The Sig Sauer M400 Tactical Carbine

By now everyone should be pretty well aware of my affinity for fine AR platform rifles.

I have fired many rounds through many different manufacturers. From Armalite to newcomers like Daniel Defense.

I have tried both piston and direct impingement gas systems.

Innovation in the firearms industry happens very fast. But unfortunately the AR platform has received very few innovative design changes in the last 50 years with exception of cosmetic systems.

Sig Sauer, I believe, has changed that with the M400. How? How is a DI gas based AR platform so innovative that it requires it's own thread on ATS?

The changes are not that big. But they are IMPORTANT. The small changes made to the M400 construction not only make the weapon extremely reliable, it also makes it inexpensive while maintaining the high quality construction known of Sig firearms.

Let us begin with the chamber. There is a pin in the chamber that keeps pressure on the extractor. The purpose of this is to mitigate the forces placed on the extractor and extractor pin by over-pressure events. But it also has the added benefit of reinforcing the extractor to effectively control failure to extract malfunctions that are common to AR based platforms. This means that firing steel cased ammo, which expands in the chamber due to heat and pressure, is no longer an issue.

The lower receiver also has a good tweak. It has a magazine release on the left side which allows the firing hand to stay on the trigger during magazine changes.

The "Wobble" or "play" between the upper and lower receivers is completely non-existent in the M400. This is a HUGE point of contention between the M400 and pretty much EVERY high end tactical rifle manufacturer. This is accomplished by a detent located at the rear takedown pin which creates upward pressure on the upper receiver and the take down pins are tight and there is no play at all.

It comes standard with a 1:7 twist rate ideal for heavier 5.56mm rounds.

The trigger is lighter than most stock triggers. 5 lbs. Most stock triggers are between 8 and 12 lbs which can be a real problem when accuracy is paramount. If you're anything like me, a 5lbs trigger is still not good enough..And yes, you guessed it, I replaced mine with a 1.5lbs trigger assembly from Jard.

This is really not your typical AR. For less than 1000 bucks you have a well constructed and accurate weapon by a known and respected manufacturer. There is more weapon here than I have found in many "high end" AR based weapons.

It is well worth the money.

3000 different rounds of varying quality and manufacture. 1500 steel case and Russian zinc and lacquer coated rounds, for a total of 4500 rounds and not ONE malfunction to report.

Great thread! Never heard of that gun until now, sounds like Sig might have a winner!

Also, this is a little off topic but now that you've mentioned it, what would you say for the DI vs piston debate? How much accuracy do you lose switching to a piston driven system? Are they more reliable jamming-wise? Also, what company would you prefer for something reliable but not the most expensive? Thanks!

reply to post by doesntmakesense


The DI vs Piston debate mostly comes down to preference and the cleanliness of your receiver.

There are some issues though.

The accuracy you get from DI is within millimeters at range. That only matters if you're sniping or competition shooting. But the effect is there. When it comes down to it, DI really is more accurate. There is also the reliability of the system. While DI forces you to clean your gun more, the DI system has no moving parts in the gas system itself. Pistons can sheer off or break due to overpressure but that doesn't happen very often. If you don't clean your piston system it will increase the chances of a sheering or a piston jam. Which means you'll have to replace it entirely and that is NOT cheap.

DI systems are cheaper. They are dirty compared to piston systems. But with the right equipment and discipline in maintenance your weapon should remain fully functional.

I do prefer DI systems. And would take it over a piston system any day.

At this point I would recommend a Sig M400. There's a couple of versions of it, but when it comes down to it they are essentially the same. It's Sig Sauer's only DI system, as they are known for producing piston systems. I payed $977 total for the rifle,background check, and taxes at Wal-Mart in Topeka, Kansas.

As for jamming in AR rifles the stock M400 has not jammed or malfunctioned on me once. That said I will be adding my list of AR steroids to it which can be found here. This list of products will increase the reliability of an AR platform.

The only exception I would make is the trigger group. I would rather use much lighter triggers these days and Jard tends to make the best ones.

I too own a Sig Sauer M400, got mine with the OD Green Magpul accessories for $1100 with a $100 rebate from Gander Mountain probably about 8 months ago.

