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Posted: 11/13/2010 4:24:59 PM EDT
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So I bought two rifle parts from BCM. I got their lower:
http://www.bravocompanyusa.com/BCM-Lower-Receiver-Groups-M4-AR15-s/117.htm ...and this upper receiver group: http://www.bravocompanyusa.com/BCM-16-Mid-Length-Upper-Receiver-Daniel-Defense-p/bcm-urg-mid-16%20ddl12.htm I took it out today for the first time and put 270 rounds through it. Ammo was from Hornady, Remington, and Winchester. I had both 5.56 and .223. The Hornady was .223 TAP FPD... so hopefully fairly high quality. Used two Magpul P-MAG's (bought at different times, so hopefully from different batches). I had a failure to feed every other round. It seems like it was always the rounds that went for the left feed ramp that wouldn't go in. Not matter which ammo, no matter which magazine, I had the same problem. This was my first time ever shooting this rifle. Every once in a while that left round would feed, but about 90% of them would get stuck. I was pretty put down. Any ideas on how I can fix this? |
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Quoted:
So I bought two rifle parts from BCM. I got their lower: http://www.bravocompanyusa.com/BCM-Lower-Receiver-Groups-M4-AR15-s/117.htm ...and this upper receiver group: http://www.bravocompanyusa.com/BCM-16-Mid-Length-Upper-Receiver-Daniel-Defense-p/bcm-urg-mid-16%20ddl12.htm I took it out today for the first time and put 270 rounds through it. Ammo was from Hornady, Remington, and Winchester. I had both 5.56 and .223. The Hornady was .223 TAP FPD... so hopefully fairly high quality. Used two Magpul P-MAG's (bought at different times, so hopefully from different batches). Why Hopefully? I had a failure to feed every other round. It seems like it was always the rounds that went for the left feed ramp that wouldn't go in. Not matter which ammo, no matter which magazine, I had the same problem. This was my first time ever shooting this rifle. Every once in a while that left round would feed, but about 90% of them would get stuck. I was pretty put down. Any ideas on how I can fix this? Now this is how to write a trouble shoot thread. No dragging the info from the OP. It's upfront. Well done. Try some other mags. You have defective mags. IMO. Not uncommon, with your choice. Try some G.I. mags. 458 |
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Single round in a mag, the mag inserted into the rig, round charged and fired, did the bolt lock back on the mag catch (catch on the face of the bolt, and not on the bottom of the carrier?
We need to know if the rifle is full stroking, hence passes the above test first before digging deeper. |
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Shotgun the upper open, and compare the center of the feed ramps to the center line of the front take down lug. the should be centered on each other.
If the upper has extended feed ramps milling into the upper receiver, confirm that the ramps match the barrel extension ramps. If the upper does not have ramps, the confirm that the barrel ramps come all the way to the edge of the receiver extension. Lastly, use a pick type tool and run up the edges of the ramp checking for milling burs at the end of the ramps that may be catching the bullet tip. |
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The feed ramps look centered to the center of the lug as close as I my eyes can see.
The upper does have the extended feed ramps, and they're not 100% on, but they're like 95% on. They look almost exactly like the top right picture in Gatorhunt's post. I wasn't sure what you meant buy run a pick on the edge of the ramps looking for burrs. I used the only pointy metal thing I could find, the tip of the file on a cheap pair of fingernail clippers. The only part I can see anything that isn't glass smooth is where the feed ramps from the extension meet the extended receiver feed ramps... but I don't think it would catch the tip of a bullet. |
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In gators top left photo, take a close look at the left feed ramp on tip of the left hand side. There is a slight bur, and some have way more than that, which really need to be removed or the butt tip can catch it.
