When I was in middle school, we had a lab where the teacher heated up a metal ring, which then allowed a metal ball to pass. Blew my mind, as I expected the ID to shrink due to expansion. But, as you say, the metal expands in all directions, which causes the ring to grow, even in ID.
When we add in coefficient of thermal expansion, we find that aluminum expands more rapidly than steel, leading to a looser fit at the barrel extension, even if you heat both the barrel and the receiver the same amount. And a titanium gas block is tighter when hot than a steel one, because Ti expands less than steel. Or, lead and copper expand more than steel, sticking harder when hot (perhaps; I haven't tried it).
Think of it this way:
If you heat a bar it gets longer.
If you curl a bar into a circle and heat it up, it still gets longer.
So when a ring is heated the perimeter of both the ID and OD increase and since the perimeter is tied to the diameter, that must increase as well.
Attachment 66988
You also have to remember that when you shoot a round there is a significant internal pressure that will inflate the bore and increase the inside diameter. After the bullet gets stuck, the bore relaxes to its original diameter and pinches the bullet.
Last edited by lysander; 12-16-21 at 08:55.
Makes sense. Heating the barrel... assuming I could heat it quickly enough that too much head didn't also transfer to the bullet might have made tapping it out a little easier. (I hope to never have to try this EVER)
"What would a $2,000 Geissele Super Duty do that a $500 PSA door buster on Black Friday couldn't do?" - Stopsign32v
FWIW, the other squib in my life: 20+ yr old ammo in 10/22 squib. Ended up whittling several sticks as I learned to cut them just long enough to protrude from muzzle. If they stuck out too far, I broke them when attempting to drive bullet out. Wonder if that would translate at all to other situations.... Anyway, had an inch to go and all bets were off. Sticks just broke. Went home and my Dewey rod handle survived.... Most interesting is that when I returned to the range, no extraction. Discovered extractor parts had blown out! Found them all in proximity, and the gun runs to this day....
I had not considered that. I suppose one should mimic this for removing a stuck bullet if that is possible. One idea I read was to fill some length the bore ahead of the obstruction with oil, place a rod with a seal above that, and hit the rod with a hammer. If this were done well I imagine substantial hydraulic pressure could be produced. What do you think of that idea?
I was still trying to wonder if taping rings along rod would have reduced flex in the bore enough for it to work, but if you, too, had to shorten rod like I did (and after comments of others in this thread), prolly not. Glad bullet was close enough for you to drill. Here's hoping the rest of our bullets clear the muzzle in appropriate fashion!....
How close were you to just buying a new barrel?
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