M1S, 1.400" case length
 

I don't know if this has already been mentioned here but the case length for the M1S rifles is 1.400". I just got off the phone with John ay M1S, he had the chamber reamer blueprints (Pacific) and the spec for length is 1.400 inches.
Just thought I would toss this out here, I know JD Jones is 1.355 some be aware of the differences

I'm not saying I know the answer but the trim length for the 300 whisper always seems somewhat mysterious. It is nice to know if you have a barrel from M1S that the length should 1.4". Curiously the recent article in the American Rifleman which makes special note of using dies only approved by SSK Industries (J.D. Jones) listed a trim length of 1.4" also and not the 1.355" you note from JD Jones.

I just reviewed data I have from Sierra and they note a trim length of 1.355" and max of 1.365" while Accurate powder lists trim length of 1.35" and max length of 1.365".

What does it all mean? For me it means I am going to get a case length gage from Sinclair and find out what my Pacnor chamber is cut to.

My barrel is also a M1S chambering and my brass chambers just fine at 1.38". Don't have any that have made it past 1.400", but I'll keep an eye on it...

Thanks for the info!

I need to measure my chambers as well. I have a Oly and a Douglas barrel, and they will both chamber brass far longer than 1.365". What was the best method to measure chamber length without specialized tools again?

I use the Pacific(PTG) reamer & it handes the 1.4 without issue. Ron

I had my first case length problem yesterday. The mouth was looking funny. like it had been flattened/stretched out. A quick measurement showed I was at 1.405" All the other cases were fine and of under 1.400". I am sure that is the length of my chamber.