I have one I bought simply for collecting purposes. Never fired it.
I have a photocopy of the manual and a sheet from the company showing that 70 grains was the recommended max charge.
There have been some rumblings that the guns have a defect and when I posted pictures of mine on a forum, I received a pm advising me not to shoot it. But the warning did not advise what this alleged problem is. (an unreliable safety wouldn't bother me for range shooting, but a gun that could blow up is another problem)
I tried several times to contact the company (in any of it's reincarnations) for some word on it and all my efforts were fruitless.
The Hawkeye pistols sure seem to bring a lot on the internet auctions. One in the box with all literature in unfired condition recently brought just over $650.00