My M&P9

[Trident]

At one time no but none of those will effect accuracy.

[Art Yeo]

At one time no but none of those will effect accuracy.

Well, it appears that some believe the premature unlocking of the barrel could be caused by a weaker than necessary recoil spring and replacing it with a Wolfe 20lb spring may solve the issue.

[Trident]

At one time no but none of those will effect accuracy.

Well, it appears that some believe the premature unlocking of the barrel could be caused by a weaker than necessary recoil spring and replacing it with a Wolfe 20lb spring may solve the issue.

Well, I tested 11,13,15 and the OEM stock 16 pound recoil springs and found no differences in accuracy. In addition, I called and spoke to several prominent gunsmiths including Grey guns, Apex, Wilson Combat were just a few and each one told me that the recoil spring would not have any effect on the accuracy.

Plus if that we're the case, then lighter loads would increase accuracy as there would be less pressure on the spring. Instead, in my testing increasing the pressure increased the accuracy just the opposite of what your implying.

With this theory installing a stiffer recoil spring then would solve the problem then right?

Edited September 29, 2012 by Trident

[Art Yeo]

With this theory installing a stiffer recoil spring then would solve the problem then right?

So, it seemed, conjectured and some proven it for themselves. I have not tried it myself but may, one of these days.

Incidentally, I have gone back to the range today to try the KKM barrel at 25 yards and compared it to my Les Baer Premier II 1911 45ACP. The performance of the KKM barrel is glaringly eye-popping when you stretch the shooting distance to 25 yards. At shorter distances, the KKM barrel looks and performed close to the Gen2 S&W barrel but once you increase the distance to 25 yards, its abilities are astounding. I had to stretch myself in my bulls-eye shooting techniques as well.

Before I post the pics, I'll have to go to the range just one more time to shoot the 25 yards target with the Gen2 S&W barrel so as to convince myself whether I was right or wrong with the original postulation. I didn't have enough time to do it today.

Edited September 29, 2012 by Art Yeo

[MarkCO]

I've gone lighter and weaker with recoil springs, still unlocks prematurely and can be pressed out of battery. Accuracy was not affected in the least.

I have now run 8 different bullets, with three different powders in 2 factory, a KKM and a Storm Lake (extended threaded) with different primers and different powder charges. The PFs were from 120 to 155 in 9mm. I'm done and the factory barrels are trash IMHO. I shoot 5 shot groups, always at 25 yards, With a 127 PF load, and Hornday 125 HAP, off-hand I am getting about 4 inch groups with the KKM. When I sit down at the bench and put on my prescription glasses and go slow and steady, I get under 3" consistently, but have not gone under 2". That same load, in the factory barrel, shot the same way is just over 10"! The Storm Lake, best is about the same as the KKM. The Storm Lake shot the Lead and Plated a tad better than the KKM and the KKM was just a hair better than the Storm Lake with Jacketed.

I finally have enough accuracy confidence to change out the factory sights for some Dawsons, which are on the bench. I'll swap those out next week and get some data at 50 yards next range trip.

[Trident]

147's will shoot the best. I doubt anything will shoot better than 3" from the MP from all my testing so it looks like you are there. I can now make the 124 shoot almost as good, if not as good, as my best 147 groups by increasing the PF of the 124's to 135. 147 will group at 125.

[nwhpfan]

I too had an impossible time trying to get my M&P9 accurate. I ended up ditching it and tried an XDM but the M&P ergos kept bringing me back. Finally I settled on the M&P45 and shoot minor loads in Production. I get sub 2" 25 yard groups with 4.2 TG and 180 LSWC from www.dardascastbullets.com

[Art Yeo]

At one time no but none of those will effect accuracy.

Well, it appears that some believe the premature unlocking of the barrel could be caused by a weaker than necessary recoil spring and replacing it with a Wolfe 20lb spring may solve the issue.

So, here is another article that supported the theory that a heavier recoil spring can extend the length of time before the unlocking of the barrel. I know that this article is talking about the 40SW cartridge but look for the phrase "heavier than factory tension recoil spring" in that article and you'll see that it is talking about a similar issue about premature unlocking except for the 40SW case, it was safety related.

Assuming swapping in a 20lb recoil spring may tune the accuracy even further, I guess the downside is that it will increase the split time for follow-up shots, wouldn't it?

PS: Does anyone know what the strength of the factory recoil spring?

Edited October 1, 2012 by Art Yeo

[mcracco]

PS: Does anyone know what the strength of the factory recoil spring?

17#

[Art Yeo]

PS: Does anyone know what the strength of the factory recoil spring?

17#

Thanks!

