Thinking of chopping my front sight blade while still ON the barrel. Good idea?

[Sheepdog Gear]

Hey guys. After MULTIPLE AR builds, I'm now putting one together EXACTLY the way I want it. Every component will be carefully considered for use as my main 5.56 battle rifle. (Tentative parts list below.) But I have a question before I get started. I'm going to need to chop my FSB in order for a free float handguard to fit. All I have for this job is a hacksaw / Dremel. I'd also like to do it while it's still on the barrel. Is this a bad idea? And yes, I'd rather mod the existing FSB than buy a low profile gas block.

Upper parts list....

PSA 16" CHF Mid-Length Premium Upper (A2 profile FN "machine gun" barrel)
PSA 5.56 Premium HPT/MPI Full Auto Bolt Carrier Group
BCM Gunfighter MOD 4 Charging Handle
BCM KMR15 KeyMod Free Float Handguard (unless somebody can point me to something better and lighter)
BattleComp 2.0 Compensator
Magpul MBUS Pro Front and Rear Sights
Aimpoint CompM4
Aimpoint 3XMAG w/ LT-649 Flip-To-Side Mount

Lower parts list....

PSA Safe/Fire Lower
PSA Enhanced Lower Build Kit
CMC 3.5lb Trigger
KNS Anti-Rotating Pins
Magpul ASAP Sling Plate
Magpul MOE Grip
Magpul MOE SL Stock (when it comes out this fall)

 

[1911ly]

You can do it on the barrel if you want. If it is going to be covered by the hand guard it it doesn't have to be pretty. Off and done in a mill would be ideal. But a Dremel will do it.

 

[magic man]

You will probably have to remove the the gas block to replace the barrel nut for the KMR. The only way you would be able to keep the gas block on would be to get a hand guard that uses the stock barrel nut such as the Samson Evo.

 

[Hookeye]

I'd make it look pretty, even if it was to be covered.
But not everybody has the artist's hands/eyes or patience (to use hand tools).

 

[xM3RC1L3SS1x]

Your fine doing it while it's on the barrel.

 

[churchmouse]

Done this before just take your time.
Retain the barrel in a proper clamping device and make it solid.

 

[30calmachinegunner]

I guess my question would be if this is suppose to be your "dream" gun why skimp on the FSB

 

[wsenefeld]

Like magic man said, unless you choose a handguard that utilizes the stock barrel nut, the gas block is going to have to come off anyways. There is a LOT of time that will go into shaving a FSB down with a dremel/hacksaw. I did it once and never plan on doing it again. There are half a dozen or more rails that use a stock barrel nut if you decide you don't want to take it off.

 

[Sheepdog Gear]

You will probably have to remove the the gas block to replace the barrel nut for the KMR. The only way you would be able to keep the gas block on would be to get a hand guard that uses the stock barrel nut such as the Samson Evo.

Like magic man said, unless you choose a handguard that utilizes the stock barrel nut, the gas block is going to have to come off anyways. There is a LOT of time that will go into shaving a FSB down with a dremel/hacksaw. I did it once and never plan on doing it again. There are half a dozen or more rails that use a stock barrel nut if you decide you don't want to take it off.

Thanks guys for pointing this out. I didn't even think of this. Every one of the rifles I have built are running the Magpul MOE Handguards. So this was a not issue. Looks like I'll be taking it off anyway. At this point in time, I'm definitely wanting to stick with the KMR over other CURRENT options because of the weight. 5.9oz.!

I guess my question would be if this is suppose to be your "dream" gun why skimp on the FSB

Good point, but I'm not seeing it as skimping. I wanted, (originally) to utilize the existing FSB for a few reasons....

1.) It's already on the gun. Unless I screw it up, it doesn't have to come off. (That is until magic man and wsenefeld told me otherwise.)
2.) It already fits perfectly. So that can't go wrong.
3.) No screws or LocTite holding things together. It's already pinned. So that can't go wrong.
4.) It's free. So that can't go wrong.
5.) Sometimes, I just like a good old project. (Which can go wrong.)

So in conclusion, I REALLY wish Magpul would come out with their MOE "Slim Line" in mid-length so I can avoid this whole deal. I mean if you REALLY REALLY sit down and think about it.... Why? Why would I spend $275 on a rail system that's heavier than an MOE, has WAY more installation work involved, doesn't have any added benefits for my use, and is $245 more expensive? I really don't know. Other than for the fact that it looks really good and you can use front flip-up BUIS, I don't see a benefit. The most I'll ever put up there is an AFG and probably a light, so it doesn't have to be that rock solid.

 

[Sheepdog Gear]

Yep. Think I've talked myself out of a KeyMod. Not quite there yet, but I'm pretty sure. Can anybody talk me back into it? As I previously stated, all my builds are running Magpul MOE's. So I don't have a ton of experience with rail systems / don't currently see a need for them.

 

[stephen87]

Why not just get a new gas block? They're fairly inexpensive.

 

[Sheepdog Gear]

Why not just get a new gas block? They're fairly inexpensive.

Explained in post #9.

 

[Roadie]

Don't they make "cut out" free float handguards that allow retention of the FSB?

 

[Sheepdog Gear]

Don't they make "cut out" free float handguards that allow retention of the FSB?

Yes, but I'm looking for SUPER lightweight, 15" preferably. And one of the benefits to a 15" is a longer sight radius.

 

[Roadie]

Yes, but I'm looking for SUPER lightweight, 15" preferably. And one of the benefits to a 15" is a longer sight radius.

Gotcha! Still learning..

 

[Sheepdog Gear]

Gotcha! Still learning..

Me too!

 

[Robjps]

Yep. Think I've talked myself out of a KeyMod. Not quite there yet, but I'm pretty sure. Can anybody talk me back into it? As I previously stated, all my builds are running Magpul MOE's. So I don't have a ton of experience with rail systems / don't currently see a need for them.

Just depends on what you want to do with the rifle if you were going precision free float rails are highly suggested. I also think its a good idea when you run an IR laser.

 

[Sheepdog Gear]

Just depends on what you want to do with the rifle if you were going precision free float rails are highly suggested. I also think its a good idea when you run an IR laser.

Well, I'm trying to think ahead as far as I can. If I ever came across a PVS-22, it would most likely go on this build next to my TA31RCO. So maybe I will be going with the KeyMod....


Edit: Actually I've heard that the ACOG is not the best optic to use in conjunction with a NVD. The tritium in the reticle is too bright. Sooo, maybe a CompM4.

 

[Jeremy1066]

You will love keymod. Never need to take the handguard off to change things around. A Dremel is all you need to chop the FSB, just take your time and wrap surrounding barrel areas with towels in case it slips on you. When you are done shaping it, tape it off and hit it with several light coats of high temp grill paint.

 

[EOC]

Cut it down.. I purchased a 20 dollar angle grinder from menards and cut it down and used it to round off the cuts then filed it down to looking nice. Then paint it i whatever you want. Its like you said free if you already have it and it will be in most ways a better gas block then a 20 dollar one that clamps on. It took about 20 minutes to cut it down and make it look nice. Im all for a project which is main reason for me to do it versus buying one.