M&P Caliber Conversions

[Dorsai]

I'll admit it, I've got an odd fascination with caliber conversion just because it's possible, and because (no matter how likely) a different caliber might be useful.

I bought an M&P 9 2.0 5" FDE when they were first introduced. I liked everything about it, especially after adding an APEX trigger. In truth, the best part of an APEX trigger kit is the striker block. Every stock M&P trigger I have ever felt, Gen 1 or 2.0, has had a lot of gritty creep. The APEX striker block is the cure. The rounded and polished top allows the trigger bar to lift it without grating over a sharp angle. Every. Single. M&P.

I had Gen 1's before, but I'd either given them (to my kids) or sold them when the 2.0 came out. As we all know, the important parts aren't interchangeable. When PSA had them on sale, I also bought a compact 9mm in FDE.

A month or so ago while looking for parts for a friend, I ran across a .40 S&W 5" FDE slide on Ebay for $66. New. After looking at it and not buying it, I got a coupon lowering the price to $59, so I bought it. I figured that getting a slide completion kit would be simple and cheap and I was right. The barrel was tougher to source than I thought, and the priciest part of the conversion. The trickiest part of the conversion was the recoil spring. I'd assumed from the beginning that it would be the same as the full size or 5" 9mm. Nope. I couldn't find anything about the recoil spring being different than the standard 9mm /.40 S&W. I had an M&P 4.6" .45acp and out of curiosity, I tried it since it was longer than the 9mm recoil spring that didn't work. And to cut it short, the .45 4.6" recoil spring assembly worked on the M&P 40 2.0 5". I took it to the range last Saturday and confirmed it worked just great. I had several sets of stock sights so my overall cost was $59 for the slide, $134 for the barrel, $83 for the slide completion kit and I don't remember how much for the .45acp 4.6 recoil spring assembly. I checked gunbroker for .40 mags and ended up buying a 5-pack of used LE mags for about $60. Add shipping costs to all parts.

Yes, I know that .40 isn't any more effective than good 9mm. Yes I know that .40 is more expensive. I believed I already announced my relationship with conversions as an obsession. If there was a .22LR kit, I'd buy it. I justify the money spent on this as an option for the next time we have a shortage of 9mm.

The next conversion might be of more interest. There is currently a sale and rebate in effect on the M&P 10mm 2.0. The 4.6" barrel with a holster and 4 mags for $599. Minus a S&W rebate for $100. I've already received the rebate (a debit/cash card) and spent it on groceries. So $499 total for a 10mm with a holster and mags. Took it to the range and tried it, recoil was less than I expected and less than .45acp.

I'm not going to bore everyone with my mistakes and the history of my progress. Suffice to say that if you want a .45 conversion, you need the .45 slide group, a .45 locking block and most tricky of all, a .45 slide stop. The latter is a slide stop that fits the .45 compact and full size 2.0, AND THE COMPACT 9MM AND .40 S&W. The 9mm, .40 S&W and 10mm use the same slide stop. Yes I appreciate that there may be some versatility and savings in using the same parts across multiple platforms is beneficial to the shooter and manufacturer, but it isn't intuitive.

I also tested this at the range last Saturday. If this does you any good and saves you some money, my purpose has been accomplished. I can shoot .40 in the conversion and it actually runs just fine in the 10mm with standard 10mm mags. .40 mags will lock, but easily unlock, so I wouldn't bother.

I like conversions for the utility of having an optional, cheaper caliber when needed. I like having a conversion without a 2nd frame. And if my mental illness helps anyone with their own, then it's been a good day.

[BobM]

I have Storm Lake 9mm conversion barrels for the “1.0” full size and compact M&P40. Limited testing seems to indicate that they are reliable I don’t think they are currently available. I bought them thinking that after I retired I wouldn’t have access to “free” practice 40 ammo. However I now own and primarily use an assortment of 2.0 9 and 40 pistols so the barrels don’t get much use.
I would have assumed that the 10 and 45 would have shared more parts.

[HCM]

Does anyone make a 10mm to 40 conversion barrel for the M&P 10?

[mmc45414]

I am all-in on the M&P, and also am intrigued by the swap barrel idea. One struggle with swapping an M&P is that often you can just get smoking deals on the pistols. They used to sell 5" optic ready 1.0 slides, but they were $350 when pistols cost $400-$500. I did finally cave and I bought one when pistol prices were high, and I put it on top of my M&P .40 (that had an APEX trigger), converting it to 9 and giving me a try at RDO (used a bargain Swamp Fox). It was a neat combo, I had the slide assembly tucked away in the ammo can with the reloaded ammo I had. Then one day my cousin asked if I was going to be loading any .40 soon, and instead I made him a deal on the ammo. Then I made a buddy a deal on the combo pistol, and then a few months later AIM Surplus had a bunch of pistols without slides for $99, and he bought one.

If I had Glocks instead of M&Ps I would probably have a bunch of stuff to swap around, but with M&Ps I tend to just get another gun....

ETA:

Does anyone make a 10mm to 40 conversion barrel for the M&P 10?

And that would be cool, probably push me closer to getting one of the M&P 10mm.

[Tannhauser]

I have M&P 40 1.0 and a 5" FDE M&P40 2.0 pistols. Picked up Storm Lake 40-to-9 conversion barrels on sale for both.

I swap the barrels and use 9mm mags with the existing recoil springs. I've shot a lot of 9mm through both without a problem.

In my case, both pistols were sold at screaming deals and the conversion barrels on clearance, so definitely "worth it". Not sure if I'd go this route buying full price .40 pistols and full price conversion barrels.

[revchuck38]

@Dorsai - You need to get a 9x25 Dillon conversion barrel for the 10mm. Because reasons.

[SecondsCount]

Soon after the 1.0 came out years ago, I picked up a 40 almost new for $380. At the time, the police at the local range were leaving bucket loads of 40 brass and a local caster had 155 grain bullets. I could make ammo for $80/1K.

Sometime after that I purchased a second hand 357 Sig barrel and a 9mm barrel. The 9mm isn't a conversion version and the fit has a tiny bit of play. I've run a few magazines through the gun without an issue. Accuracy is about the same as a 1.0 9mm, about 3" at 25 yards.

[JoeSixPack]

Every stock M&P trigger I have ever felt, Gen 1 or 2.0, has had a lot of gritty creep. The APEX striker block is the cure. The rounded and polished top allows the trigger bar to lift it without grating over a sharp angle. Every. Single. M&P.

There is currently a sale and rebate in effect on the M&P 10mm 2.0. The 4.6" barrel with a holster and 4 mags for $599. Minus a S&W rebate for $100. I've already received the rebate (a debit/cash card) and spent it on groceries. So $499 total for a 10mm with a holster and mags. Took it to the range and tried it, recoil was less than I expected and less than .45acp.

Thanks for posting this and the heads up on the 10mm deal! I just picked up one of these as I have a nice stash of 40 cal bullets and LPP's from the way-back machine. I just put a Duty & Carry Apex kit in an M&P 9 per the Stack-A-Toe thread and thought the best part of the upgrade was the striker block as you indicated. So, I ordered up one of the striker blocks to try with the new styled trigger in the M&P 10 and it's great. The break is a little forward of the Apex D&C and slightly stiffer, but the grittiness is gone. My perception is that the Apex D&C TRS is a little heavier than stock, perhaps because the take-up and break is so much cleaner. Anyway, range day tomorrow! Thanks again!