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The cryogenic treatment means as the barrel heats up during use, there is less distortion on the shot as it passes through the bore and the choke.
By Jason Harris
Wednesday, 21 November 2007
Benelli Crio semi-auto shotgun: The state of the art barrel making process on this Benelli Crio shotgun places it one step ahead of the competition.
Benelli Crio semi-auto shotgun: Benelli has adopted an open mind when it comes to the design and manufacture of shotguns, and this is evident in its Crio.
What Benelli has done is to put the barrels and choke tubes through a state-of-the-art steel treatment process called cryogenics. Maybe you've heard of cryogenics as the thing that very rich, slightly mad Americans do to their bodies when they die?
From a gunmaking point of view, cryogenic treatment is not exactly new. It's a process that has been used on rifle barrels in the USA for several years now to make them more accurate.
The rifle barrel is placed in liquid nitrogen and frozen to -195 degrees centigrade. This is cold enough to give a fine and uniform structure to the steel.
This is very different to the normal manufacturing process whereby heat is applied to the rifle barrel prior to it being placed in a tank of liquid and quenched.
This method means as the barrel cools the varying thickness in the barrel's contour create stresses in the steel. These stresses start to show once the temperature of the barrel rises during repeated shooting, causing bullet groups to wander, or open up.
The cryogenic treatment means as the barrel heats up during use, there is less distortion on the shot as it passes through the bore and the choke.
To further improve the pattern the choke tubes on this gun have been made longer, thereby giving the shot column a more gradual transition through the muzzle.
The other benefit of this treatment is that the barrel has a greater resistance to wear.
Chamber length is 3in (76 mm) which goes hand in glove with magnum proof, so with the exception of high performance steel loads this gun will accept pretty much anything you care to fire through it.
The action of the Crio remains unchanged, as it works on the proven formula of Benelli's inertia bolt system:
- When the trigger is pulled the hammer falls onto the back of the firing pin, detonating the cartridge.
- At this point the hammer also releases the magazine stop allowing a cartridge in the magazine to be freed and sit under the bolt which is still in the forward position.
- Inertia from the fired cartridge creates backward force causing the rotating head of the bolt to lock into a recess in the back of the barrel.
The gun as a whole moves backwards under recoil, but the bolt moves forwards to counter it.
The movement that's generated causes a large spring inside the bolt to compress and store energy. As soon as the force of the fired cartridge dissipates, the energy within the bolt spring takes over and throws the bolt backwards, thus releasing the rotating bolt head and ejecting the fired case. The fresh cartridge is immediately brought up by the carrier and then fed into the chamber as the bolt comes forward again.
This translates as simple physics being harnessed to produce a semi-auto shotgun with fewer moving parts - and that's good news for long term reliability.
It also means that with no gas flying about under the fore-end the makers have been able to fit the gun with a slimmer piece of wood.
Woodwork, both in quality and finish, is very good on this particular gun, with the tight grained American walnut creating a very good figure both in the stock and the fore-end.
One feature of the Benelli is that because it operates on inertia rather than gas, there is no mechanism hidden under the fore-end wood to cause movement and cracking.
The stock has Benelli's usual three position adjustment for drop, so it can be altered to suit most shooters. The chequering might well have been done by machine but it is particularly well cut.
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