Ask The Experts: Sept. 2010
January 04, 2011
Pointed bullets, Mauser M2 pistol, split case necks and more!
Pointed Rimfire Bullets In Tubular Magazines?
Q. I have a Marlin .22 Magnum bolt-action rifle that is very accurate. I purchased a box of ammo with pointed bullets because of some of the things I've recently read about the claimed improvement in accuracy and range. My rifle has a tubular magazine. Is it safe to use rimfire cartridges with pointed bullets in tubular magazines, or by using this ammunition do I have a two-shot gun?William R. Santa Fe, TX
A. It is my humble opinion that rimfire rifles having tubular magazines are safe to use with pointed bullets, assuming the ammo has not been modified since leaving the ammo plant. There are several reasons forming my opinion:
- The percussion-sensitive primer compound is located in the rim, relatively far from where a bullet tip contacts the cartridge ahead (see the accompanying illustration; it's of the .17 HMR, but it serves the purposes of the .22 Magnum as well). The compound needs to be "pinched" to activate, and the only pinch-point is at the rim.
- Recoil, the factor that creates the hazard from using pointed bullets in centerfire tubular magazines, is almost nonexistent in rimfire rifles.
- The mass of rimfire cartridges is quite small compared to centerfire cartridges, greatly reducing the energy produced during recoil that can shift cartridges in the magazine.
In spite of these facts, the ultimate responsibility of determining whether a rifle can be safely used with any given type of ammunition falls on its maker. Those who designed the equipment are the "highest court" in matters like this, and I strongly encourage you to contact your rifle's manufacturer and follow their recommendations--Allan Jones, Ballistics Editor
Q. About 10 years ago I won a pistol at an NRA event. It is a Mauser M2 in .45 ACP. SS# XXXXX182. It is in the box with all the paperwork and a spare magazine, and it's never been fired. A wooden glass front display case came with the pistol. The pistol is labeled "SigArms Exeter NH." This is a pistol that seems to have come and gone. What can the experts tell me about the history of the gun and its value? Joe T. Linden, TX
A. The Mauser M2 pistol was offered in the United States by SIGARMS from 1999 to 2006. SIGARMS had purchased the Mauser name for pistol manufacture in 1999. It is dimensionally similar to the SIG P229 pistol, but it utilizes a rotating barrel-locking mechanism instead of a cam-link system. It's also striker-fired, not hammer-fired. The M2 is no longer supported by SIG SAUER or Mauser Jagdwaffen GmbH, and the Mauser Oberndorf plant where it was manufactured has been closed. A review of the Mauser M2 appeared in the October 2001 issue of Shooting Times. I've recently seen used .40 S&W and .45 ACP Mauser M2s offered for sale online from various sources for $400 to $500. A first-year-production "Presentation Case" version might be worth a bit more to an interested buyer. Dick Metcalf, Executive Technical Editor
Marlin Model 90 Chokes?
Q. I have a Marlin Model 90 12-gauge over-under shotgun, serial number L2XXX. I can find no markings to indicate the choke on either tube. Can you help? Ken S.Parker, CO
A. The Marlin Model 90 shotgun, unlike most shotguns manufactured in the U.S., never had any choke markings on the barrels. On 30- and 28-inch-barreled guns, the top barrel was always provided with a Full choke, while the under barrel was made with a Modified choke. On 26-inch-barreled guns, the top barrel was made with a Modified choke, and the bottom barrel was furnished with an Improved Cylinder choke. By the way, Marlin's specifications for a Full choke was an internal choke diameter of .693 to .697 inch; Modified was .708 to .714 inch; and Improved Cylinder was .721 to .724 inch. Unless the chokes have been altered, they should fall within these ranges. Reid Coffield, Gunsmithing Editor
Why Did My Cases Split?
Q. I have been a very "longtime" subscriber to Shooting Times and look forward to its arrival every month. I have been handloading since 1965 and have been an avid shooter for over 50 years. My question is this: I loaded some .41 Magnum loads and drove to the range to test them. Before trying the handloads, I fired five rounds of Winchester 210-grain factory loads from a new box that I had recovered from my ammo inventory. While the box had not been opened previously, it had been sitting on my shelves for at least 10 years. When I fired the loads, I noted that there was a little more recoil than I associate with the .41 Mag. (firing a Ruger Blackhawk single action with a 6-inch barrel); however, it wasn't so severe as to concern me. I ejected the cases from the cylinder and placed them back in the box with the other unfired rounds. Then I shot the handloads, which seemed to be much more forgiving in the recoil department. I returned to the remaining box of ammo and examined the spent brass, only to find that each one of them had split at the neck. I examined the spent brass from the handloads, which showed no defects at all.
