Enlarged Primer Pockets

[p246]

I've been thinking that I'd eventually have to full length size the 303 cases. Forcing the expanded cartridges into the chamber is probably a great way to wear out the locking lugs. Do you occasionally experience case head separation in either caliber?

No so far I've been lucky. I was fortunate to have someone much older spend time with a young dumb kid. He didn't mind stupid questions and like to teach others. He had saved different cases that had failed or were close to failing, bad primer pockets, cracked necks etc. He gave me the tools to inspect brass pretty good when I was in my twenties. Without his help I'd probably have blown myself up by now.

[bigedp51]

Big Ed,

Thanks for the info. The stiff extraction I'm experiencing from the expanded 303 cases which, according to the link, is one of the signs of high pressure. As previously mentioned, I'm using starting loads BUT neck size only. These expanded 303 cases have been fired and reloaded multiple times which has probably caused or allowed progressive body expansion to reach its current size. Would you agree that a better test might be to evaluate a new or full length sized case for symptoms of stress, i.e. expansion, extraction stiffness, etc. after it's been fired only once?

Normally a full length resized case should be .003 to .005 smaller in diameter than its fired case diameter. This allows the case to "spring back" from the chamber walls after firing, and attempt to go back to its resized diameter. And a neck sized case looses its spring back ability each time the case is fired and hammered to chamber dimensions.

I think its time to "partially full length resize" your cases to reduce the body diameter, and you will need to "play" with how much smaller in diameter required for proper spring back from the chamber walls. I use a Redding .303 British case forming and trim die to bump the case shoulders back. This die does not touch the body or neck of the case and only contacts the case shoulder. If you place a fired case all the way in the form and trim die the case will fall out of the die when inverted. (Redding 83154 Form & Trim - Series B .303 British)

If you use a full length resizing die to bump the case shoulder you will over resize the case and shorten case life. In 1914 the Enfield rifles chamberers were reamed larger in diameter and longer and the chambers are no where close to American SAAMI dimensions. Meaning the dies are very undersized compared to the military chamber.

[p246]

I use Redding dies on my bench rest stuff. They are a very good product but expect to pay for them. I have slowly replaced a few milsurps rifle dies with Redding stuff, but I always hit the budget wall too fast. 303 is on my short list to upgrade. Now if we could get a flat based .311 Mark VII bullet.