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Posted: 10/20/2016 9:29:39 AM EDT
Can anyone point me to a source for a jig to align the barrel and A1/A2 front sight base for the purpose of drilling and taper reaming? Or perhaps plans to fabricate such a jig? The barrels I wish to use are readily available and so are the front sight bases. Problem is they are not available together. I have access to a mill and have some ideas as to how to fabricate a jig but I suspect that such a thing has already been invented

Yes I have searched and found a LOT of interesting, totally unrelated information. I guess I do not know the magic terms to find this thing.

TIA,

Ken
Link Posted: 10/20/2016 9:52:15 AM EDT
The only commercially available jig I know of is BRD engineering. The rest are all home brews.
Link Posted: 10/20/2016 10:00:31 AM EDT
There is a new thread. Just below this one. It's on home built tooling and fixtures.
There you can see what I did.
Link Posted: 10/20/2016 10:32:00 AM EDT
I use one of these. sight block
Link Posted: 10/20/2016 12:48:35 PM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By maxxx93:
I use one of these. sight block
View Quote

That sight block is fine for placing and removing pins, but will not secure the barrel and FSB together to drill for the pin.
BRD sells this FSB Jig.
Link Posted: 10/20/2016 6:52:44 PM EDT
Thanks AFCarbon15,

The BRD contains some of the elements of what I have in mind. For use on an industrial size mill - with a large enough table - I would probably use 3 separate parts. One would be a block bored for the barrel extension and containing the indexing slot to true the barrel radially. Then a second block at the muzzle - tapped for the flash hider threads. This block would hold the barrel parallel to the table regardless of the barrel profile. The third block would support the FSB and index it radially with a pin fit into the front sight post hole. The three pieces would be clamped independently to the mill table.

Thanks survivor45,

I missed the new thread - my bad. I guess it would be reasonable to mount the FSB once the barrel is installed on the upper receiver. However, I am working on a couple of non-flat top receiver builds so I would have to mount the barrel to a flat top receiver, mount the FSB and then transfer the barrel back to the A1 or A2 upper.

Thanks maxxx93,

That block looks familiar. I recently received an advertising email with something like that on sale. I can see that it would be very handy for disassembling/reassembling the FSB but not for the initial drilling.

And thanks Rick_Lind - agreed. And thanks for the link to BRD.

At the moment I only have one barrel which needs the FSB installed (replacing a clamp on FSB). If that works I have my eye on a couple more barrels which I would purchase and fit up. Perhaps I should try and find a local gunsmith/machinist who is already setup to do this. Or perhaps not.

Ken
Link Posted: 10/20/2016 9:46:14 PM EDT
Here is the link .
And some photos

http://www.ar15.com/forums/t_3_4/703735_Let_s_see_your_home_built_AR_15_tools_jigs_fixtures.html

.
.
Link Posted: 10/20/2016 10:12:00 PM EDT
You have "mad skills," survivor!
Link Posted: 10/20/2016 10:30:04 PM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Rick_Lind:
You have "mad skills," survivor!
View Quote


Thanks,
That photo I was drilling the gas port.
My FSB was all ready drilled. So I located the spots for the taper pins the same way. But then I hand filed slots to fit the FSB. One level on my block and one on the bayonet lug.
I think I spent about two hours on each pin slot But it worked .
Link Posted: 10/21/2016 2:03:29 AM EDT
[Last Edit: 10/21/2016 2:22:01 AM EDT by MS556]
I followed this video and got great results without a special jig. You need a good drill press and taped over Vice Grips, and, of course the right size drill bit (#30) and taper reamer (2/0).

It is in two parts:

https://m.youtube.com/watch?v=O6BlViDghKY

https://m.youtube.com/watch?v=sPf-eZf7wXE
Link Posted: 10/21/2016 9:53:35 AM EDT
Thanks survivor45 - a nice setup.

Thanks MS556,

The videos were very interesting and informative - and a little bit scary. I am not a machinist by trade but I can do the math. If the alignment marks on the (.750") gas block portion of the barrel are off by ONE THOUSANTH the tip of the front sight will be off by about 7 thousandths which with a 14 1/2" sight radius translates to about 1 3/4" at 100 yards.The technique in the video combined the errors of the barrel extension vs. the actual position of the barrel gas port,. eyeballing the position of the center of the gas port hole, eyeballing the center of the gas tube hole in the FSB, the accuracy of the sling swivel hole vs. the true vertical axis of the FSB and the parallelism of two drill bits.

I guess that is acceptable for a general purpose 16" AR barrel. I would wish to be a little more precise with my Lothar Walther barrels. I think that using the barrel extension locating pin and the front sight post drilled hole on the FSB as references is key.