Gators second picture top right, although it's marked good, the upper to lower ramps are really not mating that well, and the barrel has counter clockwise a degree or two in the upper receiver socket to the right when the barrel nut was tightened. Granted that all of this could be mute, at least we have covered the ground here, and if you barrel extension is cocked more than this, would be a good place to start. But lets move on, and now need to know what type of hammer and carrier you have, hence if the hammer has an L cut on the top FP contact surface and if the carrier is shrouded (M-16 type shrouding where the FP is hooded by the carrier or if you look at the carrier, can see the FP from the side). Here, when the B/C locks up loading a round, and you can not even walk the B/C nor round forward in the chamber with the Forward assist, it's often due to the hammer catching the FP collar, and locks the B/C up mid stroke. And why only the one side of the mag, it's the pressure of the round being stripped that can cock the carrier to one side so the hammer catches the FP collar that side only. If you can get the rig to jam like it has been, then give the FA a few hard blows to see if you can walk the round all the way in. If the round will walk home/bolt locks up, and when you pull the B/C apart, the FP retainer pin is not bent to hell, then it could just be mags and the angle they are held in the mag well. Push the mag release button in all the way, then reach over and turn the mag release (will be protruding out the other side of the receiver) one or two turn counter clock wise so the mag catch it now putting less retaining pressure on the mags. This may be enough that will allow the mag to cant a tad more at feeding in the well, and get the mag into a cleaner angle for a clean round feed. Also, since you do have extended ramps, take a look at the upper receiver extended ramps for signs that the round tip is hitting low in the ramp. The ramps are only really needed for longer ogive bullets, and if the left upper ramps has dents in it from the standard bullet tip striking it, you go a low feed problem going on. Again could be the mag catch holding the mag a tad too low, or even the mag itself not feeding the round out at the correct upward angle. To test this, insert a folded section of a match book cover behind the mag between it and the well so the mag is now angled front more upwards. If this allows a clean feed, then on the mag catch, instead of loosing it's tension, go the other way and increase it instead. |
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Also, it seems I can repeat the jams by locking the bolt back, putting in a mag, and releasing the bolt. This makes me think it isn't a stroking issue and probably not a magazine issue. I've uploaded some pictures... guns still a little dirty from when I tried to shoot it. Also, the macro mode on my camera is flakey, but I tried.
Here is a picture of my feed ramps: http://image.bayimg.com/caaeiaadj.jpg Picture of bolt during jam: http://image.bayimg.com/caaepaadj.jpg Picture of feed ramps during jam: http://image.bayimg.com/daaecaadj.jpg Picture looking through the extraction hole during jam: http://image.bayimg.com/daaeeaadj.jpg And a semi-blurry image of the feed ramps during jam, again: http://image.bayimg.com/daaegaadj.jpg After repeating the jam a few times, the bullet seems to be getting jammed in between the two sides of the feed ramp... at the very end of it. Will I ever be able to bet my life on this rifle? Aether, if you want to see how I posted your photo's for you, quote your own post and you will see the img, /img in brackets that I have added before and after your photo addresses. |
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I need you to clean the upper so I can tell for sure, but the left hand barrel extension freed ramp on the bottom inside has a nasty bur that looks like it has caught a few tip rounds. Plus the barrel extension free ramps end edges should no be protruding upwards of the upper receiver extended ramps, and when I blow up the photo using paint, looks like the tips have been catching both edge as well. Plus not a fan of the barrel extension being parkerized or painted, with the left hand tip of the left hand barrel ramp in question as well.
Really, this upper needs to go back to the manufacture to be corrected (parts corrected and the ramps polished, including the ramp tips. 
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I scrubbed down the feed ramps real quick with some Hoppe's No. 9 solvent and a nylon brush.
http://image.bayimg.com/eaaeiaadj.jpg http://image.bayimg.com/eaaekaadj.jpg http://image.bayimg.com/eaaelaadj.jpg |
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Also have to point out, your running the upper way to dry for break in. All the bearing surfaces should have a coat of CLP on them (read go heaver and let the rifle blow off what it does not need). Granted lubing may solve the problem (read should be lubing on the heavy side if you are going to run steel case ammo), but the above photo items really need to be correct before you go to run 69gr ammo or heaver since the longer Ogive bullets will need the upper extended ramps smooth/without any protruding edges to catch on.
And Hoppes belongs no where near the rifle!!!! It leaves behind a residue that will collet fouling faster that you believe, and will just foul the rifle out faster. You will find something like Sweets cleans the bore of copper a lot faster without all the needed scrubbing, and as for the rest of the rifle, cleaned and lubed with CLP (BreakfreeCLP is one form or CLP, and has a cleaning agent in it that will clean powder fouling, but does not clean copper fouling for crap, so just think of cleaning everything else beside the bore as just changing the oil (CLP) come cleaning times. Also, you have low feeding going on, so you might want to tighten the mag catch to see if that helps. 
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So I guess I should send it back to BCM?
What should I say exactly? And should I remove my vertical grip, rail covers, and BUIS? Should I remove the bolt carrier and charging handle? Had roughly 17 out of 30 rounds jam. All of the ones on the side further from the extractor and a few on the other side. |
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Yes, pull everything off the upper that you added and send it back. They are will need to pull the barrel off the upper receiver to correct the problem and items you have added on just slows them down getting the barrel off (plus may not put them back on how you like them.
As for what to tell them, either give then a full write up, or just direct them to this topic on the site so they know what to correct. |
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