Help with case length

[Martini25-308]

Since this 25-308 is a wildcat, there is very little data on this thing so I am taking some precautions and would like some input.

It is back from the gunsmith and I am ready to start reloading. I have just measured the chamber and come up with a consistant number between 2.043-2.042.
I have resized .260 Remington brass with a custom Hornady 25-308 die and they measure 2.035-2.031 in length(untrimmed). What should I look for as a clearence? .010? .015? I have read that most factory ammo will leave as much as .050 clearance for safety.

Rocky,,,, do you have any data on what your chamber measured? Just for a comparison.

I plan to seat the bullet at .020-.025 to start with and tweek it from there.

Thanks for your input, Martini

[RUMLUVER]

Martini,

I was looking in some of my manuals I see .010 difference being most common as far as stardard case length to trim length recommendations. So if your chamber is like you say I would trim my cases .010 shorter than that measurement. Hope that was what you were looking for. Rumlover

[Rocky Raab]

I swear I answered this once. Hmmmm...

Anyway, here it is again: Because it's a wildcat, there are no standardized chamber measurements. It's entirely likely that two different gunsmiths will have cut two quite different chambers.

I actually trim mine to 2.00 even, just to keep the numbers simple. Mine has a semi-fitted neck, so neck diameter is more important in mine than length.

The easiest way to tell on yours will be to fire a few rounds. If a bullet won't go in, or drags a bit right at the case lip of a fired and unsized case, the chances are that the lip of the case is being pinched in by the chamber end. Trim just shy of that length, and you should have your gun's trim-to length.

[wesattul]

The three most common cases to form 25-08 from only add to the confusion. The max length for a .243 is 2.045" a 7mm-08 is listed at 2.035", a .260 is about the same, and a.308 is 2.015 I have used all three with no ill effects(that I can tell) Since I neck down 7mm-08 cases mostly, I trim mine all to 2.030 for my own peace of mind. Rocky feels better with his at 2.00" I think the main thing, to get best performance, is to make sure the cases are uniform whichever length you settle on. Have fun !

[MarkL]

Sinclair sells a little doo-dad that you can use to determine the actuall length of your chamber.