Why

I've found the Rugers to be much more forgiving with regard to infrequent cleaning and ammo selection. I have a Kimber conversion and have used it on a couple of different lower receivers. When clean and well oiled it ran with medium (1100+) and hot (1200+) .22 ammo. As it gets dirty, medium velocity becomes a 90% proposition and then falls off, but the hotter ammo allows for uninteruppted shooting longer. Adding a drop of two of oil helps.

Currently using them in a Glock with a 4# trigger, no issues.

Depends on the application; Practice ammo, 10 throw average and load the batch Match/Load Development/Serious Effort, 10 throw average and then check 1 round every 10 or 20 rounds loaded.

most recent batch from them is 4-5 years old, no issues like what you're dealing with.

I've had good luck in full power loads with AA-7, AA-9 and Blue Dot. The AA load are more consistent charge to charge.

A guy named Jeff Maass did a bunch of research and amassed this list of loads. http://www.k8nd.com/documents/hl40sw.pdf Good starting point for a wide variety of weights and powders in .40. I’ve not used VV320 with 200 grain bullets in minor, but I’ve used Tightgroup for that purpose. I started at 3.0 grains and worked with that powder until I found what I was looking for in recoil and accuracy. Pay attention and measure everything.

So it’s always good to measure, but sometimes when working something up, I’ll take a factory round that feeds well in my gun and put it under the seating die in my press. Run the seating die out to allow the round to go in and then adjust the seating stem down to touch the bullet. It’s a good starting point and depending on bullet profile should, ensure feeding. You can make adjustments from there. As stated before, try to remember to measure and write the results down for reference.

I’ve had issues with older Winchester brass but the new stuff is ok. I prefer to load Federal/Speer for accuracy, but most times for practice ammo it’s whatever makes it past the split neck inspection. I don’t mess with crimped pistol brass and trade it to a friend that likes it for some reason. The only cases I’ve ever had fail were old Winchester and old FC nickel brass.

Short answer, yes lead and coated will work for major loads. As with most things there's a cost for whatever projectile you use. When I was starting out shooting, lead made a lot of sense. When I could afford it jacketed became more attractive (less weapon maintenance and exposure). Plated and coated added more options. It depends of what your priorities are and how much money you can spend on this endeavor.

you might have someone compare the firing pin hole and the firing pin for excess tolerance. The little pieces of brass might be from the previous primers getting pierced and leaving pieces on the breechface?

i agree with the recommendation for WST. Never really considered it before, but have come to really like it.

Swept up a couple hundred of those the other day. Big surprise after they came out of the tumbler. They loaded and shot just fine, just an extra step in the process.

Favorites are Blue Dot and AA#7 for full power.

The perimeter of the primers are nice and rounded, doesn’t appear to be over pressure. The hits look a little off center, but the interesting thing from the picture is what appears to be cracks in the primer under where it flowed back. Does the firing pin spring seem normal? Haven’t heard of problems with Remington primers recently.

Go with the 750, you won't be sorry.

Load em, I've shot plenty of lead, jacketed and coated bullets pulled with a collet die. Glad you're not injured, sorry the repair bill will hurt a bit.

Do you think the gun will swing quicker or stabilize faster with the weight reduction or are you going with cool-one of a kind?

Based on the last series of pictures, I agree with out of battery.

Are you talking about an old school look with just the underlug covering the ejector rod?