New SIG M400 (lots of mods)

[PFran42]

Hey guys! Been lurking for a while and finally though that I could provide value to this fine forum!

From my time spent reading up on this and other rifle forums, it appears that the M400 has a ton of haters. That, coupled with the fact that I have only been shooting for about three months should provide all of the forum's seasoned members complete and utter free reign to continue with said behavior. Since I have no experience with Sig Sauer other than an SP2022 that has accurately gone bang every time I have fired it for the last 3K rounds, I figured would jump in head-first on my first long gun build. Prior to purchasing the M400, I owned a DPMS Oracle for about a week. This was long enough for me to watch a few hours of YouTube AR field strip/dis-assembly/reassembly videos, purchase a bunch of armorer's tools and and learn how to take an AR down to it's last roll pin. As soon as I had the DPMS apart I switched out the lower for a billet job, quickly lost interest with the whole thing and traded it in on a M400 SRP.

Since I am new to all of this I don't feel comfortable speaking to the finer details of the rifle's accuracy just yet. All I can do at this point is turn little holes into big holes at 25 yard indoor ranges where I have run roughly 1000 PMC/Winchester/Federal 55gr rounds down the pipe. First thing I did when getting the M400 home from the fun shop was to thoroughly heat it with my wife's hair drier, and meticulously remove all signs of grease/protectant/oil with Walmart-brand 91 percent isopropyl alcohol followed by three subsequent re-heatings with generous bastings of FrogLube in between. The rifle runs like a top!

My plan is to update this thread with range reports, round counts and modification updates. If the M400 is as bad as some seem think it will be, this thread will definitely reflect it's negative performance. Many changes have been made to the original configuration but the heart of the rifle is all there (barrel, bolt, bolt carrier, upper/lower receiver). I have no special affinity to the Sig Sauer brand and I only purchased this one due to me being a lefty. I don't plan on delving into any scientific analysis that ends up turning this thread into a 48 page 1-7 vs. 1-9 twist rate debate. I am just going to shoot the crap out of it, put it through a few carbine classes and report back. If it does end up performing well then this thread's value will be that some other guy may stumble across this review in 2-3 years and gain some knowledge on the M400.

Here is my current setup:

Sig Sauer M400 SRP (base to build on)

Legend:

Sub-par (by Mil-Spec standards)
Different but adequate (in my own opinion)
Above and beyond

Stock Specs:

Bolt Carrier Group
-Chrome lined bolt carrier
-HPT bolt???
-MPI bolt tested???
-158 Carpender steel???
-Shot peened bolt???
-Black extractor spring insert
-Enhanced AR15-type bolt carrier (larger than AR15 style, smaller than M16 style)
-Properly staked gas key
-Phosphate coated bolt and bolt carrier (http://www.americanrifleman.org/articles/sig-sauer-m400-rifle-review/)

Barrel
-41V50 Steel - NOT VERIFIED (http://forums.1911forum.com/showpost.php?p=4028839&postcount=50)
-Chrome moly steel barrel (http://www.shotbusiness.com/Article/Newsbriefs/detail.cfm?newsID=379)
-HPT barrel???
-MPI barrel???
-Chrome-lined chamber and bore (http://www.shotbusiness.com/Article/Newsbriefs/detail.cfm?newsID=379)
-Chrome-lined barrel - (SIGM400_SELL-print.pdf)
-Chambered in 5.56X45mm NATO (MiniManual_HR.pdf.)
-Rifling: 1 in 7" RH twist
-M4-style feed ramps
-"F" marked A2 front sight on Enhanced models - (SIGM400_SELL-print.pdf)
-Press-fit railed gas block with tapered pins (takes a Dremel to get it off the barrel)
-Phosphate coating under FSB (MIL-SPEC is "parkerize" under FSB)
-Gas Port - .063 NOT CONFIRMED (http://forums.1911forum.com/showpost.php?p=4028839&postcount=50)
-Phosphate coated barrel - (SIGM400_SELL-print.pdf)
-Barrel Countour: Mil-spec M4 Profile - (SIGM400_SELL-print.pdf)
-Barrel Length: 16 in
-Number of grooves 6
-Muzzle end - 1/2 X 28 TPI (MiniManual_HR.pdf.)
-Ovalized composite handguard (SRP model) with double aluminum heat shields
-Pin in barrel extension for relieving pressure on extractor when bolt is in battery

