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Posted: 5/6/2011 7:37:41 AM EDT
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I have run into a problem on my first AR & first AR build, I have a BCM BFH 16" Mid Length Upper Receiver Group w/ LaRue Tactcial 9" Handguard & a Spikes BCG. Finally got everything in yesterday & started to put everything together. When I put the BCG into the upper after cleaning & lubing everything , it appeared to jam in there. The rear of the lugs on the bolt were meshed in level with the rear of the lugs on the chamber. I couldn't get it closed & it was so tight I had to end up using a hammer & soft dowel to tap the BCG out of the upper. I disassembled the BCG. The bolt itself seemed to fit in with proper clearances without the carrier when I tried it by finger without the carrier, but the carrier without the bolt jammed in just the same as the first try with the assembled BCG. I was again unable to free it with the charging handle & all the force I could generate pulling on it. I finally got it out with some gentle tapping with a hammer again. Looking at the gas tube, there is a significant amount of scuffing on the last 2-3mm of tube. I didn't notice the scuffing before assembly, but wasn't really looking for it, so it could have been there to start with. I'm not sure if the gas tube is where where things are binding or not, but it seems likely to me & I don't see any other scuffing or signs of friction & jamming showing up anywhere else on the carrier. I'll try & get pictures when I get home tonight. The upper came pre-assembled, so I'd otherwise assume Bravo Company did things correctly. Any suggestions on where I should start troubleshooting or what might be the problem? Devin |
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Is it possible that the gas tube is not straight?
Maybe you can mark the gas tube end with something and see if the marking gets scuffed off again. I'd probably remove the buffer spring so you aren't jamming things together with so much force. Which would be easier to try to see if the binding goes away? remove the gas key from the bolt carrier, remove the gas tube from the upper. |
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I'd thought about marking the tube with a black marker & checking for fresh scuffing, hadn't had a chance to try that yet though. Everything looked straight to me, but I didn't get measuring instruments involved yet. I actually didn't put the lower on until after realizing there was a problem, so the buffer assembly was not present for the majority of my troubleshooting. As far as oversized or undersized parts, it could very well be, nothing was labeled as such when I purchased it. No clue which would be easier to remove as it's my first build, I assume the gas tube, as the gas key is staked. I'm pretty sure the bolt was extended when I first tried pushing it into battery. The fact I still get the same problem without the bolt & just the bolt carrier indicates to me the bolt isn't a problem, unless I managed to mess something up with the bolt that affected the carrier. Will definitely get some photos here in a few hours when I get home, was going to try & take some last night, but realized it was way past my bed time already.  |
| Remove the bolt from the carrier. Then, try the carrier by it's self to "feel" the fit in the upper and the position of the gas tube. You should be able to feel where the problem exists. If this feels OK, then your barrel may be in a bind from an out of square receiver face or barrel over torque. |
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https://lh4.googleusercontent.com/_U249LLuFcC8/TcRsqsW1ujI/AAAAAAAAATI/c51UfN5qM60/s640/IMG_3341.JPG https://lh4.googleusercontent.com/_U249LLuFcC8/TcRtOI8HbNI/AAAAAAAAATo/wXNkk5MRNQY/s640/IMG_3342.JPGhttps://lh4.googleusercontent.com/_U249LLuFcC8/TcR8osLVFwI/AAAAAAAAAUI/a2ubspuYSjk/s1024/Gas_tube_missing_ink.jpg I'm trying to pull off the front sight post so I can pull out the gas tube, but I've only managed to pull out 1 of the 2 tapered roll pins holding the sight post to the barrel (Yes, I'm aware they are tapered and I'm only using a hammer & punch on the narrow end). I'm already hitting it harder than I'd like & nothing is budging on this 2nd pin. 1st pin to a LOT more force than I was expecting & have seen in you tube videos. Will try and get a few more pictures here soon, had a few of the full BCG, in battery as far as it would gobut they were too bury to see anything useful. |
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https://lh3.googleusercontent.com/_U249LLuFcC8/TcSBzPDejbI/AAAAAAAAAUg/GDiTpw_zvBM/s640/IMG_0016.JPG Got a decent picture of the bolt in as far as it would go (not in all the way to the point where it rotates so the bolt lugs are behind the barrel lugs. |
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Quoted:
https://lh4.googleusercontent.com/_U249LLuFcC8/TcRsqsW1ujI/AAAAAAAAATI/c51UfN5qM60/s640/IMG_3341.JPG https://lh4.googleusercontent.com/_U249LLuFcC8/TcRtOI8HbNI/AAAAAAAAATo/wXNkk5MRNQY/s640/IMG_3342.JPGhttps://lh4.googleusercontent.com/_U249LLuFcC8/TcR8osLVFwI/AAAAAAAAAUI/a2ubspuYSjk/s1024/Gas_tube_missing_ink.jpg I'm trying to pull off the front sight post so I can pull out the gas tube, but I've only managed to pull out 1 of the 2 tapered roll pins holding the sight post to the barrel (Yes, I'm aware they are tapered and I'm only using a hammer & punch on the narrow end). I'm already hitting it harder than I'd like & nothing is budging on this 2nd pin. 1st pin to a LOT more force than I was expecting & have seen in you tube videos. Will try and get a few more pictures here soon, had a few of the full BCG, in battery as far as it would gobut they were too bury to see anything useful. In this last photo.......it looks like the gas key/charge handle may not have enough clearance, it's rubbing the charge handle channel. might check that. |
| Your barrel lugs look like they aligned with the upper properly and the carrier and CH seem to fit OK maybe a little rubbing but nothing that should cause something like this ... did you feel any binding when the carrier was inserted without the bolt? If not then I would really start to suspect the bolt at that point ... are there any marks/scrapes on the sides of the bolt or bolt lugs? Maybe mark your bolt lugs as you did the tube and see if any binding/scuff marks show up. |
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Quoted: In this last photo.......it looks like the gas key/charge handle may not have enough clearance, it's rubbing the charge handle channel. might check that. I get the same results with or without the charging handle in there. Quoted: you don't have to remove the sight post to remove the gas tube, just remove the roll pin and push the gas tube back into the receiver until it clears the sight post, then rotate the tube until you can clear the sight and pull out of the receiver With the LaRue 9" handguards, there is less than 1/4" between the end of the handguard & the sight post, so no way to get the gas tube through without pulling off the sight post. Think I will give them a call here tomorrow or Monday. Thanks for the advice. |
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Sometimes the gas key and gas tube will have an snug fit initially.Ive seen a couple instances that the tolerances are so that it is possible to hang the gas key/carrier from the gas tube(parts out of the rifle).
