Search For
View CartCheck OutNews LetterNews Letter Sign-upWolfe Publishing Company
Wolfe Publishing Company
Handloader MagazineRifle MagazineSuccessful Hunter Magazine
Magazine Subscription Information
Wolfe Publishing Company
HomeShopping/Sporting GoodsBack IssuesLoaddataInternet AccessAdvertisingGun Links
Online Magazine Login:    User Name:    Password:       Subscribe to Online Magazine
American Rifle
Rifle Magazine
August - September 2004
Volume 39, Number 4
ISSN: 0017-7393
Number 230
On the cover...
The Turnbull Cowboy Classic features color case frame and carbona blue on the barrel, cylinder and grip frame. Ivory stocks are by Jim Alaimo (www.nutmegsports.com) and engraving is by Adams and & Adams, PO Box 66 Vershire, VT 05079. Photo by Gerald Hudson.
Rifle Magazine
Rifle Magazine Wolfe Publishing Company
Rifle Magazine Featured Articles
Table of Contents
Columns
Features
Product Tests
What's New
space
Rifle Magazine
Columns

According to the editor’s note on page 434 of the Speer Reloading Manual Number 12, the short essay on that page, “Why Ballisticians Get Gray” by Dave Andrews, first appeared in the Speer Reloading Manual Number 9 in 1974. The essay was written in response to folks who questioned the validity of the velocities listed for handgun cartridges published by Speer, and probably every other reloading manual that was ever published.

Included with Dave’s essay is a list of .357 Magnum handguns with a broad range of barrel lengths, from 2.5 to 10 inches, and three rifles with 17.375-, 20- and 24-inch barrels.

In a review of the velocities listed for each test handgun with 125-, 140- and 158-grain Speer factory loads, manufacturers are represented by Smith & Wesson, Colt, Ruger and Thompson/Center. Barrel lengths include 2.5, 2.75, 4, 4.625, 6, 8.375 and 10 inches, the last being a closed breech single shot, while the rest are revolvers.

The 6-inch barrel category includes three Model 19s, two Model 28s, one Model 27 and three Colt Pythons.

Of that group, one Model 19 produced the highest velocities with all three factory loads: 1,603 fps with the 125-grain load, 1,417 with the 140s and 1,284 fps with 158-grain fodder. The next highest velocity was produced by the Model 27 at 1,547, 1,358 and 1,248 fps, respectively. The remainder of the 6-inch revolvers pretty much hovered around 1,450 fps with the 125-grain load, while one Model 28 produced the lowest numbers: 1,307, 1,246 and 1,080 fps, respectively. So, the velocity spread from the highest to the lowest is between two 6-inch Smith & Wessons, with a whopping 296 fps for the 125-grain load, 171 fps for the 140-grain and 204 fps for the 158-grain ammunition.

As Dave Andrews goes on to summarize, the explanation for why the velocity can, and does, vary from one handgun to the next is simple enough: no two revolvers are exactly the same. The barrel-cylinder gap, chamber and barrel dimensions, forcing cone variations, barrel finish, etc. combine to react differently to the burning of the powder charge, and the resultant passage of the bullet from the chamber into and down the barrel.

Of course, logic would at least suggest that the handgun with the closest tolerances would likely produce the highest velocities. Conversely, the handgun with the largest barrel-cylinder gap and/or sloppy chamber and barrel dimensions would generate the lowest velocity. Then too, whether these broad assumptions are true or not remains to be seen.

The problem with any attempt to correlate data from Dave Andrews’s data using the handguns listed is that we don’t know anything about them except for barrel length. They may have had wide variations in barrel-cylinder gap and/or chamber dimensions or eroded barrels. We just don’t know.

This business of revolver barrel length versus velocity came to mind about a year ago when I built two custom handguns. One is a Ruger Blackhawk New Model that was originally a .357 Magnum but was converted to .45 Colt with a 14.25-inch Shilen barrel. The other is a Colt Single Action Army (circa 1907) I acquired in 1973. Right now, it’s a .45 Colt with a 12-inch Buntline barrel and a .003-inch barrel-cylinder gap. The Ruger has a slightly smaller gap, about .0025 inch or so.

Other particulars with these two .45 Colts include cylinder throats that average about .4565 inch for the Colt and .452 inch for the Ruger. Both barrels measure about the same: .4513 inch. Actions on these custom sixguns lock up tightly with creep-free triggers. The Ruger, of course, has adjustable sights; the Colt’s are fixed.

When I took these .45 Colts out to test for accuracy, etc., they produced about the same velocity with a selection of factory loads and handloads. Accuracy, out to 50 and 100 yards, was about the same, although the Ruger seemed to have a slight edge. Oddly, groups with the Ruger spread vertically, while the Colt spread was largely horizontal.

One of the most interesting results to come out of those tests with the 12- and 14.25-inch barrels is that the shorter barrel, along with the more generous chamber and throat dimensions, produced just about the same velocities as the longer barrel with the less generous chamber dimensions. Not that two handguns make a valid test, but that’s the way this comparison worked out.

