autoloading rifles and undersize die questions?

[cobra1414]

Hello all

I am currently loading 300 win mag for my BAR. Just recently I've been reading about needing an undersize to load correctly for autoloaders. Well my first couple loadings on the brass went fine just doing a full resize the first loading and then neck sizing for subsuequent loadings. The other day at the range though I did get a round stuck in the chamber, locking up the bolt. It appeared that bolt had not fully closed as I could see the rim of the cartridge went looking up through the mag well. I had to take apart the action mechanism to get the bolt free and the cartidge out.

Anyway I started taking measurements with my admittedly cheap calipers and could find no difference between the defective cartridge and piece of virgin brass.

I guess I'm wondering is this an indication I need an undersize die or something else?

Thanks

 

[scrat]

Too many things left unanswered. need to know what type of powder you were using. what grain bullet. What was the grain weight of powder you were using. What kind of primer. What was the cartridges overall length. Were the cases checked for trimming. If you can get answers to this im sure you can get some clearer answers.

 

[HSMITH]

You really need to full length size with an autoloader to keep things like this from happening.

 

[cobra1414]

hornady 165g SST with 72.1g IMR 4350, CCI large rifle mag primer, OAL=84.75mm, case trimmed to a tad under max case length, didn't record the #

So are you saying full length resize every time?

 

[Jacka L Ope]

Yes. Absolutely. Insufficient sizing is probably the most common mistake made in loading for an autoloader. You can get away with neck sizing only for bolt and single shot actions but NOT for the semi-automatics.

 

[cobra1414]

Ahh.. of course, after closely reading my speer manual it does say full length resizing is necessary for autoloaders. Doh!

My first rifle reloading experience, guess I shoud've read more.

Thanks everyone!

 

[DaveInFloweryBranchGA]

Cobra,

It appears you can get a bit more life out of brass with an RCBS x-die instead of a standard FL resizing die, due to the way it works, it helps a bit with separation of brass in the casehead web area.

Dave