147 Gr Lyman 9MM - Faster or slower twist rate?

[robertbank]

Ok I have two barrels for my 5" M&P Pro. Both are factory. One is 1 - 18 that came with the gun originally and the other is a 1 - 10 twist factory barrel that the gun comes with now.

I have had problems in the past with bullets tumbling. Which barrel should be the best to stabilize the 154gr bullet. Bullets are sized .357. Vel. is 860fps

Take Care

Bob

[Outpost75]

The faster twist should be better with the heavier bullet IF it "fits." Undersized bullet will still tumble. Have you tried .358" and will they chamber in your gun?

[robertbank]

The faster twist should be better with the heavier bullet IF it "fits." Undersized bullet will still tumble. Have you tried .358" and will they chamber in your gun?

I get excellent accuracy out of both barrels using 125 gr bullets at .357. Sized at .357 with either bullet are very tight in in the bore with no leading. I may load a few at .358 to see if there is any difference. I will stick to the 1 -10 twist barrel thanks for the reply.

Take Care

Bob

[tazman]

I agree that the faster twist barrel should work better with that boolit.

[robertbank]

Well when you hear from two well respected board members who both agree then you can pretty much seal the deal. Thanks guys, I always get the fast vs slow heavy vs light mixed up.

All the best

Bob

[35remington]

Just to throw some sand in the gears, I will note Smith 38's stabilize 158's at even lower velocities than you are getting with 1-18 3/4" twists.

If the bullet tumbles I would suspect fit more than twist. 154 ain't that long of a bullet.

FWIW.

[tazman]

Just to throw some sand in the gears, I will note Smith 38's stabilize 158's at even lower velocities than you are getting with 1-18 3/4" twists.

FWIW.

What you say is true. I still think Robert's faster twist barrel will do a better job with the heavier/longer boolit.

[35remington]

I would wager other factors such as barrel fit to gun and bullet fit to barrel will be far more operative. 1-18 should be a gracious plenty with a 154. Since Smith revolvers will outshoot plastikpistoles of most all varieties, I highly doubt twist is limiting here.

[tazman]

I seem to remember the Colt revolvers with a slightly faster twist than the Smith's out-shooting the Smith revolvers on regular basis. Even to the point of people putting a Colt barrel on a Smith frame.
Do I remember incorrectly?

Also, most semi-auto pistols simply don't ever shoot as well as a revolver due to the clearances required for the parts to operate where a revolver has a fixed barrel(fixed barrel autos being the exception).

I own only one centerfire auto that will shoot as accurately as my revolvers. That one being a tightly fitted 1911. Definitely not a plastikpistole.

[35remington]

If shooting wadcutters slow the Colts had some advantage over the Smiths in reducing bullet yaw. This is not the case here so it is not relevant. If twist was limiting my Smiths would shoot worse than they do. At the 860 fps RB is discussing 1-18 is plenty of twist. I already acknowledged loose autopistol tolerance fit is way more limiting than twist here.

[tazman]

I guess we will just have to fail to agree on this.

[35remington]

Taz, 1-18 3/4" twist has been the standard twist for Smith for 120 odd years and was fine to stabilize 158's at 750 fos and even slower. Smiths have a wonderful reputation for accuracy in 38 Special. If 1-18 3/4 twist was inadequate surely it would have showed up by now.

I do have considerable foundation for claiming 1-18 is really not limiting with mentioned bullet weights here. Disagree with me and Smith as you wish.

[tazman]

I didn't say that the 1-18 twist was inadequate. I said the faster twist should do a better job. Not the same thing.
Most of the factory 9mm barrels I am familiar with have faster twist rates than 1 in 18. Even S&W has decided to use a faster twist in their current M&P Pro according to the original poster.
Perhaps Smith changed their mind about that slow twist, at least for the 9mm cartridge.

[35remington]

The 9mm is pretty universally acknowledged to have a vastly faster twist rate than it really needs or has to have. Even 35 rifles like the 35 Remington are only 1-16 and shoot a much longer bullet. Such rifles shoot well with 158's at quite low speeds.

Once a bullet is adequately stabilized, spinning it faster will not increase its accuracy, especially in light of all the other factors that are limiting in a pistol. A better job? How? We are already well above what is necessary in terms of bullet stability.

Positing that a 1-10 twist will be "better" than a 1-18 is probably only provably relevant for lower speeds and heavier bullets than discussed here. As I said, 1-18 3/4 is enormously well proven. To expect a 154 grain bullet shot out of a 1-18 twist at 860 fps to be lacking in some way is unrealistic given what is already well proven to work very well.

[tazman]

As has been said elsewhere on the site-- Everything is theoretical until the trigger is pulled-- or at least something like that.
It will be interesting to see how this all plays out for Robert. It wont be theoretical anymore for him. His results are all that are going to matter for him.
My S&W 929 revolver has a 1 in 10 twist and shoots all the boolit weights well.

[35remington]

As I said, twist rate may be vastly overshadowed by other factors. Just because something happens does not mean it happens for the reasons we think it does. Some other factor or factors may be the real cause of any observed differences.

In any observed results we have to give all the possible explanations for those results their due, not just the ones we feel like focusing on.

[robertbank]

Listen the M&P Series were not noted for their accuracy and S&W finally changed their 9MM barrels to 1 - 10 twists. I bought the 1 - 10 barrel and accuracy was improved using 124gr bullets for certain. I know the smith 38's had the slower barrel twist but the 9MM is not the 38spl.
Virtually all European guns have 1 - 10 twist barrels. It maybe that in the US it is "Universally" thought the 9MM doesn't need the faster twist but the US is not the Universe and most 9MM from offshore use a 1 - 10 twist or the metric equivalent. S&W didn't make the change on a whim, their M&P 9MM pistol had some accuracy issues. Since the change you don't hear the comments quite so much.