When I went shopping for a AR15 I had done some research before hand but was still very much undecided until I reviewed each and every rifle to weigh in pros & cons. All the things you've mentioned like the 1:7 twist, chambered for both .223 & 5.56, the lack of gap and play between the upper & lower receiver all helped me decide on the M400 but there is something you didn't mention. Along with the other things mentioned I looked very carefully at the feed ramps of every AR15 in stock at both Academy & Gander Mountain because I know that the feed ramps can cause issues due to a high rise lip at the end of the feed ramp into the barrel. You want path into the barrel from the feed ramp to be as smooth flowing as possible.

I didn't find the M400 to have the best designed feed ramp but it was better than most of the other makes & models. I can't remember which brand had a better designed feed ramp but I found other flaws in that rifle that made me value it less than the M400.

I haven't shot a lot of steel case ammo maybe 150 or so rounds as I've tested probably 2 or 3 dozens of variants & grains of .223 & 5.56 ammo in both HPs & FMJs to ensure it fired everything I've fed it reliably. I imagine I have about 2k rounds through this rifle and have not had a single issue.

Now that I've become confident that it'll fire any properly chambered round I feed it, I mainly shoot Remington .223 55gr FMJs only cause it's easy to get bulk boxes of 200ct. Poor planning on my part while testing ammo I really didn't bother documenting accuracy to determine the best performer for 1:7 twist and I'd be open to suggestions on what others with 1:7 twist use.

Don't get me wrong you can get a good AR15 for less than the cost of M400 but if you're seeking the best specs for your money you can't go wrong purchasing a M400. I would highly recommend that rifle to anybody.

reply to post by Smurfwicked


The M400 has M4 feed ramps and they are very well aligned with the chamber.

I've had zero issues with them with my Magpul or factory aluminum mags.

No seating issues either.

Edit:

There is no lip between the feed ramps and the chamber. I have noticed in some of my other rifles that the ramps have a lip maybe .0015 of an inch. The M400 doesn't have that problem which is probably why it feeds smoothly.

Haven't had a double feed or a fail to feed either. I am truly impressed by the quality of this rifle. Which is why I felt compelled to write about it.

reply to post by projectvxn


very cool! I definitely appreciate the info, I think I'll leave piston systems for an AK and look for accuracy when it comes to AR's. Thinking my x-mas list this year will start with an "S" and end with a "ig Sauer M400"

What makes you think it'd have a jamming problem? The AR15, M4, M16 "reliability" or "jamming" issues are a myth. This only happens when A) you buy a crap brand such such as DPMS or Bushmaster and B) you don't know how to maintain your weapon.

You can go thousands upon thousands of rounds without cleaning a quality AR, you just need to make sure you use a quality lubrication (Froglube, Slip2000, etc) and are running it wet.

As for the Sig, it's a good rifle. It's not the best, and honestly at the price point of $950'ish you'd be much better off getting a weapon from one of the big 3 -- Colt, Daniel Defense, and Bravo Company (BCM).

Don't get me wrong, I do like Sig Sauer's but newer Sig Sauer weapons (anything past '05), whether handgun or rifle, are known to have quality control issues and they also use a lot of cheaper MIM parts.

That being said, the Sig M400 is probably one of their better and more reliable weapons at this point. The M400 is LEAGUES ahead of the Sig 556 and other previous offerings.

It's built to mil-spec, which is a good thing, obviously. But again, you can get one of the big three's for the same price as the Sig Sauer and they have a MUCH, much better reputation than the Sig in the hands of actual professionals and guys who actually go into harms way with these weapons.

The thing is, the highest quality guns do not cost any more than the lower quality guns unless you're getting one all decked out with a quad rail and other accessories. You just need to shop around and make an informed decision.


I find it rather funny that you claim no "play" between the receivers is a good thing. Generally speaking, it's better to have the receivers loose. The slight wobble effect is an intentional part of the design and has no effect on accuracy or otherwise. It's highly preferred for the ease of disassembly and cleaning.

At the end of the day, though, your Sig is still a quality weapon and the more "assault rifles" in the hands of responsible citizens, the better!!

reply to post by DriCo04


I've tested many weapons and have done a lot of extensive research.

The results, as far as I'm concerned, speak for themselves.


