Shave FSB or modify rail? [Archive]

RearwardAssist

07-28-13, 17:54

Ok so this is a centurion c4 10" rail going on a LMT 10.5 upper I want to shave the bayo lug and mill the rail to leave the FSB intact. I wanted to just make sure their isnt something Im missing that will come back and bite me later. I could shave the FSB and leave the rail as is but would prefer a full FSB . Let me know what you think.

http://i1076.photobucket.com/albums/w453/jmalone19/IMG_20130728_154730_073_zpsda22b43a.jpg (http://s1076.photobucket.com/user/jmalone19/media/IMG_20130728_154730_073_zpsda22b43a.jpg.html)

gun71530

07-28-13, 18:06

Why don't you just use the C4 Carbine Cutout rail?

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.46caliber

07-28-13, 18:17

If you screw up your modification, which is more costly to replace?

Cut the FSB first. If you don't like it, get a new FSB and modify the rail. Provided you have a rail mounted front iron on hand to test with.

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RearwardAssist

07-28-13, 18:32

Why don't you just use the C4 Carbine Cutout rail?

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Because I have this one already from something else.

Iraqgunz

07-28-13, 19:14

You can't just get a new FSB.

If you screw up your modification, which is more costly to replace?

Cut the FSB first. If you don't like it, get a new FSB and modify the rail. Provided you have a rail mounted front iron on hand to test with.

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.46caliber

07-28-13, 19:22

You can't just get a new FSB.

Thanks. Now I feel like a boob. Off to read up on FSBs.

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Sentaruu

07-28-13, 19:26

if you were doing it on the cheap your better off shaving the FSB, if not just buy a gas block. DD makes a nice fixed front sight if that's what you are going for.

MistWolf

07-28-13, 19:39

If I wanted to keep the FSB, I'd go ahead and cut a slot in the handguard. Of course, I'm used to cutting metal and hand fitting parts, so to me it's no big deal

NeoNeanderthal

07-28-13, 19:42

If you shave the FSB then you'd spend another 60ish bucks on a front sight. Cut the rail! FSB cut outs are awesome. You cant beat the durability of a taper pined fsb. I'm about to cut-out a NSR rail (inspired by 2nd.amendment).

mkmckinley

07-28-13, 19:54

mkmckinley

07-28-13, 19:55

Thanks. Now I feel like a boob. Off to read up on FSBs.

I think he means because you can't pin the new one using the existing hole on the barrel. The FSB is installed and then pinned so each FSB/barrel combo are basically mated to eachother.

SeriousStudent

07-28-13, 20:16

https://www.m4carbine.net/showthread.php?t=135631

Win-win.

Surf

07-28-13, 20:24

I have shaved, altered many rails in my time and have done the exact thing you want to do more times then I can count, since long before cutout rails were produced. Not difficult to accomplish.

mattexass

07-28-13, 20:28

https://www.m4carbine.net/showthread.php?t=135631

Win-win.

Thanks for the plug. However, I have both shaved and non shaved FSP. I just happen to have extra. It is really up to you and if you want to run fixed front sight like the DD or run the Troy flips up all the time if you want the option later down the road.

Sentaruu

07-28-13, 20:44

nice work there mattexass

MistWolf

07-28-13, 21:21

If you absolutely must keep that rail then your best option is going to be getting a low profile gas block. Then you can use a front sight mounted to the rail. If you mill the rail for the FSB you'll still have a f'd up front sight base and f'd up rail. You're going to have to refinish the milled areas of both and it will look wonky.

I'd just sell that rail on the EE and order one with the FSB cutout from the factory.

How will he have a jacked up FSB? The only thing he'll be cutting there is the lug and sling loop. A little touch up of cold blue will take care of that. If he cuts the handguard, he can touch it up with a little alumablack and make it fit the FSB the way he wants it to

panzerr

07-28-13, 21:30

FSB shave is easy to do. I highly recommend it.

http://youtu.be/FgCG4cgYc7o

Col_Crocs

07-28-13, 22:18

Ok so this is a centurion c4 10" rail going on a LMT 10.5 upper I want to shave the bayo lug and mill the rail to leave the FSB intact. I wanted to just make sure their isnt something Im missing that will come back and bite me later. I could shave the FSB and leave the rail as is but would prefer a full FSB . Let me know what you think.

There's your answer. ;) I understand the hesitation of cutting an expensive rail, but cost aside, rails are replaceable. No turning back once you shave your FSB.