Lower Receiver
-Six position buffer extension tube (MIL-SPEC) - (SIGM400_SELL-print.pdf)
-Properly staked barrel nut
-Standard carbine buffer (MIL-SPEC is "H" but since the Sig's BC is a hybrid between the AR15 and M16 styles, the provided buffer is mated quite well)
-.154" Diameter Fire Control Group (FCG) Pins
-Lower receiver - 7075-T6 aircraft grade - (SIGM400_SELL-print.pdf)
-Tensioning device for upper to lower receiver (spring, detent and hex screw)
-Ambidextrous rear quick-disconnect sling mounts built in to the lower receiver
-Ambidextrous mag release
-Flared magazine well with beveling on inside for faster magazine location and seating
-Milled serrations on front of receiver for improved purchase

Upper Receiver
-Upper receiver - 7075-T6 aircraft grade - (SIGM400_SELL-print.pdf)
-"T" marked, flat-top MIL-STD 1913 upper receiver
-Square forge marking - Brass Aluminum Forging Enterprises

Additional
-Limited Lifetime Warranty (MiniManual_HR.pdf.)


Upper Mods:
-PWS SM556 Flash Suppressing Compensator (installed after these pics were taken)
-Rainier Arms/AXTS Raptor ambidextrous charging handle
-Daniel Defense clamp-on low-profile gas block
-Troy 11" Alpah rail (switched to 13" in FDE)
-Troy M4 F&R folding battle sights
-IWC flush-mount QD points (on front and rear of rail)
-Surefire Millennium 951 w/ M93 base in FDE
-Eotech XPS2-0
-Primary Arms 3X long eye-relief magnifier
-American Defense flip-away magnifier mount
-Troy Squid Grips (2 sets FDE, 1 set BLK))
-Magpul AFG2
-Larue Index Clips (3)
-Custom dust cover

Lower Mods:
-Giselle SSA 2 stage trigger
-B.A.D.-A.S.S. ambidextrous selector (short and long selector arms)
-Stainless steel pins, and detents
-Magpul UBR buttstock
-Magpul Enhanced Rubber Butt-Pad 0.70"
-Magpul MIAD grip
-Magpul MOE Trigger Guard
-Magpul P-Mags, 30 rd w/ windows (8)
-Magpul Ranger Plates (8)

Future Plans:
-TNVC LED upgrade for Surefire 951

Accessories:
-5.11 36" soft case (not pictured - The case in the pics is a 36" Drago)
-Pelican 1700 hard case
-Larue Tactical Padded Sling (QD version)

Here are some pics:

https://lh6.googleusercontent.com/-gTWDKMfXJHo/UF-T7q-wDXI/AAAAAAAAdRs/C2kx30srd3Q/s1600/20120923_185115.jpg
https://lh3.googleusercontent.com/-sMYliyr7MMU/UF-ZBzR8srI/AAAAAAAAdL0/n5So66wrKfI/s1152/20120923_191437.jpg
https://lh6.googleusercontent.com/-otIAOctPIno/UF-ZZP4uq6I/AAAAAAAAdMU/v_TXtHodOGE/s1152/20120923_191525.jpg
https://lh3.googleusercontent.com/-Go9HeChaNJA/UF-U6Tp-uII/AAAAAAAAdEw/uEbX5mjHfyg/s1152/20120923_185830.jpg
https://lh5.googleusercontent.com/-4Cq56ikQOO0/UF-UYNdRdBI/AAAAAAAAdPg/Lmp8JokBOlo/s1600/20120923_185748.jpg
https://lh5.googleusercontent.com/-kyE8G7LZEBU/UF-UqJQ9BsI/AAAAAAAAdPo/tqBQ4hWe1WY/s1600/20120923_185826.jpg
https://lh3.googleusercontent.com/-wQT0cLOJGOk/UF-UAlJF0jI/AAAAAAAAdDY/z1KlHWC2SjI/s1600/20120923_185122.jpg
https://lh4.googleusercontent.com/-h4i8AfUo7qA/UF-TmwZBl0I/AAAAAAAAdP4/FgL7yUyxNRA/s1600/20120923_185038.jpg
https://lh4.googleusercontent.com/-phNxwKMSIc8/UF-S6bGfhpI/AAAAAAAAdBo/oyk7yPbSwoI/s1600/20120923_184931.jpg
https://lh4.googleusercontent.com/-SI5IQ_Nr4Qw/UF-XGBA05-I/AAAAAAAAdIk/KkY9pFCn3s4/s1600/20120923_190340.jpg
https://lh4.googleusercontent.com/-aHaZFSRB308/UF-YDp3SdMI/AAAAAAAAdKM/P1HmUhiOhWU/s1600/20120923_190941.jpg

Here is where I was playing with different colored Squid Grips:

https://lh5.googleusercontent.com/-h1NaTnqLcRM/UGTW7BlsEsI/AAAAAAAAd3s/Ve09AmYdoAc/s1600/20120927_184235.jpg

..and here is my ghetto dust cover!

https://lh3.googleusercontent.com/-aR4x7WDsRgM/UGJo-ff7ZdI/AAAAAAAAd3E/bligqcHp-BI/s1829/20120925_222059.jpg

MODS: Please move this thread if it is posted in the wrong section. Not sure if this constitutes a "build".

[devinsdad]

Helluva nice build! Nice to see a SIG all done up finally. How do you like the squid grips? One of your pics make them look tan rather than black. Do you have tan ones or was it the flash? Best of luck!

[PFran42]

Helluva nice build! Nice to see a SIG all done up finally. How do you like the squid grips? One of your pics make them look tan rather than black. Do you have tan ones or was it the flash? Best of luck!

Thanks!

Squid Grips

Pros:
-Improved comfort when gripping the hand guard. These can best be described as "medium-squishy" if that makes any sense.
-Better insulation from heat
-Light weight
-Protection of the hand guard. They appear to do a good job against accidental bumps and scrapes.

Cons:
-Come off rifle easier that any other rail covers I have ever tried. They aren't just going to fall off while shooting it up at the range but if you have your rifle slung while hiking all day through underbrush, my guess is that one or more of them will be absent the next time you take a look.
-Stay greasy for a long time after inadvertently getting any type of lube on them. Easily addressed by popping them off and sneaking them into the dishwasher.

Meh:
-Looks. They really aren't noticeable unless you contrast the black rail with FDE Squid Grips. Haven't gotten my new Troy Alpha 13" in FDE yet, so I can't comment on what black SGs would look like on a FDE rail. I'll be sure to posts pics when it arrives and I have everything back together.

Edit: To answer your question, the pic with the lighter looking SGs is with a set of FDE SGs installed. Looked OK in pics but I wasn't crazy about it in person.

[SigSlave]

Fire a couple thousand rounds through it and you will probably grow to love it. Mine was quite accurate and never malfunctioned. I sold it for 2 reasons. Someone gave me a lower and I wanted a mid length.

You list some things as sub par in your review but left question marks after them. If you don't know the quality of those parts listed, how can they be sub par?

The barrels are supplied buy a very well known manufacturer. The bolts are good to go too.

Have fun with the gun. If yours performs as well as mine did, you will be happy.

[kwg020]

Nice Build. I wish Sig would sell a stripped lower. I like the two single point sling attach points and the beveled magwell. I think it would be a great lower to build from. I would like to have a lightweight midlength barrel, the new MOE fixed stock, A-2 front sight and an A-2 handle. Just my vision. kwg

[PFran42]

Fire a couple thousand rounds through it and you will probably grow to love it. Mine was quite accurate and never malfunctioned. I sold it for 2 reasons. Someone gave me a lower and I wanted a mid length.