When it comes down to it poor maintenance discipline is the number one cause of failures. However there are many common failures to the AR platform. They are not 'myths'. Having dealt with military and civilian versions of these weapons I can tell you first hand that some weapons cant handle certain ammo, they overheat, they have overpressure malfunctions. It happens. Using a crap load of froglube ain't gonna mitigate those failures.

reply to post by projectvxn


I've handled the M400 and the SIG716, both of which are fine rifles, though I am partial to the 716, mainly because I like 7.62 NATO.

Both are a worthy addition to a inventory or a first weapon purchase.

I know that this is a SIG thread, but have you handled a Kel-Tec RFB?

I have not myself, I like the Bullpup design and all the reviews seem to be ok. Some have reported extraction problems but it does come with a lifetime warrenty and those problems are usually fixed according to the reviews.

But it does seem to me to be a bit plasticy (is that a word?).

Tentatively, I want one, but plunking down $1800+ requires a bit more research.

Your thoughts?

reply to post by TDawgRex


When I was living in NV I had a friend who bought one. The RFB's redeeming quality is that ot is a 308 cal weapon. Its a lot of flash for not much gun. He had a few jams and FTE malfunctions in the course of about 500 rounds. That is a combat load. I attribute many of these malfunctions to its extraction system which has more moving parts than I would like in a rifle.

The Bear Elite is the better I think.It has an ambidextrous forward charging handle and innovative ejection port cover that springs shut after each round.

www.adcorindustries.com...

reply to post by NLDelta9


It's also a 1600 dollar piece of equipment.

The whole point of this post, among discussing the attributes of the M400, was to present an affordable weapon. Affordability, reliability and durability are key.

Originally posted by projectvxn
reply to post by NLDelta9

 

It's also a 1600 dollar piece of equipment.

The whole point of this post, among discussing the attributes of the M400, was to present an affordable weapon. Affordability, reliability and durability are key.

I was just showing that it has the most innovation of them all.

reply to post by NLDelta9


An ambidextrous charging handle and a spring loaded ejection port cover is great.

But I have seen some seriously provocative reviews on why this weapon and it's manufacturer should be treated with skepticism.

This link has an in depth review of the weapon

Originally posted by projectvxn
reply to post by NLDelta9

 

An ambidextrous charging handle and a spring loaded ejection port cover is great.

But I have seen some seriously provocative reviews on why this weapon and it's manufacturer should be treated with skepticism.

This link has an in depth review of the weapon

hmm

I do know it passed on to the nest phase for the test of our nest military rifle replacement

reply to post by NLDelta9


A lot of weapons did. Including some of my favorites.

But the system has problems at the production level and those problems need to be worked out by the manufacturer.

Originally posted by projectvxn
reply to post by NLDelta9

 

An ambidextrous charging handle and a spring loaded ejection port cover is great.

But I have seen some seriously provocative reviews on why this weapon and it's manufacturer should be treated with skepticism.

This link has an in depth review of the weapon

Somebody likes ADCOR? Wow!

I had a buddy of mine try to sell me his BEAR....some buddy.

We took it out to the range and proceeded to have multiple problems. Ejection and feeding...probably due to the rounds which were British NATO. But I didn't have those problems with my old Bushmaster using the same rounds.

I offered him $500.00 as it would take quite a bit of tweaking the weapon to make it reliable. That costs money. Of course he refused, but now it is his problem. Not mine.

reply to post by TDawgRex


People have a habit of jumping onto the "next best thing". Just because it costs a lot of money doesn't mean the design and manufacturing techniques are worth their salt. From that particular review the OP complained about the lack of concern on part of the manufacturer for customer satisfaction and refused to address the problem. So not only are they running a machining process with documented deficiencies, they aren't doing anything about until their first line production run ends.

That could take years. So they are trying to sell the military and the public a sub-par weapon based on their word, and their word does not stand up to the real world experience of shooters.

Originally posted by projectvxn
reply to post by NLDelta9

 

A lot of weapons did. Including some of my favorites.

But the system has problems at the production level and those problems need to be worked out by the manufacturer.

Every gun has its own problems and that is nothing so bad given it STILL has the regular charging handle as a backup