Agnostic

07-28-13, 23:28

There's your answer. ;) I understand the hesitation of cutting an expensive rail, but cost aside, rails are replaceable. No turning back once you shave your FSB.

I second this course of action. While expensive, you can fix a mess up on a rail.

steyrman13

07-29-13, 11:30

https://www.m4carbine.net/showthread.php?t=135631

Win-win.

https://www.m4carbine.net/showthread.php?t=135657
And sell yours to him

Win win win!

RearwardAssist

07-29-13, 12:30

Well thanks for the responses. I went ahead and shaved the bayo lug and sling loop started cutting the rail so far so good. Just need some aluma hyde and some more time to clean it up. I will post pics when I get it wrapped up.

RearwardAssist

07-30-13, 01:43

Done, I am really happy with the way it turned out.

http://i1076.photobucket.com/albums/w453/jmalone19/IMG_20130729_224102_890_zpsf0798c69.jpg (http://s1076.photobucket.com/user/jmalone19/media/IMG_20130729_224102_890_zpsf0798c69.jpg.html)

http://i1076.photobucket.com/albums/w453/jmalone19/IMG_20130729_232759_226_zps697a56f1.jpg (http://s1076.photobucket.com/user/jmalone19/media/IMG_20130729_232759_226_zps697a56f1.jpg.html)

MistWolf

07-30-13, 02:31

Most excellent! I like to see people cut, trim & fabricate parts for an AR, instead of just "Leggoing" it.

What's the next project?

Mr.Anderson

07-30-13, 04:12

There are too many angles in that last picture. Something looks off. Or is it just me?

I was considering shaving my fsp down to a lo pro ver. too until just the other day when I learned (also) that a fsp wasnt a simple part

There is a thread covering a fsp diy but Id rather not chance it.

*spelling/punctuation errors curtesy of iJunk*

RearwardAssist

07-30-13, 09:02

Most excellent! I like to see people cut, trim & fabricate parts for an AR, instead of just "Leggoing" it.

What's the next project?

Thanks Nothing planned yet.

There are too many angles in that last picture. Something looks off. Or is it just me?

I was considering shaving my fsp down to a lo pro ver. too until just the other day when I learned (also) that a fsp wasnt a simple part

There is a thread covering a fsp diy but Id rather not chance it.

*spelling/punctuation errors curtesy of iJunk*
I may be how I took it Ill post another later.

eodinert

07-30-13, 09:51

I don't think that front piece of rail will be useful for anything except snagging on stuff. I'd bust out the power tools and finish the job.

cgjane

07-30-13, 10:15

Colt 6921 upper on a Centurion c4-12 inch (colt lower is on my mk18 cqbr)

The intent was to make the 6921 a m4a1 sopmod clone. I did not want gas problems later by knocking out the FSP pins to install the DD FSP rail.

So I said F it and cut the c4 - 12 rail.

12 rail used to house a 12.5:
http://i6.photobucket.com/albums/y218/gw4k/null_zps52229b8c.jpg

cut for the 14.5 Colt 6921:
http://i6.photobucket.com/albums/y218/gw4k/null_zpsf6279078.jpg

how it sits now:
http://i6.photobucket.com/albums/y218/gw4k/null_zps8c90dbf0.jpg

oh, and having the new dremel saw max is addicting, im always looking to cut something with it.

LostinKY

07-30-13, 10:47

OK I give....
How did you get the rail on and over the FSB without talking the FSB off?

I like the end result!

Colt 6921 upper on a Centurion c4-12 inch (colt lower is on my mk18 cqbr)

The intent was to make the 6921 a m4a1 sopmod clone. I did not want gas problems later by knocking out the FSP pins to install the DD FSP rail.

So I said F it and cut the c4 - 12 rail.

12 rail used to house a 12.5:
http://i6.photobucket.com/albums/y218/gw4k/null_zps52229b8c.jpg

cut for the 14.5 Colt 6921:
http://i6.photobucket.com/albums/y218/gw4k/null_zpsf6279078.jpg

how it sits now:
http://i6.photobucket.com/albums/y218/gw4k/null_zps8c90dbf0.jpg

oh, and having the new dremel saw max is addicting, im always looking to cut something with it.

cgjane

07-30-13, 11:20

OK I give....
How did you get the rail on and over the FSB without talking the FSB off?

I like the end result!

Its 2 pieces! one is the top section, the other the bottom. The top has a hole to let the fsp slide through when installing.

Here is exactly what I was trying to accomplish with the rail I cut:
http://www.centurionarms.net/images/stories/c4-fsp/C4-12FSP-TopDouble-Lg.jpg