Maybe it has something to do with the slightly smaller diameter of the 9MM barrel .355 vs .357

Take Care

Bob

[tazman]

Good point

[35remington]

Given how short 9mm bullets are, and given short bullets need less twist than longer ones, I would suggest any accuracy improvements have more to do with possible exterior dimensional changes that affect barrel fit than twist. Such has been considerably discussed with some gunsmiths that work on such pistols that I know.

Their contention was that they could measure clearances on the barrel/slide fit and predict pretty well beforehand how well the pistol was going to shoot. As I said, we must be careful not to give credit to one factor while ignoring the likely much more significant contributions of other factors.

Perhaps one needs to check the barrel twist rate of Bar-Sto 9mm barrels.....then ask why they shoot so well? For some reason the maker of match grade barrels decided the 9mm was fine with a much slower twist than 1-10.

Also a good point!

[Tackleberry41]

I use that same lyman 147 grain in several guns. Browning HP, S&W shield, Kel Tech carbine, 357 sig, works in everything so far.

[robertbank]

Given how short 9mm bullets are, and given short bullets need less twist than longer ones, I would suggest any accuracy improvements have more to do with possible exterior dimensional changes that affect barrel fit than twist. Such has been considerably discussed with some gunsmiths that work on such pistols that I know.

Their contention was that they could measure clearances on the barrel/slide fit and predict pretty well beforehand how well the pistol was going to shoot. As I said, we must be careful not to give credit to one factor while ignoring the likely much more significant contributions of other factors.

Perhaps one needs to check the barrel twist rate of Bar-Sto 9mm barrels.....then ask why they shoot so well? For some reason the maker of match grade barrels decided the 9mm was fine with a much slower twist than 1-10.

Also a good point!

What you say is certainly true, however, in the case of my M&P Pro the only variable was the barrel change. This is also true of S&W switch to the 1 - 10 twist where accuracy was notably improved. One thing worth mentioning is the popularity of the short 115 gr bullet in the US. where velocity and pricing seems to be a factor when it comes to choices for factory ammo. If the 1 - 18 twist does favour lighter bullets in the 9MM this might explain why S&W went with the 1- 18 twist aside from the fact that was the same twist as they used in their 38spl. I assume there would be some cost in converting their barrel making machinery over but I don't know that. I am no machinist.

The Lyman 124 gr bullet I use is .630" long, 147 gr bullet .685" long while the RCBS 158 gr bullet is .7" long. I don't have a 115 gr bullet to compare.

In any event I did experience tumbling with the 1 - 18 twist barrel which saw me stop using the bullet. I am now going back to the 147 gr for some applications I have in mind.

Take Care

Bob

[35remington]

As I said I suspect other things having to do with the replacement barrel's dimensioality rather than twist accounts for any accuracy differences. If the rather long 358311 stabilizes easily in my Smith revolver barrels at 700 fps I suspect your tumbling experience has something to do with something other than the twist rate.

[GWM]

I use the 200 grain 358315 in my S&W 940 9mm revolver without tumbling. It has the standard twist.
In my opinion the faster twist is more prone to leading and better suited for jacketed.

The M&P change could be a marketing stunt and they would probably induce some other refinement like tighter tolerances to improve accuracy. Not that it would be made with cast boolits in mind though.

[robertbank]

I use the 200 grain 358315 in my S&W 940 9mm revolver without tumbling. It has the standard twist.
In my opinion the faster twist is more prone to leading and better suited for jacketed.

The M&P change could be a marketing stunt and they would probably induce some other refinement like tighter tolerances to improve accuracy. Not that it would be made with cast boolits in mind though.

No I am not so sure you are right. I have never experienced leading in any of my 9MM guns, (CZ, Tanfoglio, Girsan, Beretta and S&W) shooting lubed lead bullets. Never. When the Europeans all use 1 - 10 twist barrels it leads me to believe they know something about the cartridge and the use of 124 gr bullets.

I know in my case the change in barrels in my M&P from the 1 - 18 to the 1 - 10 twist had an immediate affect on accuracy both shooting free style and off the bench using the Lyman 356402 bullet. Not as accurate as the CZ off the Bench but close.

I suspect S&W used the 1 - 18 twist rate because that is what they used in their revolvers. It likely saved them a few dollars in the early production costs of the pistols.

Take Care

Bob

[35remington]

Black powder low velocity 45-70 rifles: 1-20.

35 rifles and Bar Sto match 9mm pistol barrels: 1-16. Most 44 revolvers 1-18 3/4 to 1-20.

38-40 and 44-40 carbines 1-38. Most pistol caliber leverguns 1-20. Food for thought. All shoot longer bullets than 9mm pistols at comparable velocities. Pretty much all of them will outshoot 9mm pistols.

[robertbank]

35remington are the Bar Sto Match grade barrels the same as the S&W Match Grade barrels the gun comes with? Are they fitted or drop in. I ask only because "Match Grade" as you know is more of a generic marketing term and not a real reference point. I know they make good barrels but in today's world of CNC equipment I don't think there is much to choose from in quality between one pistol barrel than another unless it is a fitted barrel. To be fair my factory 1 - 10 twist barrel was fitted by the S&W 'smith in Victoria. How much actual fitting took place is anyone's guess. I suspect little.

Every European 9MM pistol I own have 1 -10 metric equivalent barrel twist rates. Since installing the new barrel in my gun the tumbling in the 147 bullet (Actual weight 155gr using my WW alloy) has ceased using the same load data as before. Who knows what the reloading Gods are playing at. After about 400 rounds of shooting with the heavier bullets I have decided to go back to the 124 gr 356402 bullet. Felt recoil might be slightly more but the lighter bullet is incredibly accurate out of the guns I use for IDPA and reliable as the morning sunrise.

Take Care

Bob

[35remington]

What is troubling to explain is why a maker renowned for super accurate 9mm barrels chooses to go with a 1-16 twist......if slower twist is limiting as to accuracy? The barrels have to be gunsmith fitted. If twist was truly limiting, why go to all the trouble to make a barrel with such potential and then saddle it with an "inferior" twist rate?

Why indeed.

