Cutting down a FSB

Are there any issues to be concerned in cutting down a front sight base?

I have seen where some advocate removing the entire base to do this though it was not explained why it was necessary.  Any issues with cutting it down without the need to remove it from the barrel?

If it matters, this is on a carbine length gas system.

Mojo/Mark
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Vincent from "Collateral"
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Joined: 9/30/09
Location: Northern Nevada (Reno/Sparks)

Original Post

I cut one down in the garage with a dremel.  Still have it, gas tube still attached.  I ended up rebuilding that whole upper so I didn't need it anymore but it still works.  It would have been easier with an angle grinder but I didn't buy one of those until a few years later.  Just stay above the level of the gas tube and it'll be fine.  Make sure you have some cold blue or other type of finish for the bare metal.

Joined: 10/1/09                       Location: Columbia, SC

I’ve done a bunch.

Never removed the FSB because this is N.J. and I didn’t want to cut off a $100 muzzle brake (everything has to be pinned here). Never had an issue.

Angle grinder is faster, Dremel is more precise - I prefer using a Dremel with cut off wheels.

A hit of cold blue on any nicks, and a coat of high-temp BBQ paint and you are done.

__________________________________
"Experienced cops don't have 'hunches'. They have superior observational and analytical skills which allow them to make the connection between otherwise innocuous facts, and take appropriate action to assess that perception."

~ Doug Mitchell

 

Life is Good!


Joined: 03/08/2008     Location: Sandy Hook, NJ

Same, use a Dremel cut-off wheel, rough file, fine or jeweler's file, sand paper (if you want to smooth off the tool marks), then black spray paint.  You don't have to remove it, just clamp the whole damn barrel or upper between rubber jaws in your vise.

In my head I couldn’t think of a logical reason one would need to remove it to cut it down. Thanks guys. 

Mojo/Mark
__________________________
Yo homey, is that my briefcase...?
Vincent from "Collateral"
__________________________
You want the good life, you break your back, you snap your fingers, you snap your neck... Prong/Demon Hunter
__________________________

Because...I Can. 


Joined: 9/30/09
Location: Northern Nevada (Reno/Sparks)

Thanks, I saw some  stuff last night but it was from Arfcom hence me asking here to get the real deal answer. 

Mojo/Mark
__________________________
Yo homey, is that my briefcase...?
Vincent from "Collateral"
__________________________
You want the good life, you break your back, you snap your fingers, you snap your neck... Prong/Demon Hunter
__________________________

Because...I Can. 


Joined: 9/30/09
Location: Northern Nevada (Reno/Sparks)

CReynolds posted:

Does cutting of the FSB facilitate attaching a one piece handguard? 

Yeah. I cut them down to make a low-profile gas block so I can put a free float tube on. 

From this:

To this:

I like the Troy rails (that’s a SOCC MLOK tube) because it uses a standard barrel nut. It is rock solid, slim, and light weight as well. Win, win, win, win!

__________________________________
"Experienced cops don't have 'hunches'. They have superior observational and analytical skills which allow them to make the connection between otherwise innocuous facts, and take appropriate action to assess that perception."

~ Doug Mitchell

 

Life is Good!


Joined: 03/08/2008     Location: Sandy Hook, NJ

High Exposure, LongEye, and Sinister pretty much covered it all. A vice and tape are your new best friends.  Use some wood blocks, lead vice inserts or if you’re in a pinch a bunch of layers of aluminum foil to keep from scratching up your barrel if you’re one of those guys that get torqued up about skinned up guns.  Using  a vice is is REALLY IMPORTANT if you decide to use an angle grinder.  Those things are excellent tools for removing things very quickly wether it’s an unwanted FSB,  barrel or gas tube metal, and any errant body parts that you interpose into the path of it’s rapidly spinning disk.

Oh, don’t forget to wear your frickin eye pro or better yet a full face shield.  Dremel cut off disks and those grinder disks exploding at high rpms will make you even uglier than normal and blind.

"The individual has always had to struggle to keep from being overwhelmed by the tribe. To be your own man is a hard business. If you try it, you'll be lonely often, and sometimes frightened. But no price is too high to pay for the privilege of owning yourself." - Rudyard Kipling

CReynolds posted:

Does cutting of the FSB facilitate attaching a one piece handguard? 

Yes, and no.

