Heavier recoil spring for M&P 9mm?

[opngrnd]

Has anyone tried running the 17# or 20# ISMI springs in their M&P9FS? I saw that ATEi did for the pistols that they built in their Costa Series. I'd be interested in for several reasons, with the criteria that I only shoot factory and full power ammo through mine. Mine is currently stock, but will soon have an Apex USB and Sear, and a 10-8 rear sight added, same as I did when I had a M&P45. Here's what I'd like to know about using a 17# or 20# recoil spring-
A-How did it affect recoil and tracking?
B-How did it affect accuracy?
C-If you had an M&P9 that was gradually shooting larger groups over 4,000-5,000, did replacing the recoil spring with a 17# or 20# spring help return the group sizes to normal for the particular gun?
D-What did you use to mount the new recoil spring, for lack of a better term? The factory guide rod?
I have observed that, while there are a plenty of people with M&P 9mm problems, often I hear something like "the groups got worse and worse for 5,000 rounds and I sold it because I hated the gun". If the factory recoil spring is sub-standard in life cycle and pressure, would a heavier one with a longer life help as long as it was replaced at proper intervals?
Please understand that I am NOT making light of anyone's problems or trying to sound like I just thought of something that no one else did. I shoot factory and full power loads(to the 7th Edition Hornady loading manual), and I know that there are a lot of people to set their firearms up competitively around the pressure of the ammo they shoot, and that a heavier spring might not work for them. I don't even know how Power Factors work, so I couldn't tell what PF I shoot. Thanks in advance for any feedback.

[Magsz]

Back in the day when i was running M&P's i ran 17 pound ISMI springs in my carry guns.

With factory loaded ammo the nose would dive after recoil as the pistol locked up into battery. I found 15 pound springs were the lightest i could reasonable go on a "defensive training" pistol because the 11 and 13 pound springs would allow the gun to unlock merely by shaking it. When i say factory ammo i mean ammo loaded between 132 and 147k power factor.

With hot +P loads, the 17 pound spring functioned wonderfully and going any heavier is simply not needed.

To this day, ATEI hasnt mentioned WHY they're running 20+ pound springs but i have a feeling it is to keep the gun locked up since they took so much weight off of the slide.

[jjw]

for many years i have always just almost automatically gone with 1 up form factory spring. can not think of a gun that i havent done it in. try them with 50 rds or so but it has always worked.
has worked with all my ammo but do not shoot reloads or wimpy stuff. usually shoot mil spec in most everything
+p in 9mm work guns. standard velocity in 1911's 230 gr speer gdhp full size and carry lite wt commanders.

nothing has changed when i bought smiths.and i have a shit pot full of m&ps as i really like that gun. shoot it better than any palomar gun made

YMMV
jjw

[opngrnd]

Thanks for the imput. I'm planning on running with the 17# spring.
Without derailing this thread, how can I learn what Power Factor the loads I shoot are?
For reference, this is all related to a carry gun, and when I carry I only do so with factory ammunition.
The ammo I reload is the result of taking a 5 gallon bucket of once fired brass home after attending a Combat Focus Shooting Course, policing upall the brass with the rest of the class, and taking half of it home since only one other shooter was a reloader. I use the reloads for practice, competition, and plinking, and I load it to match factory ammo.

[rjacobs]

The heavier springs SHOULD keep the gun locked up a little longer and thus alleviating some of the early unlocking issues.

When people talk about their accuracy going to hell after 5000 rounds is because the factory spring is worn out and the gun is unlocking WAY early and throwing rounds. When my spring went(I was north of 5000 rounds, but I think under 7000 rounds) I was throwing rounds off the top of an IDPA target at 15 yards. Complete misses. Nobody could figure out what it was doing(had like 4-5 guys that are better shooters than me shoot it), but then the range I was at offered a recoil spring off of one of their new guns on the wall to try out and the gun became a tack driver once again. I now keep 2-3 RSA's on hand at any time.

A new recoil spring at 4-5k rounds and shooting hotter ammo(I shoot a max loaded 115g bullet) keeps this gun running great.

I would also be interested in trying out a slightly heavier recoil spring. I think stock is 15lbs. I also havent really seen a new recoil guide rod to take aftermarket springs. I know I saw one place had a tool that held onto your spring while you disassembled the guide rod so you could use the stock guide rod. Dont remember if it was speed shooters specialties or who it was.

[kenndapp]

speaking of rods...... does anybody know what rod is the best fit for the ISMI psrings? i know the factory rod works.....but i am looking for a nice tight flush fit.

[opngrnd]

[QUOTE=kenndapp;1610307]speaking of rods...... does anybody know what rod is the best fit for the ISMI psrings? i know the factory rod works.....but i am looking for a nice tight flush fit.[/Q

The website Tactical Elitist did an article that stated the a tool for changing springs. I think the company that makes that tool makes guide rods specifically for the M&P.

rjacobs-thanks for the reply. This mirrors what I've been thinking, and it isn't the first time I've seen that a S&W product suffer premature troubles from poor quality springs. I hear that the stock spring is 15-16 pounds, so I was thinking that a 16-17 pound high quality spring with a better service life might solve some peoples problems. I won't know where I'm at until I drop in Apex parts and go test my gun, but if the gun shoots under 4" and stays that way, I'll be happy.