Precise measurements

[6.5x300 WBY]

Ok I am loading my 300BO with Sierra 125gr with H110. I am doing seating tests and seems I do mess up with consistency getting precise CBTO.

EX. trying for 1.4800 but occasionally I get 1.4795. Is that acceptable to maintain consistency? Most were at 1.4800 but had 1 just off.

It happened occasionally with my other seating depth. My worst one was supposed to be 1.4600 and I got 1.4590. Ugg

 

[338 dude]

Ok I am loading my 300BO with Sierra 125gr with H110. I am doing seating tests and seems I do mess up with consistency getting precise CBTO.

EX. trying for 1.4800 but occasionally I get 1.4795. Is that acceptable to maintain consistency? Most were at 1.4800 but had 1 just off.

It happened occasionally with my other seating depth. My worst one was supposed to be 1.4600 and I got 1.4590. Ugg

That is a fairly tight spec. I would be very happy with it but if you want to be sure, load some at each length and see if you can tell the difference on target.

 

[Beluebow]

If you can shoot the difference between .0005-.0001 seating depth with a hunting setup consistently....you're a beast. We all strive for perfection at the loading bench but if you miss it by that slim of a margin across the board, I'd say you're doing great.

 

[Rick Richard]

What Beuebow said.

 

[6.5x300 WBY]

That is a fairly tight spec. I would be very happy with it but if you want to be sure, load some at each length and see if you can tell the difference on target.

That's what I did. Got a bunch at different depths and seeing what shoots best. Ok feel better now

Thx guys.

My new Calipers are making much better and consistent loads for sure. It's crazy I used to measure 4 or 5 times and get different numbers. So glad I got these Mitutoyo's

 

[Mikecr]

The tightest seating window I've seen so far (always off the lands, OTL) is 8thou wide.
It happened that optimum was 8thou OTL +/- 4thou.
A lot of times I'm further out.
I imagine the closer you end up to the lands, the tighter the window could get.

Your little ~1thou variance should have no affect

 

[FireFlyFishing]

Ok I am loading my 300BO with Sierra 125gr with H110. I am doing seating tests and seems I do mess up with consistency getting precise CBTO.

EX. trying for 1.4800 but occasionally I get 1.4795. Is that acceptable to maintain consistency? Most were at 1.4800 but had 1 just off.

It happened occasionally with my other seating depth. My worst one was supposed to be 1.4600 and I got 1.4590. Ugg

Well, look at it this way…it's a 300 BO. Does it matter that much?

 

[6.5x300 WBY]

To me yes. I just want consistent precise ammo.
It's Long Range Huntings fault. After I joined I learned too much from you guys and what was satisfactory is not anymore. .5 used to be a unicorn for me now if that's what I get I now feel I have more work to do to get me .2 or at worst .3.

 

[FireFlyFishing]

Bolt action I assume? No way I would be that anal on my 300 BO auto loader. For me on that rifle…just needs to fit in the mag and I'm happy.

 

[Bob Wright]

That kind of variation is actually tightly controlled. Congrats. Load away.

 

[Phil Rizzo]

1 thou could be the difference in bullet length, ogive length, seating depth due to spring back, sloppy press linkage, die variance, and the list goes on.
Ever had a flattened powder kernel or piece of a fired primer end up on the shell holder between the brass and steel!?

 

[6.5x300 WBY]

Totally my fault In regards to .2 .3 groups. That's for my 6mm CM NOT my 300 BO. I just want moa and I am happy at 100 yards.

 

[Tiny Tim]

Ok I am loading my 300BO with Sierra 125gr with H110. I am doing seating tests and seems I do mess up with consistency getting precise CBTO.

EX. trying for 1.4800 but occasionally I get 1.4795. Is that acceptable to maintain consistency? Most were at 1.4800 but had 1 just off.

It happened occasionally with my other seating depth. My worst one was supposed to be 1.4600 and I got 1.4590. Ugg

If I am reading your statement correctly, you are talking about 0.0005". Most good calipers have that as a listed resolution, but your actual measurement is somewhere between 1.4793" and 1.4797". The caliper is rounding to the nearest 5 ten- thousandths. This is phenomenal consistency. Great job!

Now understanding this, the difference between your readings is probably really closer to .0003". The reality is your thumb pressure consistency will likely induce greater error than your ammo is in actuality. Some people are better at this than others and most people have to re-zero a caliper that someone else has been using, even amongst machinists.

All this is to say you are making exceptionally consistent ammo and measurements. Well done!