Bob, call them and ask them why they are so darn foolish as to give their barrels inferior twist rates. They are more willing than most barrel makers to talk over the phone. Some will not discuss technical issues but Bar-Sto will. Why not discuss it with a respected source rather than continue to labor away under a misconception. While you are at it, how do all those long range silhouette revolvers that need first rate accuracy get by with such slow twist rates when they tend to prefer long bullets?

There is much out there that contradicts what you want to believe. Find out why that is so. That is the best advice I can give you. It is up to you to be educated.....or not.

[trapper9260]

In my S&W Sigma 9mm 147gr Lyman is one of my main cast bullet I use in it with out any problems. I have not try it out yet in my M&P Shield 9mm yet.

[Tracy]

Arcane Euro magic aside (from a continent with a tiny fraction of the number of ballistics experimenters as the US; really?), the bullet preference of one individual barrel proves absolutely nothing. I plugged .685" bullet length, .355" diameter and 860 fps into the Greenhill twist rate calculator and got an optimal twist rate of 1 turn in 18.9 inches. Check it for yourself:
http://kwk.us/twist.html

BTW, the barrel and bullet neither know nor care if the chamber is 9mmP, .38 Special, 9x57, or whatever.

[robertbank]

What is troubling to explain is why a maker renowned for super accurate 9mm barrels chooses to go with a 1-16 twist......if slower twist is limiting as to accuracy? The barrels have to be gunsmith fitted. If twist was truly limiting, why go to all the trouble to make a barrel with such potential and then saddle it with an "inferior" twist rate?

Why indeed.

Bob, call them and ask them why they are so darn foolish as to give their barrels inferior twist rates. They are more willing than most barrel makers to talk over the phone. Some will not discuss technical issues but Bar-Sto will. Why not discuss it with a respected source rather than continue to labor away under a misconception. While you are at it, how do all those long range silhouette revolvers that need first rate accuracy get by with such slow twist rates when they tend to prefer long bullets?

There is much out there that contradicts what you want to believe. Find out why that is so. That is the best advice I can give you. It is up to you to be educated.....or not.

You know you try to have an intelligent conversation with someone and you get childish simple sarcasm from an adult. If you are so curious you can phone them. Assuming you have some life experiences outside the county you live in you might realize they are not about to suggest that for 124 gr bullets in the 9MM the faster rate might just be better. Too, suggesting as you have that heavy bullets in a different caliber that perform well in that caliber have something to do with the issues involved with the 9MM is bordering on moronic. Just saying.

It may come as a surprise to you but the 9MM was developed in "Europe and I suspect the folks over there know something about the cartridge. Maybe they are on to something when they make barrels with 1- 10 twist rates and this might explain why S&W chose to switch to 1 - 10 twist barrels to attempt to improve accuracy in their M&P series. They didn't do it on a whim.

Why Bar Sto chose the 1 - 16 twist might be because, in the US a lot of folks choose to shoot 115 gr bullets in the cartridge. Not so much elsewhere. Beyond that maybe they just felt like it. I am done here.

Take Care

Bob
ps Have you tried to use the search feature on this site?

[35remington]

Rb, I did not mean to appear that harsh to you but there is considerable reason to think it is not that cut and dried. I asked the question of the tech there myself, indirectly. While talking about other things I asked why pretty much everything they did was rifled 1-16. They are also aware their 9mm match barrels are used with longer 147 plus grain bullets. Still don't do 1-10. What I am challenging is whether 1-10 is as necessary as you think.

They had a good answer, I thought. Point is, there is considerable reason to believe slower twists than 1-10 are quite accurate. Somewhere out there is good information to be had that has a dissenting view. It is entirely reasonable to suggest 1-10 is not absolutely necessary given what else is known to be so.

I thought it appropriate to suggest you not take my word for it but rather should call somebody who had a respected opinion.

[35remington]

Additionally, you might see what twist rates Nowlin, Kart, Schueneman, and other 9mm barrel makers have for their match barrels. It is not 1-10, so it appears Bar Sto has a lot of company.

[tazman]

I have been researching this topic for the last 20 days and have found many differing opinions. Also a number of facts.
Many match/target barrel manufacturers use slower twists than the 1 in 10 for 9mm pistols. Often as slow as 1 in 18 to 1 in 32(these are specifically for 115 to 124 grain bullets).
I also found where 38 special PPC shooters preferred 1 in 12 to 1 in 14 twist barrels in their revolvers claiming they get much better groups. These are for 148 grain hollow base wadcutters.
Mostly, there is nothing magical about a specific twist rate.
Most important is I found that the best twist rate is more of a range than any specific number. Both the slower twists and the faster twist will work fine from an accuracy standpoint over a wide range of weights, lengths, and speeds. Of course there are limits at the extreme ends of the range. Neither of the twist rates from the original post are outside the acceptable range for the cartridge we are talking about here.
It becomes more of a question of barrel quality and precision of manufacture than what the specific twist rate is.
The best barrels will group as long as the twist rate is reasonable(the range of reasonable is fairly wide). Poorer barrels won't group as well regardless of twist rate.
Everyone posting has valid points but may be concentrating on specific details too much.

Robert-- I suspect your second barrel is of higher quality than your first. This will often happen with a production gun. Your first barrel should have been able to properly stabilize the heavier boolit. There are many instances where two otherwise identical guns will fail to group the same loads the same way.

35Reminton--The slower twist won't work any better than the faster twist since both fall within the acceptable range for stabilization. The slower twists are much easier for a factory to make an excellent barrel than the faster twists to a certain extent. Much depends on the method of manufacture.

My point is, if both barrels were of a excellent quality, they should both have worked fine. I don't think we need to be talking about twist rate here, but rather barrel quality.

[Tracy]

You know you try to have an intelligent conversation with someone and you get childish simple sarcasm from an adult. If you are so curious you can phone them. Assuming you have some life experiences outside the county you live in you might realize they are not about to suggest that for 124 gr bullets in the 9MM the faster rate might just be better. Too, suggesting as you have that heavy bullets in a different caliber that perform well in that caliber have something to do with the issues involved with the 9MM is bordering on moronic. Just saying.

