To get a better understanding of the pattern of .30-30 case stretch I measured and labelled a batch of once fired Winchester .30-30 brass, and kept on firing, measuring and labelling. The trial will finish when all cases have been culled. I started with 134 pieces, and am down to 118 (lost in grass etc). My loads were full power hunting stuff, cast and jacketed, with LeveRevolution and 748.
The once fired cases came from another rifle, but for the test were fired in my Savage 99.
I hope that the results may be of interest to other .30-30 users.
Since I don’t crimp or trim or anneal, I can just let the cases grow and watch what happens. My Savage 99 has a chamber length, including spare headspace, of 2.120”. My Marlin Rippletop has a chamber length of 2.150”. In neither instance is a stretched .30-30 case ever going to achieve this length. My case losses occur from web stretch, not neck or mouth cracking. I resize with Lyman FLS die, but set it so that headspacing is on the shoulder.
On the first reload with circlips in place (to blow cases out for shoulder headspacing) median case length went from 2.030” to 2.031” after firing and resizing.
On the second reload, case length increased from median 2.031” to 2.034”, third to 2.040”, fourth 2.044”, fifth to 2.047”. So far, median length increase has been .016” over four shots, not counting the initial case forming. My longest cases are now 2.056” after six firings. From previous experience I expect to be culling individuals for stretch between 2.060” and 2.070”.
Measuring case length with vernier calipers is fraught – three successive measurements may come up with different numbers, in part due to uneven case mouths – so I use the snap gauge method. If the case passes 2.050” but hangs up on 2.049”, I call it 2.049”.
Monitoring needs to be done over a batch of cases, not just one or two. My observation is that within a group of cases fired with hunting loads, case lengthening on one shot can range from extremes of .001” to .010”. A case may barely move for two or three shots, then throw on .010”, then go back to some lesser number.
I can generally pick up incipient separations sooner by getting the sun shining down into the case and observing the ring of shadow at the web. People who live in low light situations may prefer to probe with a bent paper clip.
What is clear is that cases do not all stretch at the same rate, or the same amount each shot, and do not all reach the point of incipient separation together. I will continue to cull as indicated by signs of web stretch, rather than ditching a whole batch when just a few show stretch.
