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Some time ago I wrote an article on case lengthening techniques. The article can be accessed at http://www.texas-mac.com/Lengt...ur_BPCR_Chamber.html. More recently I had the need to stretch 200pcs of 45-70 Remington brass as much as possible. The brand new brass was 2.095” long and the chamber of my Browning BPCR is 2.115”. From experience I know a new case will shorten about 0.005” when neck expanded to accept a bullet and will shorten approximately another 0.008” to 0.010” when fireformed. So I needed a case with a COAL (case overall length) of 2.130” (0.035” longer than new), and that’s prior to trimming to uniform length.
The neck walls can vary in thickness 0.001” to 0.002”, possibly more, with any case, whether made by Winchester, Remington, Starline or others. When the case is lengthened using the Kal-Max Case Stretching Jig or Tim Smith-Lyons swage plug, the swaging process will ensure the case wall are uniform where the swaging takes place. The Kal-Max lengthens by swaging the central portion of the case and the swage plug swages the neck. Regardless of the technique used the result is the case length will not be uniform around the perimeter of the lip. It will end up slightly longer on the side with the thickest wall prior to swaging. Therefore trimming to uniform length is required and can result in removing another 0.015” to 0.020”. So now I needed to lengthen the case a total of 0.045” to 0.050” which neither technique was capable of doing.
Since I sold my Kal-Max setup after completing the article the only method remaining was the Tim Smith-Lyons swage plug. The bottom line is I was able to stretch the Remington brass but it was a heck of a lot of work and required two annealing and two stretching steps. A 2nd annealing was required to remove the work hardening of the brass induced by the 1st swaging step. The best I could do was an average COAL of 2.130”, with a resulting length of 2.110” after trimming. The cases were then fireformed, resulting in an average length of 2.10”, 0.015” shorter than the chamber. The only other method to obtain cases of the ideal length is to purchase longer cases, .45-90 for example, then trim to length. If I did not already have the new Remington brass this is the approach I would have taken. In retrospect I should have bought .45-90 brass and kept the Remington for reforming into .40-65.
NRA Life (Benefactor) Member, TSRA Life Member, NSSF (National Shooting Sports Foundation) Member, Author/Publisher of the Browning BPCR book.
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