It may come as a surprise to you but the 9MM was developed in "Europe and I suspect the folks over there know something about the cartridge. Maybe they are on to something when they make barrels with 1- 10 twist rates and this might explain why S&W chose to switch to 1 - 10 twist barrels to attempt to improve accuracy in their M&P series. They didn't do it on a whim.

Why Bar Sto chose the 1 - 16 twist might be because, in the US a lot of folks choose to shoot 115 gr bullets in the cartridge. Not so much elsewhere. Beyond that maybe they just felt like it. I am done here.

Take Care

Bob
ps Have you tried to use the search feature on this site?

And it may come as a surprise to you that Georg Luger, the "designer" of the 9mm Luger aka 9mm Parabellum, was a firearms designer, not a ballistician. He "designed" the 9mm by simply cutting the 7.65x21 cartridge at the shoulder. Why? Because he saw that 9mm was some magical caliber? No. Because he wanted to sell pistols to the British and American militaries, and they were partial to larger calibers. And by the way, these were military sidearms. They were never intended to be super accurate, long range weapons.

George Greenhill on the other hand, was a ballistician and mathematician who wrote several books on the subject. His twist rate formula is still in use to this day. Later ballisticians accept his work, only adding minor modifications for extremely low or extremely high velocities.
Oh and by the way, this accepted formula and its later special-case modifications make no mention of what cartridge case the bullet is fired from.

[35remington]

Taz, my conclusions have never been any different than what you just posted and are a matter of record in the previous posts. My contention was and always has been that considerably slower twist rates than 1-10 are still very acceptable in terms of extracting good to optimum accuracy from the 9mm pistol with the bullets discussed here, and that barrel fit to the gun as well as other factors have more to do with any observed accuracy differences than twist rate.

My supporting evidence has been all attuned to that point, in the interest of providing an alternative to be thoughtfully considered. I have never claimed any particular twist rate was "ideal" but I did and do have trouble with the claim that Europeans have stumbled upon the perfect twist rate (1-10 or its near metric equivalent) and the implication that anything slower must be less desirable.

There is a large amount of evidence to suggest otherwise, as you have found out. Just doing due diligence to the topic.

I dare say, due to restrictive gun laws and generally low rates of handgun ownership in Europe, that American barrel making firms have quite a lot more manufacturing and sales and feedback from discriminating users of 9mm barrels intended to improve handgun accuracy than found over there. Their practices and findings that much slower twist rates are very suitable are not reasonably dismissed.

[oldsalt444]

Among bullseye competition shooters the consensus is that 9mm has to be driven fast to be accurate. 1:32 twist is a common match grade barrel twist which is quite accurate if driven fast. 1:16 or 1:18.75 is the regular factory twist meant for general purposes. 1:10 can handle slower loads and longer 147 gr. boolits. I've been experimenting with 9mm loads for a Beretta 92FS with a KKM match barrel with 1:32 twist. It doesn't like 147 grainers and throws 'em sideways at 25 yards. So to answer your question - use the fast twist for your long heavy 154 grainers. They can't be driven fast enough to stabilize in the 1:18 barrel.

[9.3X62AL]

The 9mm Luger always stirs people up. It is NOT a rule-follower.

1-10" twists are insanely fast for the short, squatty bullets usually used in the 9mm. If the Euros have a reason beyond "Because we have always done it that way", I have yet to hear it. It might be as simple as simplicity's sake--in the late 19th to early 20th Centuries, armies had just invested heavily in the smokeless powder/high velocity rifle concept, most of which were between 7mm and 8mm bore diameters. Just about all nations used barrels in those rifles with 4 turns-per-meter twist rates, which equates to about 1-9.8" twist. The USA uses 1-10" twists in their 30 caliber barrels of service-grade rifles. Europe had rifling machinery in place to cut 4 turns/meter--simplicity and economy might have dictated that pistol barrels could get the same twist rate as the rifles. Of all the explanations I've read or heard, this seems to make some sense.

9mm accuracy increases as its velocity increases. Very likely--those +P+ 115-125 grain bullets are staying hyper-sonic all the way to the target, not getting subjected to trans-sonic trajectory disturbance (that old Chuck Yeager Effect). Conversely, some of the most accurate 9mm ammo I have ever fired was some of our duty loads (W-W 147 grain JHP sub-sonic) through known accurate pistols using 1-10" and 1-16" twists. From a 5" 1911A1, these run about 975-980 FPS.

Some barrels just don't like some bullets. The 9mm has few rules that direct it, and the caliber often ignores the few rules it does acknowledge with great enthusiasm.

[robertbank]

oldsalt444 - your experience mirrors mine differing only in the yardage. I have had them go sideways in 7 yards shooting IDPA.

9.3X62AL - Al you are right on the velocity observation. My requirement for IDPA is to fire a bullet making a power factor ( Vel x Bullet weight) of no less than 125PF. We load for 130PF to 135PF to pass Chrono at matches. This translates to about 865 FPS using 3 gr of 231 for the 147 gr aka 154gr bullet. The bullets are 99.9% stabilized in the 1 - 10 twist barrel. In the 1 - 18 I would estimate about 85%. Percentages are the estimate of number of bullets observed to have gone sideways through the targets.

The M&P early in its production cycle was reported by some to have accuracy issues. Throwing out the "haters" on forums it was pretty clear the gun had some issues. A couple of years ago S&W changed the twist rate in the barrels to 1 - 10. Maybe they were just hoping it would cure the accuracy issue but more likely they were satisfied the faster twist might help. I am not cynical enough to think it was just marketing. Large corporations don't make major product changes in their main product line on whims.

