Twas the day after Christmas...

[375supermag]

And my son and I took our new toys to the range.
He got a new Glock 40 longside in 10mm and I got a Storm Lake 9mm conversion barrel(and two magazines) for my M&P 40.

My son's Glock shot great. Had no idea a 10mm auto would be so controllable. This thing wants to shoot. Functioned perfectly right out of the box.
After running a few rounds through it for familiarization, he was able to hit a 4" gong at 25yds with regularity. He is getting some negative feedback on his middle finger on his shooting hand from the cutout on the trigger guard. It didn't bother me at all. He thinks he may try to sand that cutout down a bit.

My Storm Lake conversion barrel is pretty accurate, especially with the new laser sight my son bought me to go with it. Unfortunately, it jams on every shot...it either stove pipes or fails to feed the next round. The barrel seems to be well-made and the ramp is polished with no obvious flaws. The Storm Lake barrel is supposed to be a drop-in fit and supposedly 9mm uses the same spring as 40 S&W, so I am not quite sure what the issue is. The mags are genuine S&W mags, so I am confused.

After firing about 50 rounds by hand feeding and damaging 10 or 12 cases, I gave up. Probably take it to a local gunsmith to see if he can make it function.
Too bad...I have run about 500 rounds through the gun in 40S&W with zero malfunctions and excellent accuracy.

The whole idea behind buying this gun was to have a polymer frame pistol that I could switch calibers with. I am satisfied with the 40S&W caliber, which is a new caliber for me, but I want this switch caliber concept to work. I was hoping to try a 9mm barrel and then a .357Sig. Now, I am concerned that this whole idea may not be worth the trouble. Frustrating!!!

[MrWolf]

Sounds like half the day was a success. I can't comment on the Storm Lake as never tried one. Good luck.

[tazman]

I had a similar problem in a different gun. Turned out the mag lips were too close together and not releasing the cartridge soon enough to feed properly.
Easy fix was to bend the mag lips open slightly until it functioned correctly. After that, no more problem. Your mileage may vary.

[petroid]

Are you using 40 mags or 9mm mags

[375supermag]

Are you using 40 mags or 9mm mags

Hi...
Genuine S&W 9mm magazines...brand new.

[petroid]

More info please. What style M&P? Was it factory ammo or reloads? Specs on the ammo. Did you try and slowly allow the slide to close and watch the round as it fed? This may tell you if its getting hung up on its way in to the chamber or kicking out. Also by stovepiping do you mean the empty case would stick sideways in the ejection port? This would indicate either underpowered ammo or too heavy recoil spring. Also check for any machining burrs on the new barrel and how it fits in the gun. There may be slight contact that is preventing smooth cycling. Mark all around the new barrel chamber end with a marker and install it and rack the slide a couple dozen times. Anywhere the marker is rubbed off is contact. If there are hard rub marks, it may need a slight bit of fitting. I have a conversion barrel for my subcompact XD and it took some oil, hand cycling, and shooting for it to "wear in". Hope this helps.

[sergraf]

I had a similar problem with a Glock 35 .40. I eventually changed the extractor for a 9mm one. My 35 runs perfectly with the 9mm barrel and extractor installed. Don't know if that'll work for you.

[375supermag]

Hi...
It is a full-size M&P 40.

Thanks for the idea of marking the chamber...I will try that.

The ammo was commercial reloads my son bought. We have used it in a few different semi-auto handguns (Beretta, FNH and a Helwan Brigadier)with no issues. Some did not fully chamber from the magazines during shooting...all chambered when hand fed.

The cases did stick sideways in the ejection port.

I am hoping that "wearing" the barrel in will solve my problem. I will remove the barrel and inspect the outside of it. It looked good when we installed it, but obviously a more careful inspection is in order.

I will inspect the magazine feed lips, as well.

Thanks for all the ideas, hopefully we will be able to get this conversion barrel working.

[petroid]

40 has a larger rim than 9mm so you are hoping the extractor has enough grip on the case to pull it out. This could explain your stovepiping. If the cases feed from the magazine fine by hand, I would try some quality factory ammo and see how it works
It sounds like it is not extracting/ejecting properly and likely short stroking