So I damaged the barrel on my m400 predator -- 18" 556.

Since sig wont sell me the replacement barrel Im trying to find a replacement that is at least as accurate as the original was.
I havent built or modded any ars before and Im hoping someone here can point me in the right direction.

-- Would the Wilson combat spr 18" 556 barrel be a direct replacement ?
-- Would I need to order anything else besides the barrel to do the replacement ?
-- Is this something I can do myself or should I bring it to a gunsmith for replacement ?

quote:

Originally posted by Ms0072:
So I damaged the barrel on my m400 predator -- 18" 556.

Since sig wont sell me the replacement barrel Im trying to find a replacement that is at least as accurate as the original was.
I havent built or modded any ars before and Im hoping someone here can point me in the right direction.

-- Would the Wilson combat spr 18" 556 barrel be a direct replacement ?
-- Would I need to order anything else besides the barrel to do the replacement ?
-- Is this something I can do myself or should I bring it to a gunsmith for replacement ?

Why is SIG refusing to sell a replacement barrell? I thought AR 15's barrells usually needed to be replaced aft 10K rounds.

Any standard AR barrel would work as the M400 is a basic AR. You will need to get one thats the same size at the gas block, it appears to be .750 which is common. As for tools, you'll need a pucnh or two for the gas block/gas tube roll pin depedning on if its pinned or clamp on.

Just from looking at the photos it appears to be free floated. So I dont see any special tools requires to remove the handguard but Im unsure of the barrel nut so you'll likely need an armorers wrench as well.

If you dont have the tools and don't really plan on building ow tinkering with your AR in the future, it sounds like taking it to a smith would be in best interest.

I can't speak for the barrel replacement process with a Sig m400, but I suspect standard AR barrels should work.

I have a Wilson 18" SPR barrel on one of my ARs. I am confident that the Wilson barrel will be more accurate than a Sig barrel.

I am a definite tinkerer and perform all work on everything else I own, bikes/cars/pistols... I just have not gotten into ar's yet.
Sounds like now is the time.

I have tried to get the details on the barrel and gas block configuration but havent been able to find it on sigs site.
Anyone know where I can find that info ?
Mine is the sigm400 predator with the 18" 556 barrel.


Also -- I want to get the most accurate barrel I can find under $400. The gun is a range/target toy and not used for hd.

Would the Wilson combat be a good choice for accuracy, I only selected them based on a general reputation for quality but not any specific info on ar barrels.



-- I think its ridiculous that Sig wont sell me the barrel but I spoke with Ryan at sig and that is what I am told.

With a $400 budget there are truly a zillion choices and probably all of them will be better than the stock one. fritz says the Wilson has been very good to him. I haven't used it but that's about as good a recommendation as you can get and its reasonably priced. I've personally used white oak and Noveske and can completely personally recommend them. The high power guys in my neighborhood like Kreiger but I can't say Kreiger have exactly what you need without more research, but if they do that will be way better as well.
Nothing fancy to swap a barrel.
I also am curious why Sig won't sell you a barrel, but the whole point of an AR is who cares.

Any AR barrel will work. Depending on the length of the gas system on the Sig (looks to be rifle-length), you may need to get a new gas tube. Depending on the barrel contour, you may need to get a new gas block (you can measure your barrel diameter at the gas block). Those are inexpensive parts.

While you may be able to "get by" without using specialty tools, I won't change an AR bbl without a Geissele reaction rod. The 5-prong PRI barrel nut wrench is handy too, especially on bbl nuts that have been over-torqued. Torque wrench is nice but not required. Aeroshell 33MS grease always goes on the receiver threads...

Some of the Larue barrels are on sale-

https://www.larue.com/products/5-56-stealth-barrel-k/

What free float tube does this have? Can you show a picture?

ARman

Sig's not in the AR retail parts biz. So I assume they don't want to sell a barrel do to liability issues.

I'll also assume that they'd replace it, if you send it to them.

I don't blame you for wanting to do it yourself.

If this has Tha ALG Defense EMR V2M-LOK handguard, you will have to buy a ALG Defense barrel nut wrench and new shims.

