Published vs Actual Muzzle Velocities

Are there any figures or formulas in existence that allows a person to determine how a "shorter" barrel revolver compares to a "longer" one regarding exit muzzle velocity? Most published values state that a 4" or longer barrel was used on the "test gun". I shoot my SP-101, 2.25" barrel, quite a lot. Just wondering? :?:

Yes. This is excellent: http://www.ballisticsbytheinch.com/

Shorter barrels result in large reductions in velocity. The historic "rules of thumb" are not good estimates.

Note that barrel lengths listed are measured from the breech face, as done with semi auto pistols. Also see the data on cylinder gap effects.

A chronograph is the only way to know for certain, with revolvers the fly in the ointment is the cylinder gap, which does affect muzzle velocity as the gasses escape before the bullet leaves the muzzle. Heavier bullets tend to lose more than lighter bullets as they take more time to exit.

A lot of load data numbers are derived from a barrel with no cylinder gap.

There are so many individual factors determining how fast a revolver shoots, that there is no way to even guess. From the barrel/cylinder gap to bore/chamber alignment, throat dimensions, chamber dimensions, forcing cone/bore dimensions, inherent roughness, etc.. Sometimes shorter barrels shoot faster than longer ones.

+1 on what every body has posted.

- I've got a 4" M66 Smith that was faster than a 6" GP100 I had, but its not as fast as a 4" GP I have now.

- I always felt a 25-06 needed a 24" or longer barrel, but had a 22" that was faster than 2 different 24's that I've had since.

You just never know till ya put em over a chronograph.

+1 chronograph.

Later,
Stephen

Yep, most serious handloaders have a chrono these days. 8)

Those who dote on the big bore hellblasters with 2.5" barrels should probably stay "un-informed" to ward off clinical depression brought on by the actual velocities they are getting! :shock:

:lol:

Bucks Owin said:

Those who dote on the big bore hellblasters with 2.5" barrels should probably stay "un-informed" to ward off clinical depression brought on by the actual velocities they are getting! :shock:

:lol:

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Yep. Even the "little" .357 and .44 mags do pretty poorly from short barrels (commercial ammo). At 3" and below with commercial defensive ammo you can get better muzzle energy from a 9mm +P than from .357 mag.

I really wish they'd bring back a 3" SP-101 in 9mm... In fact, if they'd put a 3" barrel on the LCR in 9mm I'd be carrying that instead of my 3" .357 in spite of the fact that I think the LCR is possibly one of the ten ugliest revolvers ever made. LOL

Oldephart you might look at what Charter Arms has to offer in the realm of revolvers shooting pistol cartridges. A .357 snubbie still out shoots a 9 mm from the same length barrel. I second the ballistics by the inch link. Very interesting. What CraigC said.
gramps

@gramps - look at the BBTI muzzle energy graphs for 9mm and .357 - at 3" and under barrel length the 9mm +P factory loads carry the same or in some cases more energy than the .357 factory loads. By the time you get down to a 3" barrel much of the powder in the .357 commercial loads is being wasted in excessive muzzle flash. You can see by the "knee" in the graph that the ammo manufacturers really expect people to use a 4" or longer barrel with the .357.

Of course, if one hand loads one can get better numbers from the .357 without the excessive muzzle flash so that's what I do (158gr XTP, fast powder, get to about two-thirds of way the between .38+P charge and starting .357 charge before flash/bang starts getting bad). Haven't had a chance to chrono the load yet but I'm thinking energy is probably close to what I get from 9mm 147gr in a 3" barrel.

It would be nice to have a 3" revolver that would work well with common factory loads, though.

When I first got my SP-101 3" .357 I took it to the range with some commercial 125gr JHP ammo. The people on either side of me started packing up as soon as I started firing it. The muzzle flash and report was pretty impressive in the fairly dim lighting of the indoor range...they probably thought I was shooting crazy hot hand loads or something. The same ammo out of a 4" model 19 is much less "impressive."

OldePhart said:

Yep. Even the "little" .357 and .44 mags do pretty poorly from short barrels (commercial ammo). At 3" and below with commercial defensive ammo you can get better muzzle energy from a 9mm +P than from .357 mag.

