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Posted: 4/20/2010 5:47:51 PM EDT
| Ok, FNG here, not sure where to post this. I have a new Bushmaster Preadator upper with DPMS lower, built by my local gun shop. I've got approx. 100 rounds through it. I've been cleaning it properly, (as per the gun shop guys and expierenced friends) Went to the range today had trouble with failure to cycle/eject. Using PMC bronze and Centurion both 55g FMJ. I did try a few Silver Bear 62gr HPs also. Same thing failed to eject. Did a good clean and lube, same thing. My shooting partner tried same ammo in his DPMS, no problems. Checked gas tube, no blockage. Tried different mags. same thing. Any suggestions? Thanks in advance! Go easy on the new guy....... |
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Get an experienced friend over.
Pull the gun apart and clean it. Clean the bolt the bolt carrier and chamber well. Inspect the bolt; check the gas rings make sure ever thing is fine. Pull and clean the extractor inspect the spring. Clean the bolt and inspect; check the carrier key inspect the bolts make sure they are staked correctly and still staked, look for signs of gas blow by. Reassemble and shoot. Report back. Good luck. |
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Quoted:
You have a predator barrel is it a 5.56 or match chamber..that could be the problem.Could also be a weak extractor spring. +1 bushy's come with standard springs and blue inserts for the extractor, the BCM upgrade kit will be a good upgrade. could also check gas key and make sure it locks open on last round. |
| You know what else I was thinking if you shot the steel cased first you do get some blow by with fouling as the steel does not expand like brass..going steel cased then brass could have exacerbated the problem..but if your cleaning and its doing the same thing right off..I was wondering when it fails to eject does the carrier move at all or stay with the empty chambered..if thats the case then it could be a gas problem. |
| Even if the bolt cycles it could be a gas problem, too much gas. That can cause the bolt to com out of battery early and attempt to extract the spent casing before chamber pressure has dropped enough for the case to have sprung back. If the case is still swelled to the full size of the chamber, the extractor isn't going to move it. |
| Rifle may be a bit ammo sensitive, but I would start with the builder first to have them give it a once over to see if they have the same problem with the rig that you are having or not with different ammo they have in stock. Also, might be a wise choice of dropping off a box of ammo that you plan on running if your going to use such full time too. |
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Update to my topic:
I think I'm mistaken on the failure to eject subject. Remember I'm a FNG! Problem is better described as failure to feed (I think). After further investigation, after being a little pissed that my new AR wasn't doing what I thought it should.... What's happening is the spent cartridge is ejecting but the bolt is failing to load the next round. I had the gun shop guy check things over, gas rings are ok, ejector and spring are fine, dissasembled and cleaned the bolt assy. All seemed in order according to the dealer. He gave me some Black Hills match 62 gr Vmax to try, ran 10 rounds without a hitch. I then tried some PMC, Centurion and UMC 55gr FMJ, with 10 rounds in a 20 round mag., (using Brownell's 20 rounders) all failed to feed the next round. Now can I assume the bolt assy isn't moving back far enough to pick up the next round? If so, can this be solved? The dealer seems to think that the lower end ammo I've tried to shoot doesn't develop enough pressure to move the bolt back far enough to pick up the next round. Now when I fired the rifle with the suspected "bad ammo" I was shooting off a rest, not necessarly holding the rifle tight to my shoulder to help stop any recoil. Would that make a noticable difference? He also mentioned that being a Bushmaster Preadator upper with a match grade chamber that there may be some "drag" involved with pulling a spent "lower end" casing out of the chamber. Any thoughts from guys who know a lot more about this stuff than I do? I guess I was looking for an AR that would be reasonably accurate that would also be able to shoot less expensive ammo for plinking at the range but have the ability to be a good varmiter at the same time. I got a pretty good deal on the new upper, would I be better off with something else? Thanks again for all the help and advice! |
| Yo Dave, I sent a email to BUSHMASTER customer service since they are the people that put your upper together. Hope to hear from then soon. See ya at work. I read on b-master web that the upper you have should shoot both .223 and 5.56. A real quandry since my DPMS has the .223 chamber and gobbles up all the ammo that your won't. Lets hope that BUSHMASTER WILL RECTIFY THIS SITUATION. LATER PH. |
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Quoted:
Yo Dave, I sent a email to BUSHMASTER customer service since they are the people that put your upper together. Hope to hear from then soon. See ya at work. I read on b-master web that the upper you have should shoot both .223 and 5.56. A real quandry since my DPMS has the .223 chamber and gobbles up all the ammo that your won't. Lets hope that BUSHMASTER WILL RECTIFY THIS SITUATION. LATER PH. DPMS barrels are reamed 5.56 nato, no matter what they are stamped. Trust me, I have one of their match barrels, it's stamped 223, and is Nato reamed. |
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