So how does the extra 50 FPS compromise reliability? I'm assuming you're just using less of the same powder and everything else is the same? What reliability problems were you experiencing?
First, excuse the typos in my initial post, I didn't proofread, as I needed to take my kids and the dog for a hike this morning.
To answer your question/s.
The recoil and magazine springs have to be working together. Timing just right. That is a major factor.
The produced load runs at 1150 FPS.
In testing, I produced a bunch of ammo that ran 1200 FPS, and some at 1225. I did not have any issues with shooting it. It did require a strong 2-handed grip, as recoil was as to be expected with such a load. I have been shooting large bore revolvers for 30+ years along with a lot of time shooting heavy loads through semi auto pistols, so I am familiar with the such things.
That said, as part of the process of developing a commercial load, I recruited a couple people who were hunters and handgun owners, but not really big time handgun shooters. In having them shoot the heavier 1200-1225 FPS loads, they would occasionally have malfunctions of various types.
Starting out and with good instruction, initially they were fine, but it did not take long before they would tire, lose focus on fundamentals and then malfunctions would happen. That was with 2 hands.
With 1 hand, using the heavy loads, it was terrible. I was essentially trying to see if they could shoot the load sitting on their butt, one handed, in an awkward position. They had a very hard time controlling the pistols, and it was obvious that this was not a good load for them.
After a good bit of T&E, I came to the sweet spot of a 200 grain bullet at 1150 FPS. Using a proper 2-handed grip, the average shooter, with a little practice could make fast, repeated shots/hits on target.
Using a 1handed grip, while not blazing fast as far as time between shots (as compared to a 2 handed grip), they were able to control the gun and still have a reliable platform.
Since the ammo was not designed for me, but for the consumer who may be a guy going to Montana, Idaho, Wyoming or Alaska, and wants a gun for bear protection, or is a handgun hunter, the 1150 FPS with a 200 grain hardcast was the Goldilocks spot of accuracy, reliability, and speed.
There is always a sort of "tipping over point" and for me, I noted that I could put more rounds into an A zone in 2 seconds with the 1150 FPS load than I could with the 1200 FPS load. I might be able to get the same amount of shots (sometimes) off in the same 2 seconds, but the accuracy was just not comparable.
Along the same lines, I have a heavy .45 ACP +P load that I make and carry a lot in bear country. It is a 250 grain hardcast at 925 FPS.
It is a personal favorite for a number of reasons. For one, I cut my teeth on the .45 ACP and have killed all manner of game with it from jackrabbits up to cow elk.
Just like the 10mm, I have made a hotter version of this load, but the sweet spot of total reliability, velocity and accuracy was 925 FPS. I have run it in everything from various 1911s, S&W 4506, Performance Center 4563 (The most awesome 3rd Gen ever made!) Glock 21s, and an HK USP among others.
I looked at a number of the loads factories offered and was never satisfied, so I decided I would make, then offer my own. It offers what is very similar to the very early .45 Colt loads in an auto pistol. I have total confidence in it, plus when I am on a hiking trip in MT, and decide to go into town, I can use the same gun/same load. A 1911 covers both.
Back to the original question of the 50 FPS. Yes, 50 FPS can make a significant difference in terms of reliability for many people who are not experienced shooters. Not everyone will have a vice-like grip and control recoil like a dedicated competition shooter or someone who carried a gun for a living for decades.
Unfortunately many will still just go with what is fastest, thinking that is the best product for them, even though they may be buying a product that may not be the most reliable.