Sig M400E

[Aggressive Perfector]

Well I finally got it out and played with it. So I guess I'll post what I think of it.
The rifle (also posted in another thread):

$1223 out the door.
Barrel- Chrome lined, 16", 1/7 right hand twist. "M4" profile minus grenade launcher cut.
Accuracy: After bore sighting it I set a 12" target up at roughly 100 yards and shot 5 rounds prone unsupported using my irons. So human factor plays a part. Ammo used was Danish made 62 grain 5.56 NATO M855 Ball. 3 shots of the 5 were in a group about the size of a JFK half dollar coin, with 2 "flyers" (or shooter error) opening the total size of the group to about 2 3/4"- 3". (will post target pic)
My thoughts on it:
The gas key is very well staked, for one (despite poor representation from a terrible camera man). The metal does overlap the screws, and my attempts to break it loose with a wrench were to no avail. If I placed it in a vise and used a cheater pipe I might succeed, but I have no intention to remove it.


The bolt carrier is also Chrome lined (internally). I don't think that was particularly necessary, but what the hell, if extends the life of my bolt carrier I ain't bitchin'.


Ambidextrous mag release? Yes. This makes shooting off hand so much more pleasant.


Now for the downside:
The take down pins are a royal pain in the ass to budge! This may be due to the holes being machined to be smaller than others for a tighter fit, or maybe the springs on the pin detents have a little too much length, causing more tension (should be an easy fix). Or maybe, just maybe... It's this damn tensioning device they put in it. Sig put this device in the lower to better lock the upper and lower together tightly. They claim it's to improve accuracy, but I do not see how this affects accuracy. And while I admit, the complete absence of wobble between the upper and lower receiver feels nice, it's never been a problem. I will be looking into removing this and see if that will help ease the break down of this rifle.


The Magpul MOE furniture is very nice, and comfortable. I was going to remove the hand guards and replace them with a quad rail... But to my delight Magpul makes rails to install on the MOE hand guard. I'll just go that route. But the pistol grip... I find it a bit too thick. With a standard A2 pg I can still flip the safety on and off with my trigger finger at the ready position. But with the MOE pg I have to maneuver my hand a little to reach the safety selector, so I do think I will be exchanging that for an A2 pg.

I'll give this thing a 4/5.

[ltorlo64]

Looks like a nice rifle. Thanks for the information.

[imanaknut]

Looks and sounds like a nice rifle, enjoy!

[Pat Garrett]

Congrats. Enjoy it!

[Schuetzenman]

Yes it looks to be a nice AR15 variant. Chrome lining is SOP, any good bolt carrier should be chromed inside to help with the carbon sticking. I like what I'm seeing in your photos.

On fit of upper to lower, the tighter the better. I have taken 4 MOA AR-15 rifles to sub 2 MOA simply by bedding the upper to the lower. Match shooters build AR rifles with a set screw behind the grip that screws the upper to the lower at the rear. The only way to take the weapon apart is to remove the grip first. So tight push pins are not a problem. They may loosen a bit in time, but for me I'd be extremely pleased to have such a tight fitting upper to lower.

On remove the tensioning device ... really? Who do you think is smarter the Sig Saur design Engineers or you? Sorry to put it so bluntly but I need to get your attention so you don't fuck up your brand new rifle. I hate seeing people trash weapons because they have an ....... "idea". To loosen an AR upper to lower fit is to degrade the accuracy. I proved that over and over again since 1995 when I bedded my first set of AR receivers. Lastly I didn't invent the concept, the Army Marksmanship Unit did. I learned about it from John Feamster author of Black Magic: The Ultra Accurate AR-15. I never bought his book but I tracked him down and had about a 2 hour phone conversation with him. Very nice guy if you can say that based on one very long phone call. I took notes.

[AK-J]

Don't ditch the MOE pistol grip. I take it from your post that you are left handed. Just get a ambi safety selector, and that will fix your reaching it problem.

And don't mess with what works, as Schuetzenman said.

[Aggressive Perfector]

^No, I'm right handed, but my hands are small. With an A2 PG I can reach the safety selector with my thumb without altering my grip on the weapon. Due to the additional girth of the Magpul PG this is no longer possible.

On fit of upper to lower, the tighter the better. I have taken 4 MOA AR-15 rifles to sub 2 MOA simply by bedding the upper to the lower. Match shooters build AR rifles with a set screw behind the grip that screws the upper to the lower at the rear. The only way to take the weapon apart is to remove the grip first. So tight push pins are not a problem. They may loosen a bit in time, but for me I'd be extremely pleased to have such a tight fitting upper to lower.

I will attempt to break them in, and if I can't manage within a few months, maybe take a miniscule bit of length off the springs holding the detents in the pins.

On remove the tensioning device ... really? Who do you think is smarter the Sig Saur design Engineers or you? Sorry to put it so bluntly but I need to get your attention so you don't fuck up your brand new rifle. I hate seeing people trash weapons because they have an ....... "idea". To loosen an AR upper to lower fit is to degrade the accuracy.