You list some things as sub par in your review but left question marks after them. If you don't know the quality of those parts listed, how can they be sub par?

The barrels are supplied buy a very well known manufacturer. The bolts are good to go too.

Have fun with the gun. If yours performs as well as mine did, you will be happy.

After having fired roughly 1000-1250 rounds downrange, I already am very fond of it. Compared to my last two ARs, it has proven superior as far as fit, finish and smoothness of operation.

As far as my "ratings", I feel the best course of action for the M400 (as well as myself) is to come in humble, err on the side of pessimism, and let the chips fall where they may. I have seen too many reviews where a forum member comes in glowing about his new purchase, paints the prettiest picture possible re: his buying decision, decides "as good as" is good enough and is shortly squashed by the Colt loyalists for not having "this" mil-spec feature or "that" level of QC. It is common knowledge that AR forums regard the mil-spec checklist as the benchmark that all AR manufacturers must be judged by. Until I see verifiable evidence on the items I listed as sub-par, I believe that "grading" them as sub-par (by mil-spec standards) demonstrates a lack of bias towards the weapon I have chosen to review.

That said, if anyone can provide missing pieces of the Mil-Spec puzzle as it pertains to the M400 platform, I would greatly appreciate it! As mentioned earlier, I too appreciate the thought that went into the design of the lower and it would benefit the M400 (as well as Sig Sauer) to have some of those red bullet points turned back into black ink.

[PFran42]

Nice Build. I wish Sig would sell a stripped lower. I like the two single point sling attach points and the beveled magwell. I think it would be a great lower to build from. I would like to have a lightweight midlength barrel, the new MOE fixed stock, A-2 front sight and an A-2 handle. Just my vision. kwg

I agree. I would slap a Noveske upper on it faster than you can say "Sheri is kinda hot."

[PFran42]

Just added a 13" Troy Alpha Rail in FDE as I was crowded up front with the 11" Alpha/AFG2/light/bi-pod combo. Rifle seems more balanced now.

I'll post some better pics when I have some time...

Notes:

I had a bit of a struggle trying to determine the optimal method for installing an AFG2 while maintaining enough rail space for a bi-pod mount. The lo-pro gas block does not provide enough clearance to run a backing plate for a longer picatinny rail that would run the full length of the AFG in addition to providing enough space for the bi-pod. The solution I came up with was to let the AFG2 hang off the back of the Troy included long 1913 rail. Since Magpul's mounting location for the AFG2 is easily accommodated, there is very little flex to the assembly and I feel that at least in the short-term, it is an acceptable solution. Someone needs to get into the business of making direct-mounted accessories for these style rails as I believe that they are going to be around for a while.

https://lh6.googleusercontent.com/-kdr93t6FXZU/UHjZDL8d4HI/AAAAAAAAe6o/gOLO5PoFDpc/s1988/20121012_225136.jpg

[PFran42]

Had the chance to get the range and once again, the rifle ran flawlessly. Had to go to an indoor range (25yd max) so I played around with the iron sights. Am I correct in extrapolating a 4X factor for 100 yd. grouping? If so, I think I would shoot 4" inch groups (until I get some experience).

So...If I am shooting these type groups at 25 yards, I just multiply by 4 and that would be a good estimation of what I would do at 100 yards?

https://lh6.googleusercontent.com/-bQBfGHrGCmE/UHtF0GOCF7I/AAAAAAAAe8U/huLTdaKwfzI/s1152/20121014_190439.jpg

https://lh6.googleusercontent.com/-hwz8p3dIx5w/UHtFssSAz0I/AAAAAAAAe8I/NwXZQBj9a1o/s1152/20121014_190449.jpg


Zero issues to report. Also of note is that since the internals are now adequately "seasoned" with Froglube, I have stopped detailed cleanings. Near the end of the range session the carrier vent holes get a couple drops of FL. I then fire off another mag and work the newly applied FL into the action. Once home I pull the CH and BCCG and do a quick wipe-down with a lint-free towel. I then pull a squirt of FL on a boresnake and run it 3-4 times though the barrel. I might break down the BCC every 1000 rounds or so and wipe/lightly apply FL, but I don't plan on using bristle brushes in the foreseeable future.

