.30 carbine crimp question

[USSR]

OAL was between 1.6785 and 1.6810. Are those sizes ok?

I ran into feed problems when I seated to an OAL of 1.680". I now make sure that my OAL is no more than 1.670".

Don

[jimb16]

OAL is controlled by the mag on the carbine, not by the chamber throat.

[USSR]

OAL is controlled by the mag on the carbine, not by the chamber throat.

Mine is controlled by the throat.

Don

[jimb16]

The bullets you are using must be a short ogive form if you are running into that situation.

[USSR]

Don

[macgunner01]

One day, I'll cast bullets. For now, it's Sierras for me.

Do you guys think I'll be ok using an OAL between 1.6785 and 1.6810? Or will I experience pressure spikes with the shorter rounds?

[jimb16]

Ok, you are hitting the front band! Size? Should be .308-.309....I'm surprised the they aren't just engraving. How hard are they?
MNac, I'd go with the longest that feeds from your mag and chambers easily. Try putting a bullet into a lightly sized cast and chamberin the round. The throat/rifling should push the bullet back into the case. Carefully remove the case and measure the OAL. If it exceeds the OAL needed for proper feeding from the mag, go with the mag length. Otherwise, back the OAL a couple thousandths and go with that.

[Jerome Cooper]

Really good advice and procedure so far for getting it right. Excessive OAL = won't enter and/stack in mag to start with. It does seem that the front band is the culprit so making sure that it is .309 is important. Normally deeper seating does effect the pressure; that would be critical in 9mm or other pistol cartridges, but it/a slight amount won't make too much difference in the 30 Carb. It does however have some relationship to the burning rate of the powder that you use. Faster powder is more sensitive. In the Ruger 30 carb Blackhawk I had to hide all of the front band (RCBS 120 grain mold) and reduce the charge accordingly as the front band+the long nose made the rounds too long and they tied up cylinder rotation on the recoil plate. JC

[USSR]

Ok, you are hitting the front band! Size? Should be .308-.309....I'm surprised the they aren't just engraving. How hard are they?

Yeah, probably is the front driving band. They are just fine at 1.670", so no problem. Cast bullets for rifles are handled a bit different than handguns. Whereas handgun bullets are usually sized to .001" over bore size, accurate loads for rifles are typically found at .002" or more over bore size. I cast mine at a 3/1 linotype/WW ratio and size them to .310".

Don

[jimb16]

Just for the record, carbine barrels are supposed to be .3075 not .308. So .309 would be .0015 ove nominal bore diameter. I size mine to .309 and get good accuracy. I can see where .310 in a slightly worn barrel would work just fine.