Learning about these actions. Anyone have one?

You mean one of these?

Yes! That is gorgeous!
Is it yours?

Yes, they are a lot of fun.

If people could post pics of their down under hammers that would be cool. I see they have a bunch of kit guns avaliable for this action. They seem quite elegant and simple. Anyone know PSI max for some of these?

I assembled this on an underhammer frame when I had to have a 4 bore muzzeloader a few years ago.

video

Mike, your 4-bore is certainly vigorous in the recoil department!
Boomie, I no longer own that rifle. It was Pacific Rifle Co. Zephyr, .62 caliber, 1:104 twist (or 1:96??) made by Roger Renner, who is a genius for designing with an eye to elegant line.

That sure set you back!
I think a 12 bore would be sweet.

I know this is an older post however, I have provided a few links to underhammers that you may find useful. I have one similar to the one pictured above in .45 caliber. These are often refered to as the Hokins and Allen style. There is also a Billinghurst style. Don't know what the others may be called but I am sure there are more.

Anyway, here are the links:
http://underhammers.blogspot.com/
http://www.underhammers.com/
http://www.longrifles-pr.com/underhammer.shtml
http://www.muzzleloaderbuilder...&product=Underhammer
http://www.pacificriflecompany.blogspot.com/

Thank you for the links. I think these are quite intriguing rifles.