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I beg to differ with you. I had a Ruger SP101 with a 2.25" barrel that clocked 1320 fps with Buffalo Bore 158gr JHPs for 611 ft lbs. No 9mm can come anywhere near that. Sold it for the longer sight radius of the 3" model. Don

Way back when Titegroup came out, it was touted as being less position-sensitive and thus better (more accurate) in guns like .38 Special and .45 LC with loads where the cartridge was not completely full of powder. I did a little experimenting with loads of that sort, including .45 LC and .45-70. My procedure, with my NEF Handi-Rifle, was to load the round, point the rifle either up, down, or level, slap it once or twice to joggle the powder, then bring the rifle to level and fire it over the chronograph. The idea was as much as possible to position the powder against the primer or against the base of the bullet, or sort-of-level in the case. My notes are not convenient to hand, but there were noticeable and fairly consistent differences with powder position. My memory may be faulty, but it seems the bullet was faster with the powder near the primer, slower with the powder "level," and slower yet with the powder near the bullet. This effect would no doubt not appear with case capacity loads. I wonder whether the advent of Trail Boss, a much bulkier powder, might reduce the effect in Cowboy loads.

Handguns on average are 30 to 35 fps per inch & Rifles 25 to 30 fps per inch.
Nothing is writen in stone though.

SweetWilliam said:

Handguns on average are 30 to 35 fps per inch & Rifles 25 to 30 fps per inch.
Nothing is writen in stone though.

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Those numbers really compound themselves as the barrel gets shorter, it isn't quite such simple math. Bore size and bullet weight also play a significant part. A typical small bore rifle barrel will lose about as much or more velocity in the 3" from 16" down to 13" than it will from a 6" loss from 22" to 16". The same holds for pistols, that last couple of inches from midsize to snubby really penalizes on the velocity. Large holes suffer less loss per inch than smaller bores due to having more volume to utilize the propellant.

My optimisms have been quashed by reality of the chrony oh so many times.........

s4s4u said:

SweetWilliam said:

Handguns on average are 30 to 35 fps per inch & Rifles 25 to 30 fps per inch.
Nothing is writen in stone though.

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Those numbers really compound themselves as the barrel gets shorter, it isn't quite such simple math. Bore size and bullet weight also play a significant part. A typical small bore rifle barrel will lose about as much or more velocity in the 3" from 16" down to 13" than it will from a 6" loss from 22" to 16". The same holds for pistols, that last couple of inches from midsize to snubby really penalizes on the velocity. Large holes suffer less loss per inch than smaller bores due to having more volume to utilize the propellant.

My optimisms have been quashed by reality of the chrony oh so many times.........

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Yes I know it's not a perfect formula but it gives you a ballpark figure. And yes revolvers are up in the air.

Yes I know it's not a perfect formula but it gives you a ballpark figure.

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Those numbers have been the "rule of thumb" for a long time, and I used to live by them. Once I started clocking my loads I was awakened. Especially with T/C Contender or Encore pistols shooting typical rifle chamberings, some folks may be really disapointed by the real speeds they are getting.

SweetWilliam said:

Handguns on average are 30 to 35 fps per inch & Rifles 25 to 30 fps per inch.
Nothing is writen in stone though.

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Those guidelines have proven to be very inaccurate. It would be better not to repeat them at all.

Not trying to be rude. Please refer to data such as that collect by BBTI, an others, which show the relation to be very non-linear, and having different slopes.

I find them to be pretty close especially for rifles. To each their own.
And like I said nothing is writen in stone.

Here's one to chew on I dug up at BBTI. A Federal 240 gr 44 mag factory load will approach 1600 fps in say a 10.5" SBH. The same round in a 2" barrel doesn't even hit 950 fps.

35 fps per inch?

Those 2.5" barrels that are touted for "bear protection" might be handy to carry but...

I'll take velocity over muzzleblast and flames! :wink:

Well all I can say is 1600fps is smoking out of a 10"bbl SBH