Is 1.500 too short for brass? Anyone trim below 1.510 and hows it work for you?

[doktarZues]

New, unfired, unsized Starline brass.. consistently SHORT. About 2/3 of a bag of 250ct are measuring well below the "trim length" I've always used of 1.510 .. averaging about 1.505. I was thinking about trimming the whole batch to 1.500 and see how they do. That would save be a lot of hassle of segregating the shorter ones, working them up differently etc.

Is 1.500 too short? Anyone trim shorter than 1.510? How's it work for you?

[FLshooter]

[biodsl]

I learned something today I've always thought that 1.510 was minimum case length. Perhaps I got that wrong impression from measuring virgin brass. Reloading data from AA says minimum is 1.520. That data is re-printed in the 6.5 Grendel Reloading Handbook. Pages 62 and 63 of Vol. II imply that the Grendel is forgiving regarding case length.

http://alexanderarms.com/images/pdfs/grendel_reloading-2018.pdf

It's rather surprising Starline is manufacturing brass at under 1.510.

[kmon]

1.500 will work great and not be too short. Look at the SAAMI sheet http://www.65grendel.com/forum/showt...endel-Drawings

SAAMI spec for case length is 1.520-.020 so 1.51 is in the middle. I like to trim to the min SAAMI case length but if the shortest case of that batch is 1.49 I will trim to that length so all are the same. It is safer to have the case a little short than too long, too long can increase pressure. Min measurement for the chamber is 1.530 and I do not want a case to jam into the end of the chamber which is part of why we trim. Factory ammo is made to spec so it will chamber on all SAAMI cut chambers.

[Klem]

Dok,

It's not a safety issue but as long as long as you are mindful of neck tension then you can trim them as short as you like, within reason of course. By that I mean don't get silly to the point the case can't seal (obdurate) against the walls of the chamber on firing.

I agree with FL, a difference of .01 or even .02 is no big deal, again as long as you are mindful of neck tension - especially in an AR.

For example, if your cases are trimmed from 1.52" to 1.5" you lose 0.5mm of neck tension. That may or may not be an issue depending on what bullet you are loading. If using smaller bullets like the 100NBT, at the usual stainless steel mag length of 2.283" COAL you have gone from 6mm of neck tension to 5.5mm. I am using metric to describe neck tension because the handloading tenet is that we should have at least the calibre of the bullet in neck tension length. Grendel is of course, 6.5mm. With the 100Nosler BT you are already starting off with less than the minimum recommended neck tension length and trimming the case is only making the bullet's grip even lighter.

With an auto loader you definitely want neck tension as the round gets bashed about by the cycling action. This is why military ammo is often crimped into a cannelure - it does not move.

.004" of outside diameter grip seems to be enough to hold the bullet in an auto loader, but this assumes a decent amount of neck tension length. If you can't get .003-.004" with your dies then surface area of shank grip becomes more important.

With heavier bullets like the 120Nosler BT there is more shank length than its lighter brother, the 100NBT. A case trimmed to 1.52" has 9.58mm of shank grip whereas a shorter 1.5" timmed case has 9.07mm. Both trim lengths have plenty of shank grip so trim length is not an issue in heavier bullets.

To sum up;

1. Holding the bullet in place is a combination of shank surface area and neck tension; not so important in a bolt gun but very important in an auto loader.
2. How short you trim your cases is more concerning when using smaller bullets with shorter shanks.

You can check this by loading your chosen bullet in a 1.5" case. Pull back on the action and load it into the chamber from the magazine, eject it and measure if the bullet has moved too much.

You can manage bullet grip by loading the bullet further into the case. That however means more jump and less powder/velocity.

If you're using an AR with light bullets and have a die that gives you decent neck tension to start with I don't think you have to worry about 1.5". For all other bullets or if you have a bolt gun it is a non-issue.

(Nosler measurements are from Quickload).

[doktarZues]

Awesome feedback guys, thanks. Puts my mind at ease. I've got a bunch of short brass laying around (more starline, that I pulled out from previous batches). I will set them aside and work on a 1.5" load down the road, or if I ever need to, but great knowing it's g2g. I'm hot on the trail of a few things, so for consistency sake, I'd rather not change my brass length right now.

Appreciate all the responses but Klem, very insightful for me I learned a few things from that one post. Thanks again