OA case length

[DaveA37]

The following question was asked of me by a friend who is just getting into reloading.

Question: What significant effect will over trimming a fired case have to the case life?


He explained that he accidentally trimmed some of his 300 WM case about .015 shorter than the specs. Apparently the collar on his case trimmer somehow came out of adjustment and he hadn't noticed the shorter case length until he had trimmed several cases.

Who out there would like to comment? I will pass the info to him and "thanks" to all in advance.

 

[jimbires]

are these .015 shorter than max case length , or are they .015 shorter than the trim to length ?

if these are .015 shorter than max length , they are only .005 shorter than trim to length no biggie at all . either way I don't think .015 shorter will hurt anything . a lot of new brass does not measure to the recommend length . just watch the rifle chamber for a carbon build up , and keep it clean in that area . if he gets a carbon build up then starts to use the correct length he could have tight chambering issues , or pinch the case neck enough to cause over pressure problems . with all this said , I'd keep the rifle clean and use them .

 

[DrMike]

Fifteen thousandths under "trim to" length will not have a significant effect on case life. The cases will stretch some, but the stretching should not be a serious problem. Jim is correct in advising the gentleman to keep his chamber clean, but even that won't be a problem.

 

[Kodiak]

Modern rifles that use smokeless powders aren't affected very much using short cases. Black-powder cartridge rifles though can't stand cases that are very short, as the fouling will build-up in the chamber, where a longer case could have chambering/extraction problems.

Don't ask me how I know,

 

[DaveA37]

Thanks for the feedback. I had told him I thought the cases would probably stretch more at the should than at the tip of the neck. Never thought about the chamber becoming fouled. Good advise from you all and thanks again. I will call him today and let him know of your response. I know he definitely did not want to dump several "short necked" cases at the cost of brass today. He will be glad to hear the reports.

 

[Rol_P]

Just to add to the discussion, many years ago I had a law enforcement friend come to me with a Colt revolver that would not accept his .357 mag. rounds.. All it took was a good scrubbing to remove the fouling that had accumulated in the cylinder as a result of him using a lot of .38 special ammo for practice. In his case the difference, as noted in the Nosler Manual was 0.135" significantly more than .015.