Friday, June 09, 2006

But what to feed them?

In JKLNX we talked about the different sizes of revolver made by Smith and Wwesson, and their various applications; with particular focus on the K and J frames.

By far the dominant chamberings discussed here in relation to S&W revolvers have been .38 and .357 magnum. They were the predominant law enforcement, and personal protection chamberings, for the best part of 100 years; and they continue to be so today.

These pistol series were both originally designed with .38spl in mind, but were later strengthened and modified to take .357 magnum. In reality they are still best used with .38spl; both for the longevity of the gun, and the accuracy, and comfort of the shooter.

Unfortunately as discussed in the linked article, .38spl is a marginal defensive chambering even from a long barreled pistol; and .357 magnum is a very high pressure, high intensity round. It has a massive muzzle blast and heavy recoil that are detrimental to efffective usage of small pistols in the chambering.

So what DO you load in a .38, or small framed .357 and still have it be effective? And what if you have a .38 that isn't specifically rated for +p+ ammunition? How do you stay effective with a chambering thats almost 110 years old?

There are four understood stopping mechanisms with regard to relatively low engery and low velocity gun shots, as produced by most pistol rounds. They are ranked here in order of speed of stop, and coincdentilly in reverse order of their reliabilty (i.e. you can count on significant exsangunation almost always occuring given a good shot, but it's slow. CNS damage is fast, but much harder to achieve):

1. Critical Central Nervous System (CNS) disruption
2. Critical organ or joint destruction
3. Wound shock (this can be several different types)
4. Exsanguination

The two primary factors in causing any of these wounding mechanisms except wound shock, are depth of penetration, and the size of the permanent wound cavity. Both are a function of the mass, velocity, diameter, shape, and construction of the bullet in question; and it is difficult to make predctions as to what bullets will wound better outside of some very basic generalizations

a. up to a point, faster is better (too fast an you overpentrate, or the bullet disintegrates)

b. Assuming decent velocity is maintained, greater mass creates bigger, and deeper wounds

c. Assuming decent velocity is maintained, greater diameter means wider wounds, but also means shallower penetration.

C above is why expanding rounds penetrate less; but assuming adequate massa and penetration, they damage the target far mroe than non expanding rounds, which may zip right through a target, leaving only a bullet sized hole; which may very will bleed very little and not effect a stop on target.

To do vital damage based solely on penetrative trauma (excluding wound shock, CNS shock, and other secondary efects) one must consistently penetrate a minimum of 4” on the “average” human.

Testing of ammunition generally consistes of calbrated ballistic gelatin, which although it isn't much like human flesh, rovides a consistent and repeatable medium for testing. Generally speaking, for every 2-4" of gelatin penetration, there is 1-2" of body penetration, depengin on body composition, shot placement, clothing, and exactly bullet construction.

Given the 4" of penetration requried to vitally damage a target, this translates into 8-16” of bare gelatin penetration.

In order to avoid overpentration, a bullet should not penetrate more than 8-10” on an averate human. This works out to anywhere from 16"- 40” of gelatin penetration; which shows you jsut how useful that test really is but anyway…

Based on these numbers, the FBI has determined that 14” is the ideal penetration amount in bare ballistic gelatin. They have also determined that 10” is unacceptable on the low side, and that 18” is unacceptable on the high side.

Clothing has two opposite effects on bullets. If the bullet still expands after passing through the clothing, it reduces the penetration moderately for average clothing, and significantly for heavy clothing (like denim and leather - for all you saxon fans). If the bullet DOES NOT expand after passing through clothing, because the hollowpoint has been plugged or crushed by that clothing, then penetration is generally drastically INCREASED. because the bullet effectively becomes an RN or SWC FMJ.

The FBI rates the ideal penetration as 14”, unfortunately no standard pressure .38 hollowpoint will do that. In fact many FMJ rounds wont even do that at the standard 800fps loadings. Most +p .38s wont do it either unless you’re shooting hardball, JSWC, or VERY hard cast lead SWC. Realy, you need a +p+ hollowpoint or SWC to ensure you make 14”.

Note that the only commercial pistol chambering and loading which recieved a 100% rating in both bare and clothed gelatin, without overpentration; was the full power winchester silvertip 10mm.

Yes, the ONLY chambering and loading, among all tested chamberings and loadings (multiple loadings of .38spl, 9mm, .357 magnum, .40S&W, 10mm, .41magnum, .44spl, .45acp, and .44 magnum were tested originally, and .357SIG was tested a few years ago).