Then too, there are other factors to consider. In Winchester factory .45 Colt loads, for example, the 225-grain Silvertips and 255-grain swaged lead bullets measure about .454 inch. So they might produce higher velocities in a Ruger with .452-inch throats, as opposed to .456-inch throats in Colts and their copies out of Europe. The same goes for my bullet cast in the RCBS 45-270-SAA mould that is sized to .454 inch from a one-in-16 (tin/lead) alloy. Seated over 13.0 grains of Blue Dot or 16.5 grains of 2400, that bullet should produce higher velocities in the Ruger, but it doesn’t.

On the other hand, we might expect the harder commercial cast bullets (BHN 16 to 24) would create higher pressures when they enter the forcing cone, and thus higher velocities, but they also facilitate the loss of some gas pressure when they fail to obturate upon entering the chamber throat - mitigating the pressure factors by allowing gas to leak by the side of the bullet before it enters the barrel.

Then there is the effect of reloading dies. Back in 1980 I decided the major problem with the .45 Colt was reloading dies that were designed for .454- to .455-inch bullets but were used with .451/.452-inch cast or jacketed bullets. In short, the case mouth wasn’t reduced enough to gain a secure hold on the bullet regardless of crimp strength. This particularly applied to loads using slower-burning pistol powders like 2400, H-110 and IMR-4227.

In the summer of 1981, I called Bill Keyes at RCBS, explained the problem and asked if he could build a proper set of dies, to form a longer case neck and include a .448-inch neck expander for use with cast or jacketed bullets sized to .451/.452 inch. I still have the dies Bill forwarded in August 1981, and RCBS .45 Colt dies were changed accordingly shortly thereafter.

In general, using a Colt SAA with a 4.75-inch barrel, the new dies resulted in an average velocity increase of around 100 fps across the board. Slower-burning powder benefited most; faster-burning powders, not so much. The largest velocity increase went to 20 grains of H-110 with the Lyman 454424 SWC cast from a mixture of wheelweights and Linotype and sized .454 inch. With the old RCBS dies that produced a short case neck and .4525 inside neck diameter, the Colt averaged about 880 fps. The new dies that formed a longer case neck and .4485 inside neck diameter boosted that to 980 fps. Both loads used the Federal 150 Large Pistol primer.

Of interest here is that until recently, Speer (up through manual number 11) and other outfits published load data that was developed with reloading dies that produced a .451 inside neck diameter, producing almost zero bullet pull when used with bullets that measure .451/.452 inch.

So, if you have an older set of reloading dies for any cartridge, not just the older numbers like the .45 Colt or .44 Special, check the diameter of the neck expander. The resultant inside neck diameter should be about .003 to .004 inch smaller than the jacketed or hard cast bullet you are using, or about .002 inch smaller than bullets cast from softer alloys - BHN 5 to 11. And make sure the case neck holds the full length of the bullet shank, to ensure maximum bullet pull for optimum efficiency with slower-burning pistol powders.

You can also tear a page out of the old Super Vel bag of tricks and use a jacketed bullet that is about .001 to .0015 inch smaller than standard for the cartridge of interest and get increased velocity with acceptable pressures Ð and good accuracy. At least the Super Vel loads I used over the years shot fine.

There is one other item you might want to pay attention to. All .357- and .44-caliber handgun bullets are designed to place the cannelure in the proper position for the correct overall loaded length for .357 and .44 Magnums, respectively. They are also designed to deal with the higher pressures produced by the magnums. So, they won’t obturate when fired at responsible pressures in the .38 and .44 Specials, or the .44 WCF, for that matter. As a result, gas blow-by (when it passes through the chamber throat) with these bullets is critical and, at least in some part, explains why they produce lower velocities in revolvers than bullets that are designed for lower pressures.

So when loading these “magnum” revolver bullets, unless their diameter exactly matches or slightly exceeds the chamber throat diameter, gas loss will result in lower velocities. Mitigating factors would include the diameter of the chamber throat, chamber diameter and the angle of the forcing cone.

The only way I know to eliminate the problems associated with factory .38 and .44 bullets (and hard commercial cast bullets) is to cast your own bullets of a proper alloy to ensure they form a proper gas seal before they leave the cylinder throat. It’s also significant that cast bullets always produce higher velocities than their jacketed counterparts of similar weight. That’s mostly because they produce less friction, but when cast properly, they also form a positive gas seal, harnessing propellant gases more efficiently.

So, it appears that any given handgun may or may not produce velocities that jive with those listed in whatever manual. Moreover, it’s impossible to predict - without the aid of a chronograph - exactly how much velocity loss or gain will occur with any given barrel length compared to barrels of different lengths. That is, a 4-inch barrel just might equal velocities produced by a 5-inch tube or a slow 6-inch barrel.

Neither does it makes much sense to agonize over 50 fps one way or another in hunting loads. What you get is what you get. No animal will know the difference if your bullets are 75 fps or so slower than you expect. And, they won’t necessarily hit the ground deader if your bullets are 100 fps faster than Speer or another outfit suggests. Either way, it’s little more than potluck.

space
Big Game Rifle
Home  |  Magazine Subscription Information  |  Shopping / Sporting Goods  |  Back Issues  |  Loaddata  |  Internet Services  |  Advertising  |  Contact Us  |  Gun Links
Wolfe Publishing Company
Wolfe Publishing Company 2180 Gulfstream Suite A Prescott, Arizona 86301    Call Us Toll-Free 1.800.899.7810