine. I don't know the exact weight. (tried several different mags, milspec and magpul)
Thanks, Hubert
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themonk
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Re: function problem

Post by themonk »

Who makes the upper? Who did you buy it from?
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rebel
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Re: function problem

Post by rebel »

When shooting the Hog hunter - where is your brass ejecting to -2, 3, 4, 5 o'clock and how far?
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Hubert
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Re: function problem

Post by Hubert »

Brass is ejecting about 3. Difficult to say how far (range benches get in the way), but in general about half as far as 5.56.
Hubert
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Re: function problem

Post by Hubert »

Would it be worthwhile to try a different bolt group?
klm109
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Re: function problem

Post by klm109 »

Yes, to narrow down the problem.
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Hoot Gibson
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Re: function problem

Post by Hoot Gibson »

+1 on trying different mags, and different bcg.

Also, does the bolt lock back on the last round out of the mag?
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