Trimming Cases to Length

[Thumb]

I set up my new WFT-2 Trimmer in the lathe and got it to trim my .223 cases to 1.751 and was wondering if that's OK to go with? The load data books say to trim to 1.750.

 

[artbosco]

What's the length of your chamber? If you don't know, you're flying blind. Take 10/1000 thds off for safety and another 10/1000 thds for growth [all from the end of your chamber]. 1.750"/1.751" may not be enough or it may be OK, with room to spare.

 

[Thumb]

Are you talking the oGive, if so it is 1.910". I've gone through many brands of ammo and found that the Lake City XM193 rounds are the most accurate so I pulled a few bullets from them and measured their cases and came up with an average of 1.755", bullet was 55gr at .745" and a COAL of 2.248". Weird thing was the powder weight differences which ranged from 26.8gr to 28.3gr.

FYI, this is for my AR-15 so the max COAL is limited to the magazine unless of course I manually loaded each round into the chamber.

 

[LawrenceHanson]

Chances are trimming your cases to 1.751” will be fine. Factory rifle chambers tend to be long and cartridge cases tend to be short. For instance, my .223 Remington rifle has a SAAMI specification chamber that is 1.783” long. My batch of Lapua cases were 1.752” long when new. That leaves a gap space of .031” in the chamber neck, but this is typical for most rifles. In the photo below are shown a Sinclair chamber length gauge on the left, a Lapua case in the middle, and a Remington case on the right. You can see that the Remington case neck is noticeably longer than the Lapua case neck. The Remington case was formed from .222 Magnum brass and trimmed .010” shorter than my chamber.