case trim length?

[briscoetab]

I am not completely new to reloading but am pretty new to precision reloading. I read the stickies at the top several times and have done some searching about what the proper trim length should be. I understand the two train of thoughts and why, I think: trimming to trim to length from book specs and trimming just short of the chamber length.

My chamber length is 2.878" for a Remington 300 ultra mag. The max case length is 2.850" and trim to length is 2.840". The once fired brass I have range from 2.843" to 2.846". For the best precision and accuracy should I just trim my cases to 2.843 every time? Should I not trim any of the brass, but if I did that the brass would be inconsistent from case to case? I want the neck length to be long as possible to have more room to seat the bullet and prevent a build up in the chamber.

I see where tresmon says in the brass prep sticky at the top to just trim to the shortest case length the first time and leave it. Will the cases grow at approximately the same rate every firing after the fist trimming? Will letting the case neck become longer after every firing affect your zero since the case length will differ from your fist firing? Is this something I should even worry about as long as it stays short of the overall chamber length? My plan right now is to trim to my shortest case length at 2.843" and then trim to my shortest case length every firing. Does this sound logical or is it just a simple preference thing? Thanks for all your help and any advice. If this question has already been answered could you point me to the post I did serch some but not in depth.

 

[427Cobra]

I seriously doubt you can shoot the difference in .003 trim length, trimming is more about safety than accuracy.

 

[bigedp51]

Watch the video at the link below, not all chambers are the same length and the manuals are SAAMI "guidelines". The gauge below will give you the chambers exact length and you could make them .010 shorter than this.

Sinclair Chamber Length Gage | Sinclair Intl

 

[briscoetab]

I already measured my chamber it's the measurement in the first post and it's not the .003 that I am talking about it's the .03. My brass right now is .035 shorter than my chamber.

Yes your right I probably can't shoot good enough to notice the difference in .003, probably no one can, but to me it seems like .035 could make a big difference in keeping the bullet aligned and helping accuracy. I doubt I will ever see my cases get that long but maybe longer than they are now wouldn't hurt.

 

[ksthomas]

Briscoetab,

It's a safety issue, and has little or no serious impact on accuracy. If you do indeed have .035" ahead of the case mouth, then you simply shouldn't have to trim anytime in the near future. The only real exception to this would be in cases where you're applying a crimp. The varying lengths will cause different amounts of neck tension. Aside from that, don't sweat it so much, it really isn't that big a deal. For some reason, this whole topic seems to have been blown way out of proportion over the past year or so.

 

[briscoetab]

Thanks for the replies. My main concern was not really increasing or decreasing accuracy by having shorter or longer case necks, other than having a longer case neck to help center the bullet when seat (although I doubt it really helps much if your seating properly).

What my main concern was is just having consistent case lengths. I guess what y'all are saying it doesn't really matter if I trim or not as long as I stay within my chamber length dimensions? Trimming has no benifit and does not change your bullet to bullet ballistics? Thanks again and let me know if that is correct.