I'm personally of the opinion that setting one gun up for the range and using a different setup for carry, then your range time is not as effective as it can be... Yes. That means a .22 as well.
While any range time is better than nothing, if you think you can use two different setups and get the same gains you're totally fooling yourself.
First off... Recoil.
A .22LR in most pistols, including said M&P22, has about as much recoil as a hamster burp. The .357 Sig isn't uncontrollable but it's definitely a round that let's you know it's there. Same with a .40, 9, or any other serious-bidness kind of round.
Noise.
A .357 Sig is f**king loud. A .40 with serious rounds is loud. My 9mm is loud... Remember, I ONLY use supersonic rounds and like my bullets like I like my cars... The faster the better. Even the fastest .22LR rounds PALE IN COMPARISON to the sound of a centerfire round. And that sound can cause a flinch.
Flash.
If you haven't shot your carry load at night, as in dark not just dusk, then you are in for a real treat. There's no such thing as a flashless propellant, unless of course you're running a can... and if you're concealing a can we can definitely be friends because that's about an 18 on an awesome scale of 1-10. But, for those of us that don't (or can't conceal) run a can for Every Day Carry... Touch a round off at night and it's bright. Period. Touch a .22 off... Yes... it flashes. Touch a centerfire round off... even one with reduced flash propellants... I can just about bet you that your centerfire round is very noticeably brighter...
Think about it like this... Which has more propellant? Now, what does that propellant do after the primer does it's thing?
I know that you know that I know that you know that it burns.
AND there's more of it...
OBVIOUSLY more to start with means more's going to be burning at the muzzle.
Magazines.
Yes, I'm nitpicking... But stick with it.
Look at most .22LR magazines... Compare them to your EDC mags. Do they even fit your pouch? Because my buddy's M&P ones don't match up. Can't use the same gear? Hmmm...
Capacity.
Yes, I'm nitpicking. I know that...
Might you need to empty that 16 shot .357 Sig M&P into someone? I damn sure hope not because that's a touch son of a bitch to stand up to that much hurt! Might you have to fire 16 rounds in an altercation? Well, the guys who love "the average gunfight" statistics will say "Not likely." I will say "I hope not." but I hope you don't need even one... But could you? Sure. Look at all the gang problems just about anywhere these days... People are resilient and take a lot of "convincing" to "get the memo" sometimes. If you shoot the .22 so often you reload at "x" because you count bullets for some reason and have made that muscle memory you may very well dump 4-xx rounds on the deck out of habit.
Well... what if you use an "identical" gun with different accessories on it?
Look, you change the gun and you've changed it and that's just the way it is. Nothing right or wrong about it, it's just no longer identical to your carry gun and that is OK as long as you understand that IT'S NOT YOUR CARRY GUN.
Let's look at my Glock 17.
I carry it with a SureFire X300 Ultra on the rail, I run big tritium sights on it (XS Big Dots at the moment), I put a ZEV Technologies-GlockWORX.com Firing Pin Safety Spring in there because my dumb ass lost the old one armory-cleaning the gun (Yes... I'm clumsy) and thought "What the hell, why not?"
Well, I shoot a factory Glock 17... I don't like the Glock sights and I never have... and it shows. Can I shoot with them? Sure. Can you tell I'm not fond of them? You can indeed because my groups are wider and shot slightly slower.
Now that I've committed to running the light 24/7/365, I've gotten used to that weight at the muzzle... and I gotta tell ya, it works wonders for reducing muzzle flip! Does that show when I shoot a 17 sans light? You bet it does!
There are umpteen thousand things you can put on a Glock and most other service pistols these days... Weighted this that and the other, heavier springs, lighter springs, all manner of sights (some better than others), extended controls, base pads for your mags, lights, lasers, threaded barrels (I hate the term extended for something that's one piece of metal... Show me the separate piece that's an EXTENSION and I won't roll my eyes at the term), and all kinds of other goodies... And some of it will probably go on YOUR gun... Or maybe it won't.
And if you want it, get it.
If you want a stock or near stock gun for carry and a souped up one for a range toy or competition piece... Go for it!
But don't fool yourself into thinking the two DIFFERENT guns (modified vs. stock or near stock) will behave the same way... Maybe it's subtle, and if that's the case you're really lucky, or maybe it's not, but I'm finnicky enough that I see the concept of using the "range gun" for "carry practice/training" nearly as ludicrous as using a separate "range holster."
Stay Frosty.
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-K.