The ALG Defense barrel nut wrench is $5.00, I would call them and ask for Institutions directions. Tell them that you are replacing a barrel and need instructions on timing the barrel nut, and the wrench, which is $5.00.

It's very easy and straight forward to replace the barrel, but you will need the ALG Defense barrel nut wrench, an action block, and vice.

Brownells has the action block,

https://www.brownells.com/guns...block-prod22385.aspx

It's $59.00, the barrel nut wrench from ALG Defense is $5.00, I don't know what the shims will cost, a buck or so.

The ALG Defense barrel nut wrench and shims are all you will need to properly torque the barrel nut.

So, remove the screws that hold the ALG Defense EMR V2M-LOK handguard to the barrel nut, remove the gas block, unscrew the barrel nut, remove the barrel, slide new barrel into receiver, install new shims and tighten barrel nut, slide free float handguard on barrel nut, install and tighten screws and there you go! It's easy.

As to the barrel, it's just a standard AR 15 barrel, so pick what you want, and get to it!

I have installed the ALG Defense EMR V1M-LOK handguard on a couple of my AR 15's and it is very easy. I really like the ALG Defense EMR V1M-LOK handguard. It's the same as the V2M-LOK except for the 12 o'clock rail.


ARman

Thanks for all the replies , appreciate the help.

So here is the damaged barrel and the hand guard. --- https://imgur.com/gmlbw15
Look like it is the alg v2.

Based on the replies so far it seems that the wilson combat 18 556 barrel will fit, just need to identify if I need the recon or spr profile.

From the pic im not sure if the gas tube is mid length or rifle -- can anyone confirm based on the pic ?

Also -- any recommendations for decent tools to get it done correctly.
This is my first venture into ar work but it surely will not be my last.


Hope you all enjoy your thanksgiving and the upcoming holidays!!

Arman -- thanks for the detailed info.

The instructions are downloadable on the alg site but there is no place to order the shims, waiting for a reply on how I can get them.

In the instructions they refer to a geissle reaction rod. Is that needed ? I would prefer to get whatever tools I need to be sure I do it right , especially if I will wind up using the tool again in the future.

Based on reading about it it seems like a good idea to get it instead of the vise block, or is that not what is usually done in actual practice ?

Get the Reaction Rod

The gas system looks to be 12", that's Rifle length.

ALG Defense should be able to supply the shims, I don't believe they cost much.

The reaction rod is perfect for the job. It cost more than the action block that I linked to, but it is better in some ways. If the cost isn't an issue, get the reaction rod.

I have the action block I linked to, when I got it, it was the only game in town.

To remove the barrel nut, and reinstall the ALG Defense barrel nut and torque it properly you will need ALG Defense "trick" barrel nut wrench. It cost $5.00 and it makes the handguard system simple straightforward and foolproof.

The ALG Defense EMR V2M-LOK handguard has to be one of the easiest I ever installed. They might be less expensive than some, but are very well made, and the barrel nut interface is great!

ARman

The only tools that you should need are the reaction rod, "trick" barrel nut wrench, a couple of pin punches and the shims.

If you can't get the shims from ALG Defense, you can get them from here.

http://www.gandrtactical.com/A...t-Shim-Set_p_16.html

I have never ordered from them, and I have no affiliation with them. But it is an option.

ARman

Cool,

thanks for all the info.
I believe im all set except for being sure about the profile.

If I order the SPR barrel and the gas block/tube I have on the current barrel doesnt fit I am assuming I can then order a new gas block/tube to fit the contour of the spr barrel.

Am I correct ? -- wc has the barrels on sale today so Im planning to order to 18 spr barrel.



Thanks again for the help, feeling much better about being able to replace it correctly.

The gas block might be a PAIN to get off. In which case it would be easier to buy a new gas block for your new barrel.

Agree you need the $5 tool and shims to install the barrel nut properly as the shims that are currently installed are not likely to be the proper fit for the new barrel.

Gas block came right off.

Now just trying to find a way to get the shims.
The only place I can find besides alg is the link above but its out of stock and backordered.

Not sure if this will work, but good ole Brownells has this.

https://www.brownells.com/rifl...m-kit-prod96013.aspx

ARman