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Posted: 5/3/2001 5:50:33 PM EST
the troubleshooting forum?  I got a doozy and I guess there is no other place to put it.

OK, I have some other posts about this sort of, but this is the main one after two days of experimentation.

Problem - AR carbine that goes into burst mode.  Only three times but that is enough.

Equipment -
Rifle 1 (the one with burst problem) is a frankengun.  Wilson 16" bull barrel, freefloat handguards. FN upper flattop, ASA bolt, bushy lower built with bushy parts, RRA NM trigger, buttstock & plunger/spring from SP1.

Rifle 2 is a spacegun 20" douglas barrel, freefloat, flattop, ASA lower and buttstock, Jewell trigger, NM bolt.

The problem started when I was breaking in Rifle 1.  I was shooting Federal Eagle ammo.  The rifle had two occasions where it burst about 3-4 rounds.  While bursting I could feel the trigger pulse with each shot fired.  I also fired Q3131A ammo and never had a burst.

Returned to the range a second time, and again, with Federal Eagle ammo it burst once in about 20 rounds.  Never again with Q3131A.

Soooo, I thought I would experiment.  I swapped lowers with Rifle 2.  Expecting that the problem was related to the trigger I tried shooting the Spacegun upper on the frankengun lower.  Except it would not cycle.  Short stroking.  I can only assume that the different tension in the buffer springs prevented a full cycle.  However, the Spacegun (which shot fine once reassembled) only eats Federal Match ammo.  So I don't know if it would have been a valid test.

At this point I was out of Federal Eagle ammo, and never had a burst again.

The conclusion I have (???) is that the carbine has a powerful buffer spring (can't cycle in spacegun) and that it is slamming the bolt back hard - into fairly soft Federal primers and the firing pin is actually extending when it closes to battery.

If this seems a valid conclusion, does anyone have any suggestions for fixing this?  I don't want to worry about which ammo I use in this gun so would prefer an answer other than "don't use Federal Eagle".

Thanks all.

James
 
Link Posted: 5/3/2001 5:58:23 PM EST
[#1]
Link Posted: 5/3/2001 6:58:38 PM EST
[#2]
That would'nt happen to be the gun that got thrown across the counter would it?[:)]
Link Posted: 5/3/2001 8:07:04 PM EST
[#3]
Garandshooter,

Thanks for the tips.  I am taking it to my gunsmith for a checkup.

CIB,

No.  Well, parts of it are.  Maybe the parts have a long memory???  :)

James
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