Today I am chopping up my M4

[AR-10]

I just ordered a Troy MRF-MX for my LMT M4.

I'm chopping off my front sight and shaving it down to fit underneath the handguard:

http://img37.imageshack.us/img37/1368/img1205f.jpg

I assume that when I am done, I have to trim the handguard cap?

What about the bayo lug, is that going to fit under the handguard or do I need to chop that off too?

[AR-10]

Ok I'm an idiot, that wasn't a washer it was part of the delta ring which is now gone, along with the spring and circlip - original post edited, I still haven't touched the front sight, cause I'm scurrrrrred.

[Paulo_Santos]

Watch these videos. It should be two parts:


http://www.youtube.com/watch?v=I3kH908oaXI

As far as the FSB, just cut that down and you will have to cut the sling mount and bayo lug. You should be able to leave the Handguard cap. You also have to trim abound the FSB. You'll see how much you need to trim once you have the handguard.

[chazthebiker]

Well, good luck to you! I understand that one might want to chop up the FSB to fit under a hand guard. I guess this saves a little money? Or is it that a new gas block will not fit at the proper location with that particular barrel contour? Just seems like a new gas block would look cleaner. A person could always sell the FSB. I'm just wondering why folks do this. I am not being critical or anything like that. I may just be missing something I don't know about. At any rate, good luck and I hope everything goes ok for you! Can't wait to see the pictures.

[Paulo_Santos]

Well, good luck to you! I understand that one might want to chop up the FSB to fit under a hand guard. I guess this saves a little money? Or is it that a new gas block will not fit at the proper location with that particular barrel contour? Just seems like a new gas block would look cleaner. A person could always sell the FSB. I'm just wondering why folks do this. I am not being critical or anything like that. I may just be missing something I don't know about. At any rate, good luck and I hope everything goes ok for you! Can't wait to see the pictures.

He has a 14.5" barrel with a permanently attached muzzle device. He pretty much doesn't have a choice unless he wants to spend money to get it removed and another one permanently attached.

[AR-10]

Great video!

Paulo is correct, my flash hider is permanently attached so I am chopping my FSB for two reasons:

1) I get a longer handguard out of it

2) I can keep my front sight out of my FOV when it's not needed

Those are two things that were really bothering me, when I'm done with this upgrade I will be a lot happier with this carbine.

Also as an added bonus: my barrel will now be free floating, my old handguard was a drop-in unit that did not FF my barrel.

Here it is, I'm not done shaving the FSB down:

http://img8.imageshack.us/img8/9639/img1207fr.jpg

I'll post a better pic after I get it painted, I'm waiting for the handguard to see how much more I have to take off.

[AR-10]

A person could always sell the FSB.

When they drill the holes in an FSB, they do it with the FSB installed on the barrel and both components are drilled at the same time.

This means you can't really use an FSB that has already been mated to a different barrel.

[chazthebiker]

Got it! I knew there was something I was missing. My rifles don't have the FSB and your explanations helped me shed some ignorance. BTW: Looks like you did a great job cutting that down. Thanks guys.

[AR-10]

No problem, here's another pic so you can see exactly what I am doing - I think I'm done for the day, I have metal all over my skin and clothes.

http://img525.imageshack.us/img525/55/img1208g.jpg

[AR-10]

I'm trying to shave it down like this, because this is how it has to be shaped in order to fit under a quad-rail handguard:

http://img821.imageshack.us/img821/3816/yhma.jpg

[Paulo_Santos]

Looks good.

[AR-10]

Thanks!

That Dremel did a great job, I was surprised at how easily it cut through the FSB.

I haven't decided what to touch it up with when I'm done shaping it, I was thinking about masking off the barrel and spraying the whole section with black BBQ paint.

I figured that stuff will work since it's obviously made for high temps, it's either that or engine spray paint unless someone has a better suggestion.

[Quib]

Try some G96 Liquid Cold Blue for touching up the exposed steel.

http://www.g96.com/Gun_Blue.html

[AR-10]

Thanks, I may have to try some of that instead of spraying paint on my barrel.

I'm anxious to see how this all comes together, I have a T-1 and one of LaRue's new skinny mounts on the way too.

I hate waiting for new stuff!

[madcratebuilder]

Nice job on cutting the gas block. Best part is it's still pinned. I guess a setscrew gas block is OK if under the hand guard.

You can get a tapered reamer for mating a pinned gas block to other barrels or new barrels/gas block combinations.

Think Aluma Hyde II for paint, it is bullet proof, available in rattle cans.

[AR-10]

Thanks, it wasn't as scary as I thought it would be and now that I've done it I'm confident that I can do it again.

I just now finished cutting off the sling tabs and bayo lug, hopefully the new handguard isn't any skinnier than my old one:

http://img401.imageshack.us/img401/1161/img1215d.jpg

There's maybe 0.100" between each side of the sight base, and I can still shave down some more without getting too thin so we'll see when I get the new handguard this week...

[sdoperator]

Looks good.

I'm pretty impressed. Just though I'd mention that just in case you don't like it for any reason, there are alternatives to cutting your sight post.
I have a pinned 14.5" and saw this problem coming. My solution was this:
Specter Gas Block (http://yankeehillmachine.com/store/gas_blocks.html#23)
...which will obviously require cutting your gas block completely off. Just thought I mention it for you, and anyone else that's in a similar predicament.

[AR-10]

That's a nice looking part, and they made it long for guys like me who have barrels that aren't parkerized under the GB.

[lmtrocks]

I've done several FSB cuts for gas blocks and love it simply because it is pinned and should you have to remove it any time you're not worried about loctited set screws being hard to remove or them coming loose because of the dynamics of the barrel. Get some hi-temp black and paint it. All of the gas blocks I've cut down have had that paint and it works very well for the application.

[AR-10]

Honestly it wasn't that bad and I would have no problem doing it again.

I found that an 80 grit flapper wheel on the end of my Dremel worked great for shaping the sight base after chopping the top off.

I never thought about the whole pinned vs. set screw thing, but I am glad I left mine the way it is.

Something I noticed, LMT uses straight pins, they don't have a taper...I thought that was a little odd.

[Stickman]

It looks good, and like you said, once you have done one, its easy to see doing more. Good job working through everything, and doing it all yourself.

[AR-10]

Thanks Stickman, I originally planned to send it out but I figured why spend the money.

This thread wouldn't be complete without pics of the fnished project, so here it is, finally ready for some abuse:

http://img407.imageshack.us/img407/8104/img1223t.jpg

http://img249.imageshack.us/img249/2203/img1222ik.jpg

I must say, I am much, much happier now that I have 10" of M1913 goodness.

Now that I have one build finished, I can start working on the middy and the .308 but not until I put a bunch of green tip through this little guy.

[Paulo_Santos]

That looks great.

[TripleBravo]

Looks like a great rifle. Good work on the modification. As a side note, I'm interested to hear your experience with the Troy grip after your next class.

[AR-10]

I will definitely let you know, thanks for all the help guys!

I spent many nights up late reading this forum, what amazes me is you can find solid info on pretty much ANY product related to the AR platform which is great.

I bought this upper and realized it had some features that I didn't care for, WEVO helped me turn it into something that I will now enjoy shooting!

[CLBME]

This is a great thread. It answered questions I had in my mind. Thanks for posting it and your rifle looks great. I hope you enjoy it. Nothing better than working on something yourself and then enjoying the outcome!