Problems getting valid OAL measurements

[esaabye]

I have a Sinclair OAL gauge and now just picked up a Hornady gauge with the 223 adapter. I am getting very different results from the 2 when working up a SMK 80. Same chamber, a WOA Wilson with 2000 rnd gives me a 2.51 on the Sinclair and a 2.39 on the Hornady. I tried 2 other barrels with similar results, all 223 Wylde.


Anyone know why? Should I trust the sinclair and return the hornady?

[Alpha2]

I have the Hornady, so am awaiting opinions on this...

[Artema]

I just use a caliper. What kind of machines are these?

[XC700116]

Kinda confused on what you're seeing here, are you talking about using this type of gauge?

http://www.hornady.com/store/Lock-N-...ullet-Inserts/

And similarly the sinclair version of the same thing?

If so, you're probably seeing some minor variation on where the comparator contacts the bullet. As long as you consistently use one gauge when measuring a specific load/chamber combination you'll have no problems as they should find the same spot. Either way with each barrel/bullet combo you'll have to measure each time when setting up the load for the rifle.

[Hound]

What he said. Just use the same gauge. You cannot even use the same brand and expect the same results. There are too many variables.

[spqrzilla]

The results are comparative, not absolute, OAL. You can't get the same measurement with two different tools.

[Great-Kazoo]

I just use a caliper. What kind of machines are these?

Likewise, Caliper for the win.

[spqrzilla]

Well, I do agree that I see these kinds of tools as really only useful for benchrest shooting games.

[Alpha2]

These tools are for measuring the distance from the bolt face (case head) to the lands in the bbl. It can show if you are getting a uniform seating depth measurement, and allow you to adjust the setback to a specific jump to the rifling.
True OAL measurements will generally give you varying numbers even with the same instrument because few bullets are the exact same length. Try measuring a bunch of SMKs sometime. The bullet seating die doesn't push on the tip, fortunately.