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Posted: 10/10/2015 10:49:07 AM EDT
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Specs for the rifle are here:
New Build Runs great with 208 a-max bullets with either lil gun or 1680. I recently picked up some of these: Missouri Bullet 215gr OEM I can't seem to get these to feed in any way shape or form. I've tried different mags, OALs ranging from 2.220" to 1.990" and constantly get this result: 
I have the gas block turned down to where the bolt holds open on an empty mag. I have tried turning it up to 4 or 5 clicks past that with similar results. Gun is clean and well lubed. When I cycle the bolt slowly by hand it looks like the meplat hangs on the feed ramps and allows the bolt to ride over top. Is a little judicious dremel work a terrible idea?  . I've done similar on 1911s with good results. I'd rather not if this is really a tuning or load issue of course.
Suggestions? |
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Bolt over jam, meaning that the bolt never go behind the rim of the case to drive the round out correctly (rifle action is short stroking), or the mag is not recovering correctly if the bolt did manage to make it past the rim of the case so the round is pushed out of the mag from behind the rim, or the mag is not retained correctly in the well (threaded section of the mag catch tip should be flush to the face of the mag release button. As for weeding out if it's the load or the mag, single round loading into a mag, mag inserts in to the rig, round chambered with the empty mag still in the well, fire the round for effect, and the correct effect is that the bolt locked back on the bolt catch (catch in front of the bolt face and not below just on the carrier instead). |
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Quoted:
Bolt over jam, meaning that the bolt never go behind the rim of the case to drive the round out correctly (rifle action is short stroking), or the mag is not recovering correctly if the bolt did manage to make it past the rim of the case so the round is pushed out of the mag from behind the rim, or the mag is not retained correctly in the well (threaded section of the mag catch tip should be flush to the face of the mag release button. As for weeding out if it's the load or the mag, single round loading into a mag, mag inserts in to the rig, round chambered with the empty mag still in the well, fire the round for effect, and the correct effect is that the bolt locked back on the bolt catch (catch in front of the bolt face and not below just on the carrier instead). More info and experience...the bolt holds open on an empty mag. Other things I've tried: Mag catch is turned out until threaded portion is flush with the button. Swapped in a full auto BCG I had here. (Re-tuned gas) slight improvement over the lightened BCG OAL tests...feeds much better at longer lengths i.e. 2.070-2.120". But at these lengths the rounds jam in the lands to the point you have to mortar the rifle if the bolt even closes. The longer length problem led me to: chamber length meets Saami specs, determined by seating a bullet such that .308" diameter is at 1.565". That round loads and ejects fine and is not jammed. (Was my logic good here? At this point the best I can guess is that maybe the free-bore is particularly tight/short on this chamber? Thoughts on that? ETA: rethinking this because it just didn't make sense. I loaded an OEM Bullet to 2.100" and gave it a good tight crimp. As expected it fed, but jams in the lands without allowing the bolt to close. When removed the marks on the lead Bullet from the lands are at about 1.425". OAL was unchanged so the bullet hadn't moved. Leading me to think the chamber is short. Am I making sense with this? |
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Bolt locking back on the catch means that rifle is stroking correctly.
So now the problem is either the mag not recovering correctly, the mag not retained high enough in the mag well, or the tip of the bullet too dam wide to ride up the barrel feed ramps correctly, and instead as the end of the much wider tip bullet is riding up on the outer edges of the ramps ( instead of up the center), the center of the case off the end of the mag feed lips is cam'g down the back rim of the round to allow the bolt to rim over the rim during the push of the round round in the mag forward instead. To weed out the mag being retained too low, strip a mag down to its body, lock it into the well with the bolt locked home, then using a pencil to push the mag release button in all the way down, shove the mag upwards in the well until the top of the feed lips bottom out of the bottom of the carrier. Mark a quick line on the mag at the bottom of the well, then pull the mag back down until it locks back in the catch. Hence the mag locked in the well should have the feed lips off the bottom of the carrier about 1/16", and if the mag is being retained lower than this in the well, could be some of the problem. As for the bullets, That is a large nose tip that is trying to ride up a narrow feed ramp, and if push came to shove, would nose angle reform a few bullets to narrow down the tips to see if the that would solve the problem. If all you are going to be shooting is the wider noise bullets through the rig, then widening the barrel feed ramps may be a solution as well. Remember, the round is coming off the side of the mag, so not only is the tip of the round riding up the barrel feed ramps forward, but also at a angle up the ramps until the round clears the mag feed ramps as well. So with wider ramps, it prevents the the back of the round being cam'd down in the mag as the tip if riding up the ramps instead. 
To add, post a photo of your feed ramps, since with the barrel being 300blk, should be wide to begin with. 
Hence the problem would be that your barrel just has standard 223 ramp barrel extension and the problem at hand with the ramps too narrow for a wider bullet (read can get away with it if the bullet tip is pointed, but on a flat nose bullet, going to be problems instead). |
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Quoted:
almost looks like its catching on the lip of the casing. Take a look again, and note that the bolt face is not behind the case rim pushing the round forward at this jam, but instead the bolt face bottom edge on the center of the round case with the whole works just bound up instead. So the problem is either the bolt is not pushing the round out of the mag from behind the rim to start with, or the as the case is being pushed out of the mag and up the ramps into the chamber, the back of the rim is being forced down to allow the bolt to get past the rim during the feed angle of attack instead.
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