Full length guide rod problems

[9X23Guy]

I have a 9mm Pro. Bought a SS guide rod for it and a 15 pound ISMI spring. The gun hated it, three malfunctions on the first mag. I'm shooting a 124 grain MG JHP over 4 grains of TG at 140 PF. Put the stock 16 pound spring in and it runs like a top. Thoughts?

[FightFireJay]

I use just about the same setup and load with no issues... I use a 13lb ISMI spring. I also use a 17 lb spring with some fast .40 loads.

Does it feel "different" when hand cycling the gun?

[CHA-LEE]

9X23Guy> Are you using a standard round wire recoil spring? If so, that is your problem. The M&P uses flat wire springs. The same type that are used in the Glock pistols.

[9X23Guy]

Nope, flat wire ISMI. I might try the 13 pound spring before I give up.

[Taylor Murphy]

I'm running the 13lb spring with the standard guide rod and 125 grain loads with 4.5 grains of Solo that make 130ish power factor. No problems so far and I've ran probably 1000 rounds through it.

[CHA-LEE]

Can you elaborate on what kind of jams you experience? Dropping 1lb in recoil spring weight shouldn't make any difference in how the gun feeds or cycles from a reliability standpoint. It sounds like there is something binding or something like that which is causing the failures.

[9X23Guy]

Not really sure. I'll have to go back and watch the video. I put it in before a match and it choked three times o you the first stage so I took it out and the gun ran fine.