This would be my last ditch effort, and even then only after I've researched how it goes together and what could go wrong. My name isn't bubba, and trashing rifles isn't within my nature. If it's within my skill level, requires no permanent alteration to the rifle, and my first two plans don't work, I may attempt it. I just don't see any reason why I should have to use a punch to drive out my td pins for a simple field stripping. I'm used to using a bullet to start them until I can get a grip on them with my fingers. But driving them most of the way out with a punch I find ridiculous. If/ when I have to strip my weapon quickly, these pins really hinder me. If my first two options fail and this proves beyond my capability I will leave it be and suck it up.

On accuracy: Unless there is a substantial amount of slop between the upper and lower, I don't think this will make a large difference. My DPMS wasn't this tight (though I wouldn't call the quality exactly on par with Sig), and it still shot every bit as good of groups as the Sig does. I'm not saying you're wrong, there may be other factors at play I'm not seeing. But unless the degree of slop is significant I doubt this will cause a very noticeable difference in accuracy. If I do wind up going this route and find that accuracy suffers, I will gladly put the tensioning device back in place, make a Youtube account bitch slap myself and apologize for doubting you in the least and post it in a thread in GD for all to see.

[AK-J]

^No, I'm right handed, but my hands are small. With an A2 PG I can reach the safety selector with my thumb without altering my grip on the weapon. Due to the additional girth of the Magpul PG this is no longer possible.

Dang, your hands must be really small! Another option is that Magpul does make the MIAD grip. Using the slimmest back strap gives it a similar size as the A2 pistol grip. Just giving you a better option. PM me if you need an A2 grip, I've several of those things lying around collecting dust. I would be happy to send you one at no charge.

[Aggressive Perfector]

MIAD does look like a good design, I'm interested. For now though, I have simply swapped grips with my DPMS AR (now designated as a range toy). I do thank you for your offer though.

[Schuetzenman]

On accuracy: Unless there is a substantial amount of slop between the upper and lower, I don't think this will make a large difference. My DPMS wasn't this tight (though I wouldn't call the quality exactly on par with Sig), and it still shot every bit as good of groups as the Sig does. I'm not saying you're wrong, there may be other factors at play I'm not seeing. But unless the degree of slop is significant I doubt this will cause a very noticeable difference in accuracy. If I do wind up going this route and find that accuracy suffers, I will gladly put the tensioning device back in place, make a Youtube account bitch slap myself and apologize for doubting you in the least and post it in a thread in GD for all to see.

Define ... substantial. If the upper can be rocked side to side, (yaw) it is effecting accuracy. This will spread the shots in an arc. If it can chuck up and down then you can get vertical stringing. Now this isn't the only thing that can impact accuracy there are several.

1. The quality of marksmanship / skill sets of the shooter operating the weapon. (Not saying you suck, I have know way to know your skill level).
2. The ammo, not all weapons shoot off the shelf ammo well, nor do all weapons shoot all bullet weights well.
3. Sights, are they really tight. Sights that jiggle around will effect accuracy. A sight that moves .005" will toss your accuracy off by 1" or more at 100 yards.
4. Free floated barrel vs. not free floated. The AR greatly benefits from floated handguards. Unless the shooter is extremely consistent in how they hold the weapon right down to check pressure against the stock, accuracy usually suffers to some degree.
5. Barrels; twist, weight, chromed vs. not chromed, relative retained stress levels. Retained stress in the barrel will manifest by good accuracy initially when cold, but as it heats up the groups open up or pull off in one direction. I've had weapons that did that. Shoot a good group for maybe the first 5 shots, then the group would shift a couple inches but continue to cluster like the initial 5 rounds. The cure for this is Cryogenic treatment of the barrel.

If you can take a bullet and use it to push the pins out so that you can grab them that IS EXACTLY as it should be. If they are loose enough to push with your finger they are too loose in my opinion. My long range Match AR, the pins are so tight on it that a bullet will shove back in the case. I do have to get a Pin Punch to start the pins out or it isn't coming apart.

I always look at weapons for how to make them as accurate as possible. This is why I've always had a problem with most AK rifles as they really can't be made overly accurate. This is a topic for another thread, back to the AR rifle. For my two piston drive carbines, a bullet tip is needed to start the pins out. I have an Accuwedge in the light barreled rifle to put some tension on the upper to keep it from flopping around under recoil. That device you have in your Sig looks to be a spring loaded ball detent Allan set screw. We use things like this in Injection Molds to act as a retainer for moving sections of the mold so they don't vibrate out of position easily when the mold is open. Can you see it from underneath, I'm wondering if you can put an Allan wrench on it and back it down a half turn or so.

[Aggressive Perfector]

Substantial= Enough to notice. I'd have never noticed it with my DPMS had I not read discussions about the topic. And I really had to pay close attention listen/ and feel for it. It was a such miniscule amount amount that you really couldn't visually tell. And it still shot as well after break in as the Sig does right out of the box. While I do not doubt for a second that lateral movement between upper and lower receiver can cause minor (depending on just how bad it is) change in point of impact from shot to shot, if I'm hitting the target within a 3" circle I'm happy. If I wanted to drive the head of a nail into a board I wouldn't even think of using a semi automatic personally. But yes, it is a set screw holding it in place. I am assuming it is just a spring loaded detent.

On a good note, however, after applying a little additional oil And beating the rear td pin out several times over the course of an hour and a half, it does seem to be coming out a bit easier than before. I'll just keep at it until I can simply push it out using my palm and a bullet.