257 Roberts cases. Max length 2.233; trim-to length: 2.223.

I have a bunch of cases that are over max, but they chamber. My question is, I've trimmed 20 cases back to 2.213 vs 2.223. Any problem trimming back .010 or .020 under minimum of .223

I've done the same thing and have wondered how it would affect things.

Should be no issue. Nosler .308 brass I use is usually short right out of the bag. For knowing what max is, there is a tool you can get, of course I don't remember the details, that measures what is the brass length actual max is for your chamber.

The important factor in trimming cases is that they're all uniform length, while trimming to the "trim to" length is preferred .010 - .020" shorter is no big deal. Next time you have your dial/digital calipers out set them to .010" and .020" and you'll gain an understanding for how miniscule these measurements really are.

So long as they are under trim length I've never had a problem. I've had lots of case'e where the length varied a thousandth or two and it was no problem. I suppose that in a case headspaceing on the neck it could be a problem. I was reading yesterday that .004 is about the thickness of a human hair, it isn't gonna matter other than there a hair difference in how much neck is holding the bullet! I really believe if people put the effort into learning to shoot well that they do in trying to become ballistic specialist, they'd be much better off! I think a good example of that is how many thousand's people want to be off the lands. It may make a small difference on a paper target but it won't on a live target!

The chamber in the your gun is the important issue . A max factory chamber vs a tight custom chamber could be very different .

As I understand it over max brass length can form a crimp on the bullet and increase pressure.

A chamber cast of your gun chamber will tell you what your max length is. Use cerrosafe or melted candle wax in a chamber sprayed with silicone. Be sure and put a wad of

cloth or a cleaning patch at the point just beyond the chamber. When the cast is cooled push it out with a rod from the muzzle.

I regularly trim .223 brass short. That way I only have to do it once in the life of the brass. Doesn’t hurt a thing.

Good to know, thanks everyone.

If crimping bullets, it is important for cases to all be the same length.

had a co-worker that was loading 7mm mag. in a discussion about what we used when trimming cases, he replied he had never trimmed ANY cases! he is now educated on the subject.

I use this:



Giraud tri-way. Trims, chamfers, deburs. If you don't have one, all you'll need is a drill.

I do that also. 223’s are the only cartridge I trim for.