brass - how short is to short

[Nor Cal Mikie]

Two examples chambers are my 6 and 22 BR. Maximun length is 1.560".
Both chamber, measured with the Sinclair Chamber Length Gauges are
1.580". That leaves lots of room before I want/need to trim. One thing to keep an eye on is carbon buildup just ahead of the shorter case neck. I've never had that problem but some shooters have.
I size with Forster Precision Bushing Bump Dies. Size the neck and push the shoulder back maybe .001 to .002. Throw in a body size once in a while if the bolt gets hard to close.
I've never had to trim my brass. It just doesn't grow.
The brass gets longer if you full length resize by the expander ball pulling the necks on the up stroke.
20 to 25 times resized and my brass is still like new. Primer pockets are tight.
All mid range loads so the brass doesn't get hammered. Anneal as need when the brass won't go back to the specs you want. Hard brass won't move like softer brass.

[Hippy]

I think it depends on the Caliber--Hornet brass has a tendency to grow more that most--Usually trim 15 thousands below max--others such as the Br Calibers and the 20 Practical very seldom need trimmed BUT they are Custom chambers and not factory.


Jim

[varmintshooter]

I've been away for a few days but thanks for the replies. What I want to know is if a person shoots 223 ammo (min trim length ) in a 223 Ackley imp chamber it will end up 10-15 thousand of an inch short of SAMMI min length after it is formed, is this the reason you don't have to trim often or is it the 40 degree shoulder that keeps the brass from stretching? I know it will shoot well but don't know what harm it may cause.

[Old Hawkeye]

The 40 degree shoulder will slow case stretching considerably & the fact that it is shorter than min will probably result in not having to trim for a considerable number of firings. You may get loose primer pockets or split necks before you have to trim. The shorter than SAAMI length will cause no harm.

[brians356]

As I noted earlier, if you buy new Nosler 223 brass, it will already be shorter than SAAMI Minimum Case Length before you even fire form it! The standard 223 Rem has an awkwardly short neck as it is, so let's make that even worse, as a service to our customers, shall we?

So, if making a 223 AI, I suggest you avoid starting with Nosler brass.

[brians356]

Originally Posted by varmintshooter

if a person shoots 223 ammo (min trim length ) in a 223 Ackley imp chamber it will end up 10-15 thousand of an inch short of SAMMI min length after it is formed,

I think you must mean shorter than Trim-To Length, assuming the brass starts life at the Trim-To Length (as most brass does - Nosler excepted.)

If it started at Trim-To, then finished up .015" shorter than Minimum, that would represent a total swing of .025" - unlikely.

I personally would not brass at all before fire forming, just to leave as much length as possible. If you ever want to shoot the lightest bullets you will need all the neck length you can get, if you like the bullets seated out near the lands.