| Load Number | # 1 | # 2 | # 3 | # 4 | # 5 |
|---|---|---|---|---|---|
| Avg MV (fps) | Avg MV (fps) | Avg MV (fps) | Avg MV (fps) | Avg MV (fps) | |
| Rossi Model 88 - 3 inch barrel | 778 | 701 | 770 | 824 | 807 |
| Taurus Model 66 - 6 inch barrel | 902 | 787 | 882 | 978 | 989 |
| MV % Increase | 15.9 | 12.3 | 14.5 | 18.7 | 22.6 |
Ten shots were fired in each revolver from each loading. The average muzzle velocity(MV) is listed in the table above. What we can see from this table is that the muzzle velocity for the Taurus with the 6 inch barrel is 12 to 23 percent greater for each loading than the Rossi with the 3 inch barrel. Granted it is a rather small statistical sample but this is typical with snubnose revolvers and short barrel pistols, a significant drop in velocity.
- Load # 1
- 38 Special
158 grain Lead Hollow Point
3.4 grains Alliant Bullseye
Federal 100 primer
- Load # 2
- 38 Special
158 grain Jacketed Hollow Point
3.4 grains Alliant Bullseye
Federal 100 primer
- Load # 3
- 38 Special
158 grain Lead Flat Point
3.4 grains Alliant Bullseye
Federal 100 primer
- Load # 4
- 38 Special
125 grain IMI JHP Hollow Point
4.3 grains Alliant Bullseye
Federal 100 primer
- Load # 5
- 38 Special
125 grain IMI Jacket Hollow Point
5.3 grains Alliant Herco
Federal 100 primer
Looking at load numbers 4 and 5, they both use the same components with the exception of powders. Load number 4 uses Alliant Bullseye which is one of the fastest burning pistol powders available while load number 5 uses Alliant Herco, a slower burning pistol powder. In the three inch barrel, the load which uses Herco as the propellant, slightly under performs compared to the load using Bullseye but yields a higher velocity in the 6 inch barrel of Taurus. In addition the increase in velocity with load 5 is slightly higher at 22.6% versus 18.7% with load 4. I can say from my own experience that there will be a great difference in velocities of a given 38 special or 357 magnum load using Herco are when fired in a longun versus a handgun. When using cartridges, loaded with the faster burning Alliant Bullseye, there will likely be a higher muzzle velocity generated when fired in a rifle. The velocity difference will however be much less dramatic than with loads using Herco. Both are fine propellants but they are designed for different applications.
Lead bullets vs Jacketed
For any given bullet weight all else being equal, lead bullets will a produce a higher muzzle velocity than jacketed bullets. Comparing Loads #1 and #2, load #1 uses a 158 grain lead bullet and load #2 uses a jacketed bullet. There is a significant difference in velocity as fired from both revolvers. Of course there are a number of factors which can affect the muzzle velocity of a projectile but lead alloy bullets produce less friction than jacketed.
Same gun, different barrels
Let us look at another example. One of the nice things about the Colt 1911 design is that it is easy to change barrels and the pistol will operate with different length barrels. In this experiment I used two barrels in a Rock Island Armory 1911. One barrel was 6 inches long and the other was a standard 5 inch barrel. I chronographed 20 rounds of Russian made, Wolf brand 45 ACP ammunition loaded with 230 grain full metal jacket bullets. Five rounds were fired at a time in each barrel. With ten rounds fired in each barrel from the same gun the average muzzle velocity from the 6 inch barrel was 832 feet per second and 752 feet per second from the 5 inch barrel. A difference of 80 feet per second.
Comparison of a Handgun and Carbine
Using Winchester manufactured 357 Magnum cartridges with a 125 grain softpoint bullet, I chronographed 10 rounds fired from a Rossi model 92 lever action with an 18 inch barrel which yielded an average muzzle velocity of 2015 feet per second. Ten rounds of the same ammunition fired in a Ruger GP100 revolver with a 4 inch barrel had an average muzzle velocity of 1296 feet per second. That is a velocity increase of over 55 percent.
There are a number of factors that determine whether or not a longer barrel will deliver higher velocities and by how much. Generally slower burning powders will produce a greater return in terms of muzzle velocity in a long barrel than will a fast burning powder at a given pressure level. I suspect that in this particular loading, Winchester used a rather slow powder because of the very significant muzzle flash that resulted when I fired these cartridges in a revolver having a 4 inch barrel length. Muzzle flash and muzzle blast are caused by the combustion of the powder gases outside of the barrel. Essentially, it is wasted energy that might otherwise have been used to propel the projectile.
The law of diminishing returns
At some point, you gain little or nothing from lengthening the barrel. It is even possible to start slowing the bullet down with a barrel that is too long, although for the most part, that is not really something to be concerned about.
Many older 22 rimfire rifles designed for use with iron sights have barrel lengths of 26 inches or more.
Generally, the optimum barrel length for the 22 long rifle cartridge is considered to be about 19.5 inches. While it may be true that the velocity from these older guns is very slightly less than it could be, the long sight radius is often of far more benefit to the shooter than a few more feet per second out of the muzzle. Another benefit is that the rifle will likely be quieter for the extra barrel length.