Sinclair bullet comparator insert bore does not match my rifle bore.

[denwhit]

I'm trying to experiment my loads by first adjusting seating depth of the bullets in respect to the lands. I have the Sinclair bullet comparator insert for .22 and I have their OAL gage for measuring. When I received my rifle from the gunsmith, he provided an inch long "critter" which is an exact representative of my chamber but only the neck and barrel. I have found that the Sinclair comparator's bore size is slightly larger than the critter's. Any bullet will drop into the comparator about 1/16" further than in the muzzle part of the critter or the actual barrel of the gun. Has anyone else found this? I'm sad because the "critter" is not near as handy as Sinclair's comparator body that receives the insert and clamps on to the calipers. What is the best way to do this? Maybe make up a dummy round that perfectly touches the lands and save that for "the standard" and measure everything to that? ???

 

[aj300mag]

Maybe make up a dummy round that perfectly touches the lands and save that for "the standard" and measure everything to that?

Yes. The Sinclair tool is a comparator, you use it to compare your measurement with a known standard (your dummy round).

 

[BoydAllen]

Since barrels and chambers vary in their dimensions, no comparitor is likely to duplicate them all, nor are they designed to. They are used to take measurements of loaded rounds that are more consistent than if they were measured from tips of bullets. Once a seating die is properly set, the resultant round is measured with a comparitor and that number recorded for future reference (noting the comparitor used, since they are not all the same). That way bullet to bullet variations in how their tips are formed will not result in differing setups, and bullet to rifling relationships.