Different case lengths from brand to brand

[rsbhunter]

I was checking some 223 cases today and noticed some big differences in length. From 1.746 to 1.772.....Per my Nosler book, it shows 1.760 in the case diagram. I havent trimmed any cases except for the ones over 1.760.....i'm not shooting benchrest or anything, more coyote than anything.....my groups stay around <1.00 so i'm not to worried, but how much effect do short cases have on group size? Thanks for any help, rsbhunter

 

[Bc'z]

223 brass should measure 1.75" with 1.76" being max length
556x45 brass will measure 1.76" trim to length1.75".
So you should trim so you don't have chambering issues. Setting trimmer to your shortest case of 1.746" .004" short won't hurt, and it will keep everything uniform.
I'm prepping 50 pieces of hornady brass right now. Every piece is over 1.91" trim to length

 

[Ned Ludd]

As Bc'z mentioned, most chambers give you a little extra clearance for the neck over standard trim lengths. For example, a .223 Rem reamer I have that was designed for 90 VLDs gives the base to case mouth dimension as 1.760", with the taper to the lead extending even further to 1.774" (see red box on reamer print below). Clearly, chambers cut with this reamer have room for the neck to grow in length by as much as 7 to 9 thousandths without causing major difficulties closing the bolt. Some claim letting the neck grow a few thousandths longer may help prevent formation of a "carbon ring" in the region of the chamber right off the end of the neck/case mouth, but I clean my rifles well after each firing and have never observed carbon accumulation in that area. For that reason, I always trim my .223 Rem brass to 1.750", even though I could let it grow just a tick. IMO - the most important thing is that the neck length be consistent from prep to prep, or within the same prep. If you have a few cases within a new Lot of brass that start out at a length slightly less than 1.750", within a firing/resize cycle or two, they should grow out enough that you can trim all the cases to a minimum 1.750" length. Until then, I wouldn't agonize over it too much.

 

[rsbhunter]

Thanks for the information...i would rather have the cases at 1.760, than at 1.745 because of the reason stated...don't know if the 223 has a problem with carbon build up more or less than other cartridges, but it is a condition that deserves watching.... think i'll seperate brass into groups of lengths, with some wiggle room, and not sweat the small stuff....I really appreciate the feedback, this site and it's members have solid information...rsbhunter

 

[Richard Coody]

I was checking some 223 cases today and noticed some big differences in length. From 1.746 to 1.772.....Per my Nosler book, it shows 1.760 in the case diagram. I havent trimmed any cases except for the ones over 1.760.....i'm not shooting benchrest or anything, more coyote than anything.....my groups stay around <1.00 so i'm not to worried, but how much effect do short cases have on group size? Thanks for any help, rsbhunter

is this new brass or fired brass. the reason i say this is if you trim new brass to trim length most likely after fireforming you will have short necks.

personally for me i let necks grow until they have to be trimmed. most chambers have plenty of room over trim length for brass to grow. if you are curious about your chamber you can do a chamber cast. when i do trim it is only to halfway between trim length and max.

 

[rsbhunter]

I don't trim till they are over max, and then only a couple thou under max. Luckily, I haven't experienced any major case growth, I would love to have them all exact length. But as I full length resize, I'm gonna trim the over max ones and let the rest catch up.....Rsbhunter