As High Exposure posted, yes, if you are planning on using the type of tube which will attach to your original barrel nut, yes.  Normally you will have to remove the barrel to take off the delta ring.

If you are wanting to use a tube which requires a different barrel nut, you will have to take off the FSB and uninstall the barrel.

For this particular project, I have already picked up a Bravo keymod rail.  So,  looks like I will still have to remove the newly modded FSB/gas block anyway.  Thanks all.  As usual, great info. 

However, for future reference, what rails, other then Troy, will fit over a shaved FSB and use original barrel nut?  Thanks! 

cead mile failte

Centurion

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Mark

Swear allegiance to the flag Whatever flag they offer

Never hint at what you really feel

Teach the children quietly For some day sons and daughters

Will rise up and fight while we stood still

 

Joined:  2/24/2003                          Location:  Nevada, USA

Ya know, lo pro gas blocks are everywhere and cheap.  Geissele's are awesome and $40 new on arfcom.  But rock on.  😎

-------------------------

IT'S A COLT.  THEY'RE LIKE THE HK OF GUNS.

HRH (Ret.) The Most Reverend Consig

Stupidity is not a skillset.

 

 

 

 

 Joined: 28 Nov 2004: 0037hrs        Location: The worst run state in the U.S

I agree with John on the Geissele gas blocks. My stepbrother and brother-in-law are both getting Geissele rails for Christmas. I'm not cutting down their FSBs; I'll just put the Geissele blocks on. I'd use the Geissele block as my first choice on anything that was 0.750"; BCM for the thinner ones.

Joined: 30 May 2003                  Location: SE PA

Consigliere posted:

Ya know, lo pro gas blocks are everywhere and cheap.  Geissele's are awesome and $40 new on arfcom.  But rock on.  😎

Agreed 100000000%

Like I said, the main reason I cut down is because I don’t want to cut off a pinned $100 brake and I don’t mind the Troy Handguards so there is no need to swap barrel nuts.

If I was assembling my own upper, I would - and have - used a low pro gas block (I have a couple of BCM blocks on guns). But once installed, there isn’t much out there more rock solid than a standard FSB block. In my mind - may as well keep it.

__________________________________
"Experienced cops don't have 'hunches'. They have superior observational and analytical skills which allow them to make the connection between otherwise innocuous facts, and take appropriate action to assess that perception."

~ Doug Mitchell

 

Life is Good!


Joined: 03/08/2008     Location: Sandy Hook, NJ

My whole reason for asking initially was because I’m ultimately probably just going to go with a  drop in 2 pc. Midwest Industries carbine length M-LOK handguard (MI-17M).  Reasonably priced and perfectly suited to my needs. 

Mojo/Mark
__________________________
Yo homey, is that my briefcase...?
Vincent from "Collateral"
__________________________
You want the good life, you break your back, you snap your fingers, you snap your neck... Prong/Demon Hunter
__________________________

Because...I Can. 


Joined: 9/30/09
Location: Northern Nevada (Reno/Sparks)

I totally get the run what you brung philosophy and the practically.   Certainly been done a million times and is bomb proof.  It's easy for me to say when Jojos will build and upper for me while I wait for a large pizza or some subs. 😎

-------------------------

IT'S A COLT.  THEY'RE LIKE THE HK OF GUNS.

HRH (Ret.) The Most Reverend Consig

Stupidity is not a skillset.

 

 

 

 

 Joined: 28 Nov 2004: 0037hrs        Location: The worst run state in the U.S

CReynolds posted:

Agree also,  but this was going to be a do-it-yourself project and my confidence level in properly pinning the Geissele block is very low.  Figured I'd use the FSB and not have to worry about my skills.  

The Geissele Carbon Steel blocks are the only thing I use on .750 gas block journals that I plan to keep or give to a relative.  I get them from ALG:  https://algdefense.com/carbon-steel-gas-block.html

They are easy to install with simple tools.

Here are the instruction so you can take a look-see, just scroll down to super gas block:

https://geissele.com/installation-guides

There really isn't any need to pin the block.  I pin mine because I have a drill press and I need to show my wife 'see I really needed a floor mounted drill press.'

 

I like that plan DLEHR. I need a floor-mounted drill press because when I mentioned needing a drill press to my Dad (as he's soon liquidating some of his tools -- poor guy is losing eyesight quickly), he told me to get a floor-stand one, not a bench-mounted one with a larger class motor than his.

Joined: 30 May 2003                  Location: SE PA

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