View Full Version : Update SigSauer M400 jam.

September 29, 2012, 08:01 AM
Thanks for all for the input. Found out later that the DANGEROUS jam configuration during firing was reproducible with two different Sig polymer mags during successive manual chambering and eject down to about 5 or 6 rounds left. The PMAG tried later has no such problem. A Sig rep said that these polymer mags were discontinued a few years back. It appears everyone was right.... the mag. THANKS

October 11, 2012, 08:01 AM
Bought one of these M400 Enhanced.
It came with a Pmag and jams constantly with;

Pmag(s) of six Pmags
Metal Mags, 3 different kinds
Winchester 5.56, 223 Remiongton, 223 Wolf Steel Case, 223 PMC
Included Lube, Hoppe's (2 kinds) Oil, Tri-Flow, Moly Lube (dry lube)
HEAVY, MEDUIM, LIGHT, and Practically NO Lube.

How you like this? I'm SUPER impressed wig SIG. What a great gun, how badly can an AR platform FAIL, here is THE benchmark. Double loads, Fail to load, Fail to catch bolt on empty clip...

Sometimes, seemingly random, SEVERELY dented brass. 223, 5.56, all mags/lube combo's.

The only thing I can even guess is some kind of timing failure, a possible gas malfunction, or my hunch: a buffer spring failure of some kind.

This gun is at Sig now and I am expecting them to find nothing, fix nothing, clean it again, send it back and have the same problems after shooting 30 rds.

Do Not Buy One Of These Guns. There are sooooo many options out there, you don't even need to EVER even look at Sig AR's.

Lets's hear from the pro's now.

October 11, 2012, 09:41 AM
Pasting the same post on multiple threads is typically bad form.
Double loads,
Double feeds are usually due to a bad magazine, specifically the feed lips.
That sounds like a short stroke issue, due to gas leakage (improperly staked gas key or at gas block).

October 11, 2012, 09:44 AM
Dented brass is pretty standard for AR-15s. If you don't like dented brass, you won't even be happy with a BCM, LaRue, or Noveske.

As for your other failures, sure, there could be issues with gas leakage or magazine fit. But a guy complaining about a sample size of one (the world isn't overrun with M400 complaints) is hardly a "don't buy this hunk of junk."

December 22, 2012, 09:38 AM
So sorry about the form destructo. I'm forming an opinion here so thanks for the ed-e-cut lesson.

1. Dented brass is a non issue.
THANKS Technosavant!
That was an answer.

2. The gas was an issue as was determined by Sig when I sent the gun back and they replaced the o rings for the gas return.
It got better... But still jams occasionally.

3. The short stroke is an issue as well. The m400 Enhanced has a shorter stroke as a design. I believe this is the problem. Normally this would not happen with a standard travel bolt but I think having even one system out of perfect sync makes the cycle more susceptible to error when the stroke is shorter by design.

See this: http://www.youtube.com/watch?feature=player_embedded&v=mSbLragkC54

BTW I wanted the answers and I got at least two. Success.