s&w m&p 15 barrel nut trouble

ok so I am replacing the quad rail on my s&w m&p 15 rifle with a yhm free float quad rail. flash suppressor is off, front sight is off and gas tube out. barrel nut will not move. turning counter clockwise tried 2 different barrel wrenches, the 3 peg variety and the variety with teeth. tried loosening it with a hammer quite a bit, tried break free, then tried Kroil oil. even tried putting it in a freezer in an attempt to change temp and maybe contract the metal to loosen. and nothing, running out of ideas.

must have spent 6 hours today trying to get it to budge, no movement at all, can break it loose by hand or with hammer.

hesitant to take more drastic measures, for fear of exerting so much pressure or temp change I destroy it

any ideas? anyone???

I'm interested in this as well as i have this rifle and I'm looking at changing this out.

This should have grease on the threads, so I am going to strongly caution you about applying heat before you try it or someone suggests it. Grease when heated up is very flamable and will shoot globs all over you and your work area. It also will have some pressure build up because of it being traped in the threads. If you decide to try this, have someone help and make sure you have eye protection as well as a very clean work area.... a fire extinguisher would also be a good idea because grease that is on fire will stick to whatever it comes in contact with. This is of course if you plan to use an open flame.

If you are going to use an oven, make sure you have something under the upper to catch any grease or oil that dripps out while heating.

If you stil can't get any movement out of it it may be galled and at this point stop and contact S&W. They will most likely have you send in the upper, and if they find that there is a problem, they should take care of it.

Contact S&W, if they used Loctite you will have to heat it up.
You can find the amount of heat needed on the Loctite website.
Also you need to clamp on the barrel not the upper.

a 2-3 foot length of pipe

that's what it took to break my colt's barrel nut loose after kroil, heating with a torch, freezing, etc

thanks for the advise, it has been sitting soaking in kroil oil over night, when I get home i think I am going to try the pipe idea, if it still doesnt work, I will call s&w.


had this idea today to put a car jack under the 3 peg wrench, but scratched the idea, just seems to dangerous, if something is really wrong with it,
i dont wanna have to try to explain to s&w how its now totaly screwed becuase i tried to use a car jack for gun smithing,


although I have feeling s&w probobly wont be to happy about the whole situation to begin with, i can just see them saying something like "any work on the rifle that is not done by s&w will void the warrenty, but we will see what they say.

ok, I just snaped a peg off of my yhm 3 peg barrel wrench!!!!!

Put the whole upper in the freezer, and leave it for 45 minutes. Not much longer. Have everything set up (including a LONG cheater for your wrench) and then get the upper out and on the vise fast. Put the wrench on the nut with the cheater and it should move rather quickly.

Properly greased threads DO NOT make for an "easy" nut removal. The grease prevents galling and seizing, that's all.

I use a DPMS Multitool, which grabs ALMOST ALL the notches on the barrel nut. Instead of breaking my GI wrench, I stripped at least half of the notches on the first barrel nut I removed from a factory upper. That taught me a very important lesson!

sorry to hear. i just took my 15X appart tonight and put on YHM;s as well. i dont have a vice, so i just bear hugged my upper and twisted away and the nut came right off. so maybe if you show some love towards it that will help.

tried the freezer trick yesterday, and no luck


however, tonight I finally got the f@ckin thing off. I put the 2 peg side of my remaining wrench on, and sat there for 2 hours, pull with all my might for 1 second then stop for 2 seconds then pull for 1 sec, and so on, every 2 or 3 pulls I re adjust the wrench so that the pegs are torqueing on a different part of the nut. kept at it for 2 hours. then finally POP! thing unscrewed no problem!! I seriously thought the thing had been cross threaded or something, but nope it was just on there beyond crazy tight, yhm free float went on no problem. also I thing I pulled something important in my back. hurts like hell just to sit here.

hell yeah, woooo, I have spent 2+ days on this thing. but cant calibrate just yet.

I also have to put an armalite free float on my ar-10, hah also it wont fit in my receiver block, so I will have to call around tomorrow and see if anyone has barrel block attachment for a vice or a receiver block for an ar-10.


but hay I got the s&w done, wooooo. you all have no idea how happy I am to finally have it finished after a 2 day stone wall

Sweet!

I just put a MI SS12 on my S&W. The barrel nut was the toughest i ever had to remove. Not nearly as hard as yours. I tried for about 20 minutes then a couple of sharp taps with a hammer on the wrench started it moving. I never use the 3 prong wrenches on a milspec barrel nut. I always use the teeth kind. The 3 prong kind bend to easy. The 3 prong kind work great in the free float barrel nuts.

yeah, I had 2 wrenches the dpms one with the 2 prong side and the teeth side, and a 3 prong yhm one, the yhm is the one that broke. reason i went with the prong side is the teeth side kept sliping off even after only a few trys with very little force exerted i could already see noticable stripping on the barrel nut. was afraid of making no real progress and stripping it so bad it was done.

glad to hear yer s&w went ok

Ha great now im afraid to attempt free floating my M&P for fear i may have to visit the gym for a few weeks first. Glad you got it to budge, sorry it turned out to be just how its made... Or at least i soon will be.

Heat (or cold), LEVERAGE and persistence will overcome a properly installed barrel nut every time. The freezer trick works because of the different thermal characteristics of the steel nut and aluminum upper, the same way heating the nut works. But leverage is essential, which requires a long cheater bar and a really solid hold on the barrel. This is why using a receiver vise block for barrel work is a problem: you can't get a really solid hold because the receiver will twist (often far too little to see) and absorb a good bit of your effort.

I recently took the nut off my MP15 and there was zero grease/antiseize on it from the factory, Mine was snug but came off with moderate effort. IMO I dont care what some manual says REAL anti seize is far superior to any grease "Milspec." or otherwise to prevent galling of parts especially dissimilar metals such as in this application, With 25 yrs in the steel industry as a fabricator I found this to be true every time.

The amount of grease one is supposed to use is quite small, and almost all of it gets squeezed out as the nut is installed. If it came off with "moderate effort," there WAS grease there.

The MIL-G grease specified has some specific qualities: it's got a synthetic base that won't deteriorate, it tolerates both high temperature and high contact pressure, and it has at least a minimum amount of molybdenum disulfide to prevent galling. AND it was already a standardized grease in the supply system. This same grease is used in what I call "serious" aviation applications, where safety of flight is on the line, to prevent galling and seizing. It may not be the steel industry's choice, but it works. If you have a better grease suggestion, I'd like to hear it.

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