Home Forums Reloading Big Game Rifles Brass trim length, how critical?

For hunting accuracy, how important is brass trim length, as long as it’s under max? Is a few thou variation gonna make any noticeable difference? How much variation in length is acceptable?

Also, I know brass too long is bad and can cause pressure issues. But can brass be too short? Is that potentially damaging to the rifle? Excess throat erosion or something?

In my book, hunting accuracy is more critical that paper punching. Accuracy is rarely harmed by generating a consistent product. Take the time to do it right, then one need not worry.

It depends on the cartridge. You wouldn't want to be too short on the 300wm neck, as the neck is already "too short". A lot of other cartridges have enough to spare that you would be fine with .040" shorter than recommended trim length. As you stated in the op, you don't want to be too long or over sami spec on any cartridge, but being short won't hurt a damn thing. It has to be a lot shorter before it starts affecting accuracy as well. I too like to keep things as consistent as possible, but every once in a while you'll have an oops and end up trimming a piece a bit too short. I haven't seen that affect accuracy enough to worry about though... I, however, don't shoot benchrest competition either. If I'm shooting centerfire competition or what my club calls "precision" rifle comps, I'd leave anything out of the normal at home or use it for practice. Eventually it will stretch and catch up....

Trimming should be a rare event. The end of the chamber is usually so long that should brass stretch that much IMO it should be retired. Many chambers are .050" to .070" past the length of cartridge when new.

Naturally it is good to start with all brass the same length for consistent tension/bullet release.

Many loading manuals suggest trim length .010" shorter than standard length. I think trim suggestions were created so the uninformed handloader won't get into trouble.

Informed handloaders KNOW the distance to end of chamber. It is quite easy and will save you a ton of time wasted on trimming:

https://www.youtube.com/watch?v=JKnXJxaAw2U

To answer your question. I have never noticed any difference in any trim length vs untrimmed brass in a hunting rifle. I used to trim and occasionally made the case too short then corrected the issue. Mixed the cases and had good accuracy.

Thanks all. I’m not worried so much about losing a minuscule amount of accuracy. I’m more concerned that a short case would somehow cause more throat erosion or something.

I don't like trimming, so when I do, I trim my brass short.

Just keep the length even and you will be fine.

I bought the case length measurement plugs from Brownells. Put them in a lightly tightened neck that is trimmed way short. Insert into chamber and bolt in. Eject and “walla” you have your max brass length. I have found my chambers have max brass lengths anywhere from 15-45 thousandths longer than book max length. I make a note for each individual rifle of its max brass length and as long as I am 10 thousandths lower than max, I don’t trim. I hardly ever trim brass now unless I am really fine tuning a load.

https://www.brownells.com/reloading...clair-chamber-length-gage-prod32925.aspx

I carved one out of wood, prior to finding Brownells done thought of it too. Good little tools.


(That was when I had one rifle and was self-teaching myself to reload and didn't have a case trimmer. I was trimming with a deburring tool. Had read that a kaboom was a possibility with cases too long and it seemed a sensible way to figure out how long was too long. Nowadays I tend to trim a little short, and collet neck resize and retrim infrequently. But, thinking this over, trimming too short could be hampering my accuracy? Will have to take another look at it.)

If you have a lathe you can make your own. Thanks to Varmint Al's website I found the dimensions and did just that:

https://www.varmintal.com/alath.htm#Chamber_Length_Gauge

Cool. Thanks for the link.

I just run them on a Lee trimmer in a drill. Easier then measuring them and they won't need it again until five or more loadings depending on the case.

Very short cases could increase throat/chamber erosion but it is like shooting 38s in a 357 mag chamber or 44 special in a 44 mag. It will take several thousand rounds to scorch out the chamber to the point it will affect accuracy. In a rifle the throat will be toast usually before the chamber transition goes.

I'm another that believes in taking the time to do it right. But I doubt that most of us can shoot the difference if the length varies a few thousands. Its probably different with different cases too. Like the difference in the neck length between 222 and 223.

Buy a WFT or WFT2. Set it to length at the start of load development. Trim every time. Do it right.

I check case length periodicly and trim to the trim to length. Cases that are shorter than the trim to length are set aside and checked to determine just how short they are. Most times my cases aren't over the maximum length just not of uniform length, trimming remedies this. I can't conceive that a short case would cause any significant chamber erosion.