Finished my tang sight installation thinking about putting a set of Unertl blocks on another rifle. Some questions on set up.

Barrels round tapered, thinking clamp in a pair of V blocks question is how to set up level and square.

Front to back block Y axis set up on top center of the round no problem. Taper won’t affect it.

To keep the two blocks perfectly in line want to set up X axis on one then use the mills table to move from first block to the next one. Would normally check set up with the dial Indicator, just like traming the vise.  Barrels tapered indicator will follow it & not show in line. My tang sight job indicated on the fixture block not the action . Should I set up on a 10 -12 inch fixture block instead of individual V blocks ?

How about vertical alignment should I shim the barrel so both blocks holes are true 90 degrees to the drill & tap, I think so.

Way I did it on the action tang was piece of drill rod in the chuck close to the tang, Quill locked. Measured the gap with a feeler gauge shimming one end from bottom until the feeler indicated the same gap both holes.

Last one question  drill & tap all 4  holes same time or drill & tap one hole each block install one screw mark the 2nd hole with a fitted punch remove blocks then drill. Tang sight base was hole one end slot the other, makes hole spacing simple. Hit the mark no problem but blocks don’t have that wiggle room. What’s best pratice.

All advice appreciated 

Boats

Strickley for what it is worth. Assume 7.2" mount spacing and 6" mill vise, also DRO and uniform taper.
Use a piece of 4 oz. leather to clamp the small end of the taper. Nothing wrong with using "V" blocks.
Your feeler gage technique should work well to level.
Blocks are usually pretty standard, but would check them.
Center drill to spot the holes, twist drills walk without it.
Guide the tap and go gently. Best of luck.
Chuck

Good tips, & am a center drill first fan.

Don’t have a DRO am well indicatior equipped. I have a set up like John shows that will indicate hole spacing. Except the T slot attachment just like the one I run on the lathe. 1 inch travel indicator.Also like to run indicator on depth when it’s critical.

Thing I will have to sort out is setting up the variable taper barrel.  Have a shot out M 1903 barrel same thing variable taper, will run some test set up drill & tap on it first. Mixed lot of odd bases and screws in my parts box.  Actual job will use MVA blocks, MVA B5 is the intended scope?

Thanks guys 

Boats 

May as well chime in.  It is possible to measure the Hole Spacing on each block by using Drill Blanks or Pin Gages.  For me a few Thou off won't make a difference so I Trust the Dials on the Mill Table for Spacing.  Now be aware that "Backlash" will haunt you if you don't pay attention.  I prefer to do each hole complete before moving to the next one.  I am a big fan of Chucking the Tap and starting it by turning the Spindle by Hand.  Can also go full depth if you're careful.

Boats, good to hear your venturing into for you, Uncharted Water.  David