Different shoulders trimming .223?

[sbwaters]

With my new Frankford Arsenal electric trimmer I started trimming about 50 .223 Lake City brass to a Lyman Trim-to length of 2.750.

Almost one third of the cases stopped three thousands long. Two-thirds of the cases trimmed to size. Would this be because the cases were created on different machines where the shoulder is different?

I separately trimmed them the extra three thousandths so they would all load the same in my single stage seating die.

--

Another set of brass bought “trimmed” were short -- 2.735 to 2.745. Why would they be sent to users so short? It makes it hard to standardize on a length.

 

[higgite]

That trimmer indexes off the shoulder. If the shoulder to head dimension is different for 2 cases, their lengths from mouth to head will be different by the same amount after trimming. By the way, I think you meant 1.750 trim-to length, not 2.75.

As for the already trimmed brass that you bought, I hope you meant 1.735 to 1.745. If so, that is within SAAMI tolerance for .223 Rem brass. You might want to check the shoulder to head dimension on that brass, though, to make sure it isn’t “short” due to the shoulder being bumped back too far and then trimmed with a trimmer similar to yours that indexes off the shoulder. That’s a good idea with any “new” brass, once-fired or not.

 

[sbwaters]

1.750 trim-to length, not 2.75

Doh! Thanks.

 

[homatok]

Brass should be trimmed after resizing, not before.

 

[sbwaters]

Brass should be trimmed after resizing, not before.

Absolutely.

 

[Walkalong]

.003 is nothing to lose sleep over. If they all fell in a .003 spread (1.750 to 1.753), I'd call it good.

If you want perfection from base to case mouth, get a Wilson hand trimmer.

 

[heymarine1833]

different lots of cases will yield different measurements. for example: had my trimmer set to 1.745 and trimmed my last bunch of lake city cases. i opened a new bag of once fired sized cases and found the new cases were a mile off. a real pain. would be nice if all cases were exactly the same wouldnt it?

 

[Laphroaig]

I've been following this thread with some interest. I also have a Frankford Arsenal case prep center, but haven't really trimmed many cases in mine.

One of my sons had about 50 .280 Rem brass that had never been trimmed and were way over length and needed trimming, so we set up the Frankford tonight. All RP brass, just full length sized, set to trim to 2.530". We measured cases until we were certain that they were being trimmed to the desired length. Most were +/- .001 except the second one that we measured at 2.533". No explanation other than that might be the tolerance of that trimmer.

.003 is nothing to lose sleep over

+1

Laphroaig

 

[SARuger]

I have the same Franford Arsenal trimmer, I trim thousands of .223 cases of all brands.......after running them through the resizing die.

It won't work right any other way. Even for new "sized" brass.

Its a great trimmer. My only complaint is my hands start to cramp after about 50 cases and by the time I get to 500, they are done! I need a better way to hold the cases and still make quick work of the only task in reloading I loathe, trimming.