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9/22/2017 12:11:25 AM
Posted: 8/26/2005 10:16:18 PM EDT
One of my carbines (~5,000 rounds through) has been short cycling lately when using the MGI RR buffer, presumably due to the heavier weight and/or Wolffe +10% spring. Pretty obvious when the bolt can't even clear the mag follower on the last round to lock open. I shoot only LC XM-193, so it sure ain't under-powered ammo.

The rifle runs 100% flawlessly with the stock buffer and Wolffe +10%. I don't believe there is significant leakage under the gas block, as it is not loose and there is only a tiny bit of residue on the barrel. Which makes me believe maybe the carrier key and gas tube aren't fitting as snug anymore, making it more difficult to move the heavier buffer and stronger buffer spring.

This is why I don't alter my other carbine that I keep for SHTF, but my range gun I don't mind experimenting with.

Any thoughts?
Link Posted: 8/26/2005 10:27:10 PM EDT
[Last Edit: 8/26/2005 10:28:26 PM EDT by eklikwhoa]
check your gas rings
carrier key
gas tube

try swapping out the +10 spring with a regulare one and see if it will work with the mgi buffer.

just noticed but your a team member so you should search it or even look in the troubleshooting forum

Link Posted: 8/26/2005 11:24:11 PM EDT
Yep, ran a search and nothing comes up within 3 months. I'm having one of the mods move this thread to troubleshooting. Didn't find anything there regarding buffer weight and short stroking either. Just mostly talk about loose carrier keys and gas rings.

We're thinking the same thing. I am gonna try the standard buffer spring with the MGI. Thanks.
Link Posted: 8/26/2005 11:30:44 PM EDT
checked the tacked threads.

tweak has written out a long list of troubleshooting stuff.

think its the thread titled " read this before posting" or something like that
Link Posted: 8/27/2005 6:29:46 AM EDT
FWIW, I'm running the MGI buffer with a standard CAR spring and have no problems whatsoever. I also use LC XM193 ammo exclusively.
Link Posted: 8/27/2005 6:59:24 AM EDT
Tubb offers weights for bolts. In the instruction manaul there is some interesting information regarding the buffer length and the spacing required between the bolt and the bolt stop.

The following is some information I also found on the web (http://yarchive.net/gun/rifle/ar15.html):

Short cycling:
If rounds are sometimes not chambered it is due to the bolt not coming back all the way. This also causes jams since the case may be ejected. The problem is either something is binding or the gas system is leaking or plugged. The gas tubes are supposed to be self-cleaning and seldom plug up unless perhaps you are using wimpy loads that produce a lot of carbon.
It is important to know your gas system and where the possible leakage points are: near the front sight, at the carrier key, at the gas rings, and where the bolt extends through the carrier by the firing pin. There will typically be some leakage at the front sight as seen by some black deposits, but if the tube fits tight it is probably OK. The bolt post to carrier hole clearance is typically very tight - less than 0.5 mil and I have not had a problem there. If the bolt does not fall out of the carrier when you invert it, the gas rings are probably OK. Gas rings will rotate when you fire the gun and are not like car rings that seal into position. Sometimes people experience problems when all the ring gaps line up, but I have not had that problem. It is a good idea to separate the gaps each time you install the bolt anyway. The biggest source of gas leak trouble I have found is the carrier key to gas tube contact.
Carrier key:
There are a lot of bad carrier keys out there.
This is the one item that should be looked at very carefully. Not only are they a source of potential bolt/carrier binding, but also they can cause excessive gas leakage if the fit to the gas tube is bad.
Gas tubes have a little ridge on them where they fit into the carrier key that determines the degree of gas leak sealing.
All the new gas tubes I have seen have a quite uniform diameter ridge and have not been a problem except when they get worn down.
The ridge can wear down a couple mils, which then can cause excessive leakage. I have had that happen after 1000 rounds or so, but the quality of your carrier key can definitely affect this.
My first carrier key caused binding as described above. The next one had a bit of a ridge inside increasing the inside diameter after a point. This caused the worn gas tube and excessive gas leak problem. The next key I selected to make sure it was uniform, symmetric, and had a nice smooth inside surface that made a good fit
to the gas tube, and this one has lasted a long time and is still giving good service. Even supposedly GI issue carrier keys I have seen can have fairly rough inside surfaces, so pick them carefully.
Link Posted: 8/28/2005 6:12:56 PM EDT

Originally Posted By M4Madness:
FWIW, I'm running the MGI buffer with a standard CAR spring and have no problems whatsoever. I also use LC XM193 ammo exclusively.

Problem solved. Downloaded to the regular CAR spring and things ran perfectly today. I guess a heavy buffer + heavy spring is a little too much resistance.
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