Precision Hand loads, case oal trimming/length

[ARH77]

I started hand loading in January and I had a about 150 Lapua brass cases from factory loaded match ammo that I kept after firing. Then I bought 200 new Lapua brass cases, although I prepped the cases I didn't trim the length of the case. I measured them to make sure they were all below the 2.015" saami spec, and they were.

I didn't trim them because I knew after they were all fire formed I'd neck size them only and the case OAL would change, I wanted to wait until this point to sort and trim them all to the same length as it seemed the most logical time to do it.

Now the majority of them have been fire formed and only neck sized (no shoulder bump and no full length resizing).

I was going through and measuring/sort all of them to see where the length sit to decide where to trip the length at. I was surprised by the range of lengths that I had, my shortest case is measuring 2.000 and my longest case is measuring 2.015. The brass that was from the factory loaded match ammo is in the 2.000 to 2.007 size range and the new purchased ammo is in the 2.008 to 2.015 range. Now i'm sitting hear scratching my head, I've read that you shouldn't trim the case below 2.005" and some places said not below 2.008". I'm not sure how wise it would be to trim them all down to 2.000, I have about half the cases that are below the 2.005 mark and about half above the 2.008 mark.

I'm partially resizing the neck with a Redding competition neck resizing die, about 2/3" of the neck length is resized (about 0.180"). 0.015" difference in case OAL is close to 10% of the bullet seating contact area, that feels like it's too much variance and that I need to make it more consistant.

Any guidance the precision reloads can offer me?

Thanks.

 

[CanuckR]

By the sounds of it you have enough brass to brake it down into 2 separate lots of different lengths. Or if you only have a few that are too short, cull them (hard to with lapua brass) or keep them separate.
I'd hazard to bet you have a hard time shooting the difference between the 2 or 3 lots of brass if you did it that way.

But there are many with far more experience than me that will probably weigh in

 

[silverfoxdj]

I'd load 10 samples from the cases from the two groups and see what your results are accuracy wise to start.

 

[damadama]

What has this got to do with "Precision Rifles"' it should be in the Reloading forum!

 

[ARH77]

What has this got to do with "Precision Rifles"' it should be in the Reloading forum!

Ya and then I get 100 responses from the handgun and AR guys saying I only need to be under saami spec.

 

[FLSTFO2]

use a body die or an fl to bump the shoulders back so they all match, then trim to the shortest oal.

 

[nevanevan]

I trim all my brass to 2.005". The brass that ends up shorter than this will grow with mulitple firings. I would not be throwing out lapua brass because it is a couple thou short.

 

[bolbmw]

use a body die or an fl to bump the shoulders back so they all match, then trim to the shortest oal.

This. From my experience and from my reading OAL has very little or no effect on accuracy whatsoever. Trim to consistent length and go and shoot. Trim them back down when they're at max OAL. It's a measurement for safety not accuracy.

 

[pilot_dc]

The length of the neck will have an effect on bullet friction as it leaves the case. It will be a very small difference but if you're going for the most consistent ammo possible, I'd recommend what has already been said, and FL or shoulder bump, then trim. I'd also turn the necks, again, for the sake of consistent bullet retention. This isn't something you'll have to do for every single loading of the case, but periodically it will be required. I generally get low single digit SD when I take the time to prep the brass properly. I notice an increase in SD when I cut corners, so it does make a difference. Whether or not 5-10 fps of SD matters to you will depend on your application.

 

[maynard]

I use a Type S Redding bushing die to resize and bump the shoulder back .002". I do this because my Gracey trimmer needs a FL resized case to get a consistant trim to length. I trim all my .308 Lapua cases to 2.000" so I only have to trim them every couple years. ( I have 2400 Lapua cases) Make them all the same or as close as you can to being the same. I doubt that you will be able to tell the difference down range between a case trimmed to 2.000" and one trimmed 2.015".