The change had the effect Smith was looking for because folks started to report improved accuracy and today you don't hear the buzz about the guns lack of accuracy we once heard. I would not argue with anyone if they said it might have been a placebo effect but I do know my M&P PRO off a bench shoots tighter groups at 15 yards with the 1 - 10 twist vs the original 1 - 18 the gun came with using 124 gr bullets. Maybe the Service Centre in Victoria did actually fit the barrel to the gun and it was this fitting that allows for tighter consistent lock up of the gun leading to improved accuracy. What the barrel did do was improved the stability of the heavier bullets. Unfortunately not near enough for my purposes so I will stick to the 124 gr 356402 which is accurate and feeds through all my guns like butter. I can deal with the marginal increase in felt recoil.

35Remington I apologize for my over reaction. I read your post wrong and that is on me, not you. I should know better.

I would not dismiss the Europeans experience quite so fast as some might though. To quote our JTF 2 boys moto- "Action Not Words". The Euro gun designs dominate the 9MM production gun market for a reason.

Take Care

Bob

[35remington]

I am not dismissing anyone's experiences. I am just unsure that effects observed are due to any one factor until we can quantify just what has changed other that twist. We do know a fitted barrel was involved in the before versus after. Since two identical twist barrels can shoot dramatically differently due to differences in fit (see my Bar-Sto versus GI barrel 1911's) if we want to know what the major contribution came from we have to account for one variable at a time to be sure of their relative importance.

Ideally a loose fit 1-18 versus a tight fit 1-18. Once that is known then throw in a tight fit 1-10. Fit would still possibly be a player in accuracy with both tight fit barrels with different twists (fitted barrels cannot be fitted perfectly identically) but presumably not so much as before when tight fit was contrasted with looser fit.

[robertbank]

Yup I would not attest to much fitting done by the Service Department. Maybe they did maybe they didn't. S&W won't sell their barrels direct to us up here they insist the slide be sent to their service department for fitting. There was no evidence on the barrel or slide that it had been fitted ....but maybe. I am and was more concerned whether or not it improved the accuracy of the gun and it seemed to from the results I achieved. I am not a gunsmith nor a machinist but both barrels appear to fit equally tight when the slide is closed. The guns as you know lock up at the breach and do not rely on barrel bushings and slide cuts. I can live with thinking it was the rifling twist that accounted for the change. If nothing else it validates S&W's change to the faster twist rate. :>)

Take Care

Bob

[35remington]

Until differences in barrel dimensions and fit are quantified in some way it is prudent for me to suggest that twist may not be a major player in accounting for any difference in observed accuracy. Additionally, both well defined and respected formulae and evidence obtained from other 9mm barrels with slower twists suggest twist may have a minor role here.

In other words.....multiple variables make me suspicious of attributing great improvement to single causes. Call me a skeptic that has good supporting evidence for his doubt.

[robertbank]

Perhaps but the notional evidence with my gun and beyond since the introduction of the faster twist rate barrel s on new production gns would seem to suggest otherwise. I would also suggest that it is not just mere chance the Europeans stick with the 1 - 10 twist barrels for their Production guns. If it were just one manufacturer you could build a case for convenience but it isn't nor is it limited to one country of origin. Maybe they know something we don't. It would not be the first time and based on recent events it won't likely be the last time.

Take Care

Bob

[35remington]

Well, rb, you've received considerable evidence here than 1-10 is neither absolutely necessary nor necessarily "best", and Al's speculation that 1-10 was used for simplicity's sake in Europe is quite plausible.

In other words, considerable opinion here and elsewhere thinks you are more convinced of the importance of a specific twist than you really should be.

Beware of the significance of your "example of one" when all variables are not accounted for.

[robertbank]

I have received several opinions of which I respect all of which may or may not relate to my gun or this model of firearm. I do know what i have observed coupled with what I know S&W did in response to the known accuracy issues their gun had. It may have been one of several things they did to tweak the gun but certainly the most obvious. I am now of the opinion based, in part on the comments above:

1. For 124/125 gr bullets the 1 - 10 twist rate provides better accuracy in the M&P than the 1 - 18 did.

2. Based on the comments above clearly the heavy 154 gr bullets are not being driven fast enough which likely counts for some if not all of the tumbling. The twist rate is likely not the culprit. The slow twist rate results in tumbling was worse not better.

3. For the purposes I use my 9MM guns the 147 aka 154gr bullet is not ever going to stabilize completely no matter the twist rate due to the relatively low velocities I shoot the bullets at.

Take Care

Bob

[9.3X62AL]

I have exactly ZERO time-in-grade with the S&W M&P-series pistols. If at one time their barrels had 1-18" twists, they would be almost alone in using that pitch in a 9mm barrel. I can guess at its genesis, though--S&W has used a 1-18.75" twist in their revolver barrels since about forever. "We've always done it that way!" Did I mention the 9mm's respect for law & order earlier? As in, 'Little or none?'

1-10" or 4 turns/meter does work in the 9mm. 1-16" has done good work for me with jacketed 147 grain bullets (one make of same). But most of my past pistols and all of the present-day 9mm occupants of my gun safe use this faster twist rate. I agree that the Euros stick with the fast rates for some reason, though the hows and the whys aren't readily discernable. To me, it is enough that the insanely-fast twists seem to work, though the 9mm's quirks and oddities make a North American handloader appreciate his/her good old tractable 45 ACP. The 45 ACP spoils us rotten with its user-friendliness and consistent dimensioning. The 40 S&W and 10mm are mixtures of the 45's "Good" and the 9mm's "Evil".

[35remington]

Rb, given the very wide range of twist rates available in 9mm, the presumption that a relatively short 147 or 154 grain bullet "isn't ever going to stabilize completely" given the actually not so slow velocities you are shooting (860 fps) is another very questionable one.

Contrast this with the fact that the 1-18 3/4 twist of the Smith revolvers maintains long 200 grain bullets nose forward at only 600 fps and you'll see why that's in left field in my opinion. You are shooting much shorter bullets much faster. Throw in faster twist rates available in 9mm and well.....it still looks like you are laboring under some false assumptions about twist and the need for same. Your bullets are still quite short, velocities are not so low and the twists ample for the job.

What is evident is you don't have enough sample size to know if your results can be correctly attributed to the factor you give it credit for.

