When to trim brass?

[Deleted old_dood]

Is a .003"-.004" difference range that important to correct? I recently set to trimming some Lapua 6mmbr brass on my Forster trimmer. The brass had been neck sized on a Forster bump die with a .264 bushing. The brass would not fit into the mandrel on the trimmer so I used a Sinclair expander to open up the neck a little. Funny thing, after doing that, the case length changed about .002"-.003" shorter. I'm wondering if .003"-.004" difference is enough to be concerned about.

Al

 

[Shynloco]

old_dood,
You could quickly cure your issue about trimming simply because you possibly have the wrong sized bushing in your neck die. But that could also depend on the size of the chamber in your rifle. You'll need to make up a test cartridge without powder or a primer and see if you can chamber a casing with a seated bullet into your rifle. I did the exact same thing and found when using the .264, the casings wouldn't fit onto the trimmer mandrel. But consider buying a .267 or 268 bushing and all your problems will be cured and you can trim Lapua brass without having to "open " the neck up for the brass to fit onto the trimmer mandrel. Plus your issue of having to trim your brass will probably disappear after the initial first two loadings and firing. BTW, with those two bushing I suggested you'll also have that .002 - .003 neck tension that is critical for best accuracy in your rifle.

Alex

 

[Deleted old_dood]

thanks Alex. actually I solved my problem after posting above. after using the expander I neck sized again (same .264 bushing) and then the cases fit on the trimmer mandrel. I have a feeling that my problem was caused by the fact of initially neck sizing, then cleaning, and then annealing which may have reduced the neck dimensions. the .264 bushing is correct for my cases since I did turn them. the neck, with a seated bullet, measures .265-.266.

 

[jcampbellsmith]

Is a .003"-.004" difference range that important to correct? I recently set to trimming some Lapua 6mmbr brass on my Forster trimmer. The brass had been neck sized on a Forster bump die with a .264 bushing. The brass would not fit into the mandrel on the trimmer ..

Q1. I don't worry about trim lengths varying up to +- 0.003 inches. I measure all my cases and only trim and deburr cases that are too long.
Q2. Can I suggest that you get the mandrel on your trimmer polished/turned down so that you can carry on following your current process? I used mandrel based trimmers for a while, but I have recently changed to Sinclair's trimmer, so mandrels aren't an issue any more.

Regards JCS

 

[Erik Cortina]

thanks Alex. actually I solved my problem after posting above. after using the expander I neck sized again (same .264 bushing) and then the cases fit on the trimmer mandrel. I have a feeling that my problem was caused by the fact of initially neck sizing, then cleaning, and then annealing which may have reduced the neck dimensions. the .264 bushing is correct for my cases since I did turn them. the neck, with a seated bullet, measures .265-.266.

You correct order is to clean, then anneal, the resize.

 

[Deleted old_dood]

thanks Alex. actually I solved my problem after posting above. after using the expander I neck sized again (same .264 bushing) and then the cases fit on the trimmer mandrel. I have a feeling that my problem was caused by the fact of initially neck sizing, then cleaning, and then annealing which may have reduced the neck dimensions. the .264 bushing is correct for my cases since I did turn them. the neck, with a seated bullet, measures .265-.266.

You correct order is to clean, then anneal, the resize.

I'll do it that way next time.

 

[searcher]

When using the expander, helps to be sure you have it well lubed with Imperial wax, etc., as the friction when running the expander in will otherwise easily change your overall length

 

[Shynloco]

Q2. Can I suggest that you get the mandrel on your trimmer polished/turned down so that you can carry on following your current process? I used mandrel based trimmers for a while, but I have recently changed to Sinclair's trimmer, so mandrels aren't an issue any more.

That's all well and good...BUT what that mandrel on the trimmer does is to help make sure you have a .001 - .002 neck tension. If you don't have any other means to check it, you'll have a heavier neck tension and the incur the strong probability that you accuracy will pay. Now I use both the Redding 2400 (with mandrels) and Wilson trimmer (without mandrels) but still make sure the neck tension is right using a Mandrel die to be sure.

Alex