After a few cycles the two mate perfectly. If the fit is too tight to go into battery with the force of the action spring,or is enough to cause difficult manipulation of the action by way of the CH, I would take a look inside the gas key port and inspect it for rough bore(machine grooved) or possibly undersized bore. The port in the gas key should be around .181" +/- ,and the bulb of the gas tube at or slightly less diameter. Before I did anything to the upper I would drop an email to Paul at BCM and see what course of action he recommends. |
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As best I can measure, the inside of the key is .178 ish, calipers don't fit in all that well, so in the ballpark as much as I trust the tool. No way I can measure the diameter of the gas tube without removing it, and it's trapped by the sight post with the unmovable tapered roll pin. And I don't have any spare parts or know anybody nearby with an AR15 to try a different carrier. I tried calling Bravo Company, but just got voice mail, so shot em an E-mail & will try calling again on Monday. The excessively tight sight post roll pin bothers me too, as I'm thinking about putting on a flip up front sight post here at some point. Was really hoping to have this gun up and running for my birthday range trip this coming weekend. Thanks for all the help guys. |
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Quoted:
As best I can measure, the inside of the key is .178 ish, calipers don't fit in all that well, so in the ballpark as much as I trust the tool. No way I can measure the diameter of the gas tube without removing it, and it's trapped by the sight post with the unmovable tapered roll pin. And I don't have any spare parts or know anybody nearby with an AR15 to try a different carrier. I tried calling Bravo Company, but just got voice mail, so shot em an E-mail & will try calling again on Monday. The excessively tight sight post roll pin bothers me too, as I'm thinking about putting on a flip up front sight post here at some point. Was really hoping to have this gun up and running for my birthday range trip this coming weekend. Thanks for all the help guys. If you have a selection of drill bits or punches,go through them and see if you can find one close to .181" or slightly less on the shank.You can use the shank end as a bore gage. |
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Made it into Specialty Sports & Supply here at lunch. The gunsmith stole a BCG out of one of their AR's and it fit just fine... Looks like I get to talk to Spikes and/or AIM surplus about replacing a defective BCG. Devin |
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Quoted:
Made it into Specialty Sports & Supply here at lunch. The gunsmith stole a BCG out of one of their AR's and it fit just fine... Looks like I get to talk to Spikes and/or AIM surplus about replacing a defective BCG. Devin Please give Sarah a ring and we will send you a new BCG with a call tag for the old one. |
Replacement is on the way, sounds like there might have been a problem with a batch or something. Still looking good to take my new AR to the range this weekend for my birthday.  Nice to see people standing behind their products & making things right with minimal hassle. Even if I didn't already have the RMA setup, not excited about pulling off the gas key with everything all staked in. It wouldn't do me any good in getting the gun running either as I don't have any spares & I doubt shipping on a full carrier vs just the key would be any faster. |
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Quoted:
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Good show Spike's......everyone fouls up.......the difference shows in customer care AFTER the sale! This... Glad to hear you'll make the BD range trip OP.  +1 Yeap....good folks at Spikes.. I had some undersized/rough bore gas keys from a different name brand manufacturer not too long ago.I did not get a call tag issued for the return though.Thats going the extra mile for the customer IMHO. 
I bet Tom has a bore gauge made up for gas key inspection from now on though.
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Quoted:
Good show Spike's......everyone fouls up.......the difference shows in customer care AFTER the sale! +1 on the kudos for Spikes. I'm doing business with them for the next build! BTW, I had a very similar problem on my build (can't post pictures) but it was the gas tube. I mistakenly bought and installed an AR 10 gas tube...embarrassing. |
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Bolt made it in on Friday & fits fine. Today we put 350ish rounds of XM855 & 100 rounds each Brown Bear & Silver bear through it. Had 1 failure to extract (I think) when hand cycling a 30 round mag of silver bear though to make sure everything worked, and 1 failure to feed of the XM855 that got stuck on the M4 feed ramp on the receiver first round out of a fresh mag. Chalking both up to operator error & it other ran flawlessly. Well I did have repeated failures of the AR-15 Rail Covers for Handguards Black UTG Package of Twelve 2"x1.375"x0.75" and had to keep putting 2-3 of those back on every few mags, but I can handle replacing those with something that's a little more than $7 quality. Nice & accurate. It was pretty darn easy to get the red dot & BUIS dialed in as well. I'm happy with it. Thanks for the advice guys. |
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