Why SMG Bolts often have this curved lines cut at the bottom?

[Defiant Dan]

Can someone explain ? I mean , the Bolt is supposed to be heavy and its needless extra machining so i cant think this are lightning cuts to save weight. The Designerr would be happy to slice an inch of the Bolt to save on overall length.

Is it perhaps to glide over the Magwell ? But it doesnt look like it would be neccessary.
And you find this cuts on nearly all blowback smg , dont matter if the bolt goes over the chamber or not.

So it really puzzles me why this cuts ?

Edit; Is it perhaps to vent Gas in Out of Battery Detonations ? But Open Bolt SMG in general dont care about OOB Detonations since the Gas blows out the shell exit hole.

There are many Slow-Mo Videos where clearly out of batttery detonations happen but the user only noticed as he watched it on Video frame for frame.
But perhaps they did not know 80 Years ago

I mean the roller-lock was a happy accident too... the real Lockup in this Protoytype Sturmgewehre failed, so they found sheered lugs but all else looked normal and there was no catastropihical failure, and thatt made them realize thatt the Roller-Delay alone is enough, which a certain Theodor Koch then patended.... the rest is H&K History...

So they did not know as they designed the Gun and did their calculaions, thatt the delay alone was enough... it was happy accidentt. So perhaps the Early SMG Designers just added this Cuts as margin of safety to reduce bolt thrustt in case of out of batttery

[Michanicks]

Can you mention SMGs you talking about? I am assume since they are open-bolt guns, their bolts should be lighter, otherwise they will start to shoot with more noticeable delay and their recoil will be even higher - open bolt by itself causes delays in shooting and high recoil.

That's what i've learned why tried to figure out why so many SMGs have open bolt.

[Defiant Dan]

Originally posted by Michanicks:

Can you mention SMGs you talking about? I am assume since they are open-bolt guns, their bolts should be lighter, otherwise they will start to shoot with more noticeable delay and their recoil will be even higher - open bolt by itself causes delays in shooting and high recoil.

That's what i've learned why tried to figure out why so many SMGs have open bolt.

The delay is what you want and need in a open bolt without any lockup.
The weight of the Bolt is calculated to a single oz. It would make no sense to machine it longer then needed and then cut out weight in the front.
That is what ponders me...

Mp40
https://www.ima-usa.com/products/german-wwii-mp40-smg-bolt?variant=25651828933#mz-expanded-view-1570567259440

M3 Grease Gun
https://indianapolisordnance.com/image/cache/catalog/products/dscn6736-450x300.jpg

Sterling
https://cdn11.bigcommerce.com/s-wstuuz5n2e/images/stencil/1280x1280/products/757/3925/20210529_165600__57725.1622325601.jpg?c=1

I thing the only thing which makes a bit of sense is to clear the magwell, but in the Game it really does not look like it would be a problem when it would not be cut.

You find this Cuts on basically all SMG Bolts

[Kaewon]

It's to go over the magazine feed lips. Go into operation, click to hide parts to see better, then slow mo fire, pause and scroll and you'll get a clear view of it. It's not just smgs but any gun that uses box magazines. Although slides on pistols are not bolts, you'll see channels for clearance for the same reason.

[Defiant Dan]

Originally posted by Kaewon:

It's to go over the magazine feed lips. Go into operation, click to hide parts to see better, then slow mo fire, pause and scroll and you'll get a clear view of it. It's not just smgs but any gun that uses box magazines. Although slides on pistols are not bolts, you'll see channels for clearance for the same reason.

Yeah feed lips and follower when the mag is empty..., for some reason i was only thinking of the mag-well itself . Now it makes sense ;)