Once more I loaded several of the factory loads and fired them, and just as the others had done, they split at the neck. I fired more of my handloads and sample rounds from other factory loads that I had with me, which evidenced no problems at all. I examined the gun, and it appeared to be fine. The revolver was not new, having had probably 200 rounds fired through it without incident. The cylinder walls were smooth; the forcing cone was clean, as was the barrel. Everything appeared normal. However every case that I fired from that one box of ammo split. None of the handloads nor several boxes of other factory ammo exhibited any problems. Temperatures were in the 50s. The ammo storage area is a cabinet that has a constant dehumidifier running to keep the humidity at 40 percent. Does Allan Jones have any idea why those case necks split? Frank B. Mechanicsburg, PA
A. I suspect there is nothing wrong with your fine Ruger nor your storage conditions. Split necks almost always indicate a minor metallurgy problem with the case dating to the time of manufacture. It can arise from improper heat-treating, age, or the two factors working together.
After coming off the final forming operations, most cartridge cases are stressed and harder than needed. The aspect ratio of the case (length divided by body diameter) affects the stress build-up. The .41 Magnum has one of the higher ratios, meaning it went through one more forming (draw) operation that the maker would apply to a case the length of, say, a .44 Special. Formed cases usually go though either an anneal or a stress-relief stage (less aggressive than annealing) to relax the metal to a point where the m
etal is more flexible.
Nonferrous metals like copper and brass have a tendency to slowly migrate to a harder state with age. The anneal or stress relief forces a change to the fabric of the alloy that is a little softer than the "natural" state. Nature tends to slowly overcome our efforts to change metals, and that is usually manifested as a case that is harder today than it was when it was tested at the time of manufacture.
It is common to find very old cases (like more than 50 years) that split at the neck simply due to the long-term stress of holding the bullet. You can find this on ammo that's not even been fired. Even if the case is properly annealed, there is a modest stress applied to the neck when the bullet is seated, work-hardening the neck; it is more prevalent with nonyielding jacketed bullets than with soft lead bullets.
I'll admit that this is not very common with handgun cartridges. However, if the ammo has been on your shelf for at least 10 years, it could have been on a dealer's shelf for a long time before you bought it. Twenty-year-old ammo doesn't usually sound a "hard case" alarm in my mind, so what you see is unusual but not without precedent or explanation.
Both annealing and stress relieving require incredibly tight temperature tolerances, in the order of a few degrees out of hundreds. Temperature is measured with thermocouples, and a quarter-century ago, those electronic devices were not as capable as those today. Combine that with the huge leap in digital control technology in the last decade and today we now have ways to control oven temperatures to the narrow ranges required for superb heat-treating. In the 20+ years I was associated with CCI-Speer, I saw a huge leap in this technology, from tray ovens with one or two old thermocouples to new belt-fed linear ovens with arrays of many sensors, all feeding data to a computer that controls the material feed rate and the temperature to "bullseye" the desired heat-treating effect required.
I suspect that your old ammo was made at a time sensors were not as good as today's, so the temperature was detected as being in the proper range. However, with the "plus/minus" nature of the old sensors, the actual temperature may have been just a few degrees under the sweet spot for a level of anneal or stress relief that would let the cases survive unchanged for decades. Your batch of cases probably passed every test that Winchester applied at the time they were made. It is the normal action of time combined with the challenges of older temperature-sensing technology that every manufacture once faced that caused the cases to harden with age.
As for the greater recoil, that's probably not related to the splits either. When there were few options in .41 Magnum ammo, I recall thinking the factory 210-grain jacketed loads produced as much felt recoil in S&W revolvers as full-power .44 Magnum 240-grain loads. Felt recoil can be affected by something as subtle as the propellant burning rate. If the batch of factory ammo was loaded with a faster-burning propellant than your handloads, the kick would be applied to your hand over a shorter time interval and feel more severe.
The bottom line is that you and your revolver are safe. I've never seen a handgun damaged by a split case neck. Although you lose the case for future reloading, it is otherwise almost a "nonevent." Allan Jones, Ballistics Editor