BPCR BRASS - STRETCHING OR SHORTENING OVER TIME? By Wayne McLerran
Although I’ve been shooting a Browning .40-65 BPCR since 1997, I did not actively participating in silhouette matches until mid 2012. Since then, the same 200 pieces of Remington brass, which were reformed from .45-70, have been collectively reloaded a total of 7600 times. So each case has been reloaded an average of 38 time so far, and none have been lost due to cracking or splitting although the primer pockets of a few have loosened up (more on this later). Initially, after reforming, all were trimmed to an overall length of 2.120”, 0.005” shorter than the 2.125” overall all chamber length from the face of the breech block to the start of the chamber-to-throat transition step. If your cases are stretching significantly or splitting prematurely you may be interested in reading the article Case Stretching & Separating in BPC Rifles.
After firing, each case has been cleaned using ceramic media in a Thumler’s tumbler and the necks annealed. Although I “thumb-seat” bullets with minimal tension it’s my opinion that annealing after each firing results in increased accuracy due to uniform neck tension and also extends the life of the case by delaying neck splitting. To make the annealing process fast and simple I purchased a Vertex brand Bench Source semi-automatic annealer.
Earlier I mentioned the primer pockets in several cases were looser than normal. Using a 0.210” pin gauge all 200 cases were measured and 28 had pockets that had loosened up a bit although they all still held the primers in place. Rather than tossing the brass due to too loose pockets, the life can be extended by flaring the pockets using a simple technique covered in the following You Tube video: https: //www.youtube.com/watch?v=1ST25CUpqhY&app=desktop. After purchasing the two pin gauges and 5/8” chrome ball bearing on Amazon, I used the technique on the 28 cases and it works great – how long the pockets will stay tight remains to be seen. By the way, filing the bases flat afterwards was not required with my brass.
Prior to reloading, since the Browning has a generous chamber neck diameter, the case necks are resized using a neck resizing die and then expanded to the correct size for thumb seating the specific bullet diameter being used. The necks are also flared slightly to ensure a tight fit in the chamber to center the rear of the bullet and help in preventing hot gases blowing back along the case (“blow by”).
As reported in a previous article discussing my test results of various brass cleaning techniques (Case Cleaning - Ultrasonic vs Tumbler with Ceramic Media & Stainless Steel Pins), some case lip peening has been noted as a result of the cleaning process. When the collective amount of peening becomes an issue (bullets hard to thumb seat), it’s removed using a mandrel inserted in the neck resizing die as the necks are resized. I.e., the peened lips are flattened out rather than by removing any brass. Here’s a link to an article on the process I posted some time ago: Removing Case Peened Lip Edge. By the way, I experience peening more so than some others since I anneal after each firing.
During the many reloading sessions the brass length has been spot checked to ensure the lengths were within the maximum limit of 2.125”. Some shooters report their cases have shortened over time, but that has not been my experience. I just measured all 200 cases for the first time since they were initially reformed and trimmed, and found an average length of 2.123”, some a little more and some a little less. I also found the case lengths were not uniform around the perimeter of the mouth or lip. I.e., the length could vary by +/- 0.002” to 0.003” depending on the location of the measurement. So I decided to trim all 200 back to a uniform 2.120” using a Hornady Camlock Case Trimmer as displayed in the following photo. With fingers crossed, maybe I’ll get another 38 loading per case before they start to split.