04-21-2008, 13:01
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#1
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Quiet Professional
Join Date: Jul 2006
Location: Germany
Posts: 400
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CAR-15 Problems
I'm an SF Weapons man, but need a second opinion before I proceed further...
I built a CAR-15 from an NFA lower. M-4 flattop, quad rail, 11.5" barrel, pneumatic buffer.
The weapon function flawlessly in semi-auto, but when I flip it to full-auto, I get 3-4 rounds then a light primer strike resulting in a failure to fire. This only happens on full auto. Never encountered this type of problem before...
I'm thinking weak hammer spring or firing pin. Any other ideas?
226
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ODA 226 is offline
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04-21-2008, 13:54
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#2
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Quiet Professional
Join Date: Apr 2008
Location: 18 yrs upstate NY, 30 yrs South Florida, 20 yrs Conch Republic, now chasing G-Kids in NOVA & UK
Posts: 11,901
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Quote:
Originally Posted by ODA 226
CAR-15 from an NFA lower. M-4 flattop, quad rail, 11.5" barrel, pneumatic buffer.
I'm thinking weak hammer spring or firing pin. Any other ideas?
226
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If that doesn't fix the problem,,
1)swap out the buffer
2)check alignment of upper & lower & buffer
3)lap the bolt/carrier/upper for a couple hundred rounds
Also if the gas port position or barrel length was altered, the gas port size may need to be altered to account for the timing pulse..
ref:
http://www.armalite.no/downloads/Tec...,%20030824.pdf
Good Luck..
Jim
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JJ_BPK is offline
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04-21-2008, 14:13
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#3
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Quiet Professional
Join Date: Jan 2004
Location: Free Pineland
Posts: 24,804
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Sounds like the weapon is out of time.
Before I did anything else, I would pop in a 2xH or 3xH buffer and see if that fixed it.
Then consider the other dynamics of the timing.
Best of luck!
TR
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The Reaper is offline
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04-22-2008, 09:00
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#4
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Quiet Professional
Join Date: Jul 2006
Location: Germany
Posts: 400
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Roger that fellas. When I return from Germany, I'll go through your suggestions step-by-step. Thanks!
226
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ODA 226 is offline
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04-22-2008, 16:07
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#5
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Guerrilla Chief
Join Date: Feb 2008
Location: VA
Posts: 859
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Quote:
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I'm thinking weak hammer spring or firing pin. Any other ideas?
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Without being able to see the rifle first hand, or knowing the manufacturer(s) of each part, It could be the gas tube, or like you stated, the firing pin. Is the hammer spring seated correctly? Brownell's sells a pigtail tube that may correct the deficiency. Here is the site with a description of what it does.
http://www.brownells.com/aspx/NS/sto...GTAIL+GAS+TUBE Hope it provides an option for you.
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BryanK is offline
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04-22-2008, 16:14
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#6
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Quiet Professional
Join Date: Jan 2004
Location: DFW Texas Area
Posts: 4,741
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Could it be weak Sear and/or Disconnect Spring(s) allowing the hammer to follow the bolt occasionally??
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Ambush Master is offline
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10-22-2008, 11:27
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#7
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Quiet Professional
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Final consensous...H-2 or H-3 Buffer?
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ODA 226 is offline
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10-22-2008, 11:31
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#8
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Quiet Professional
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Buffers are cheap. NFA lowers are not.
I would get both buffers, and start with the H2, though I suspect that it will run better with the H3.
Best of luck.
TR
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"It is not the critic who counts; not the man who points out how the strong man stumbles, or where the doer of deeds could have done them better. The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood; who strives valiantly; who errs, who comes short again and again, because there is no effort without error and shortcoming; but who does actually strive to do the deeds; who knows great enthusiasms, the great devotions; who spends himself in a worthy cause; who at the best knows in the end the triumph of high achievement, and who at the worst, if he fails, at least fails while daring greatly, so that his place shall never be with those cold and timid souls who neither know victory nor defeat." - President Theodore Roosevelt, 1910
De Oppresso Liber 01/20/2025
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The Reaper is offline
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10-22-2008, 13:23
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#9
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Quiet Professional
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Quote:
Originally Posted by ODA 226
Final consensous...H-2 or H-3 Buffer?
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We had buffer problems with ours in SVN, but it has been so damn long I cannot remember how the wpns folks resolved the problem. Seems to me that they boosted the spring strength somehow, but I cannot be sure. But then I am not sure what I had, or even if I had, for breakfast this morning 
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Jack Moroney (RIP) is offline
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10-22-2008, 13:26
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#10
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Quiet Professional
Join Date: Jan 2004
Location: Central TX
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The H2 will be by far cheaper and easier to come by. Start with that. Also, when was the last time you changed the action/buffer spring?
Good times,
Blake
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Air.177 is offline
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10-22-2008, 13:33
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#11
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Quiet Professional
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You have a timing issue. TR's suggestion for the 2xH buffer is a good place to start. You can also check out bolt carrier weights. There are a number of other drop-in aftermarket solutions, all of them intended to add weight/inertia to the reciprocating parts and delay unlocking. Gas system tweaks are more involved. I've used the pigtail; they work but will interfere with some handguards. My personal solution is a mid-length gas system (which doesn't help you with an SBR  ). Get the Brownells AR specialty catalog for a convenient reference. HTH
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Peregrino is offline
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10-22-2008, 15:39
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#12
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Quiet Professional
Join Date: Jan 2004
Location: Central TX
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Toying with Gas systems/buffer weight/action spring strengths can quickly lead down the path to madness.
I would highly recommend going to an H2 Buffer and a good standard weight buffer spring first, and going from there.
My .02
Good times,
Blake
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Air.177 is offline
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10-23-2008, 04:22
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#13
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Quiet Professional
Join Date: Jul 2006
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I'll start with the H2 and let you guys know the results. Thanks!
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ODA 226 is offline
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10-23-2008, 11:32
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#14
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Asset
Join Date: Apr 2004
Location: Phoenix, Arizona
Posts: 48
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ODA 226
I am not a LEO or a MIL, and have very limited experience with automatic weapons. So take this information for what it is worth.
I purchased a NFA Bushmaster lower more than 20 years ago. It ran for a time, and then developed the identical problem you describe – 3 or 4 rounds fired full auto and then a light primer strike on the 4th or 5th round. I tried everything, and was never able to fix it. I finally just put the rifle away. It’s now the oldest safe queen I own.
I went shooting with Team Sergeant last year. While shooting, I asked TS if he had any suggestions to the problem. He gave me a standard buffer and spring from a rifle he changed to a collapsible stock, suggested I clean the rifle, lubricate it well and shoot it. He stressed that cleaning and lubricating are important.
His ideas worked. I ran 3 mags through the rifle the first time, and about 10 more since. Ammunition is too expensive to shoot more, and tell the truth, shooting it semi is more enjoyable. When I was single, it did have its appeal though.
I don’t think changing the standard buffer or spring had much to do with the remedy, as I’d changed them before. I do think the cleaning and lubricating the heck out of the it had everything to do with it. I really used a lot of Slip 2000.
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WRMETTLER is offline
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10-23-2008, 16:31
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#15
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Area Commander
Join Date: Feb 2004
Location: Phoenix, AZ
Posts: 1,691
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If all else fails you can contact Ken or Tina Elmore at Specialized Armament Warehouse specializedarmament.com/ (add the www.)
ken@specializedarmament.com
or
(480) 940-7397
Ken and Tina are extremely knowledgeable and very .Mil friendly.
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