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Posted: 7/13/2005 10:44:57 PM EDT
[Last Edit: 7/13/2005 10:45:16 PM EDT by asu174]
Took my M4 out today and I experienced 3 problems
1. Light primer hits (failing to discharge, light dimple in primer, but ammo checked out okay in another rifle).
2. Random 2 round burst firing
3. Feeding issues

The problem is that I have done a few recent mods to the gun and I don't know which might have caused the problem. Here are the newest mods on the gun:
- RRA 2 stage trigger- (but it really just feels like a hair trigger- I can't feel the 1st stage at all)
- Gemtech suppressor (I was having accuracy issues with this the other day- could a suppressor cause a gas issue?)
- New bolt carrier- (I upgraded to a chrome one)

Any ideas?
Link Posted: 7/13/2005 11:05:22 PM EDT
[Last Edit: 7/13/2005 11:05:58 PM EDT by Shadowblade]
Link Posted: 7/13/2005 11:25:16 PM EDT

Originally Posted By Shadowblade:
Are you sure the light primer strikes are actually strikes? Do you hear the hammer fall?

I ask because just chambering a round will leave that small dimple on the primer because of the floating firing pin.

The hammer could be following the carrier and then when the round chambers it can either A) fire a round, or B) do nothing. This is the simplest answer, solving both problems with one faulty part ( new trigger).

If you do hear the hammer fall when you get the no bang... You might be out of battery, probably caused by the new carrier.


Suppressors do cause gas issues, usually causing more gas and carbon to blow back into the reciever than normal. I suspect they actually lessen the chance of short stroking, but I'm not sure on that one.


What kind of feeding issues?



Spent cartridge is partially extracting, next round is jamming into it.
Link Posted: 7/14/2005 12:16:31 AM EDT
RRA trigger,

The disconnector is binding up in the trigger, and the light primer strikes are actually the hammer following the carrier back down closed. The same causes the bursts, but the disco is holding the hammer until the bolt slams closed then the hammer is freed.

Pull the trigger and make sure that the disco is moving freely in the trigger, and not binding on the pin. This binding is both the no second stage problem, and the doubling/fail to fire problem.



Dropped case,

The can is causing the rifle to over cycle (read gas port too large with can, and the bolt is opening too fast with the spent case still highly pressure bound to the chamber wall). Options are either drop in a #60 O ring around the extractor spring to add tension to the extractor to assist it in dealing with the greater surface tension of pulling the more pressure bound case, or install an adjustable gas tube to allow a smaller port setting for when the can is used (read get the action back in tune with the added back pressure when the can is used).

Adjustable gas tubes go for around $60, O-ring goes for a dime.
Link Posted: 7/14/2005 2:10:33 AM EDT
Link Posted: 7/14/2005 6:29:03 AM EDT

Originally Posted By Tweak:
what buffer are you using?



Whichever one comes with the 6 pos collapsible stock. The short one.

Dano, thanks for the info!
Link Posted: 7/15/2005 1:48:17 AM EDT
Link Posted: 7/16/2005 4:55:33 PM EDT

Took my M4 out today and I experienced 3 problems
1. Light primer hits (failing to discharge, light dimple in primer, but ammo checked out okay in another rifle).
2. Random 2 round burst firing
3. Feeding issues



A lot of times hammer springs get put in backwards, causing this. #2 could be disco spring, disco, trigger or a combo.
Link Posted: 7/16/2005 7:33:22 PM EDT
Looks like the 2 stage trigger has a bad disconnector. I had it replaced and it fired fine. Now I just need to test it with the suppressor.
Link Posted: 8/13/2005 7:47:37 PM EDT
tweak...what is an H buffer

also what part on the RRA trigger is the disconnector>? Did they replace it you did you have to get a whole new trigger?
Link Posted: 8/13/2005 8:28:06 PM EDT
wouldnt adding a stronger buffer spring help in this case?
Link Posted: 8/15/2005 4:04:26 AM EDT
Link Posted: 8/15/2005 4:43:31 AM EDT
Link Posted: 8/15/2005 5:05:29 AM EDT
Did you try different magazines?
Link Posted: 8/15/2005 6:06:27 AM EDT
Link Posted: 8/26/2005 7:41:34 PM EDT
I forgot all about this thread. TheRicker hit the nail on the head. The 2 stage trigger was defective. Bad disconnector or something. I put a new 2 stage trigger in and now all is better.

I still have occassional issues on my 10.5" upper when using the suppressor, but I think I need to play with the gas tube or buffer.
Link Posted: 8/26/2005 10:55:37 PM EDT

Originally Posted By asu174:
I still have occassional issues on my 10.5" upper when using the suppressor, but I think I need to play with the gas tube or buffer.



Both!!!!
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