My Old Hi Power will not feed many JHP's. What can I
do? The question posed is a common one from folks shooting Hi Powers
manufactured before the advent of the "straight" feed ramp circa 1982.
(Hi Powers having the straight, non-humped ramp normally feed any JHP
ammunition. This would include late-run classics, as well as the Mk II's, right
on up through the current Mk III pistols.) While it may be that you
are able to find a brand of expanding ammunition that feeds smoothly
out-of-the-box, you may not. That usually depends on the individual
pistol based on what I've seen over the years.
It can be argued that the solution is simply to have your barrel's humped ramp altered and the process is simple enough so long as care is taken not to relieve the chamber at the 6 o' clock position where it meets the ramp. Any gunsmith familiar with the Hi Power can perform this relatively simple task, but some folks prefer not to have this sort of thing done.
There is no guarantee of success, but on more than one occasion, I've been contacted by folks with the same feeding issues with their classic-style Hi Powers and much of the time, simply buying a new Mec-Gar magazine solves the problem. Though Mec-Gar has been making the magazines used in FN-manufactured Hi Powers for years now, I am not sure exactly when that began. In any event, the Mec-Gar's seem to hold the top round at a slightly more upward angle. It appears that this is frequently enough to solve the problem.
If that doesn't do the trick, remove the barrel and look at the ramp from the rear. On the bottom left of the feed ramp, there may be an obviously flat area near the edge. Sometimes, rounds "nose dive" when being pushed out of the magazine and balk at moving up the ramp when the non-rounded ogive or edge of the hollow cavity smack into that flat. Rounding and smoothing it out sometimes works, particularly if done in conjunction with a new Mec-Gar magazine.
It may be possible for folks to obtain reliable feeding in older Hi Powers having humped ramps by changing brands of ammunition, but if not, perhaps these suggestions can help for those preferring not to have the barrel's ramp altered.