[SigSlave]

Groups like those are typical with iron sights. It is a very accurate rifle. Mine shipped with a test target that measured at .674

Nice shooting

[jesuvuah]

I have not owned a sig, but I have fondled a few. From what I could see, they seemed like a quality product. I have also seen them on sale in the price range of guns like bushmasters and I would definately take the sig over a bushy. That being said, my first AR was a bushy and I put thousands of rounds through it with out any trouble.

[ST911]

So...If I am shooting these type groups at 25 yards, I just multiply by 4 and that would be a good estimation of what I would do at 100 yards?

It can be an approximation, but usually a best case scenario instead of a likely result. Distance is less forgiving, and in a non-linear way.

[PFran42]

It can be an approximation, but usually a best case scenario instead of a likely result. Distance is less forgiving, and in a non-linear way.

Thats what I figured. I think a good goal to start with for 100 yds. will be to land three-shot groups within a 6" circle.

Edit:

Added a UBR with aluminum striker plate today in order to address forward weight bias. Rifle feels more balanced but the ounces are quickly starting to add up and I am not crazy about the look. May try out a SOPMOD tomorrow.

https://lh3.googleusercontent.com/-0MUb5fntzGc/UIDSWQTNfZI/AAAAAAAAfJE/P5KEXFoIbv8/s1024/20121019_000503.jpg
https://lh5.googleusercontent.com/-LY7fxJ8qZwU/UIGnFs65EWI/AAAAAAAAfSY/6A_11Lhkk9Y/s1600/20121019_145113.jpg
https://lh5.googleusercontent.com/-SL0kHRJ3-f0/UIGhdB9bknI/AAAAAAAAfPA/ru_Dryl4r5Q/s1600/20121019_144810.jpg
https://lh5.googleusercontent.com/-IDrxISqB35w/UIGjtF8_lqI/AAAAAAAAfN8/WTwUpZaWACo/s1600/20121019_144904.jpg
https://lh3.googleusercontent.com/-ZuZhXyPKU9k/UIGlUahAJkI/AAAAAAAAfQg/qIKxn8e0oWU/s1600/20121019_145005.jpg

[PFran42]

Range report:

Got another 250 PNC 55gr. rds. downrange and had zero issues. My groups are still tightening up. This is either due to the barrel being properly broken in, improvement of my marksmanship skills or a combination of the two.

Just had a baby so it will be a while until I will be able to shoot between 100-300 yrds. but I will update this thread with any further developments.

On a side note, I just completed my first Pelican case foam cut-out for the M400. I read somewhere that SCUBA divers like coating the foam with Plasti-Dip as it guards against moisture and foam damage from equipment going in and out all the time. I gotta say that I love how the PD changes the feel and handling characteristics of the foam. Time will tell if this coating holds up.

https://lh6.googleusercontent.com/-C4qUtfPtRCw/UImdi4sxQYI/AAAAAAAAf4w/WowZEiKUWCk/s1600/20121025_160840.jpg

[Rage Ape]

Range report:

On a side note, I just completed my first Pelican case foam cut-out for the M400. I read somewhere that SCUBA divers like coating the foam with Plasti-Dip as it guards against moisture and foam damage from equipment going in and out all the time. I gotta say that I love how the PD changes the feel and handling characteristics of the foam. Time will tell if this coating holds up.



Seriously considering a SIG as the next addition.

Also, extremely interested in your results with the Plasti-Dip.

[P4Plenty]

Nice weapon. That dust cover is great !

