LeadDispenser

A lot of good advice from previous posters - it sounds like the primers might not be properly seated. You might want to press the handle forward twice on your SDB to make sure the primer is properly seated (first time when you've just lowered the shell plate, second time after you've placed a bullet & new piece of brass, before cycling/lowering the handle). If you're still getting failure to ignite after you've made sure primers are properly seated, I'd start swapping ignition parts one by one with good quality components (EGW for example), in this order: 1. heavier main spring 2. up to spec firing pin & and firing pin spring 3. firing pin strut 4. hammer (normal weight steel hammer) You could try swapping parts from your 2011 to find the culprit, so you're not buying parts you don't need. FWIW, cutting off coils from the FP spring doesn't sound like a good idea to me.

You'll probably have better luck finding 6mm ARC data at snipershide.com or similar forum.

Yes, still ok to fire. When the round "plunks but doesn't turn", the bullet is making contact with leade / beginning of the rifling, but the bullet is not being jammed into the rifling. The problem you might experience is "tolerance stacking" (ie. variations in brass, bullet dimensions, seating depth variation from your press etc. adding up) and eventually loading a round that wont chamber. If the round is short enough to "plunk & turn" you have a little bit more margin for error, if that makes sense.

You're not wrong - your case gauge is just a little bit tighter than the chamber of your barrel. Bullet might be contacting the rifling. You could put some marker on the bullet and see if this is the case.

Sounds interesting. Which gun did you use the modified 9x25 brass in?

Yes. Nope, not even close. Carry Optics division was introduced in 2020 in IDPA and it has very quickly become by far the most popular division - it will probably only grow in popularity in the future. Production 15 is much better idea than Lim Min0r for several reasons: 1. Production 15 makes it very easy & inexpensive to get started in the sport with a stock gun plus 3-4 mags and a rig. 2. We already have Lim, Lim-10 and Lim Optics - adding Lim Min0r doesn't really make sense. 3. It costs much more to get a competitive setup in Lim Min0r, so beginners are not likely to start there and very few current shooters would transition to that class (maybe some from Lim).

I have larger than average hands and using strong hand thumb works best for me & requires no grip change.