The lower power 10mm “fbi” load only scored about 90%. The higher power norma 10mm proof load scored 100% but sometimes overpentrated. The same happened with the federal .357 158gr load at 1185fps (from a 3” barrel). That same federal 158gr semi-wadcutter load in .38spl at 900-1000fps forma 3" barrel was the FBI standard load for .38spl for years; until the miami shootout.

When only that one 10mm load was able to pass the test, the FBI redesigned the test. Now several .45+p, 9mm +p+, .40s&w +p, and .357 sig loads have also passed the test, some with 100% ratings. No .38spl has passed it with 100%, but the 125gr and 158gr +p+ loadings come close to 90%.

Ok so what do you shoot in a light weight, short barreled gun?

The key to controlling recoil in a light weight gun, is to use a lightweight bullet. The key to penetration in a light bullet is velocity. Out of a 2” lightweight gun, you really want a light bullet at the highest possible velocity. For a 3” or 4” gun I would recommend a heavier load, but still at the highest possible velocity.

I GENERALLY wouldn’t recommend any standard pressure .38 loads for defensive purposes, especially not from a 2” gun, except MAYBE one of the 110gr low velocity expanding loads. The heavier loads simply do not have the velocity out of the 2” barrel to penetrate consistently (even in hardball). The Federal low recoil loads are specifically designed to be fired from short barreled, light weight guns, and still retain similar performance to the higher power loadings. Hornady and others are both producing similar loadings.
A note on extremely light, and extremely heavy loads: In very light weight guns, the extreme weight ranges of bullets have issues. Particularly, high pressure loads under 120gr in .38 or .357 may pull under heavy recoil in the extremely light weight guns; which could bind the cylinder, or in an extreme case result in a chainfire. The reverse problem, and possibly the more dangerous one, exists for very heavy loads; in that high pressure loads over 147gr may set back in the case under heavy recoil, and cause excessive pressures (and thus possibly a blown cylinder). Also if the seating depth or crimp are insufficient on the very heavy loads, or too deep on the very light loads, the problems can reverse.
My wife has the 3” SP101, and I LOVE shooting the Cor-Bon 125gr at 1125fps through it, which I think shoot like .22s; but my wife doesnt like the recoil and muzzle flash. SHE really likes the 110 gr federal low recoil loads. Those are standard pressure, but loaded up to 1000fps (because of their low weight) from a 2” gun. They are in theory able to penetrate adequately but I’d really like to water box them just to be sure. Also out of the SP, they shoot softer than the standard 148gr or 125gr FMJ at 800fps.

Of course theres no such thing as a free lunch, but these loads should have adequate penetration and expansion from a 2” gun, without being punishing (in comparison to other loads anyway) from the lightweights.

That said, either are what I would consider rather light loads (because standard .38 is such a low pressure chambering), chosen because of their low recoil, not maximum performance. From a 3” or 4” gun chambered in .357 that you want to shoot .38spl out of, I’d HIGHLY recommend one of the medium or heavy weight +p+ loads from several manufacturers.

A 158gr Semi-jacketed HP at 1150fps is nothing to sneeze at (buffalo bore from a 4” barrel). Thats 350fps over standard pressure velocities; and in fact it’s near the low end of .357 magnum pressures (the same .357 loading would be at 1250fps for standard and 1350-1450fps for heavy magnum loads). The loading itself is roughly ballistically equivalent to a .40s&w.

The big thing is to find a bullet weight that shoots to near point of aim with your gun, at your chosen range (for a 2” gun max of 7 yards). In that weight, then try different loads to see how they group.

That said, don’t go for any load that doesn’t push at least 1000fps from YOUR barrel (typically a 2” gun will shoot 100 fps less than the 4” guns they usually publish the numbers for).

Now personally, I’m not very recoil sensitive, so if I were carrying the 340pd (and I’m still thinking about buying one), I’d probably stoke it with one cylinder of full bore ultra light weight .357, and carry medium weight +p+ .38s loaded to maximum pressures as reloads. I’m thinking along the lines of 125gr at 1250-1350fps nominal (and about 100fps less from the 2” J-Frame).

Buffalo bore stocks a 125gr load that pushes 1050fps with the low velocity gold dot JHP (they are designed to expand at 800fps but not shed mass at higher velocities) from a 2” j frame, which is about 1150 nominal from a 4” barrel. I figure I can probably load up to 1150, and MAYBE as high as 1250 out of the 2” without pressure issues, using the same LV bullet (the equivalent .357 load from buffalo bore is at 1600fps from a 4” and 1475fps out of a 3” j frame).