[Art Yeo]

*******************************

*** 2 More conjectures ***

*******************************

1. Weight of bbl: I have recently measured the weights of the gen2 bbl vs the KKM bbl and they are the same on my postal electronic weighing machine. I no longer have the gen1 S&W bbl. If anyone still has it, could you kindly weigh it and let us know the weight, please? So, here's the theory ... Heavier bbl means higher inertia and higher inertia takes longer to move it; thus, reducing the premature unlocking issue.
   
2. Lowering the discharge load: if increasing the recoil spring would slow down the premature unlocking of the bbl, wouldn't reducing the discharge load of the ammo do the same to attack this problem? Anyone tried that?
   

[MarkCO]

Increasing the recoil weigth does NOT affect or correct the issue. I've run loads as low as 110 PF with a 19# spring and the accuracy was still terrible. Don't chase things that have proven to not be beneficial.

[Trident]

I think you need to re-read what has already been posted. BTW, who said the problem has anything to do with premature unlocking?

[Art Yeo]

[...]

That coupled with the lower velocity makes me wonder just WTF is going on with the gun itself, as I assume you've made sure it's not the powder throw coming out of your press. I'm far from an expert in those types of workings with the gun, but it makes me wonder if I'm getting better lock up or if something is going on with the barrel itself-- the latter possibility being the least likely, considering the manufacturer.

There's obviously a lot of factors to consider here-- powder lots (should be pretty consistent, but I've had fast ones before), true projectile diameters (MG's run small, but not by much and don't fluctuate notably from lot to lot), our variations in OAL, possible crimp differences... and eleventy billion things that may be different about the guns.

[...]

I think we're forgetting that with the same type of hand-loaded ammo, quite a few of the other competing pistols performed about the same --- very good.

Why is there so much need to tweak every single parameter just to make the M&P9 perform close to par?

I don't think it is the ammo (bullet, powder, OAL, etc) because I 'd bet that all of your ammo will perform fine on other competing pistols at 25 yards.

I'm going to do some more testings in comparison to my other pistols at 25 yards just so we have a base to discuss. Since I no longer have the S&W Gen1 bbl, it'll be with the Gen2 bbl.

Edited October 2, 2012 by Art Yeo

[Art Yeo]

I think you need to re-read what has already been posted. BTW, who said the problem has anything to do with premature unlocking?

Google "premature unlocking M&P 9" and you will see them all.

I am curious what you think is the cause of the accuracy?

[Sin-ster]

I think you need to re-read what has already been posted. BTW, who said the problem has anything to do with premature unlocking?

Google "premature unlocking M&P 9" and you will see them all.

I am curious what you think is the cause of the accuracy?

Slow barrel twist, projectiles with little bearing surface, loose and long chambers in the factory barrels, and perhaps most likely of all... the shooters themselves.

S&W found the early unlocking occurred in less than 1% of the guns they tested-- and there were several hundred in the data pool. (No link for that-- it was a personal conversation, with several different folks.)

These tests really need to be performed in a controlled environment with a Ransom Rest. Not to question anyone's prowess here, but I've seen guys who can punch 1" groups at 25 yards with their 1911's off hand lob 6" groups from a bench with a variety of stirker fired guns that were all verified at sub-3" and better.

If your gun is unlocking early, you'll see vertical stringing more than anything else-- and there should be evidence in your primers as well (i.e. smears). If it's a buckshot pattern, there's something else going on.

[Art Yeo]

[...]

If your gun is unlocking early, you'll see vertical stringing more than anything else-- and there should be evidence in your primers as well (i.e. smears). If it's a buckshot pattern, there's something else going on.

Why would vertical stringing be the symptom for premature unlocking?

Could you elaborate on it a little, please?

My question is why are the competing guns from other brands behaving just fine with any of the ammo?

Thanks!

[FightFireJay]

[...]

If your gun is unlocking early, you'll see vertical stringing more than anything else-- and there should be evidence in your primers as well (i.e. smears). If it's a buckshot pattern, there's something else going on.

Why would vertical stringing be the symptom for premature unlocking?

Could you elaborate on it a little, please?

My question is why are the competing guns from other brands behaving just fine with any of the ammo?

Thanks!

I assume, because the first part of unlocking is the chamber swinging down into the frame (as well as backwards) so as each firing has slightly more or less unlocking, there is slightly more or less elevation added to each shot.

Which makes me wonder... if anyone that has had accuracy issues in a 9mm that has been blamed on early unlocking, if they have had their barrell fitted by a gunsmith to ensure a good and repeatable lock up.

[Art Yeo]

I assume, because the first part of unlocking is the chamber swinging down into the frame (as well as backwards) so as each firing has slightly more or less unlocking, there is slightly more or less elevation added to each shot.

