Why AR and not AK?

[red-beard]

Originally Posted by m21sniper

I was shooting one of these last night. What a "blast."

I need more ammo for mine. CMP still has some cheap ammo, but it is taking them 5 months to fill an order.

[m21sniper]

Originally Posted by HHI944

If you keep yours eyes open and are patient you can snag Century CETME's for ~500 pretty consistently. That's a lot of stopping power for the $$$.

Yep. They're really solid weapons, if money was no object i'd have one with wood furniture in my safe just because of it's lineage.

[flatbutt]

Ohhhh! I like that one.

[red-beard]

Yep, I'll pick up one of those too, one of these days. I'm not a fan of blowback operation, whatever the flavor.

[m21sniper]

Blowback has some real advantages, especially in pistols.

1) Fixed barrel for greater accuracy
2) simpler and more reliable design
3) Fewer moving parts and easier to clean
4) greater cyclic rate of fire in automatic weapons
5) No chance of a gas system becoming diasble due to fouling

Of course it does have some disadvantages too

1) Greater comparative recoil compared to gas operated designs
2) More slide/slide mass required when compared to a comparable gas operated weapon of the same caliber.

[red-beard]

And after a while, the barrel will wear in the cartridge area, leading to leaks.

Simple? Yes. Better? No.

[m21sniper]

A HK P7 is blowback operated, i don't think you'll find any reference of them doing such.

Same for the new Sig .22's, and many legendary submachineguns.

I think the reason that happens to many blowbacks is becuase they're inexpensive zinc junk.

[RPKESQ]

Almost all semi (or full) auto pistols are blowback. Most above 9mm kurz or .380 is "locked breech" or delayed opening.

Colt 1911s, Browning Hi Powers, CZ75s, MAB, Glocks, etc. are often called a locked breech, but in reality all just delayed breech opening.

HK P7 is gas retarded blowback.

The most elegant solution to the problem was on the P-08. A delayed locked breech so efficiently engineered that the barrel pressure was zero when it finally unlocked (but expensive to manufacture).

All sub-machine guns (by definition pistol calibers) are delayed blowback, some like the HK are roller delayed breech. Most are "locked" by bolt mass only.

Small caliber pistols are just simple delayed blowback with the breech locked by bolt mass only( most .22s, .25s, .32s, 7.65mm, etc.).

I have never seen wear in the barrel (even in poorly made or home made) that prohibits operation from "leakage". At worst with extensive firing the barrel is burnt out as far as land wearing away under high heat so that accuracy suffers. I do not believe that the excessive hot gas wear would travel backward into the chamber when the barrel is the path of lease resistance to the expanding gas and the cartridge case expands to seal the chamber for approximately 1/100th of a second, which is all that is needed.

Properly designed, a delayed blowback pistol will wear the barrel lands first and then the locking surfaces and finally the slide "fit". These all effect accuracy, but not functionality until the locking surfaces actually break away.

Blowback is the optimum engineering solution until you get to rifles, then gas operation has some weight/reliability advantages.

[m21sniper]

To me pure blowback and delayed blowback are actually two different operating systems, i think a lot of people think that way.

The only pure blowback centerfire pistols still made nowadays that i'm aware of are the little cheap-o pocket pistols like Jennings, Lorcin, Raven, etc. I assume those are the ones that had the barrel wear problems he was referring to.

[RPKESQ]

Originally Posted by m21sniper

To me pure blowback and delayed blowback are actually two different operating systems, i think a lot of people think that way.

The only pure blowback centerfire pistols still made nowadays that i'm aware of are the little cheap-o pocket pistols like Jennings, Lorcin, Raven, etc. I assume those are the ones that had the barrel wear problems he was referring to.

Actually, there is really no difference between them except for the manner of retardation of breech opening. A mechanical "lock" of about 1/100th of a second or a "lock" by bolt mass for the same period of time.

What makes the gas-operated system different is they all use some kind of true locking breech. Almost all have a turning bolt type of lockup and would remain locked if the gas port in the barrel was plugged.

No gas, means no unlocking. In effect a turn bolt (bolt action) type of weapon that only automatically opens the breech by unlocking the bolt with a twisting action delivered by the force of the gas.

All Colt, Ruger, High Standard, Walther, S&W, Hammerlli, etc. .22 autos are bolt mass delayed blowback, both current as well as out-of-production. The quality does not matter as they all work exactly the same from the cheapest zinc POS to the Hammerlli Rapid fire Olympic pistol.

This mass delayed system works fine in all low-powered calibers up to about a .32 or 7.65. Some high quality .380s or 9mm kurz have also been made (Walthers for example). But beyond this level of power the bolt/slide weight becomes too great and a mechanically (or gas in the case of your P7) delay is used so that the weapons does not have to be excessively heavy.

[red-beard]

The only true blowbacks I own are Colt 1903s/1908s in .32 ACP and .380 ACP. How does the CETME delay?

[RPKESQ]

Originally Posted by red-beard

The only true blowbacks I own are Colt 1903s/1908s in .32 ACP and .380 ACP. How does the CETME delay?

Roller-locking. Two small rollers are held in recesses until the pressure on the bolt face drops and then they are allowed to retract out of the recesses allowing the bolt to retract. Nothing more than a mechanical delayed blowback.

The mass of the bolt, camming surfaces for the rollers and the power of the cartridge are all balanced to give a 1/100 of a second delay.

Early Spanish made copies used the Spainish version of the 7.62x51 which operated at a lower velocity that NATO standard 7.62x51 and could break when used with the more powerful loading. This has been changed some time ago.

Just for clarity sake, all blowbacks are true blowbacks. As the delay is either bolt/slide mass or some mechanical delay. There is no true locking in blowback weapons.