[ARCHIVED THREAD] - Cycle issue in Colt M4

Posted: 3/15/2015 4:37:40 PM EDT

I've got a Colt 14.7in mid-length upper that will run wolf .223 just fine on my Colt 6400MT lower, but won't cycle .223 on the M4 marked lower. Both have a H Buffer.

I got the 14.7in upper and the M4 lower separately. The upper cycles fine on the other lower receiver, so my guess is a spring issue??

I'm new to AR's so any help would be appreciated.

thanks!

Posted: 3/15/2015 4:46:51 PM EDT

[#1]

Colt Midlength? Really?

Posted: 3/15/2015 4:50:33 PM EDT

[#2]

Colt 14.7in mid-length, do not think this exits as a OEM.

Posted: 3/15/2015 4:58:57 PM EDT

[#3]

ok, so my upper may not be factory, or maybe it's a carbine length and I'm just confused, I think the root of my question is about the lower --

what potentially would cause one lower not to cycle while the other cycles fine when using the same upper?

Posted: 3/15/2015 5:33:43 PM EDT

[#4]

Since both Colt lowers have H buffers, perhaps a comparison of spring lengths might reveal a difference.

eta: if your upper has a FSB, 7" handguard = carbine length, and 9" handguard = Midlength

Posted: 3/15/2015 8:06:22 PM EDT

[#5]

Thanks -- I'll check the springs.

Posted: 3/15/2015 8:51:25 PM EDT

[#6]

Looks like it's buffer weight. I'm going to order a standard carbine buffer and see how that impacts things.

Also, for what it's worth, it is indeed a carbine length gas system. Noob mistake. Thanks for setting me straight.

Posted: 3/17/2015 10:58:37 AM EDT

[#7]

How about describing why it won't feed, what is exactly happening?

NCH

[ARCHIVED THREAD] - Cycle issue in Colt M4

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[ARCHIVED THREAD] - Cycle issue in Colt M4

[ARCHIVED THREAD] - Cycle issue in Colt M4