[DWFan]

What's are correct dimensions for the .30 Carbine? Is it 1.29" case length and 1.68" overall length? Just how long a cartridge can be used and still feed thru the action? What about bullets over 125 or 130 gr? What is the twist rate of an M1 barrel?

[Acropolis]

Per SAAMI: Case Max Length is 1.290, Case Trim Length is 1.280, OAL Max is 1.680, OAL Min is 1.625. Go to data.hodgdon.com/cartridge_load.asp for some load data for 85, 100 and 110 grain bullets
CMP says Win 296 is the powder designed for the carbine.
Go to the CMP site and read some of their articles.
Look around this forum and find considerable information; I sure did.

[jimb2]

I use WC820. Its carbine pull-down.

[DWFan]

I'm not asking for load data. I'm asking what the M1 Carbine normally functions with and what is possible. I'm wondering if the cartridge/carbine is stuck with the likes of the 85-100gr RN style bullets or if it can be fed longer profile SP and HP profile bullets too? If it is possible, is the twist rate sufficient to stabilize longer bullets?

[jimb2]

The answer is not really. The bullet design is too long. The bullet would need to be set too far back into the case to work in the mag, increasing chamber pressures beyond what the carbine was designed for. Although you could use some of the lighter ones, you would be using them as a single load, one shot at a time. And the twist rate on the carbine is so low that stabilization would be doubtful.

[DWFan]

Thanks. That's what I was after. Any idea what the twist rate is exactly?

[Mooseman684]

My Hornady Manual says 1: 16" Twist for military Barrels....

[jimb2]

According to the TM, the twisty rate on the carbine is RH 1:20. Hence the inability to stabilize longer bullets.