Every Revolver is a law unto itself as far as velocity goes.

[JoeJames]

Each revolver is a law unto itself.

First of all. I chronographed the Model 67 using the same loads I'd chronographed before with the Model 15-3. The Model 67 was produced in 1974, and the Model 15-3 was produced in 1970. Both 4", and both 38 Special. The load was: 4.1 grains of Win 231, CCI 350 small pistol, and 160 grain cast swc's. Exact same load from the same box of my reloads. The 67 chronoed at: 803, 818, 769, 781, and 770 - for an average of 788 fps, and the Model 15-3 chronoed at: 840, 877, 836, for an average of 851 fps. (not as many but still decent for a range). Anyhow there is a difference of an average of 63 fps between the same load in the model 15-3 and the Model 67. Only thing I can figure is that the 67 is bored a tad looser.

236866236867

[M-Tecs]

Different cylinder gap would be a cause.

[lefty o]

heck, every barrel as far as it goes. one barrel off the line may be fast, the next may run slow.

[Outpost75]

In .38 Special firing standard-pressure lead bullet ammo you can expect a Delta-V of about 10 fps for each 0.001" change in cylinder gap. +P may be more, depending upon barrel length, as some loads are optimized for short barrels and others are not.

Here are chronograph data of factory .38 Special loads fired in 4" vs. 2" barrel revolvers,
both having the same cylinder gap of Mean Assembly Tolerance:

.38 Special chronograph data, S&W Model 15, 4” with 0.005” cylinder gap 6-22-93.

Federal 125 Nyclad HP 852 fps, 25 Sd
Remington 148 HBWC 747 fps, 6 Sd
Winchester 148 HBWC 742 fps, 13 Sd
WCC87 Ball M41 130-gr. FMJ 748 fps, 21 Sd
Winchester X38SPD 158-gr. LHP +P 920 fps 21 Sd
Winchester Q4196 158-gr. LRN 793 fps, 10 Sd
Federal HydaShok 147-gr. JHP +P+LE 965 fps, 33 Sd

Same ammunitions fiured from S&W Model 10-2 with 2” barrel and 0.005” cylinder gap 6-22-93
______________________________________Vel.Loss 2” vs. 4” barrel:

Federal 125-gr. Nyclad SWCHP 772 fps, 33 Sd_______80 fps
Remington 148-gr. HBWC 702 fps, 12 Sd___________45 fps
Winchester 148-gr. HBWC 697 fps, 18 Sd___________45 fps
WCC87 Ball M41 130-gr. FMJ 718 fps, 31 Sd_________30 fps
Winchester X38SPD 158-gr. LHP +P 831 fps, 10 Sd____89 fps
Winchester Q4196 158-gr. LRN 728 fps, 24 Sd_______65 fps
Federal HydraShok 147-gr. JHP+P+ LE 920 fps, 6 Sd__45 fps

Column Mean______________________________57 fps, ~29 fps/inch.

[JoeJames]

Thanks, that was a factor that had not crossed my mind. Not a big deal, both are quite accurate; velocities just came out more than a little different.

[RED BEAR]

You bet ya. I have two 32acp loads that work fine buldge the cases in the other to the point of rupturing. Sorry missed the revolver part.

[TNsailorman]

I would guess that the answer lies in the cylinder throats. You might want to measure them and see if the correlation holds. james

[Larry Gibson]

Were they chronographed consecutively on the same day under the same conditions? If on different days under different conditions with a different set up of the Chronograph the 63 fps difference could easily be from other variables. Also, back to back tests of the same load, especially just 5 shot tests, out of the same firearm will show some variation.

[Rick Hodges]

I remember an article in the beginning of an old Speer reloading manual. They took 6(?) consecutively numbered 4" S&W model 19's and with the same .357 mag 158 gr. ammo got a velocity spread of 960 fps-1200+ fps between the guns. Same load, same guns (as close they could get off the assembly line.) way different results. Their point was that no two guns are the same.

[Texas by God]

Velocity is usually the biggest difference between two seemingly identical guns. You have a nice pair of Combat Masterpieces there.

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[mozeppa]

i'd think a tighter bore (not looser) would generate more pressure and spit a pill a little faster.

am i wnorg?

[Silver Jack Hammer]

I’ve chronographed 2 Colt’s 4 3/4” .45’s side by side and found 100 FPS difference. The one does have an excessive cylinder gap.

[JoeJames]

i'd think a tighter bore (not looser) would generate more pressure and spit a pill a little faster.

am i wnorg?That is my theory. "The 67 chronoed at: 803, 818, 769, 781, and 770 - for an average of 788 fps, and the Model 15-3 chronoed at: 840, 877, 836, for an average of 851 fps. (not as many but still decent for a range). Anyhow there is a difference of an average of 63 fps between the same load in the model 15-3 and the Model 67. Only thing I can figure is that the 67 is bored a tad looser." I reckon I could have said the Model 15 is bored a tad tighter. But I am going to check cylinder gaps.

[Outpost75]

i'd think a tighter bore (not looser) would generate more pressure and spit a pill a little faster.

am i wnorg?

Tighter cylinder throat diameter also boosts pressure and velocity a bit.