[jbasas13]

hows the plasti-dip holding up thats a pretty neat idea

[PFran42]

Seriously considering a SIG as the next addition.

Also, extremely interested in your results with the Plasti-Dip.

I placed some thoughts on the PD below. As for the rifle, it continues to perform flawlessly!


Nice weapon. That dust cover is great !

Thanks! I'm surprised so many people understand what it means.


hows the plasti-dip holding up thats a pretty neat idea

The Plastidip is performing above my expectations. I still want to get through 4 seasons before officially giving it the thumbs up but for the amount of use the case has seen thus far, I am very pleased.

For a waterproof test, I took the pistol liner out and placed several drops of water on it. It has been sitting on the kitchen counter for a couple of hours with no sign of water making it into the foam. I even pressed the foam down every 30 minutes and still no moisture is making it's way into the foam.

This isn't the greatest picture but basically the water puddle has spread out after having been pressed on multiple times in my attempt to stress the foam.

https://lh3.googleusercontent.com/-Si8hHsqBleg/UJ6l7wmxiLI/AAAAAAAAgOw/s-cYhLTh11w/s720/20121110_140416.jpg

https://lh4.googleusercontent.com/-9rFDZtbMDYM/UJ6oqDRpREI/AAAAAAAAgQA/-_nFXDzkgC0/s720/20121110_141748.jpg

[JJay03]

Looks nice I really like that lower. I also want your XPS2.

[thehun]

I'd love a Sig AR...however my S&W has been exceptional with thousands of rounds down range:agree:

[bobsolla]

excellent post!my buddy picks his up this coming weekend!

[Swiftmotoring]

Great looking set up! I am new to AR's and also just bought an M400, really enjoying it so far. Nice to see your additions and modifications.

[PFran42]

Here is the latest incarnation of the M400.

https://lh6.googleusercontent.com/-6enNfYyBZjk/UM_ViuDolyI/AAAAAAAAiZM/h-jaT4gb7jc/s800/IMG_5099.JPG

I purcahsed a T1 for it but it was not mounted for this pic.

[retnug65]

Which pelican hard case is that and did you custom cut everything to fit in the case or did the case come that way?

[Bedouin2W]

Which pelican hard case is that and did you custom cut everything to fit in the case or did the case come that way?

Looks like he has the Pelican 1700 Long Case, but that is just an educated guess....

[PFran42]

It is indeed a Pelican 1700.

[eodinert]

Is that picture of the foam with or without the plasti-dip treatment?

[PFran42]

Is that picture of the foam with or without the plasti-dip treatment?

Bottom of case is has been treated with PlastiDip in that photo.

[Spikele]

Did you weigh her?

[MTShooter]

Did you weigh her?

I'm curious too. What's the final weigh in? Building one VERY similar because i love what you've done with your M400.

[DarkJ]

ive been really looking at that same case, curious to see how to holds up with plasti dip

^ also curious on weight.

[Torch]

Any updates or range reports? My new M400 Enhanced is at my FFL waiting for me to get back home so that I can pick it up.

[JS-Maine]

Almost bought an M400 from Walmart back when they were in stock for less than $800. Good looking gun, and your mods have added a lot to it.

The pelican case is new to me though-glad you guys mentioned it. I might have to scoop up one of those bad boys down the road. I especially like all the cut-outs you've made to make it a rifle/pistol combo case. Very nice rig.

[.46caliber]

Almost bought an M400 from Walmart back when they were in stock for less than $800. Good looking gun, and your mods have added a lot to it.


I did and it has been great. Only minor complaint was swapping out the trigger guard. I put a Magpul aluminum guard on today. I don't know if Magpuls roll pin is a little large or if Sigs holes are a bit small or both, it was a very tight fit.


Sent from my PG86100 using Tapatalk 2

[jayband]

love the sig build!

[Nka727]

Good lookin case ya got there... Could be a professional hit-man with that thing.

[PFran42]

Good lookin case ya got there... Could be a professional hit-man with that thing.

