M&P conversion barrels

[Mad Professor]

I was just wondering if anyone has or does run a conversion barrel in their M&P? I have a M&P 40 which I picked up with a Storm Lake 40-9 conversion. I’m actually thinking that I will probably run it strictly as a 9mm, but was wondering if anyone here has any experience with this as far as reliable or unreliable performance. Any practical experiences or stories would be appreciated.

As a plus, I put up a poll, cause they’re fun. ( For me anyway.)

I have two M&P .40s with Storm Lake conversion barrels. Both have been 100% reliable. Accuracy with the Storm Lake barrels has not been that great.

I have test targets shooting both guns with the Storm Lake barrels using my reloads (124 grain Montana Gold Jacket HP) and factory Blazer Brass 115 grain. These were shot from a ransom rest. The Storm Lake barrels prefer my 124g loads.

Results are all 25 yard 10 shot groups from a ransom rest.

With 124g handloads, the 5” pro conversion barrel shot 3” groups. The 4.25” gun with a 5” threaded conversion barrel shot 5” groups. With BB115g the groups open up to 5” and 7” respectively.

Similar 9mm stock barrel guns depend heavily on the individual gun. 2.5”-4.5” with the 124g handloads.
Two samples using an Apex barrel will easily bring the 10 shot groups under 2” with 124g handloads. The BB115g drop to only 1” larger with the Apex barrels.

Small sample of only two Storm Lake conversion 40/9 barrels and 3 Apex non-conversion barrels, but I would use an Apex conversion barrel if accuracy at 25y is a great concern. I think I’m going to buy one to put in the 4.25 gun. Regardless, test different ammo to see what your barrels like.

Edit:
BTW, both of the two gun above using the conversion barrels are accurate shooting with the factory .40 barrels. This is one of them with 3 rounds from hand resting on a sandbag. 25yards. Group is about 1.5”

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[Mad Professor]

I shoot an M&P Pro in .40 for the Major power factor in USPSA competitions.
It's not the most accurate gun I own, and accuracy counts in competitions.
I've read about the 9mm conversions that are great, but the same company doesn't make the .40 barrels.

KKM makes a .40 barrel
I have one in a gun I recently bought, but have not had a chance to check out the accuracy of it yet.

 

[NINEROUND]

.

This type of accuracy and 100% reliability is all I ask. Even mass produced arms should be, with a very few exceptions, should be able to accomplish this as the norm. I’ve never understood why the .40 S&W seems to suffer in the area of accuracy. It’s parent case, 10mm, has in my experience been a consistent tackdriver.

 

[beastep]

I dont own an M&P but I have a conversion barrel for a glock and I would and have carried it. It its reliable then its reliable.

 

[NightShade]

It’s parent case, 10mm, has in my experience been a consistent tackdriver.

I believe that most of the 10MM's are not polymer except for one that Glock made. That would give the weapon a little more mass reducing the perceived recoil and making them feel more accurate IMHO. I have had no issues with my 40 and I am sure it is probably much more accurate than I am.


As far as the OP I didn't buy into the "conversion" barrels. I just bought a factory 9mm and 357SIG barrel for my M&P and I can say that the 9mm works flawlessly. I in fact used it for a USPSA and over the course had no failures due to the barrel. The one issue I had was I did not have 9mm mags and was using the 40S&W mags so the last round could be a pain and a couple of the rounds popped out in my pocket.

The bad thing is to get them you have to troll some place that gets them in and when it's available click the buy button or just backorder it and wait. I got mine through MidwayUSA and the price is less than half of the conversion barrels. The Pro M&P's are harder to find and the 9mm one is more common than the 40 so their a conversion barrel is pretty much what you are stuck with unless you bought the 40 and can find the 9mm. As far as I know there are no 357SIG barrels available in the PRO unless you but a conversion. If you want a threaded one it's as equally hard to find as the PRO for factory barrels so again better off buying an aftermarket one.

With the correct mags however I would have ZERO doubts about carrying any one of the barrels I have in my M&P. It's all factory and works just fine. I researched before buying a conversion as a lot of people were saying the recoil spring was different or that the mating surface would have gaps and that just has not been the case. The same factory spring is marketed for them both and the surfaces match up just fine. In fact one thing I did learn is that most 40's and 357SIG's would probably be better off with a slightly heavier recoil spring (17 to 20 pounds) than what comes from the factory which is supposed to be around 16 pounds. And if you want to run hotter 9mm loads you would also want to increase the recoil spring to something slightly higher.

 

[Gunbuffer]

The only Mp barrels worth a lick are the apex ones. The gunsmith fit ones.

 

[Ignored Member]

The only Mp barrels worth a lick are the apex ones. The gunsmith fit ones.

I wish I knew a gunsmith who could fit one for me.

I used to know one. He was a grumpy old cuss, but a softie at the core. The only guy in the state I trusted to put sharp things turning rapidly near my guns.

 

[Shadowrider]

I wish I knew a gunsmith who could fit one for me.

I used to know one. He was a grumpy old cuss, but a softie at the core. The only guy in the state I trusted to put sharp things turning rapidly near my guns.

Ditto! I'm still not sure he didn't find a monastery to join though.