Perhaps you need to have a Bar Sto, Wilson Kart or other barrel fitted before you are ready to proclaim 1-10 the "be all and end all."

Any statistician or 9mm barrel maker would view your statements with deep suspicion.

[robertbank]

Rb, given the very wide range of twist rates available in 9mm, the presumption that a relatively short 147 or 154 grain bullet "isn't ever going to stabilize completely" given the actually not so slow velocities you are shooting (860 fps) is another very questionable one.

Contrast this with the fact that the 1-18 3/4 twist of the Smith revolvers maintains long 200 grain bullets nose forward at only 600 fps and you'll see why that's in left field in my opinion. You are shooting much shorter bullets much faster. Throw in faster twist rates available in 9mm and well.....it still looks like you are laborimg under some false assumptions about twist and the need for same. Your bullets are still quite short, velocities are not so low and the twists ample for the job.

You know you can only go to the well so many times. My father in law used to say anyone can get lost only a fool stays lost. I am not labouring under anything. First S&W made a change and it solved their problem with their 9MM M&P pistol. Why you think this has to do with S&W revolvers is anyone's guess. I do know the 1 - 18 twist at 865 fps had more bullets going sideways into targets at ranges of 7 yards than the faster twist barrels. I know the accuracy in the gun improved with the faster twist barrel because I did side by side testing enough times to note the improvement. This would seem to validate S&W change in twist rates. Given the M&P is their flagship entry into the striker fire market I would respectfully suggest they know what they are doing and did not put their platform at risk on a whim.

FYI my 125 gr 356402 bullet runs along at 1,100 fps and shoot fine and seem to be more accurate through side by side testing out of the 1 - 10 twist barrel. I should add not nearly as accurate as my CZ 75 Shadowline or 85 Combat but then both those models are bushing based barrels and the CZ's are incredibly engineered and built guns for the money we pay for them. Entry level 75B to high end Shadow2 / Canadian Edition the guns are amazingly accurate with 1 - 10 twist barrels I might add. For IDPA though the lighter M&P PRO gets the nod for the style of shooting that sport demands. For IPSC I would favour the CZ's.

Al right now my right shoulder is no fan of the 45acp using my 1911's. The kid has to have his shoulder joint replaced in the coming months, or so says my South African surgeon over in Pr. George. Right now the 1911's at 43 oz empty are just to hard on the joint to mess with BUT my oh my are the guns a treat to load for and the brass lasts virtually forever. Next spring will see the return of JMB's favourite toy along with my CZ 97B in the same caliber. The latter sells lightly used for around $700Cdn up here and will shoot with my Dlask prepared 1911. Big holes are easier to see than little holes. Thanks for your insights my friend.

Take Care

Bob

[9.3X62AL]

No sweat, Bob. I hope the doctoring fixes things well and lets you enjoy that big bore stuttergun to your heart's content.

I do agree about that "Going to the well" 1X too many. What a twist rate or a bullet diameter or an alloy or a lube type does or doesn't do is far more important that what it is alleged or supposed to do. Ultimately, what YOUR BULLETS do through YOUR FIREARM are the valid barometers. A part of this hobby field is the experimentation and test-drives and work-ups, certainly. Most of us here are rather deeply experienced in this art/science/addiction, and it has been many moons past since our first rodeo. My view is that the 9mm pistol is just a bronc that won't stay saddle-broke, and gets barn-sour without much notice and needs some vigorous reining to keep on the trail when cast bullets are involved. 9mm is NOT a good beginner caliber for either a reloader or a caster, and it has thrown more than a few experienced riders. If you have found a load that shoots well and groups tightly, you are already ahead of the curve.

[35remington]

I found it odd because identical diameter bullets of the same approximate weight are stabilized fine from as slow or slower twist barrels than 9mm's possess. The bullet knows only spin and revolver or auto don't figure into it.

I wonder how they managed all those years, and the weight of that evidence says 147-158 grain bullets are no great trick to stabilize or get to shoot very accurately. Seems quite odd you would say such bullets are impossible to stabilize. Especially out of a faster or comparable twist 9mm.

Nobody else seems to have much problem with it. I am wondering why you do. You already know I don't buy the twist thing so some other things would get investigated if it were me. I understand that is maybe not what you are interested in doing.

I would be examining barrel fit as near as you can measure it. One barrel to another. Several relevant clearance areas could be measured. That may not explain the tumbling which I do not think is the twist, but it might explain any observed accuracy differences.

[9.3X62AL]

It is kinda weird. But at times you just need to cut your losses--go with what works--and enjoy the match or the hunt. I have a lot less patience for ghost-chasing these days than I did in years past.

[tazman]

On 2 occasions I had supposedly identical weapons that would not perform the same. One would shoot only jacketed, the other would shoot anything.
These gun were A pair of Taurus PT92 9mm handguns and a pair of Springfield Armory P9 40S&W handguns. I owned these many years apart.
I tried everything possible to get them to shoot since one would shoot cast and the other would not.
Neither sizing, lube, or alloy made any difference.
I finally found out what the trouble was after weeks of pulling out my hair. The rifling in the barrel was too shallow and the edges were too rounded. The driving bands of the lead boolits were shearing because the rifling would not properly grip the boolits. They worked fine with jacketed.
In the case of the P9, the gun went down the road. In the case of the Taurus, I put in a Beretta 92FS barrel which was a cheap and easy fix since the barrel was a drop in replacement.
This solved the issue entirely.
I have been reading recently about 9mm barrels and what it takes to make them work. Apparently, the 9mm doesn't behave as expected unless things are perfect. By that I mean, it just won't follow normal rules. Many people are finding that, in this caliber, it often takes a faster twist than expected to make things work correctly.
Science and theory can only get you so far. Results are what matters.

Robert---Since the faster twist works for you, go with it and don't worry about the theory. You aren't shooting some one else's gun. Each gun makes it's own rules.

35remington--While in theory, your statements should work, in this case they don't for whatever reason. Continuing to repeat the same stuff over and over will not make it work in this case.

