Real Steel Square Bolts?

[Meleager7]

have been watching me some Forgotten Weapons.....and i've been wondering why so many blowback smg bolts are square?

Can they be any shape in theory?

Would a square bolt work in a blowback paintball gun, and do you think it would be really cool?

[Ecapnation]

Easier to machine and fit it stamped sheet metal bodies

[Toestr]

Probably because it's easier to get the mass required for a blowback to operate. If they spent the time rounding out the bolt on a lathe they'd have to increase the dimensions in some way to make up the mass they lost in material.

Paintball bolts are round because of paintballs and orings. You could probably make the striker for a blowback square but you'd also have to make some proprietary seals or have some very tight tolerances.

Sent from my Pixel 4a using Tapatalk

[Meleager7]

Orings, of course!

But in my theoretical square receiver blow back, my bolt would have no orings, but tight tolerances, and I'd run it on liquid co2 !

[DocsMachine]

Yep. O-rings and the fact it's a round projectile is the key, here.

Years ago, just for giggles, I wanted to make a 'Cocker with a square bolt and square hammer- it'd actually be pretty easy, as neither one needs O-rings. Just one of a whole list of lunatic ideas over the years....

But yeah, in an SMG it's a mass thing. A 1-1/4" wide square block weighs more than a 1-1/4" round bar, but even then, it's pure choice. There's a ton of SMGs out there with round bolts (like the Sten, H&K, etc.) as well as a bunch with square (Uzi, Ingram, etc.)

Doc.

[Seajay]

Might make it a little hard seeing how we don't use combustion and firing pins to shoot. A square bolt and receiver is fine with a bullet because it's job is just to put a cartridge into breach and seal the chamber.

Definitely could do it with a closed bolt marker and just make for a "breach" that can hold the ball in place with the square bolt sealing up against it and the body. It would need to be very precise on timing and clearance or you'd smack the crap out of the internal body. I don't see anyway it would be better though.

[bellicose]

What if the bolt face was a rubber type material? Could that seal the breach easily? Might wear quickly.

[Seajay]

Ya, that would work, you could do all sorts of things to cup the ball and create a seal. The tolerance would still be tight though unless you allowed for an extended face that would just act like a bolt does today, by extending into the barrel a little. I guess you could have a large rubber face and create a super seal for a closed bolt design...

[gabe]

We also have a major difference in projectile handling. Firearms use a cartridge with a rim and an extractor on the bolt face to positively hold the cartridge all the way into and back out of the chamber. On a paintball gun the ball is just kind of dropped into the breech and rammed into the barrel. If the breech were square you'd have problems with the ball moving around and you'd also have a step where the breech transitions to the barrel. All that would create a high probability of paint chopping or breaking in the breech. Oh and that's another thing, guns can be as rough on their ammo as they like without causing issues.

[Seajay]

Well the paintball only has 4 points of contact, plus the bolt on the rear, and the detent on the front. As long as those surrounding 4 points of contact can be made consistent and smooth enough for the ball to ride along I don't think that would be an issue. It would be more like a sled pushing the ball into the barrel. We jam paint into under-bored barrels all the time that squeeze them. That's actually a huge plus in this case.

[gabe]

While the ball is supported on 4 points it makes you're assuming a square bore that is only just slightly oversized to the ball. Most bolt bores are massively oversized which would allow the ball to move quite a bit. At least with a round bore the ball is equally supported on ALL sides not just 4 corners.

Another thing I should mention is how much harder it is to broach a square hole rather than just drill a round one. A square bolt body would be quite a bit more complex to make.

[Cunha]

I wanna make a square bolt square hammer autococker, with a square barrel with a square bore.

I bet it will shoot fine.

[Toestr]

I wanna make a square bolt square hammer autococker, with a square barrel with a square bore.

I bet it will shoot fine.

Pez dispenser.

Sent from my Pixel 4a using Tapatalk