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Posted: 3/17/2011 8:58:51 PM EDT
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Hi guys, sorry for the following lengthy post, but I've done about four hours of searching forums for an answer and can't find that anyone has encountered this issue before. I was hoping for some help.
And I attempted a search here and was returned with no results. I also looked through six pages under troubleshooting forum and did not find anything, either. I have a question about an interesting malfunction I encountered recently. First, my rifle: Sabre Defense 10.5" upper with Noveske KX3 Troy Drop-in rail Troy Rear BUIS Aimpoint CompM4s Surefire M962XM07 BCM Gunfighter Mod-4 F/A BCG Young MFG RRA lower with CMMG LPK BCM Receiver Ext. tube, H3 buffer, std. carbine spring Magpul ACS, MIAD, AFG, B.A.D. lever Trusty PMags (ones I've never had a malfunction out of). The most recent addition is the KX3. Prior to the KX3 I've put about 2,600 rounds through the rifle with zero malfunctions or hiccups using the std. A2 flash hider. I have shot with the KX3 since adding it, approximately 200 rds, with no errors. Now, the description of the mystery malfunction. While shooting at the range the bolt catch would catch randomly on the bolt carrier face, not the bolt face. I would shoot several rounds with no error, but then randomly (this happened 3x during the course of shooting) the carrier would lock back at the carrier face and not the bolt face. Now, the bolt continued to lock back upon empty. No failures to extract. The rifle continued to function normally with the exception for the random locking during battery. Which, of course, felt like a lock back on empty, but after inspection the magazine still had ammo and the bolt carrier was locked against the bolt catch. Depressing the bolt catch sent the carrier forward and the rifle would fire, several rounds even, before another random lock back. I inspected the BCG after shooting and observed a slight spur on the bottom of the carrier at the ledge on the face (where it was engaging the bolt catch.) This was not present before. Almost as if the metal in that area had been impacted in some way creating the spur/deformation. I am clueless as to the cause of this malfunction, but these are my thoughts on the issue: -The spur on the bottom of the bolt carrier was creating extra friction "pulling" the bolt catch upwards as the BCG cycled causing it to strike against the lugs, then catch on the carrier face before the BCG could completely cycle rearward. -The extra back pressure from the KX3 was causing some sort of BCG or bolt catch movement during battery somehow causing the carrier face to engage with the bolt catch during cycling. -A weak buffer spring (not sure why, but I figure with the rounds fired out of the rifle it's probably weakened by now). -The BCG. I compared the bolt carrier to a BCM carrier and observed that on the BCM there is an angled cut on the bottom of the carrier at the carrier face. It's almost as if the cut was designed specifically to prevent the bolt catch from interfacing successfully with the carrier face. I attempted to recreate the malfunction using a BCM BCG and was unsuccessful. Manually attempting to lock the bolt carrier back at the carrier face on the BCM was not possible due to the cut in the BCG. I could successfully recreate the malfunction on my current BCG. The mystery, friends, is what caused/is causing this type of malfunction? I believe a BCM BCG and maybe a stronger spring will fix it, but I'm confused as to the what/why/how of this malfunction. Like I said, I've put a lot of rounds through this rifle and never experienced a malfunction. My first thought is the KX3 is the cause, but how? Anyone have any ideas? Any information would be greatly appreciated. I haven't shot the rifle since. I'd like to figure out the cause or at least try to understand it since the BCM BCG will "solve" it. Respectfully, Night Shift. 
PS. Gas system inspected. Carrier key tight. No other obvious signs of trouble in the rifle or obstructions in the gas tube or carrier key. |
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Quoted:
Take off the BAD lever and see if still jams. This. Sounds like it may be a recoil induced malf attributed to the BAD. Or maybe just take it off and make sure its installed properly. Sounds similar to what happens when the slide release spring is above the locking block pin on a glock (although I know this is apples-oranges). |
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Thanks for the replies, guys. I don't think it's the BAD lever as I've never had a malfunction in the 1000 rds since I put it on, BUT I'm going to take it off anyways and see if that corrects the problem. It could be the changes in the gas pressures from KX3 are just bringing to light any problems with the lever. I like the idea of the lever for certain things, but I was taught how to shoot without one, so I can manage. Once I get it out to shoot, I'll post an update. BTW, I did order a red spring from SPRINCO and installed it as I figured my old one was probably wearing out. With the new spring and BCG I can't manually recreate the malfunction anymore. The carrier will not lock against the bolt catch due to that nifty little cut on the bottom of the carrier.
Still, gonna try with and without B.A.D. lever. FWIW, based on the BAD lever replies, I did some looking on the forums and found it's a 50/50 item. It functions without error for some and it's a bear for others. With my current set-up I could just be 50 it doesn't work for. I don't want to get rid of the KX3, my co-workers appreciate it, so I'll see about getting rid of the BAD lever. Thanks. |
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