H&R Topper 158 question

This link may or may not help you, but at least it's a start:
https://bradtrumbo.com/portfolio/a-brief-history-of-the-hr-topper-model-158/

I have never seen a 22 Jet Topper, and have been gunsmithing since dirt was young! I'm not sure how you would get an off-center firing pin hit on a 22 LR cartridge using the S&W inserts. You have a very interesting gun. Take care of it!

You do have an interesting gun! The cast iron receiver will not stand the higher pressure cartridges but you should be good to go with 357, Hornet, 45-70, maybe 44 Mag. If it were mine, I would ream a Jet insert to 22 Hornet. Jet cases can be formed from 357 but the die set is expensive and the loss rate is very high.

H&R would only fit 357 mag and 44 mag barrels to the shotgun frames. Below is a link to the H&R gurus. These guys know everything there is to know about those kinds of guns.

https://www.gboreloaded.com/forums/index.php?topic=26264.0

Choctaw said:

H&R would only fit 357 mag and 44 mag barrels to the shotgun frames. Below is a link to the H&R gurus. These guys know everything there is to know about those kinds of guns.

https://www.gboreloaded.com/forums/index.php?topic=26264.0

Click to expand...

Great website! From it, this is an important consideration on what cartridges are appropriate for your receiver

H&R won't fit Rifle barrels other than 357mag and 44 mag on a shotgun frame since the shotgun frame is not heat treated to handle the pressure. Since rifle frames are heat treated investment cast alloy steel, they are safe to use higher pressures, the lower pressure shotgun barrels don't present a hazard to the firearm and/or user as the inverse does. The larger firing pin and surrounding hole in the frame is also an issue.

I don't know if your receiver is the shotgun frame. But something to understand, if it is the shotgun frame, then exceeding the pounds per square inch loading of a shotgun shell, on the breech face, the material will give way, and it will recede.

If you ever get to talk to the architect of the Millennium Tower in San Fransisco, be sure to ask him about the advisability of putting a building on ground so soft, that the building sinks 17 inches.