Naval gun rifling cutter photo's

[rogn]

Yeah, very deep. I wonder what the jacketing material was?

For the most part they used a type of gilding metal driving bands. Basically rings shrunk into groves on the projectile. "Jacket" was usually some steel type alloy.
I know in the WW11 era the driving bands went down to at least 5".

 

[rogn]

96 grooves, 0.150” deep
Twist of 1 in 25 must be 25 feet. If my math is right equivalent to a .308 with a 5.77” twist.

16-inch/50-caliber Mark 7 gun - Wikipedia

en.wikipedia.org

That twist might be calculated in calibers. That was often a standard of measure in artillery

 

[riflewoman]

For the most part they used a type of gilding metal driving bands. Basically rings shrunk into groves on the projectile. "Jacket" was usually some steel type alloy.
I know in the WW11 era the driving bands went down to at least 5".

Driving bands go all the way down to 20mm.

 

[M-61]

Here it is on a 30mm. Never saw one on a 20mm but I surely haven't seen everything.
I've heard of plastic being used also. Gerald Bull, one of the most 'out of the box' engineers in artilleries, was obsessed with driving bands and eliminating them. He was obsessed with many other artillery ventures that probably led to his premature demise.
(Not by his own hand)

 

[rogn]

Large Magnum at least.

I trembler reading about this stuff years ago. The priming system used some form of igniter that was a percussion primer or even an electric ignitor( I guesss so fire could be controlled by the computer systems of the time. The ignitor , again if I recall set off a black powder charge that gave enough OMMFFP! to get the ball rolling. I think also each bag of powder(96# in the reference I read, but years ago) had an igniting charge of black that kept the fire going at a predictable rate. Would take a heck of a spark to get 660# of powder going at the same rate every time to eliminate all the vertical..

As an aside to all this the grouping they achieved was in the minute minute of angle range. The current land based self propelled artillery I've heard uses a 4x8' sheet of plywood as a target at about 20 miles. That would make most of us bench resters look like babes in tall grass.

 

[Steve Blair]

View attachment 1234779View attachment 1234779

Like H4895, a little fast for the heavies.

 

[Matt in Virginia]

Ah,...hey you two private’s! Get the “drum” of bore solvent and grab the chimney brush.....the brass one. Okay scrub that bore clean......on the double

Just remember anchor crankers prefer to be called sailors...;-)

Regards, Matt.

 

[Rustytigwire]

"Here it is on a 30mm. Never saw one on a 20mm but I surely haven't seen everything."

This is 20 x 138 for a Lahti. I do not know the source. Looks like the driving band as described. Not a separate softer metal band on a steel bullet though.
Thanks for pointing it out to me!
Tom