Guys:

Thanks for looking at this.

I am not a gunsmith but a hobbiest with some marching equipment access and want to verify that my thinking is correct

I have a rifle with custom fitted Talley steel bases.

I am wanting to change out the front base to an extended version, so need to take an off the shelf base and Lower it to match the height of the one on there

My question- the key height reference point is the middle “saddle” portion of the base, correct? My understanding is that it is this surface that the ring indexes on.

Hopefully that is clear and thanks for any guidance. Thanks

BB

Whatever datum point that the ring sits on; should be obvious as you already see. I should start charging for advice.

Thanks DCPD.

Just wanted to confirm my thinking on this and that I should not pay attention to the very top of the surfaces of the base.

I was surprised to see how much they varied (top surface to ring contact surface)when I put a depth mic on them, by the way. Thanks e

Blackbart2

The top does matter.
Seating the new base properly to the action is one thing.
When completed, the new base top must line up with the rear base top.
Since your original base was modified, the new alignment should be checked and adjusted with with the rings snugged up on a lapping bar. Small variations can be overcome by lapping.
Should be best left with someone who has done several like maybe dpcd.
When in doubt, ship it out.

Talley rings can be very difficult to lap.

As for the mating surfaces, use the top of the dovetail as a reference point, I like to measure to the top of the dovetail from the flat on the bottom. Both bases should be the same distance above that flat. Try to contour the new base radius to match the front ring.

If you want a set of lapped talleys to re-lap (if it can be done) to your new bases, send me a PM. I’ll sell them cheap.