9.3X62AL--Your last post was spot on. You reach a point where you stop trying to figure out a theory and just go with what works. Life is too short to shoot inaccurate guns.

[robertbank]

I think our old friends Felix Robbins and Bruce B is up there with a smile on their faces.

Thanks guys

Bob

[35remington]

Unless I am sure of being able to quantify the possible differences involved to the necessary degree, I do not have confidence in the "explanation."

What I did suggest needed quantifying was not in the realm of theory... that is, suggesting measuring fit tolerances on the two barrels. Measuring dimensional differences is really easy to do.

I understand some people may not care about looking for answers to this degree but that is not me. There is more that I could be doing. Agreed that it is not life or death if you do not look for it, but I myself want to cover all the bases to the extent possible.

This tends to make me more confident in any answer I come up with by eliminating alternative possibilities which seems the logical way to do it. Just explaining how I roll.

Since 1-10 or in that metric vicinity is the fastest twist offered, and aftermarket barrels range slower to much slower with 1-16, 1-18ish, 1-24 and 1-32, it is worth pointing out that many people also apparently think a slower twist is needed to make everything work correctly. Yes, theory here that has little to do with the topic. But... how many cartridges have such a wide twist range? Few I can think of.

After pondering all that, this guy really would be measuring the barrel/gun fit.

[9.3X62AL]

35--

I respect the disciplined analysis you allude to in your text. I have no answer to the 38/357 and 9mm disparities. I do know that they exist, and that the 9mm is not commonly encountered at 2700-series pistol venues. The 9mm is accurate enough for felon repellent, relatively affordable to run, and when loaded to its full potential can be an effective defensive pistol caliber. That is enough for me--though it is more of a varmint gun than felon countermeasure in my circle.

[35remington]

Call "disciplined analysis" a personal failing if you wish. I want to have a reasonable assurance I have addressed possible variables, and if I focus on one possibility without at least attempting to eliminate others or test that assumption versus others, well, as I said, I cannot be sure that my conclusion is right. I am not much for guessing yet still being confident about it.

I do know the 9mm is not as common in formal Bullseye matches, but I tend to think that has more to do with the limitations of the guns it is used in (relating to accuracy tunability and trigger deficiencies) than anything to do with the cartridge itself.

[robertbank]

35 no offence but at the end of the day how much time and money do you think I want to spend on a $700 pistol that out shoots my meager talent as it sits. If there was a reason to choose the 9MM for any form of Bullseye shooting then you can bet smarter men than you or I would have been all over it like a dirty shirt. The fact that they haven't in any numbers tells me the cartridge is best used in other disciplines.

One thing we Canadian boys learn early in life is you don't have to pee on an electric fence to understand the perils of doing so. The dumb kids lick metal fences at -20F once and it is they, who just have to find out for themselves how quickly electricity moves along in water. I am wise enough to differ to Al and Tazman both of whom I am sure no better than trying interesting actiivities with electric fences.

Take Care

Bob

[35remington]

Well, as I pointed out, measuring the relevant areas takes little of either time or money. It is not asking a lot.

[robertbank]

Well, as I pointed out, measuring the relevant areas takes little of either time or money. It is not asking a lot.

No but once you discover a variance then what? The only thing you can do to the M&P barrel fit wise would be to buy another barrel if the barrel in the gun was not locking up tight on the slide, at the breach. Tight is tight and the barrel was fitted, or at least within specs of S&W. Having a 'smith fit yet another barrel to the slide might be a "better fit" than the barrel that is in it, then what. You test again and if the same thing happens you cross out that variance and the $200 - $300 you spent chasing a solution that may not exist. Curiosity I am told kills cats and it can kill pocket books as well. At some point you have to decide when to move on particularly when in this case, 124 gr bullets over top of 4.1 fr of 231 or 3.4 gr of 700X zing through the 8" Down Zero scoring area of an IDPA target at 20 yards with boring rapidity free style under the stress of a timer. (or where the sights were actually aiming which sometimes is different.)[smilie=f:

The while object of pursuing the heavier bullet was to reduce felt recoil and muzzle flip which would have the potential of improving shot split times. It did but the cost was accuracy due to wobbly bullets out to 50 yards and the improved splits would never overcome the loss in potential scoring.

Take care

Bob

[35remington]

Bob, you are working yourself into a froth over this. It is not that hard.

Measure the more and less accurate barrels in the relevant areas off the gun, then check the possible clearances when they are mounted on the gun. I am not asking you to buy anything new, just to discover any differences in dimensionality that might explain observed accuracy differences if present.

[tazman]

35remington---It isn't your gun and Robert obviously is not interested in hearing from you further. Please let it drop.

[35remington]

Well, I thought I would let him tell me he isn't interested in measuring relevant dimensions that likely have a bearing on his results.

My comments have to do with discussions with guys who regularly fit barrels. They tell me they can measure several areas and predict how well the gun will shoot, and also figure out why a particular combination is or is not shooting. Thought I could pass that along. If he isn't interested I'll let him tell me that, thanks. I just needed to reassure him I was not asking for any expense and very little time.

[9.3X62AL]

How the h--l do you interpret my text as disparaging? It was anything BUT THAT. You must be craving a confrontation--I'm not interested.

There is NOTHING like twist rates and RPMs to get the swords unsheathed and the pistols unholstered on this site. SHEESH!

[35remington]

Al, I did not at all interpret your post as disparaging (quite the contrary as your phrasing was clear) and I do thank you for the comment. I was just going along with the sentiment that I was asking too many questions about a topic nobody seemed to care about to any great degree. And, I was interested in getting more information that might help support or contrast with other information.

I was, in effect, pouring ashes on my head with my first sentence response.

I may have stated my first sentence in my response better by saying "Call disciplined analysis a personal failing some of the time." I did get the feeling some regarded my questions as being overly nosy but I really am curious about what can be learned from this.