Ken
Link Posted: 10/21/2016 10:53:54 AM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Rick_Lind:

That sight block is fine for placing and removing pins, but will not secure the barrel and FSB together to drill for the pin.
BRD sells this FSB Jig.
View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Rick_Lind:
Originally Posted By maxxx93:
I use one of these. sight block

That sight block is fine for placing and removing pins, but will not secure the barrel and FSB together to drill for the pin.
BRD sells this FSB Jig.


I have used it several times and it works just fine for drilling the tapered pin holes. I simply set the barrel in a couple of V blocks and clamp it to the table of my mill.
Link Posted: 10/23/2016 10:20:24 AM EDT
Ken,

I replied to your email in regard to our FSB jig.

There are around 300 FSB jigs in circulation and some in use by manufacturers.

Jake
Link Posted: 10/23/2016 11:03:17 AM EDT
[Last Edit: 10/23/2016 11:18:17 AM EDT by Kornbread]
I went through this same thing last year. Ended up making my own jig. Indexes off of the barrel pin and a rail thru the A2 "ears" and secures the fsb by a screw into where the front sight goes. I'll try to post a picture, let me know if it doesn't work. Hope this helps.

Link Posted: 10/23/2016 11:32:42 AM EDT
I've done 3 without the jig.

https://www.ar15.com/forums/t_3_4/226782_Assemble_your_own_LOWER__UPPER__FREE_FLOAT__TRIGGER__GAS_BLOCK___Step_by_step_instructions_.html&page=25#i5724417

For alignment, I dimple the barrel under the gas port as if I was going to install a low pro gas block.
I tap the bottom hole of the FSB for a set screw.
The set screw in Sheffield aligns the FSB and prevents rotation during drilling.
Link Posted: 10/23/2016 3:08:10 PM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Desert_AIP:
I've done 3 without the jig.

https://www.ar15.com/forums/t_3_4/226782_Assemble_your_own_LOWER__UPPER__FREE_FLOAT__TRIGGER__GAS_BLOCK___Step_by_step_instructions_.html&page=25#i5724417

For alignment, I dimple the barrel under the gas port as if I was going to install a low pro gas block.
I tap the bottom hole of the FSB for a set screw.
The set screw in Sheffield aligns the FSB and prevents rotation during drilling.
View Quote


I've used this method before as well. Only concern being gas port timing being correct.
Link Posted: 10/23/2016 10:03:27 PM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By comp1911:


I've used this method before as well. Only concern being gas port timing being correct.
View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By comp1911:
Originally Posted By Desert_AIP:
I've done 3 without the jig.

https://www.ar15.com/forums/t_3_4/226782_Assemble_your_own_LOWER__UPPER__FREE_FLOAT__TRIGGER__GAS_BLOCK___Step_by_step_instructions_.html&page=25#i5724417

For alignment, I dimple the barrel under the gas port as if I was going to install a low pro gas block.
I tap the bottom hole of the FSB for a set screw.
The set screw in Sheffield aligns the FSB and prevents rotation during drilling.


I've used this method before as well. Only concern being gas port timing being correct.


I check it with a piece of thread tied around the index pin and centered on the muzzle to make sure the thread passes over the gas hole.
Not super precise but would indicate something off more than a few thousnadths.
Link Posted: 10/25/2016 9:29:14 AM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Desert_AIP:


I check it with a piece of thread tied around the index pin and centered on the muzzle to make sure the thread passes over the gas hole.
Not super precise but would indicate something off more than a few thousnadths.
View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Desert_AIP:
Originally Posted By comp1911:
Originally Posted By Desert_AIP:
I've done 3 without the jig.

https://www.ar15.com/forums/t_3_4/226782_Assemble_your_own_LOWER__UPPER__FREE_FLOAT__TRIGGER__GAS_BLOCK___Step_by_step_instructions_.html&page=25#i5724417

For alignment, I dimple the barrel under the gas port as if I was going to install a low pro gas block.
I tap the bottom hole of the FSB for a set screw.
The set screw in Sheffield aligns the FSB and prevents rotation during drilling.


I've used this method before as well. Only concern being gas port timing being correct.


I check it with a piece of thread tied around the index pin and centered on the muzzle to make sure the thread passes over the gas hole.
Not super precise but would indicate something off more than a few thousnadths.


I think I used a laser. Been a few years. Lots of ways to skin this cat. I'm actually coming out with some set up blocks that may come in handy for guys.


Link Posted: 10/25/2016 12:21:44 PM EDT
Thanks to all for some great information.

Ken
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