I just traded into a 2.0 .40 Compact. I have no issues with .40, as I've shot and carried one for years. But I would like to get a 9mm conversion barrel for it. I thought I read a factory 9mm barrel for the 2.0 compact will work in the .40 2.0 compact (or maybe that was for the 1.0 version)?

Any recommended conversion barrels? And I'm assuming I'll have to use 9mm mags?

Anyone do a comparison of 9mm vs. .40 in the compact? What were your opinions (I might just also buy the 9mm)?
Thanks.

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Watch & Pray

Wrong breach face and extractor location for 9mm.

That's what I figured, but if you read the reviews in the link, it seems to be working? And I'm assuming that's for the 1.0 guns?

Smith & Wesson Barrel M&P Compact 9mm Luger

__________________
Watch & Pray

I don't know if they changed the upper for the 2.0's but the 1.0 compacts allowed the use of 9mm conversion barrels (such as Storm Lake) in M&P 40 Compact guns. I used a 9mm stock barrel with 9mm mags in my M&P40 full size for years and many thousands of rounds. The only snag was that unless my 120g 9mm loads were > 1100 fps, the cases would eject erratically, sometimes only a foot or two to the right, sometimes onto my head, sometimes into my forehead. A full M&P9 slide cured all that. I got a great deal from a member here.

They don't make a conversion barrel for the compact yet, so you have two options. One would be to get a full size 2.0 conversion barrel and have the less that quarter inch cut and recrowned to be flush with the slide. The second option, which is the way I went because of a great deal. is get an Apex Gunsmith Fit Barrel in 9mm for the 2.0 Compact. I had my gunsmith fit it for me and lock up is TIGHT!! He ran a box of ammo through it with no failures. I took it to the range today, no cleaning, and put another 400 rounds of target and defensive ammo, and again zero failures. It has an ejection pattern that is pretty close to my full size 2.0 in 9mm and it was dead nuts accurate.

This was the last 70 rounds (Magtech FMJ) of today's session, from about 10 meters. I was getting fatigued from lack of sleep, and I was trying to counteract that with Monster and coffee. I am very happy with the results.

300 rounds of Magtech 115gr 9mm FMJ
50 rounds of Sig M17 V-Crown 124gr +p
25 rounds of Federal HST 124gr +P
25 rounds of Hornady Critical Duty 135gr +P

When changing to a 9mm from a .40, do I need to change the spring? I have both 115 and 124 grain ammo.
Gun is a M&P M2.0 compact 40.

No, the recoil spring assembly is the same for both 9 mm & .40. .