Five Ways To Break Your Auto Mag
September 1999
by Bruce Stark
As soon as people started shooting Auto Mags, the guns started breaking. The inventor, Harry Sanford, always blamed the Auto Mag’s bad reputation on people shooting ammo that was way too hot for the gun. “If they wanted a rifle, they should have bought one,” Harry would say.
1. Bad Ammo
The Auto Mag was designed to shoot a semi-auto counterpart to the .44 Magnum. A 240 grain bullet moving at about 1250 feet per second will provide enough recoil to reliably cycle the gun and not beat it to death. There have been several articles published over the years containing Auto Mag reloading specifications. Most of these loads are too hot for the gun. Some of the published loads were intended for large game hunting, and weren’t to be used for a weekend’s plinking. The older articles were written at a time when a new bolt could be had for $45!
With continued use of hot ammo you will see the bolt lugs chipping or bending rearwards, and the accelerator will begin to mushroom the frame where it strikes it. The mushrooming of the frame can be so severe that it will prevent the barrel from being removed from the frame.
The first available loaded ammo came from CDM in Mexico. The only way to get this ammo to reliably cycle the gun is to lie about it. CDM ammo has dirty powder which makes it inconsistent, and it quickly dirties up your gun with unburned powder. The next available loaded ammo came from Norma in Sweden. Norma ammo is too hot and can’t be recommended for extended use in the Auto Mag. Both CDM and Norma ammo have become very collectable and are too expensive to shoot nowadays. Through the years Lee Jurras, Kent Lomont, Bob Beal and several others have cooked up and sold their own Auto Mag ammo. It too has become very collectable. Some of it is hot and some of it is not. Never shoot “mystery” ammo if you value your gun.
Ammunition with the wrong case dimensions for your chamber is also bad ammo. A case that is too long will usually prevent the gun from going into battery. A case that is too short for your chamber can damage your gun.
A properly seated round with the correct case length will allow the bolt face to sit flush up against the rear of the case. If the case is too short and the base of the case is not up against the bolt face, the case will recoil into the bolt face, piercing the primer and maybe breaking the extractor. Sometimes the spent brass will show an indent where it has slammed into the ejector.
A .357 AMP case of the proper length, but with an improperly located shoulder, can behave the same as a case that is too long or too short. .357 AMP brass must be tailored to your chamber. Know what you are shooting.
2. Loose Recoil Rods
The Auto Mag’s recoil rods screw into heli-coils that are located in the cocking piece. The type of heli-coil is a 10-32 screw-lock type. The locking feature of the heli-coil lessens with each removal and replacement of the rods. If any lubricant gets into the heli-coil area, it will also lessen the locking feature.
If the rods become too loose, they will allow the cocking piece to tilt backwards during recoil. When this happens the top ear on the back of the bolt will be broken off, or the top of the cocking piece will be broken out, or both. The heli-coil area must be kept clean and dry. After every magazine of ammo that is shot, the recoil rods should be checked to see if they are coming loose. If the recoil rods need to be tightened after every magazine fired, you need new heli-coils to be installed into your cocking piece. Loctite is a bad idea because you could unscrew the recoil rods and find the heli-coils attached to the end of them. Keep those recoil rods tight!
3. Mag Slam
The Auto Mag’s magazine will hold seven rounds. Loading the sixth and seventh round into the magazine can be very difficult. When loading the seventh round into the magazine you will notice that the spring is almost fully compressed. If the bolt is forward in the gun and a full magazine is inserted into the frame, the top round will press into the bottom of the bolt. If you push the magazine into the frame further, to engage the magazine latch, you will compress the magazine spring even more. If you were to slam a fully loaded magazine into a gun with the bolt forward, the chances are pretty good that you will break the floorplate out of the magazine. On original magazines the floorplate is only welded on three sides. Most people only load the magazine with five rounds, and don’t slam in a loaded magazine like they are in combat.
4. Bolt Slam
It’s not a good idea with any semi-auto weapon to manually feed a round into the chamber and drop the bolt into battery on top of it. The first concern is that the firing pin could come forward when the bolt stops, and the round could go off. With the Auto Mag there is a further concern that you could break the extractor doing this. The extractor slams into the rim of the chambered round and must pivot upwards and then back down to capture the rim. There is a cut in the receiver, barrel extension, specifically made to receive the extractor as it pivots upwards to capture the rim of the chambered round. If this cut is mislocated, or filled with dirt, there is no place for the extractor to go. Also, the whole bolt is rotating while it’s trying to pivot and capture the rim of a round that is stationary and seated in the chamber.
5. Poor Lubrication
Stainless steel requires special lubricants. A standard mineral oil will cause stainless steel to gall or catch due to friction. Nowadays there are several off- the-shelf gun oils for stainless steel guns. This wasn’t the case when the Auto Mag was first introduced. Then and now people will experiment with exotic oils in their Auto Mags. Some of these oils give great results, but there are concerns other than just a smoothly functioning gun. It might not be all that healthy to have a fine mist of automatic transmission fluid blown back into your face. Some lubes will lock up your gun at temperatures below freezing and others will coagulate with time.
If you don’t know what lubricant, or what combination of lubricants, have been used on your Auto Mag, it’s a good idea to strip all the lubricants out of the gun. This is best done with a good carburetor cleaner such as Gumout. Remove the grips beforehand so that they won’t react to the harsh chemicals.
After a thorough inspection, a modern lubricant can be applied. Two very good lubricants are Break-Free and FP-10. Do not oil the heli-coils, the firing pin or the firing pin spring. Do not forget to oil the accelerator.
Closing
If you plan on shooting your Auto Mag I have listed the most common ways to damage the gun. Of course you could always just drop your Auto Mag onto a pile of rocks and break the rear sight assembly. The author has personally damaged an Auto Mag using the first three methods, as well as dropping the gun onto a pile of rocks. Learn from other’s mistakes.
If you don’t plan on shooting your Auto Mag, the worst thing you can do to the gun is to leave it in the case it came in. The foam used by the factory in the black plastic Auto Mag gun case will deteriorate into a black goo that will literally eat away at the stainless steel. It’s the pits.