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:



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:



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:



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.

[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:

[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.