Help wanted: Problem with trimming 9mm

Discussion in 'Ammunition & Reloading' started by Shopfox, Feb 7, 2020.

  1. partdeux

    partdeux Well-Known Member Supporter

    be careful with wet tumbling. It can weaken the grain boundaries.
  2. rock185

    rock185 Active Member

    shopfox, I've been reloading 9MM since 1967, and since 9MM is a favorite of mine, I'll share my 2¢ worth. I have never trimmed a 9MM case. A gunsmith building a pistol for maximum accuracy, would want headspace to be tightly controlled. I have measured a lot of 9MM brass and have VERY RARELY ever found a piece of brass as long as .754". I've checked headspace on something over 30 9MM pistols and revolvers. The average was approx. .762". So trimming 9MM cases, which average about .74X" in length, does nothing but increase the headspace.

    The tightest 9MM headspace I ever measured on a semi-auto pistol was .748" on an HK Expert. Since that's .006" tighter than the SAAMI minimum spec, I wouldn't want it on a combat or carry pistol. That being said though, the Expert was as accurate as any pistol I've ever owned, and in using quite a variety of ammo, never a malfunction of any kind.....

  3. PaBushMan

    PaBushMan Well-Known Member

    I used to have problems with some of my 9mm loads not fitting in tight chambered guns. The slide would get stuck partway open from it. A Lee factory crimp die solved it. It may help with the s and b brass too. One thing to watch out for is some casings have an inner wall part way up from the bottom. I forget the brand. But when i find them. I scrap those. Just to be safe for pressures. Smaller area = higher pressures.
    Shopfox likes this.