WHAT'S SHIPPING: Detailed Look at the Sigarms M400

AR/M4 AR Technical Discussion
1

The Sigarms M400 AR-type is becoming increasingly common in stores and on the ranges. Sigarms has also been able to secure a number of LE customers either in other product, or standardizing on a single p/n. Current production M400s incorporate several desirable (“chart friendly”) criteria in production/assembly, as well as some proprietary features.

Given those developments, I obtained a sample for use and abuse. The following information is posted to add to the knowledge base and serve as a reference for future inquiries. I’ll add to the info for the duration of the project and as pertinent.

Manufacturer: Sigarms
Model: M400, p/n RM400-16B-C
Serial Number: 38B000###
Production Date: 06/2012

On the web: http://www.sigsauer.com/CatalogProductDetails/m400.aspx

Unboxing

External shipping container, internal container and wrap. Contains carbine, 30rd NHMTG magazine w/ Magpul follower, users manual, trigger lock, sample tube of lube, misc literature.

Receiver markings

Moving from the muzzle back.

A2 type flash hider, “5.56 NATO” marking on barrel near muzzle, F marked FSB, GI sling swivel with rivet under FSB, bayonet lug, 4 position square FSP, GI type dual heat shield hand guards. Barrel is ~.740 at muzzle, steps down to ~.650, steps up to ~.750 at FSB, steps down to .710 under hand guards, steps up to ~.980 at barrel nut. Chrome bore and chamber. M4 type feedramps cut pre-anodizing. Chamber passes Ned’s 5.56 chamber gauge.

Bolt Carrier Group… Semi-auto bolt carrier, short tang, shrouded firing pin. Key properly staked. Bolt unmarked. Extractor spring is five coil with black insert and o-ring. Standard GI charging handle.

Upper receiver… Detachable carry handle, laser etched rail addressing (T marks), case deflector, forward assist.

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Lower receiver… A2-type grip retained by hex screw, aluminum trigger guard, safe/semi markings L/R sides, nub on selector on R side, too small for positive ID with gloves. Selector is not ambi or reversible. Machined vertical slots on front of mag well for grip. Integrally machined sockets for push button sling mounts, standard semi-auto FCG. Ambidextrous mag release. L side release is in close enough proximity to bottom of bolt lock that it can prevent activation with gloved fingers. Lower receiver has a definite billet feel overall.

Worth it’s own mention… The lower receiver incorporates a feature which allows the fit of the upper and lower to be adjusted so that there is no play. With the pistol grip removed, the screw is turned into a dedicated slot in the lower receiver until the spring loaded bearing provides enough resistance to the upper to prevent play. The screw was installed and removed easily. There is no stop to prevent over insertion, and over insertion can prevent closure. When removed, the screw contained no thread locking compound. Removal of the screw leaves the threaded hole empty, and a normal amount of play between the upper and lower receivers. There is no negative affect to leaving the screw out.

If this carbine is used for life-support, or otherwise receives hard use, removal of that adjustment screw seems prudent. At a minimum, it should be removed and reinstalled with a thread locking compound.

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Stock group… Receiver extension is mil dimension, six position adjustable. RE incorporates five holes into the interior of the RE, presumably as drain holes. Four are in the adjustment stops and shielded by the stock. The fifth is at the end of the RE. Receiver extension nut installation is well staked at two points. Stock body does not collapsible to flush with receiver extension nut, leaving a gap of ~.650. This is approximately one position out on another GI stock. Stock body has a decent weight and heft. Unmarked carbine weight buffer, GI

M400 top, LE6920 bottom

Several desirable procedures are incorporated and reportedly standard. The inclusion of ambidextrous sling sockets and magazine releases is helpful to some, but the lack of an ambidextrous or reversible selector is a strange omission.

Shooting to follow.

4

still a sig… after their track record the last few years, wary at the very least.

5

There are things I like, and things I don’t. I will not recommend one to people.

6

These rifles are high quality. Mine was a tack driver at 200 yards with Sig’s cheap red dot.

I bough one right when they were introduced and it ran fantastic. I sold it to fund a midlength build. If Sig made a midlength carbine, I would have just bought that instead and been quite content with the rifle overall.

Its a lot of rifle for 900 bucks, carbine buffer, AR bolt carrier group and all. The rifles are not over gassed either. They have in spec gas ports.

7

Kinda my thoughts, not to mention the things on the gun designed for the uneducated like the thing to reduce wobble…

Now the things I do like about i are the enlarged drain hole in the RE and the extractor support in the barrel extension but thats about the only things I like. I like them because they help reduce the chance of KB from water and reduces KB damage.

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Skintop1911, got any accuracy/shooting tests planned?

Great info. If the evidence about Sig changes, my opinion will change.

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It does look better than I expected… FWIW… Ron

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A search on arfcom showed great experience with these. Theyre available at walmart for around $900. my colleague put one on layaway when they were out of the 6920

11

ARFCOM generally boils down to I put 200 rounds trough y rifle and it worked amazing thus its amazine.

There was a recent post of somone claiming his AA system was the beš system ever after putting 70 rounds through it, the following comments agreed.:blink:

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Did you happen to measure it? I’m going to pop the FSB off this one and measure, but I was hoping others out there might have that data to compare to as well.

Gimmick to sell guns, as you know. I was glad to see that it can be left out.

Yeah, test design is underway. Whether it’s specific or more casual/progressive is TBD.

13

Skin,

Nice to see that level of build quality. Pardon me if I missed it, but what did it retail for in that configuration?

Ken

14

Conversations with the Sig folks indicate that some understand that there are differences, and what it takes to be counted among those who are worthy. It’s a start. Common response from those seeing this gun is that they expected less.

Retail seems to be running $950-$1050 pretty consistently in competitive vendors.

15

Good to hear. Although not a fan of the SIGs I see at work, I like the one I own and would like to see this company “come back”.

16

Are the barrel, bolt, bolt carrier, and small parts built of the correct material?

17

Skin- correct me if I’m wrong, my friend… I assume the barrel steel is 4140 and the bolt might not be c158. Is there any confirmation? If my assumptions are true, I’d place this in the $800-$850 range.

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Stay tuned on that stuff.

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I’ve been looking at the Sig ARs…i like how the lower has ambi mag release, ambi sling mounts from factory…like the detent on the rear tang…i’ve handle one…never shot one…but they will nice and tight

20

Sig stated CMV for the barrel and that the bolt is HPT/MPI, but I’m not sure about material.