Grunt
Member
Hmm, I should try setting up the chronograph to see what the velocity is of an ejecting case. Probably higher than the bullet! They do love to fling them out quite a ways, don't they!
Retarded Blow-back Mechanism………………………..
There is one queer thing, however, that is common to almost all blow-back and retarded blow-back guns, and that is that there is a tendency to rupture the cartridges unless they are lubricated. This is because the moment the explosion occurs the thin front end of the cartridge case swells up from the internal pressure and tightly grips the walls of the chamber. Cartridge cases are made with a strong solid brass head a thick wall near the rear end, but the wall tapers in thickness until the front end is quiet thin so that it will expand under pressure of the explosion and seal the chamber against the escape of gas to the rear. When the gun is fired the thin front section expands as intended and tightly grips the walls of the chamber, while the thick rear portion does not expand enough to produce serious friction. The same pressure that operates to expand the walls of the case laterally, also pushes back with the force of fifty thousand pounds to the square inch on the head of the cartridge, and the whole cartridge being made of elastic brass stretches to the rear and , in effect, give the breech block a sharp blow with starts it backward. The front end of the cartridge being tightly held by the friction against the walls of the chamber, and the rear end being free to move back in this manner under the internal pressure, either one of two things will happen. In the first case, the breech block and the head of the cartridge may continue to move back, tearing the cartridge in two and leaving the front end tightly stuck in the chamber; or, if the breech block is sufficiently retarded so that it does not allow a very violent backward motion, the result may simply be that the breech block moves back a short distance and the jerk of the extractor on the cartridge case stops it, and the gun will not operate.
However this difficultly can be overcome entirely by lubricating the cartridges in some way. In the Schwarzlose machine gun there is a little pump installed in the mechanism which squirts a single drop of oil into the chamber each time the breech block goes back. In the Thompson Auto-rifle there are oil-soaked pads in the magazine which contains the cartridges. In the Pedersen semiautomatic rifle the lubrication is taken care of by coating the cartridges with a light film of wax.
Blish Principle….There is no doubt that this mechanism can be made to operate as described, provided the cartridge are lubricated, …. That this type of mechanism actually opens while there is still considerable pressure in the cartridge case is evident from the fact that the gun does not operate satisfactorily unless the cartridges are lubricated.
Thompson Sub-Machine Gun: … Owing to the low pressure involved in the pistol cartridge, it is not necessary to lubricate the case.
One characteristic of the fluted chamber is that you have to keep the flutes clean and use ammunition that is relatively clean burning or the flutes get clogged up.
This gun, to me, ... it's more like an AK-47 that fires 7.62x51mm NATO
I bought this rifle . . . as . . . an AK-47 that grew a pair!!
I've always been interested in the HK roller delayed blowback weapons.
From an engineering standpoint the design has obvious advantages in theory: no gas system so you can make lighter and cheaper firearms and the weapon stays cleaner.
In practice the engineering and materials required to make the guns work make them as heavy and as expensive as gas operated guns, while dumping carbon in the receiver.
The Pedersen used a hard wax, something along the lines of cured carnuba, not paraffin. More like the poly coating seen on 5.7. Army just didn't want to switch ammo at the end of the day, since 276 basically exceeded all competition in testing. Didn't really matter ultimately, though, since a quality rifle was chosen.Oil, grease and wax were all very messy
To be fair, the CETME/G3 design does require a lot more precision than most/any other designs to function right (bolt gap, chamber depth, locking piece angle, cocking tube gap, receiver straightness). Reproduceable enough via tooling (and quality control), but kind of a pain to develop or assemble, compared to something like a long-stroke gas action or anything with a barrel-extension lockup design (which the CETME sorta kinda is; the cocking system is what causes the most complexity imo)The problem with the HK design is you need decent steel to manufacture the bolt head, rollers, and locking peice. If you use crap steel those parts will be beaten into unusable shape before the first basic load goes through the gun.
The Pedersen used a hard wax, something along the lines of cured carnuba, not paraffin. More like the poly coating seen on 5.7
...the woman unit looked over at my direction and said "I don't like that"....
just curious, but has a more awesome weapon than the HK91/G3 family of rifles ever been made?.