FSB alignment jig - pics inside

AR/M4 AR Technical Discussion
1

The FSB jig prototype lives. This is one I have been thinking about for a long time and finally got it into CAD and had one made. I already have a few changes I want to make but nothing major. It may work with clamp on sights as well, depends on if the 5/16" key stock would fit.

Barrel started out as a RRA heavy with no FSB. I had it turned down to 0.800" under the handguards and did the F marked FSB install pictured below.












2

Very nice!

I need a mini-mill!! :cool:

3

Pretty slick setup. Any plans on selling them, or providing the service?

4

I need to get pricing from the shop. I hope to be able to offer these for sale.

5

Sweet, work out some pricing and let me know. I’d be interested.

6

Excellent set up, nice job.

7

That is very slick. do you power ream 2/0 after drilling. I use a simular rig made from white oak but keys from receiver instead barrel pin, very cool. I’m starting work in the morning on new one, hope you don’t mind as they say it’s a compliment.

8

I wish I had a big mill so I could make them myself. I have to sub most of this stuff out to shops that have the equipment. My mini mill could probably do these, I’ll probably try to do one one of these days.

I do power ream with the mini mill at a low speed and lube. I do the final fitting by hand though.

9

Here is some constructive advice to improve your set up.

That square bar which goes between the block and FSB post hole should be atleast twice as thick so there is no chance of it flexing.

You also need to devise some type of spacer to put under the square bar to compensate for a 0.040" difference in a F marked FSB so your jig can be used for both FSBs.

-OR-

I would mill down one side the square bar and have it be flippable to compensate for a F marked FSB.

10

Thanks for the feedback.

11

Very nice work. You must post an update on how well the rifle shoots and if it needed much windage dialed in :slight_smile:

12

Wow, very very very nice job!!

I think that product would sell.

13

PS: Cool mousepad !:smiley:

14

very slick !

15

Works as a work pad too. :smiley:

Thanks for the F marked FSB’s got one yesterday along with a Vltor gas block for this project: https://www.m4carbine.net/showthread.php?p=317054#post317054

16

Very good!

C4

17

Thanks Grant.

18

For hobby use, why can’t you just tap a set screw on the bottom hole and use the barrel dimpler jig? I figure it would work just as well as any low profile gas block with a bottom set screw set up.

19

I thought that too but found that the hole isn’t in always in the same location or the right location for that matter.

20

Thanks, you just saved me a big head ache. By the way any ETA on your gas block taper pin jig ?