Apologies for poor editing on an iPhone during a night out when I was distracted. My first sentence was more vague than it should have been but I hate typing on a little phone and that is the best excuse I have got.

The comment was directed at the persistence of mine about getting more info that seems to annoy. I truly am sorry if I have annoyed anyone and that is what prompted the remark you took offense at.

I actually am just curious about what could be discovered if someone wants to look. Trying never really hurts anything. If guys tend to be problem solvers, I am at the far end of the guy spectrum, admittedly.

Rather than alluding, let me be specific. Calipers will suffice. If there is any interest, measure the length from locking surface to hood, and lower lug feet to the locking surface, and diameter of front of barrel. Compare between the two barrels. Width of chamber area and end of hood are worth getting but the first three are the most operative in terms of accuracy improvement.

Something worth knowing as to having an effect on accuracy. My interest in this topic is not really on twist, per se, but rather on what else can be found out about what is going on.

[tazman]

I can see how such measurements would effect accuracy, but fail to see how they would effect or cause boolit tumbling. Can you clarify that?

[35remington]

I have already said, I think, that tumbling is some issue I cannot explain via either twist or exterior dimensionality. That may have to do with barrel internal dimensions like (too large for cast?) groove diameter or a too abrupt or poorly dimensioned throat. I am going after exterior dimensions as they are easiest to get first to explain accuracy disparities in the bullets that do not tumble.

Slugging the barrel takes more effort and that may be perceived as asking for too much effort in investigation. But it could be done to get useful information that clears things up some. If the barrel is five groove a decent diameter measurement will be hard to obtain but possible to approximate.

I am already aware due to specific comment on the matter that some may not care about this all that much and that I am being annoying in suggesting alternative causes. Really, though, all along I could have specifically suggested where else to look right away and saved everyone the waste of bandwidth. I probably have been too vague as I did figure everyone knows where else to look for problems already.

They probably do.

[35remington]

Some things are counterintuitive if you come from a 1911 barrel fitting background like I do and go about fitting a plastikpistole barrel. I am dumb enough to have fitted the single plastic pistol barrel I have done myself, but smart enough to have asked for help as I went along.

The two areas that are fit are the locking engagement surface at the chamber/barrel junction and the lower lug feet. The diameter of the barrel is whatever they supply and may be a little larger than stock or maybe not so much. The first two areas are most important. It seemed to me that a wider chamber area in aftermarket barrels would reduce side to side play between the wings of the locking block along with an exactingly fit hood width but surprisingly to me my sources as well as the technician at Bar-Sto (one of the few makers that is willing to discuss barrel fitting) say side to side play does not affect accuracy that much.

One "modern" (not 1911) pistol barrels that must be fitted hood width is not even addressed or fit. Some makes do not have much for hoods anyway. So much for that. In a 1911 it is different.

In all this my situation was much like rb's in many particulars. I replaced an original factory barrel with another and accuracy got a lot better. So I can relate to some degree.

[9.3X62AL]

Awright, 35--now I think I get your drift. I avoid the Smart-*** Phones for the reasons you mentioned--my big hands and fingers flatly can't work the things. I think their core market share is teen girls of petite stature.

I haven't had a pistol barrel be bad enough to cause tumbling bullets. If the projectiles fit even close to proper dimensions, they flew nose-first enough to cut round holes downrange. "For how long" came to the fore on a couple occasions, both due to fouling (one by black powder, the other by lead deposits)--so those issues were fairly easy to remedy and resolve (use enough correct lube, and size bullets correctly--respectively). In absence of a profound diametric problem or indicia of same (like a lead mine forming down-bore), Bob's issue defies diagnosis. Bob knows his hobby work well--I've discussed a lot of casting- and shooting-related matters with him over the years. He is not one to walk away easily from a challenge.

I don't know the proximate cause of the bullets tumbling from the slower-twist barrel, but I don't think it is simply rifling twist--35/36 caliber bullets longer than the 147 grain castings have been very well stabilized for 125 years+ with 1-16" to 1-20" twists. It would interest me to see how factory 147 grain JHPs (either ammo or component bullets) behaved through the offending barrel, as well as both jacketed and cast 125 grainers. FWIW, I don't think real highly of the 147 JHP 9mm sub-sonic loads as a goblin stopper, but the ammo can be SUPERBLY ACCURATE in an arm capable of exploiting same. Several streetlights expired decisively (1-shot stops) to 100+ yards using a Colt SMG with these loads.

[35remington]

Again, Al, sorry about that. Brevity, conciseness of thought and cell phones do not go together as you note.

In regard to tumbling, I think of a Microgroove Marlin 45-70 I bought in 1991 and still own. I bought factory issue 340 and 405 Lee moulds shortly thereafter. Both cast to .4575 to .458."

From a clean barrel, the 405's would tumble, then, as the barrel leaded, they would stabilize and shoot only sorta acccurate groups, then would shoot larger and larger groups as the barrel continued to lead.

The 340's, despite being the same diameter, never tumbled. They were not accurate, but they did not tumble. Since this is identical to rb's experience with lighter and heavier bullets in his original 9mm barrel, I suspect an inside the barrel thing regarding tumbling, somehow.

That part is harder to diagnose, but exterior dimensions affecting accuracy less so.

The rifling twist being so inadequately slow to cause tumbling does not at all seem likely as you suggested. Jacketed bullets seem more tolerant than cast bullets regarding stability if the barrel is oversized from what I have seen and read about.

[9.3X62AL]

I may get to tear my hair out like Bob soon enough. I have Glock pistols in 40 S&W and 10mm that will be getting my first misadventures with cast bullets through their OEM barrels. I have run castings through Storm Lake barrels in Glock 40s without a problem, even though the barrel was a drop-in fit it shot right where the OEM barrel did at 15 and 25 yards. I am not real keen on spending the grass for 4 aftermarket barrels, nor am I enthused about buying jacketed bullets to feed the plasticating monsters with. The girls just LOVE their Glocks, though--2 more of them will get some range time with me this month, and I see 2 more handguns heading north in some fashion afterward.