OAL Tolerance

[Gnzrme]

Ok, if you were loading bullets for a match or ultimate accuracy, what would be your tolerance for deviations in OAL? I am seating some 308's to 2.744 and I am getting as deep as 2.741 to 2.747...I am satisfied with a .02 margin in either direction...or is this too anal and I am just wasting time...I am using a redding competition seating die on a Redding Big Boss II press...

Whatcha think...

I think I know what the problem is...Inconsistant brass trimming, using a redding hand trimmer. I like the Sinclair trimmer, but its $144.00...

[Beelzy]

One cannot even fathom Match Ammo creation unless the cases are of at
least the same length.

To answer the question about deviation: Anything more than a thousanth
and I start looking.

[30Cal]

Measure a bunch of your match bullets. You'll find they vary in length. That's where it's coming from. What matters is keeping a somewhat consistant jump (distance between rifling and the bullet's ogive), not consistant OAL. Your seating die is taking care of it.

The tips of the bullets have almost nothing to do with how well the bullet flies. Maul one with a pair of pliars and you'll find that it still goes into the same hole as the rest of them.

[Gnzrme]

Yeah, I saw that one where they completely cut off the tip of a bullet any there wasn't any appreciable difference.

[Gnzrme]

So then I shouldn't waste my time ensuring there all seated to the same depth? When I get a better trimmer, I can ensure there all the same length (cases), and then with the Comp die, just seat and then not worry about it...If my bullets are of different lenght, then how do you keep the jump consistent?

[ocabj]

So then I shouldn't waste my time ensuring there all seated to the same depth? When I get a better trimmer, I can ensure there all the same length (cases), and then with the Comp die, just seat and then not worry about it...If my bullets are of different lenght, then how do you keep the jump consistent?

The jump is based on the ogive, not the tip. If you measure your seated rounds by the ogive, you'll see that they're going to be within .001-.003 of each other, depending on what seater you are using, what seater plug, and what bullet.

So yes, you should make sure that your rounds are seating very close to the same depth, but not on bullet tip. Measure from the bullet ogive.

[rksimple]

One cannot even fathom Match Ammo creation unless the cases are of at
least the same length.

Not really. How are you trimming? Based on OAL or distance from shoulder to case mouth? Like a gracey or giraud would trim? It makes a difference in neck length. Having a consistent OAL doesn't mean you have consistent neck lengths.

I get fluctuations all the time in case OAL and load great match ammo. Hell, I've even forgot to readjust my seating die after loading hunting ammo. I loaded a few 155 Scenars down to 2.790 from my normal seating depth of 2.830. They went to the exact same POI as my normal load. I've done that now with my 260, loading from 2.820-2.850 in load development and every single one was to the exact same POI, down to a tenth of a mil.

Gnzrme-you'd be surprised at how much you can get away with and load fantastic match ammo. Just load it and shoot. Repeat. Many times.

[30Cal]

I think I know what the problem is...Inconsistant brass trimming, using a redding hand trimmer. I like the Sinclair trimmer, but its $144.00...

The neck on a .308 is something like 0.31" long. It's going to take a heck of a lot of variation for it to start making a difference. 0.003" is 1% and I doubt that even matters.

[rksimple]

Don't worry about getting a better trimmer unless its going to speed things up (Gracey, Giraud). Trimming is the least of your worries. Like 30cal says, even small fluctuations are a miniscule percentage of neck length. Wind and trigger control are going to play an exponentially larger role than a few thousandths neck length or seating variation.

[Gnzrme]

Ok, that makes me feel better...because it seems inconsistant the way the case chucks up into the redding trimmer and sometimes you do not get it square...

[J-cat]

Ok, if you were loading bullets for a match or ultimate accuracy, what would be your tolerance for deviations in OAL? I am seating some 308's to 2.744 and I am getting as deep as 2.741 to 2.747...I am satisfied with a .02 margin in either direction...or is this too anal and I am just wasting time...I am using a redding competition seating die on a Redding Big Boss II press...

Whatcha think...

I think I know what the problem is...Inconsistant brass trimming, using a redding hand trimmer. I like the Sinclair trimmer, but its $144.00...

It's not inconsistent brass trimming. That has nothing to do with OAL. What you are seeing is inconsistent OAL due to variance in seating pressure and projectile length. Bullets and brass are made on multiple machines with multiple dies. No two are exactly alike. Bullets that feel harder to seat than others often result in a longer OAL because the harder the case neck the more the bullet is crammed into the seater stem during seating.

If you sort your brass, sort your bullets, and use a K&M arbor press with a strain gauge, you can make perfect rounds. If you use ordinary equipment, you cannot improve on what you are seeing.

[ar15barrels]

Ok, if you were loading bullets for a match or ultimate accuracy, what would be your tolerance for deviations in OAL? I am seating some 308's to 2.744 and I am getting as deep as 2.741 to 2.747...I am satisfied with a .02 margin in either direction...or is this too anal and I am just wasting time...

Measure a box of bullets from the bullet base to the tip and you will find that the variation in the length of JUST the bullet is what's probably causing your measured OAL variation.

Quit worrying about it.
There's not much you can do unless you want to meplat trim bullets.

[Darklyte27]

ya bullets are not perfect, i get COAL from 2.80-2.83 when im trying to seat for 2.81

the tips are not always perfect.