It sounded like you are saying premature unlocking is progressively worse for every subsequent shot. That's why there is vertical stringing. Why would each subsequent shot unlock with an ever increasing/decreasing elevation? Wouldn't one expect it to prematurely unlock at about the same instance?

It's still not making sense to me.

In my experience with the Gen1 S&W bbl, even though my POA is about the same, I am seeing shots hitting high and then low and they oscillate high/low on alternate shots. But, there's no fixed windage either; i.e. along the horizontal axis, I do not see any patterns.

Which makes me wonder... if anyone that has had accuracy issues in a 9mm that has been blamed on early unlocking, if they have had their barrell fitted by a gunsmith to ensure a good and repeatable lock up.

I doubt if there's any compelling reason to send in a plastic gun for gunsmith fit. Again, I want to bring out the fact that there are many competing products out there that certainly do not need a gunsmith to fit the barrel nor need me to buy a match barrel to shoot 3" or better at 25 yards.

Edited October 3, 2012 by Art Yeo

[Art Yeo]

KKM bbl difference

I just spoke to KKM and what I have gathered so far made sense:

1. External dimensions: they said they have increased the external dimensions to improve the lock up tightness when the barrel is in battery.
   
2. Internal surfaces: they are significantly more polished. You can verify this by looking into a KKM barrel and compare it to production ones.
   
3. Rifiling: they claimed that button rifiling is more consistent through the length of the barrel vs the broach rifling method. Button rifling also cost more in terns of time and resources and cannot be effectively used in mass production.
   

[Sin-ster]

[...]

If your gun is unlocking early, you'll see vertical stringing more than anything else-- and there should be evidence in your primers as well (i.e. smears). If it's a buckshot pattern, there's something else going on.

Why would vertical stringing be the symptom for premature unlocking?

Could you elaborate on it a little, please?

My question is why are the competing guns from other brands behaving just fine with any of the ammo?

Thanks!

As noted, the major movement during the first part of unlock is the barrel tipping down at the chamber end and up at the muzzle. Vertical stringing has been the symptom of early unlocking since JMB's days. (That's also what causes the primer wipes-- before the metal has actually cooled enough to re-solidify, it's moving against the firing pin/striker/hole and causing odd marks. NOTE-- the tear drop shape left in primers by the M&P is standard across the board, due to the relief cut in the breech face. You'd be looking for the dimple made by the striker to be elongated.)

As to your other question...

The newer production barrels (2012 IIRC) have a slower twist and overall better profile, much like the KKM drop-in. The previous batches (at 1:18.25") were not optimized for any projectile weight, and thus didn't shoot anything very well. The XDm is 1:16-- the "golden standard", and at 5.25" (still measured from chamber to crown, so the actual rifling is shorter) gives a bit more stabilization. Glock's polygonal rifling is a beast unto itself and produces solid accuracy coupled with LONG barrel life. CZ's have a twist of 1:9.7", incredibly tight, though they don't seem to struggle with the heavier stuff. Sig's come factory with a 1:10, so ditto the CZ-- and they are typically known as two of the most accurate platforms out there, right out of the box. Almost ALL after market drop in's are 1:16 for a 9mm platform.

Now I'm no ballistic expert or engineer, but that's pretty telling-- and several gunsmiths and physic phreaks that I know seem to agree. You couple that with relatively shoddy lock-up in general and you'll get the propensity for a "picky" gun.

All I know for sure is that my gun still outshoots me, and it's an M&P running the blasphemous 124 grain projectile. The back up with the same load and FACTORY (2012 Production) barrel is only a scant bit less accurate-- and that's still sub-3" @ 25 yards. Did I get that lucky twice, or is there something going on in other folk's testing that's missing from mine?

Speaking with another shooter at Double Tap this year, and a couple of Super Squad guys who had tried the platform, only two of us reported such accuracy-- and we were using the exact same load in the exact same drop in barrel. A load that the other two had never tried. Go figure...

Edited October 4, 2012 by Sin-ster

[FightFireJay]

I assume, because the first part of unlocking is the chamber swinging down into the frame (as well as backwards) so as each firing has slightly more or less unlocking, there is slightly more or less elevation added to each shot.

It sounded like you are saying premature unlocking is progressively worse for every subsequent shot. That's why there is vertical stringing. Why would each subsequent shot unlock with an ever increasing/decreasing elevation? Wouldn't one expect it to prematurely unlock at about the same instance?

It's still not making sense to me.

In my experience with the Gen1 S&W bbl, even though my POA is about the same, I am seeing shots hitting high and then low and they oscillate high/low on alternate shots. But, there's no fixed windage either; i.e. along the horizontal axis, I do not see any patterns.

