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Posted: 5/19/2009 2:00:19 PM EDT
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I just completed a build and am having feeding issues.
I built a piston system with Adams arms. MSTN LILJA 16" mid length barrel and matched bolt LMT bolt carrier Sun Devil flat upper Sun Devil lower Magpul UBR DD Omega 9 rail The system looks nice but am having problems with a short stroke when firing. The bolt carrier does not come far enough back to catch the next round. It ejects the spent round sometimes. Without the magazine the rounds are ejected at 4 o'clock as expected. It ejects shells flawlessly. With the magazine the carrier rubs hard on the rounds in the magazine. Also the bolt catches the next round and dents the crap out of it when firing. The magazine is very hard to push into the lower. Below is a pic of where the rounds are rubbing. Also a pic of the dent in the round. This dent happens ~ each cycle. I read that adjusting the magazine catch screw might help is this true? http://farm4.static.flickr.com/3379/3547218728_c3031cbdb6.jpg?v=0 http://farm4.static.flickr.com/3331/3546411913_c13363b449.jpg?v=0 |
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It seems fairly normal to see those rub marks on the bolt carrier from the carier running over the lower casings in the magazine. If it is indeed short stroking, then I would check alignment of the gas block feeding to the piston. Ensure that your gas port and gas pathway are not obstructed.
As to the mag being tight, how many rounds are you loading? Trying to insert a fully loaded mag against a closed bolt can be difficult. |
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Thanks for the input.
What you say makes sense. Rubbing on the carrier is normal. What about the bolt striking the casing? The bolt strikes the case hard, causing a large dent. I feel that the bolt striking the bullet is the cause of short stroke. The gas block and gas port are aligned properly. I justify this statement because without a magazine shell ejection is proper @ 4 o'clock. |
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Quoted:
It looks like bolt doesn't engage the new cartridge properly, possibly bullet dives down in the mag. Change the mag for one with self leveling follower. I had some shitty mags that I could not load one cartridge properly The dent in the cartridge would make me think the round is up a bit in the front before the bolt gets to it. Maybe a self leveling follower as the other poster mentioned or it could be a feed lip issue. I would definitely try different mags. Did your stock come with the buffer and spring as a complete package? If the incorrect buffer spring is used you could get short stroking or bolt bounce issues. |
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