[Outpost75]

I remember an article in the beginning of an old Speer reloading manual. They took 6(?) consecutively numbered 4" S&W model 19's and with the same .357 mag 158 gr. ammo got a velocity spread of 960 fps-1200+ fps between the guns. Same load, same guns (as close they could get off the assembly line.) way different results. Their point was that no two guns are the same.

In that era the differences would be greater because S&W was still establishing final cylinder gap by hand with a file. By late 1980s everything at Ruger was CNC and any random set of parts could be assembled into a gun without using hammers or files.

[Bookworm]

I've done the same with 2 SW model 10's, and also 2 SW model 14's.

Chrono them the same day, one after the other, different velocities. 50+ fps differences. No big deal, just different revolvers.

If I can find another model 15, I'll do it again. I'm certain they will differ also.

Velocities posted in loading manuals are guidelines, just as is the loading data.

[JoeJames]

I've done the same with 2 SW model 10's, and also 2 SW model 14's.

Chrono them the same day, one after the other, different velocities. 50+ fps differences. No big deal, just different revolvers.

If I can find another model 15, I'll do it again. I'm certain they will differ also.

Velocities posted in loading manuals are guidelines, just as is the loading data.Or another way of stating it: the velocities in the manuals are merely advisory. That's why a chronograph is a necessity in my opinion, along with a trigger gauge.

[JoeJames]

I am so glad threads like this one comes along. All the OCD statisticians and experimenters drive home all the intricate details of how one conducts tests, info about the gun and whether if was the dark of the moon or how one held their mouth as they chronograph. It is a CONSTANTLY changing thing this thing of chronoing pressure testing etc.. Even in the same gun on the same day changing a lot of the same components different results are obtained.
But if the OCD people get their kicks by doing it it is good I guess.

Again I mean no hurt, harm, anguish or turmoil by my post I have posted on this posted subject. I am not baiting, trolling or calling out anyone. I am making a post based on my experience, knowledge and/or belief or opinion. That is all.
None of any of this is anything new.That indeed is exactly how I have described myself. I have more than a few times said I was not OCD on anything at all, except for my reloading. And I didn't get too bad on that until I got my chronograph a couple of years ago. Man! that thing opened up a whole new world! And also as you stated there are always new variables to consider, like cylinder gap, which had not dawned on me until this thread. All in all it is a good thing.

[JoeJames]

Its comical to see someone that is like that. Firearms, ammunition and reloading components are ever changing. Someone will put forth so much effort to chrono, pressure test, make sure the firearm specs are recorded etc, etc, etc and more etc.. That is good until something is changed. Then the process goes on again.
The old saying "If it is worth doing it is worth doing right" is the comforting motto they live by until they change something then it is back to the drawing board again.
I am just too simple minded to care about the minute details of an ever changing process.
I chrono just to get an IDEA as to what is happening. Nothing more, nothing less because after all it is ever changing.
But, if it makes them happy I am all for it. I am not a wet blanket at all.

Again I mean no hurt, harm, anguish or turmoil by my post I have posted on this posted subject. I am not baiting, trolling or calling out anyone. I am making a post based on my experience, knowledge and/or belief or opinion. That is all.There is some truth to that. But as one of my cousins said "If you get a new gun, you need to buy about $200 worth of various ammo to see what it likes best". With me, I try to find out what is the most accurate of my reloads when I get a new one. For example I had a heck of a time figuring out what 44 Special loads would not just plain key hole in my Henry Big Boy 44 Special/44 Magnum. Figured out a good load, and then decided the dern Henry was just too heavy to tote through the woods at 8.67 pounds. So got a Rossi R92, discovered it would not feed 44 Specials; so had to work up reduced 44 Magnum loads comparable to 44 Specials., and be accurate.

[Texas by God]

When someone asks what velocity my loads are I reply "probably slower than I think".

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[Walks]

Well,
I look at it as something to do with our 'stuff".
I tried this last year with A Ruger Speed-Six .357mag 2 3/4" bbl. a blued revolver made in 1978. And a Service-Six .357mag 3' bbl. a STS revolver made in 1988 (last yr of Prod).

I used a .357Mag load of 170gr #358429 over 6.5grs of Unique. I got anywhere from 950fps to 1010fps. No discernable difference between the two.

This was just a sort of pick up test. I had the 2 revolvers & ammo, the guy next to me had the Chronograph. He was getting wide deviations
in his .38 ammo out of a 8" PYTHON. Asked to try my S&W Model 14 6". Got a lot of variation in the "14" too. So tried the 2 short Rugers also. Got wide variation out of those Revolvers too. So tried My ammo in My Guns.

A 50ft deviation between 2 different revolvers.

Found out he was loading the Speer .38cal 158gr swaged SWC over 3.5grs bullseye. Had trouble setting up the OLD used dillon 450 loader he was using. I went over to his house and helped him out. Called dillon, they sent Him a NEW Powder Measure. even though the press was 30+yrs old. It came, but I never got to help him, transfered to New York. Poor Dude.

[Three44s]

Perhaps one gets a barrel made from HSS every once in a while. That’s what I told a friend who was testing out his 416 Taylor and it was running fast.

Three44s

[Texas by God]

Perhaps one gets a barrel made from HSS every once in a while. That’s what I told a friend who was testing out his 416 Taylor and it was running fast.

Three44sI saw what you did there[emoji16]

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