Subs through a Semi-Auto 22LR

[TattooedGun]

I haven't got either a beard nor sandals, so I'm probably wrong, but:

There are two types of mechanisms that make semi-auto (and fully-auto) firearms operate, recoil and gas. In every case though, one of the most important things is to ensure that the bullet has left the barrel and therefore pressure in the barrel has dropped, BEFORE the bolt opens. Otherwise bad things happen to the person holding the gun.

For low-pressure rounds like .22LR, the weight of the bolt and it's spring pressure are enough to keep the bolt closed until the bullet has left the barrel. These are called blowback mechanisms.
For higher pressure round like 9mm /.45 etc, there must be some mechanism to lock the bolt and barrel together initially, until pressure in the barrel has dropped. These are commonly the swinging link in 1911-type pistols or Luger's toggle mechanism. Often I think these are called the recoil mechanisms and the firearms are recoil operated.
There are also those guns designed to be fired from an open bolt (eg Stirling & Sten guns). They operate by blowback, but the cartridge is fired before the bolt is fully home and the necessary delay given by the inertia of the bolt - this is advanced ignition.

Gas operation is more often used in rifle calibers - I guess because there needs to be even more control of when the bolt/barrel become unlocked. There is a gas-port drilled into the barrel part way up and high-pressure gasses are ducted off to operate on a piston, which unlocks and operates the bolt. eg AK47's, FN-FAL and M16's. Just like the pistol recoil mechanisms, there are variations on the design.

Triffid

I thought the Tommy Gun was a blowback mechanism - that's .45 ACP...

[Triffid]

I believe (and stand to be corrected) that the original Thompson did have a locking mechanism, but they found that it wasn't needed so didn't include it in later models. It fires from an open bolt so the inertia and mainspring delay the bolt opening.
Watch this from about 5 minutes in;
https://www.youtube.com/watch?v=bcBKnn8mGc0

Now that is something I've always wanted to fire..
https://www.youtube.com/watch?v=tAdJ3hy_TDc

Triffid

[Triffid]

No I think I was talking sh1t on that one. The Tommy gun that Hickok45 is using fires from a closed bolt, so I assume it's got the original locking mechanism as shown in the first video.

[Triffid]

This one's shooting from the open bolt and looks much more fun.
https://www.youtube.com/watch?v=x4QWrha3HLw

[Blackstuff]

I'm really confused about the differences between recoil operated, inertia operated and blowback operated actions here and I don't think I'm the only one, what's more I think two of them arête same thing.

Could someone with a beard and sandals step in and help us all out?

:)

I think there's an issue of terminology involved here; 'recoil operated' isn't a term i'm familiar with and suspect its a colloquialism for 'straight blowback' action (Although it would probably better describe 'inertia operated' ). Thats the action vast majority of .22lr semi autos work on, simply the weight of the bolt retards the action moving backwards long enough for the chamber pressure to drop to a safe level before the breach is opened, the bolt is not locked in place at all. The SGC LRA9 9mm works from this action aswell, i'm not sure about the 45ACP version.

'Gas operated' is another popular operating system, and as mentioned there is a gas system within the gun that usually taps off some of the gas from the barrel which powers a piston to push the bolt back (or the gas directly does it, in rifles such as the AR-15 - hence 'direct impingement' gas system). The bolts in gas guns are locked until the system unlocks them, which requires a degree of 'timing' with the gas system to operate properly.

'Interia operated' is a concept which i THINK came from Benelli for shotguns, whereby the bolt locks into the barrel and is rotated out of the locked position by the recoil of the cartridge. The time it takes the bolt to rotate to the unlocked position (providing the gun is working properly) allows the chamber pressure to drop to safe levels.

JUst my two penneth. There are dozens of permutations of the basic operating systems though.

[TattooedGun]

This one's shooting from the open bolt and looks much more fun.
https://www.youtube.com/watch?v=x4QWrha3HLw

I managed to a couple of years ago... a hell of a lot of fun, if not a bit recoil heavy.... Kicks like a mule!

[safetyfirst]

Awesome. They always felt too long for me, LOP is set to huge GI from Iowa.

[ovenpaa]

Just swapped the suppressors around so I am on the old one, picked up a some CCI Segmented subs and have ordered a few thousand CCI Standards for the range to see how they perform. The segmented has a less than ideal reputation in come circles so I am particularly interested to see how they go when it comes to noise and cycling.