[smokingfrog]

Don’t see a gas tube or recoil buffer.

[marktwain]

Don’t see a gas tube or recoil buffer.

Correct.

It is a straight pull bolt action.

Works very well with a suppressor.

Use any loads that will put a bullet out the barrel.

[DMZFrank]

That AR-15 pistol is probably chambered for the .22 LR rimfire cartridge. That is strictly a blowback mechanism, and therefore does not need a gas system. You can tell by looking at the area behind the ejection port door recess.