Home Forums Hunting & Shooting Handguns 9mm velocity in increasing barrel lengths

Went out this morning and chronographed some typical 9mm ammo in four pistols with increasing barrel lengths and thought I'd share the results.

The pistols and barrel lengths are;
Sig P365 - 3.1"
Sig P365 XL - 3.7"
S&W M&P 2.0 Compact - 4"
S&W M&P 2.0 Full size - 5"

Ammo is S&B 115 FMJ, S&B 124 FMJ and Speer 124 GDHP standard pressure. Ammo was fired over an Oehler 35, readings are 12' instrumental. Five shots each for the S&B and four shots for the more expensive Speer. (My $2.8 million government grant for this study failed to come through so I had to economize).

Results are highest velocity in a string......lowest...... average

S&B 115 FMJ
3.1"..........1130..........1104..........1117
3.7"..........1178..........1134..........1162
4.0"..........1192..........1152..........1171
5.0"..........1222..........1199..........1211
Highest to lowest avg. is 94 fps.

S&B 124 FMJ
3.1"..........1045..........1039..........1041
3.7"..........1081..........1070..........1076
4.0"..........1109..........1074..........1091
5.0"..........1136..........1111..........1126
Highest to lowest avg. is 85 fps.

Speer 124 GDHP
3.1"..........1013*
3.7"..........1093..........1057..........1069
4.0"..........1087..........1038..........1062
5.0"..........1136..........1124..........1129
Highest to lowest avg. is 116 fps, but that one shot for the 3.1" barrel makes this number suspect.

* I screwed up this string and only recorded one round. But the stats are amazing - extreme spread of 0 and standard deviation of 0. Center to center group size, had I recorded it, would be .000"

Some observations. All bullets gained an average of just under 100 fps going from 3.1" to 5.0" barrels, with a slightly bigger gain going from a 3.1 to 4" barrel than from the 4" to 5". This is in line with what I've read about 9mm ammo being optimized for 4" barrels. Whether these velocity differences are significant is up to each reader. I think with well constructed bullets they'd all leave a mark no matter which barrel length you used.

One subjective impression is recoil. It was 28 deg. this morning with an 8 mph wind and my fingers got a bit cold. The P365 had a 12 round mag in it so I could get my hand fully on the grip but recoil was still snappy. My chilly trigger finger really felt it after the first five rounds.

Going to the 365 XL with a longer and heavier slide showed a noticeable decrease in felt recoil, it was a slower recoil impulse. I've no way to quantify this, it wasn't a huge difference, but it was definitely noticeable. Going to the M&P Compact was a "really big difference" (technical term) in recoil, and the 5.0" full size M&P was again a smaller but noticeable difference from the 4" barrel; it was a real pussycat compared to either Sig. This is all to be expected but I was a bit surprised at the difference between the two Sigs. I've noticed this at a warm indoor range firing both but my cold trigger finger this morning was really sensitive to it.

Anyway, no big surprises here but I've been wanting to get some empirical data on this for a while.

Also, I'm still happy with the Speer 124 Gold Dot standard pressure ammo in 3.7" or 4" barrels.. The 365 XL has become my primary carry gun when I need the most concealment and I'd not feel unprotected with it in most any civilian self defense situation. However, I'm still evaluating compact 4" models which are preferable. The difference in velocity is negligible - the average actually went down 7 fps in this trial - but there is a significant difference in felt recoil and shootability.

JIm,

Thanks for the nice write up!

This is the kind of evidence based approach we can all benefit from.

Thanks for taking the time to type that up. Always interested in what the chronograph has to say. I agree with Antelope Sniper, everyone can benefit from your approach.

Thanks for the kind words. I've been rightly accused of being totally left brained so enjoy doing this kind of thing.


Looking at the data again and how the numbers from the 3.7" Sig to the 4.0" Smith are so similar, and the Sig actually has higher numbers with the Speer ammo, I'm thinking that has more to do with the individual barrels than their respective lengths. The Sigs are probably a bit tighter.

Speaking of, those Sig P365 models are amazing little guns and are more accurate in slow, aimed fire than any of my other 9mm pistols except a full size Sig P320. The Glock 34, 19 and both Smith M&P's can not group as tightly as both of those Sig sub-compacts. However, as noted in my first post, when you get to shooting fast the bigger grips and lower felt recoil give the bigger guns the advantage and they are definitely more comfortable to shoot in extended sessions at the range. But even in rapid cadence shooting the difference on paper is not nearly as much as one might expect.

Great write, thanks for sharing! I’ve been thinking about getting a Sig 365 XL and was wondering if there was any noticeable difference in felt recoil.

Thanks for sharing! I always enjoy seeing the results of these kind of tests.

Very solid test, thanks

Good stuff Jim. The chronograph is the grim reaper of BS and wild speculation.

Good work, Jim! Thanks for taking the time to conduct the test and provide the write-up. Great stuff!

Thanks Jim!
Those little Sig pistols are amazingly accurate.