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A2 Front Sight Base mount?

CalG

Diamond
Joined
Dec 30, 2008
Location
Vt USA
I wish to mount an "F" height front sight base on a .750 barrel.

I "could" drill and taper pin, but would rather not.

I "could " drill for four opposing set screw that snug down into flats machined in the barrel.

I would be happy with clamp on fixed bases if they didn't cost $100 more and are continually out of stock.


Bravocompany has the .750 bases in stock for 30bucks. Drill to suit.
Still need the sight pin spring and detent.

Any suggestions?
 
Maybe take a regular base reamed for taper pins, or unreamed if available, tap for suitable screws, and slit the spaces longitudinally so they could be compressed.

Shop made clamp ons.
 
Maybe take a regular base reamed for taper pins, or unreamed if available, tap for suitable screws, and slit the spaces longitudinally so they could be compressed.

Shop made clamp ons.


I gave that angle a go on a .730 barrel diameter. There is not enough meat on the FSB to pass a pull bolt. Not even a #6. Unless a flat/channel is milled in the barrel.

But, that is not out of the question... But then.. may just as well fit the taper pins (the horror of barrel deformation) ;-)
 
Use the 4 opposing set screws. They work and give you the ability to set a no wind zero. That is how we used to build the military match rifles before optics.
 
Use the 4 opposing set screws. They work and give you the ability to set a no wind zero. That is how we used to build the military match rifles before optics.

Yep Thanks

I just put the order in for another "F" marked FSB.

drill and tap 6-32 four places. Those forgings can be hard on small drills and taps ;-)

I might put a drop of "wick-n-seal" on after position is confirmed.

I would rather use the windage adjustment on the rear A2 instrument for wind comp.
 
There is not enough meat on the FSB to pass a pull bolt.

Forgot about that. I guess I would make my own FSB, then.
 
Use a larger diameter screw. If I remember correctly it needs a #8 of #10 to fit after removing the taper from the original holes. If you're going to use a #6 screw on gun work, use a 6-40 of 6-48, they are a stronger screw. The 6-32 has the worst root diameter to thread diameter ratio of any thread and are therefore the easiest tap to break.
The windage adjustment on the front is used only to set a no wind zero with the rear sight centered, then use the rear sight for all shooting adjustments. This allows a full range of rear sight movement.
 
Use a larger diameter screw. If I remember correctly it needs a #8 of #10 to fit after removing the taper from the original holes. If you're going to use a #6 screw on gun work, use a 6-40 of 6-48, they are a stronger screw. The 6-32 has the worst root diameter to thread diameter ratio of any thread and are therefore the easiest tap to break.
The windage adjustment on the front is used only to set a no wind zero with the rear sight centered, then use the rear sight for all shooting adjustments. This allows a full range of rear sight movement.

Thanks for the additional thoughts.

The FSB is coming un drilled (as did the previous one I put on the .730 dia barrel, That one didn't work out due to the high pic rail on the upper I had used.)

I'm sure I have some 6-40 set screws around here somewhere ;-)
 
There is not enough meat on the FSB to pass a pull bolt.

Forgot about that. I guess I would make my own FSB, then.

The option to just make one has crossed my mind, but Looks are a thing... and an original pattern FSB "just looks right". I have no interest in a space gun.
 
....Any suggestions?

Put the front post in the base and align the sight base to mechanical wind zero with a good collimator and use red 271 loctite or green 638 loctite to "glue" it in place per USAMU practice on A2 service rifles. After adhesive sets you can drill/ream and set the taper pins if you think it will come off. It wont. Til you want it to. Then a little heat (400 deg+) and she'll cut loose. With my Sweany Sight A Line I can get to within 1/2 moa of mechanical zero.
 








 
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