SD9VE vs MP 2.0 Full Size: barrels and velocities

[1sdfellow]

At the same time I bought the SD9VE I got a new MP 2.0 Full Size 9. The 4” barrel on the SD9VE actually measures 3.86”; the 4 1/4” MP 2.0 is really 4.18 for a difference of nearly 1/3 inch (.32). The breech blocks have similar external widths (.592”, .594” respectively) while the MP has extra metal on bottom (Height .672, .722 resp). The mid barrel thickness is .571 SD, .562 MP. Interestingly, the minimum chamber wall thickness on the SD is .096”. By comparison the minimum for the following .357 Magnum revolvers is: Model 60/ J frame .056”, Model 64/K frame (.38 Spl) .072”, Model 686 Plus/L frame .092”.
For chronograph results: MP, Winchester 90 grain zinc super clean rated at 1330 fps gave average corrected to muzzle of 1303 fps at 95 degrees; SD9VE gave 1300 fps corrected at 61 F.
With a somewhat hot handload of Hornady 147 XTP, 5.3 grains IMR 800-X, CCI 500 primer, Winchester brass, cartridge overall length of 1.076”, MP turned in an average velocity of 1062 fps at 86F, while the SD did 1060 fps at 61F. Both were corrected to muzzle.
So despite having nearly 1/3” less barrel length, the SD9VE produced almost identical velocity in somewhat cooler temperatures. Very interesting, to me at least.

 

[Echo40]

Are sure you were measuring the barrels correctly? Sometimes a bit of the chamber is counted as part of the barrel, depending on how far back the chamber is seated and how deeply the cartridge is seated within.

It just seems odd that they would have identical velocity despite having supposedly different barrel lengths based on your measurements, yet equal barrel lengths according to Smith & Wesson.

 

[1sdfellow]

Sure enough, you’ve taught me something: if you measure the barrels installed, using the depth measurement of the dial caliper, the SD measures 4.02” deep from crown to breech face, while the MP 2.0 measures 4.26”. Now that you mention it, I think this is the method used by the ATF to check legal barrel lengths. So by this method barrels are almost exactly as advertised: 4” SD9VE vs 4.25” MP 2.0, for an advertised difference of a quarter inch.
As to the velocity difference, there’s going to be variation from gun to gun of the very same model, but is interesting that the sd9 did so well even with the disadvantage of lower temperatures and 1/4” shorter barrel. Could be this SD9VE just has a tighter bore. I’ll try to chronograph the two at the same time using a greater variety of loads. Thanks for your thoughts, Callahan.

 

[Skeptic 9c]

My old First Sergeant referred to "Pole vaulting over mouse turds."
Geoff
Who suspects variations round to round eat up the difference.

 

[Echo40]

Sure enough, you’ve taught me something: if you measure the barrels installed, using the depth measurement of the dial caliper, the SD measures 4.02” deep from crown to breech face, while the MP 2.0 measures 4.26”. Now that you mention it, I think this is the method used by the ATF to check legal barrel lengths. So by this method barrels are almost exactly as advertised: 4” SD9VE vs 4.25” MP 2.0, for an advertised difference of a quarter inch.
As to the velocity difference, there’s going to be variation from gun to gun of the very same model, but is interesting that the sd9 did so well even with the disadvantage of lower temperatures and 1/4” shorter barrel. Could be this SD9VE just has a tighter bore. I’ll try to chronograph the two at the same time using a greater variety of loads. Thanks for your thoughts, Callahan.

Most duty ammunition is designed for 4" barrels since it's currently the most common barrel length among duty weapons, so it's not really surprising that an extra ¼" of barrel didn't effect velocity.

Folks often assume that longer barrels always beget higher velocity, but that isn't always true. Longer barrels only really aid velocity up until the point that all of the cartridge's propellant has burned off, after that it will actually start to slow down the bullet as it drags against the rifling of the barrel, although it really doesn't make much of a significant drop unless it's fired out of a pistol caliber carbine with an extremely long barrel.

 

[Papa_D]

Also don't forget that 9mm is a high pressure round and is very efficient at getting to higher velocity in shorter barrels than say a .38spl or .357mag that require longer barrel lengths to get to optimum velocity.

Sent from my Vivo XL4 using Tapatalk

 

[1sdfellow]

I appreciate all the thoughts. The predictive power of comparing one SD9VE vs one MP 2.0 Full size is really nil, but I like to measure and chronograph things, and share numbers with my fellow shooters wherever possible. Ballistics by the Inch shows pretty convincingly on their website for their 9mm barrel cut-down tests of velocity that every 9mm load they tested increased in velocity up to 9” of barrel length. The average increase going from 4 to 5” of barrel across their 10 loads tested was 58.5 fps.
The 800-X load I tested is particularly interesting to me because the powder is slower than most for handgun and should favor any increase in barrel length. I got that load by the way from an old IMR file. It’s really hard to get much 800-X data. It is a truly great powder for the 10mm. FWIW