I have owned airguns for approx. 15 years. I've owned a number of pistols and rifles in .177 and .22, powered by spring, CO2 and pump pneumatic. A few years ago I decided to aquire a large bore PCP rifle to add to my collection and I was on the same search mission.
I looked at the 'off shore' large bores, but decided I would like to buy a NA made gun if possilbe. I checked Quackenbush, but as mentioned above he has a wait list of approx. two years. His guns are very well made, but the price reflects that.
I searched some more and found out that a fellow in Louisiana makes large bore PCP rifles as well. Jack Haley is the owner/builders name and Southern Airguns is the name of the company.
Link to site -
http://www.southernairgunconversion.com/southernairguns_003.htm
The price of one of his .45's was very close to the off shore guns, so I now own a Jack Haley PCP air rifle! When I ordered my gun the .45 was the largest he made. Just when my gun was finished (approx. 6 months wait) he introduced a .58!!!
My .457 will shoot 515 gr "pellets" at around 750 fps on a full charge (3600 psi). Although after shooting a variety of weights, I found my gun shoots very well using 340 gr pellets, so I ended up buying a bullet mould and cast up my own. Using the 340 gr slugs 120 - 150 yard lethal shots are well within reach.
I recall his .58 will shoot something like 750 gr "pellets"!
If you go to the Bigbore site you will see that guys are hunting the likes of wild boar, deer, water buffalo, etc. with these airguns!
http://www.bigboreairguns.com/
http://www.bigborebob.com/
After owning them all, if you have some 'play money', PCP is the way to go with any airgun. But you have to be prepared to buy an air tank, charge hose, etc. to refill the gun. However, once you have these you can charge/operate any PCP airgun.
As I am moving more into powderburners, a while ago I had my Jack Haley posted for sale on here, but no one 'nibbled' so I still have it in my safe.
Here is a link to photos of my .457 JH.
http://s277.photobucket.com/albums/...k Haley PCP/?action=view¤t=P9161063.jpg
Here it is in action with one of my sons shooting a 515 gr pellet at 60 yards! You can just catch the mud flying in the top right of the screen. I wish I had taken a photo of the trench it dug in the ground, it was about 20" long by 8" wide and 6" deep at the end.
http://s277.photobucket.com/albums/...ction=view¤t=VID00004-20101104-1751.mp4
When you get up into this size/range of air gun, they are pretty cool to shoot.