Gun Design

There are exactly two major factors that you need to account for when designing a firearm to hold a controlled explosion in the chamber. First there is pressure, second is recoil impulse.

Recoil impulse is pretty easy to deal with, and is the basis for semi automatic firearms everywhere. Manual action firearms such as bolt action, falling block, radial lock, or revolver are designed to keep the brass in place. There are a lot of different ways to stop the rearward movement of brass, and a couple different ways to allow it to move rearward in a controlled manner. Recoil impulse begins when the brass begins to expand from pressure and ends after the projectile leaves the bore and the gas pressure equalizes with the ambient atmospheric pressure.

The other major factor is pressure. Pressure is what causes guns to go "kaboom" and turn from functioning machines into scrap metal in the blink of an eye. Pressure is your best friend for reliability and worst nightmare for barrel life.

For example, a few "low pressure" rounds, the 30-30 Win and 416 Rigby. Now one is a "marginal deer round" and the other is a classic "stopper" cartridge. How can they both work at low pressure? Surely the one that pushes more energy has to work at a higher pressure?

Not necessarily true. Pressure is what pushes the bullet down the bore, nothing more. The faster the bullet needs to go then more pressure is needed for the same bullet. Comparing the working pressure of the 416 Rigby and the 416 Barret shows that the Barret works at a higher pressure than the Rigby.

The "water capacity" of a cartridge has a lot to do with how much pressure it can generate by how much powder it can store. The burn rate of a powder has a lot to do with how pressure is generated. The faster the burn rate the quicker the pressure spikes and then drops off as the projectile travels down the bore. The slower the burn rate the slower the pressure will spike as the bullet travels down the bore. The chemical energy in a fast powder is exactly the same as a slow powder, but the burn characteristics will have a tremendous impact on the pressure spike experienced by the firearm.

Now that we've taken a look at how pressure is generated we can take a look at how firearms are designed with a maximum working pressure built in. All metals have a fatigue point, where they have been work hardened to be brittle or work softened out of tolerance. If you take a 30-30 Win in a model 94 lever rifle the locking mechanism cannot handle the same pressure as a Savage 10 bolt action rifle in the same chambering, the reason why is that the pressure will either cause a the metal to expand beyond designed range and fail, or expand beyond normal range and the locking mechanism will fail.

You can always generate more pressure by packing more powder or a faster burning powder. PO Ackley even did destruction tests of common milsurps after WWII. Everything fails eventually with enough abuse.

Now, to get specific, let us talk about bolt action rifles. The amount of steel around the cartridge and the amount of interface between the bolt lugs and recess area are going to determine how much pressure the rifle can take. The more the better the steel surrounding the chamber and the more and better steel surrounding involved in bolt lug engagement the stronger it will be. This means that the amount of steel in the barrel shank contributes more to withstanding pressure than the outer receiver ring diameter.

I bring this up because of the Turk m38 Large Ring Small Shank style Mauser rifles. They take small ring barrels, which means that the receiver ring is actually thicker than a normal Large Ring Mauser. This does not mean that they are safer, it means the opposite because the first ring of steel around the cartridge is thinner than in a normal large ring m98 action.

Comparing a Mauser barrel with a Savage barrel brings the point even closer to home, a Savage barrel shank is really just a threads cut into a barrel blank. When the Winchester Short Magnums were introduced Savage increased the barrel shank diameter because that is the number one factor in strength.

So what follows is almost blasphemy in some circles, the M98 is not the strongest, safest action ever built. The M98 is a strong and safe action, well designed and capable of handling any cartridge from the 22-250 all the way up to the 458 Win Mag, but in terms of stronger and safer there are modern alternatives. In practical terms it doesn't mean much as M98 is suitable for all hunting on the planet.

UPDATE: BORE TIME