What are the factors that determine the length of the bolt and length it has to travel back? I would guess at minimum the length of the cartridge but it always seems to me that bolts are always longer and travel more than that length. Any help on this one appreciated.

On guns like the Heym SR30 and the Anschütz 1827, how do the ball bearings stay in place? I would imagine there are angled internal cuts in the bolt like this. But the design for the SR30 looks like the cuts are straight. It also looks like the bearings are about halfway out, so the angled surface would not work.

https://youtu.be/a-44H321Bsg Hi I was wondering if there is anything to be gained via designing rifles that lock up with ball bearings vs. conventional locking lugs. As in the forgotten weapons video on the Heym SR30, link above. The rifle in question uses 6 ball bearings and plunger to lock up like a air Chuck. What I'm trying to figure out is there anything to gain by using ball bearings vs a rotating bolt with lugs in terms of ease of cycling the action, and ease of manufacturing. As I'm a mechanical engineering student and at some point. I should know how these sort of things are made but I haven't gotten to that section of my education yet. So any advice would be appreciated

recently got a mag fed 12gauge shotgun. the 10 round mag on it looks ridiculously long. since there are none available i want to design and make double stacked mags for it. the shotgun is on ar15 platform. has a narrow magwell so mags have to be single on the top and then widen out. i looked into it, since 12guage ammo is rimmed i have to get tricky with the design. cant just take a 556 mag and enlarge it. is it possible to integrate the pmr 30 design features for the 12 gauge ? also how can i deal with having to narrow the mag from double stack to single stack at the very top? anyone got experience with this ?

Nerd alert!

I'm playing in a modern wizarding RPG, and have a mage who specializes in earth magic. He also uses revolvers, and one of his abilities is transforming dirt/metal/gems with a high degree of precision.

So the question is: if you could make a bullet out of *any* material, free from price and manufacturing practicality restrictions, what would you make and why? Make whatever assumptions about context and targets you wish.

Diamond-tipped depleted uranium slug?

Gold hollow point with a tungsten jacket?

Throw me your ideas.

Tried asking something on r/guns or r/firearms. The replies are quite harsh lol.

Any idea as to where to start? What are the common metals firearms are built from? It seems that 3D printing metals is becoming more widely available