Brass bulge

[Kevin Alexander]

    I just cleaned my brass and getting ready for the next loading. I noticed almost all of my brass has a very slight bulge about a 1/4” down from the base. You can’t feel it but you can see the brass is discolored at the area. I don’t think it’s even enough to measure. Any ideas what could cause it. Fired in a Browning 45-70 BPCR. Load is a 525 grain elliptical paper patched bullet, starline brass with maybe 4 firings, 76.6 grains of Swiss 1.5. CCI BR2 primers. LDPE.06 wad. Notebook paper between primer and brass. No compression. Finger seat and no neck tension.


Should I be concerned?

[Hiwall55]

After 4 firings with about 80 grains of powder its finally fireformed to your chamber, my 44 Maynard does the same thing.

[desert deuce]

If the clean fireformed case drops into the chamber all the way under it's own weight I ignore it. If the case stops short and has to be thumbed in I first use the 45-70 FL die, that doesn't work I use the 44 Maynard die to full length size and then fireform with corn meal. Have not noticed this on the 45-70

[Kurt]

I have that problem with my Browning .40-65 and I even had the cases separate about a 1/4" ahead of the rim. I think it has to do with the generous chamber the Browning has and the .499" diameter of the head on the Starline cases. After a few shots fired the case expands to match the chamber wall and the case gets thin at that point and eventually separation occurs.
I sent several cases to Starline with this problem but never got a reply from them.
I think this might start when they run their draw die through the case stretching a weak spot. ????

   

[Kurt]

I might add;
I have a CPA .40-65 I had them chamber that rifle with my reamer I had ground for the Starline brass and it's a PP only chamber and so far I have not had this problem. That chamber is .5020" ahead of the rim. But the cases shot in the Browning won't chamber in the CPA.