Which makes me wonder... if anyone that has had accuracy issues in a 9mm that has been blamed on early unlocking, if they have had their barrell fitted by a gunsmith to ensure a good and repeatable lock up.

I doubt if there's any compelling reason to send in a plastic gun for gunsmith fit. Again, I want to bring out the fact that there are many competing products out there that certainly do not need a gunsmith to fit the barrel nor need me to buy a match barrel to shoot 3" or better at 25 yards.

To clarify, I don't mean that each shot will walk further in one direction (up or down). I mean that you could track the vertical stringing by the velocity. The variance in velocity (energy) will determine how fast a gun would unlock (for that bullet type and weight). How quickly a barrel unlocks (in an early unlocking scenario) will determine if the barrel is pointed straight(ish) or if it's pointed up. Sooooo..... While you are shooting a gun that unlocks early, the vocity of each round (up or down) determines the vertical stringing.

My second theory is that the accuracy issue that some shooters see is due not to "early unlock "but poor lockup". By that I mean that for those few that legitimately have accuracy issues due to hardware, have barrels that don't always lockup pointing in the same direction.

[Sin-ster]

My second theory is that the accuracy issue that some shooters see is due not to "early unlock "but poor lockup". By that I mean that for those few that legitimately have accuracy issues due to hardware, have barrels that don't always lockup pointing in the same direction.

I think that's the biggest issue, based on some of the talk of how certain slides, locking blocks and barrels mic out. No surprise then that a gunsmith fitted (read: oversized) barrel would improve accuracy in even problematic guns, and a redesigned locking block would do the same. (A la the stuff that APEX is working on.)

[Art Yeo]

As for why S&W has chosen the 1:18.75" twist, it was due to their success with .38sp revolvers implementations. The question we need to ask is this: since the .38sp revolvers shoot bullets from 110gr - 200gr accurately with this twist-rate, why do we need any other twist-rates?

New findings with Gen2 Barrel and How to make 9mm Accurate

Pertaining to the 9mm Luger cartridge, I have been digging around and testing loads myself. It turns out that the 9mm Luger favors higher loads (i.e. with higher pressure). In the mid-1980's, this has been consistently shown by the US Army Marksmanship Units testings and their use of these heavy loads for national bullseye competition. Some of these can be found here (Article: The 9mm can be Accurate). Most of their loads made their bullets fly at 1200+ fps and they are getting 2" groups and better at 50 yards. I think Sin-ster and Trident have also confirmed (in the earlier pages of this thread) that the higher they push the power factor, the tighter their holes grouped. I believe this is contrary to the 45ACP cartridge, which is considered a low pressure cartridge. Obviously, higher pressure in the 9mm would entail larger recoil and slower follow-ups, which the bullseye competitors don't really care. Fast shooting games (like IDPA, IPSC, etc), however, may need to compromise and balance between good splits and accuracy.

Among the various tests I have done, here's one particular load that may be interesting to you all:

Ambient Tempt: 55 deg F

Powder: Win231

Charge: 4.7gr

Gun: M&P9 FS + Gen2 bbl

Bullet: MG 124gr FMJ

OAL: 1.1440" +/- 0.0005"

Distance: 25yards

Group: 2.5"

I'll re-test this to see if it was a fluke or it is reproducible. As you can see, accuracy which you guys wanted is achievable with a production M&P9 that used to be a failure with a Gen1 bbl is now scaling the wall with leaps and bounds using the Gen2 bbl and the proper load.

Disclaimers:

1. I am not liable if your gun, hands or face is blown off to space. Use the loads and the partial magazine article at your own risks.
   
2. Win231 is reported to be sensitive to temperature and atmospheric pressure. So, do not trust your loads if you are loading at low altitude and competing at higher altitude or vice-versa.
   

My next step is to fine tune around this locus and see how the rest of my 9mm guns behave. I have a deep feeling that the Beretta 92A1 will perform better with an even hotter load based on the US Army's data. So far, I am not seeing flattened primers ... yet.

PS: Having said all these, I must underscore the fact that the 9mm Luger cartridge is one of the most sensitive cartridges I have ever dealt with in terms of trying to achieve accuracy. It's like getting the stars to align before you shoot and if someone sneezes after the discharge, you may miss the bullseye. Compared to 9mm, the 45ACP cartridge was a walk in the park.

Edited October 11, 2012 by Art Yeo

[KSwift]

and perhaps most likely of all... the shooters themselves.

Dun dun dun, while something people don't want to hear, this is the single most important detail in this thread.

Just to throw in my vote, my Pro 5" (updated style without breech steps) can shoot sub 3" with factory 124gr bulk grade ammo off sandbags.