Thanks! I quickly learned that sort of thing will never happen again. As much as I play with the configurations of various rifles, it is far easier just to have a border piece and a few longer strips to keep things from bashing up against each other.

Fun project but ultimately of little use.

[jks123]

That said, if anyone can provide missing pieces of the Mil-Spec puzzle as it pertains to the M400 platform, I would greatly appreciate it! As mentioned earlier, I too appreciate the thought that went into the design of the lower and it would benefit the M400 (as well as Sig Sauer) to have some of those red bullet points turned back into black ink.[/QUOTE]

I just picked up a second Sig M400 because I love my 1st one so much.
I called Sig today and asked about barrel steel. This is what inwas told: The newer barrels (October 2014 - current, approx.) are now 4140 'chrome moly' with Nitride treatment. Mine was manufactured in March 2013 and is phosphated outside, chrome lined inside, and is 4150 Chrome Moly Vanadium. Personally, I'd rather have the nitride treatment. Even if the barrel steel IS 4140 "chrome moly". That QPQ Black Nitride is the sh*t!!! I also asked about their 'enhanced BCG' but got nowhere as far as C158/MPI/HPT/ShotPeened etc. I've already ordered an H buffer and a BCM bolt carrier group (theyre just amazing). So i have a practically new "enhanced, chrome lined, Sig BCG' for sale if anyone's interested. It's C.L'd. Also C.L'd. inside the carrier key... gas key staking is excellent. $60. I know this is an older post, but in case you were still wondering about barrel specs, here ya go. Keep in mind this is just what a C.S. Rep told me about the barrels. I also read in another thread that the Sig M400 and Sig 516 share the same barrel and apparently on the German Sig webpage, it states that the 516 barrels are CHF, so who knows, maybe the barrels dating from October 2014 and earlier are actually 4150 CMV and CHF *high hopes* and time will tell.. I wish Sig would just be ALOT more descriptive about the specs on this AR15. Everything in the description on their webpage is so vague. Anyways, GLHF, STAY SAFE. 34756347573475834759

[Iraqgunz]

Your post has nothing to do with the Custom Build thread. Please post it in the General Discussion Area.


That said, if anyone can provide missing pieces of the Mil-Spec puzzle as it pertains to the M400 platform, I would greatly appreciate it! As mentioned earlier, I too appreciate the thought that went into the design of the lower and it would benefit the M400 (as well as Sig Sauer) to have some of those red bullet points turned back into black ink.

I just picked up a second Sig M400 because I love my 1st one so much.
I called Sig today and asked about barrel steel. This is what inwas told: The newer barrels (October 2014 - current, approx.) are now 4140 'chrome moly' with Nitride treatment. Mine was manufactured in March 2013 and is phosphated outside, chrome lined inside, and is 4150 Chrome Moly Vanadium. Personally, I'd rather have the nitride treatment. Even if the barrel steel IS 4140 "chrome moly". That QPQ Black Nitride is the sh*t!!! I also asked about their 'enhanced BCG' but got nowhere as far as C158/MPI/HPT/ShotPeened etc. I've already ordered an H buffer and a BCM bolt carrier group (theyre just amazing). So i have a practically new "enhanced, chrome lined, Sig BCG' for sale if anyone's interested. It's C.L'd. Also C.L'd. inside the carrier key... gas key staking is excellent. $60. I know this is an older post, but in case you were still wondering about barrel specs, here ya go. Keep in mind this is just what a C.S. Rep told me about the barrels. I also read in another thread that the Sig M400 and Sig 516 share the same barrel and apparently on the German Sig webpage, it states that the 516 barrels are CHF, so who knows, maybe the barrels dating from October 2014 and earlier are actually 4150 CMV and CHF *high hopes* and time will tell.. I wish Sig would just be ALOT more descriptive about the specs on this AR15. Everything in the description on their webpage is so vague. Anyways, GLHF, STAY SAFE. 34756347573475834759[/QUOTE]