I don't get how the piston moves with the bolt.

>>35036173
I'm pretty sure the piston and bolt are one piece and the gas from the gas port is what locks the rifle by pushing the entire assembly up into a 'locked' position and it can only move from there after pressure has dropped so it can drop back down

>>35038265
>piston and bolt are one piece
You mean separate pieces right? In OP's pick the gas piston quite obviously locks up the bolt until the pressure drops enough.

>>35036173
http://www.forgottenweapons.com/stg-45-horn-prototypes/

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What determines the fire rate of an automatic weapon?

>>35040622

On a gas operated firearm its how fast the gas can get into the gaschamber and how strong the recoil spring is.

>>35040622
What parts inside are moving? How heavy are they? How far can they move? How much force is applied to move them? How long is the force applied?
Stuff like that.

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That's not the insides of an StG 44. The piston and bolt carrier are rigidly connected in that rifle, and the bolt carrier has a hook that catches the bolt on the way back.

>>35036173
It seems to run on a similar principle to that of the gas/piston delayed HK P7M8 pistol. The bolt wants to come back but the piston can't move downward into it's captive hole due to gas pressure pushing up from below. Once the pressure drops the piston is now free to be pressed into that hole through the leftover inertia of the bolt. Basically a gas delayed blowback.

>>35040622
how light/robust the recoil spring is
how short the action
number of parts involved in cycling
After a certain point magazines can't keep up with ROF, you you'll need something like belts.

>>35043019
Disregard these labels. I'm a dumbass who speaks before fully understanding what we're talking about. I didn't even realize there were late-war STG trials until I thought to google the OP file name.

The piston does not move with the bolt through the entirety of the bolt's rearward motion (it's not in the recoiling parts group). If the piston dia is smaller than the cartridge rim dia, the gas pressure pushes on the piston with slightly less force than the bolt. coupled with the fact that the bolt's breech force only fights the horizontal component of the piston force (ignoring piston friction), the net external force on the bolt (and thus the bolt's acceleration) is reduced compared to a direct blow-back design. Since there is still a net rearward force on the bolt, it will accelerate. The bolt drags the piston rearward, and the piston's bore being angled relative to the rifling means that the piston also moves down. At some point, the piston clears the bolt and the bolt moves back against the recoil spring alone. This is not a locked breech, since the bolt accelerates as soon as gas force overcomes friction.

Reading the Forgotten Weapons article left me wondering how the piston being in the "locked" position causes a "nasty double feed type malfunction." I can see how it would keep the bolt from going into battery if the front of the bolt had too sharp a leading edge, but I don't see how it would cause the bolt to pick up two cartridges from the magazine, either in sequence or at the same time (what happens in an AR-15 if the magazine sits too high). Maybe the bolt bounces off the piston far enough to catch a second round?

>>35040593
Thanks pham