Re-using a used FSB

koesdibyo

koesdibyo

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I have an old FSB kicking around, which was obviously installed on a barrel at some point - so the holes were drilled.

That barrel I had it with originally is now gone.

I am awaiting my Modern Sporter, and one of the uppers I have planned is for a 7.62x39mm.

The 7.62x39mm will be my hunting rifle, and I'll be using an optic, but want also like having back up sights as well. Im not overly concerned with it being a sub MOA gun, just minute of deer vitals.

That being said, with my FSB - would it be possible to grind the bayo lug off, and drill tap from below for a set screw?

Obviously the taper pins are used vs the set screws because of their ability to truly lock it in place. But I figured maybe utilize the holes from the existing taper pin holes on the FSB to create an extra 4x set screws as a clamp method?

Seems easy enough to me to throw in a tap and set it up for set screws vs redrilling holes on a FRESH barrel, considering I dont have a taper reamer

6wUDTt6.jpg
 
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It should be possible to grind off the bayonet lug and use a set screw, but its not something I like. I don't care for ground off bayonet lugs on anything, unless its a short short rifle where you can't use the lug anyway. What I'd do if I was in your position would be to drill out the tapered holes for roll pins, or else still drill them straight through and use brass rod and peen the ends over like a rivet.
 
Sniper_485 said:
It should be possible to grind off the bayonet lug and use a set screw, but its not something I like. I don't care for ground off bayonet lugs on anything, unless its a short short rifle where you can't use the lug anyway. What I'd do if I was in your position would be to drill out the tapered holes for roll pins, or else still drill them straight through and use brass rod and peen the ends over like a rivet.
Click to expand...

My worries is when drilling and using the the FSB essentially as a jig for where the holes will be, having the drill bit catch on the round of the barrel will be difficult and either a) snap the drill bits, or b) cause walking and a not-straight hole.

I contemplated the roll pin, or straight pin method since I dont have a reamer, but the problem above is still the one I'd get hung up on.
 
Solution 1:

setscrews.jpg

Drill from the underside and put in 1 set screw on each of the "rings"

Also drill 1 at the sides and put in a set screw as well to prevent it from twisting easily.

Solution 2:
setscrews2.jpg

Drill from the underside as the same for option 1, but rather than drill another hole, utilize the ones from the previous taper pins and drill/tap them for set screws.
Obviously since theyre down towards the bottom of the barrel, the set screws wont bite nearly as much, but it prevents additional material off the gas tube
 
koesdibyo said:
My worries is when drilling and using the the FSB essentially as a jig for where the holes will be, having the drill bit catch on the round of the barrel will be difficult and either a) snap the drill bits, or b) cause walking and a not-straight hole.
Click to expand...

The solution to that problem is to use a carbide end mill to drill the hole instead of using a drill bit.

Put the end mill bit in the drill press, line it up and take it slow. It will not walk like a drill bit will.

You can drill through and use a straight pin if you don't have a taper pin reamer and you should be fine. The taper pins just create a tighter fit.
 
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When I built my SLR with a pencil barrel I forgot to order s gas block from brownells. All I could find in town was a used FSB. Needed a low profile so ground off the sight, ground off the lug, two set screws in the bottom, two on the side. I ain’t a rocket doctor and used the crappy tools in my garage from C Tire.

Has not failed me yet. A little ugly yes, would I trust it if my life depended on it... no. Has it been functional for ~500 rounds? Yes.
 
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