Comparator ID question

[07yzryder]

I have 2 338 lapua inserts, the hornady measures .327 and the sinclair .337. Based on the data on the lapua wiki these measurements line up with the hornady measuring till the bullet touches the lands and the sinclair measuring touching the grooves.

Now the question - Which is the proper measurement when measuring bearing surface and OAL using the Ogive?

thanks
Robert

 

[mdmp5]

Not fully understanding your question. Are you talking about the comparator inserts that you slap on a pair of calipers? And are you stating that the inner diameter of these comparator inserts is 327 and 337? These tools will only give you a relative measurement and not a true one. To get a true measurement for 338, you would need an insert that measures .330 inner diameter, which know for sure Sinclair doesn't make one.

 

[hlee]

So long as you remain consistent in which insert you use, both are correct. Use the hormady OAL gauge then measure the result with either comparater insert. The comparater is for COMPARATIVE measurements. You either want your bullet jammed into the lands by so many 0.001"s or you want the bullet to jump by so many 0.001"s. If you are consistent with which comparative tool you use, you will get the same relative result with either tool. In other words, if you use the Sinclair tool to measure the OAL of the chamber and then set the jump on your cartridges (lets say - 0.05" from the lands), you will see the same difference if you measure the OAL of your chamber and your new cartridges with the Hornady tool.

 

[07yzryder]

ok as far as measuring bearing length (was looking at the reloading stickies) he measured the bearing length using 2 of the inserts. so same concept as long as im consistent i should be ok?

seems thats the common word in reloading, consistent.

 

[Powermac]

If you want a good comparator, that gives a accurate and true reading. Look up Bob Greens BCG, it's far superior to the caliper style comparators, and has done wonders for my bullet seating consistency.
The sinclar bullet sorting stand or tubbs comparator is also a nice product if you only want to measure bearing surfaces.

Lands and grooves are neither a diameter that's identical between barrel mfg's, so the info is not correct in all cases.