I have been shooting both the older Contenders and the new'ish Encore's for some time now. My first Contender pistol was an older framed gun with the swing position hammer selectable for rim/center fire. It came with a heavy 14" 44mag bbl on it. After about a year I sent it off to J.D. Jones and had it re-chambered to 444Marlin. IIRC this was in '84 or '85. I loaded this gun to full power and shot the then new 265gr Hornady bullets thru it. I killed moose,bear,and several of the bigger NW deer with this gun.
About three years later I ordered another bbl from Jones(then SSK)chambered in the "new" 375JDJ. Again I killed everything that could be killed in the mountains of Maine with the pistol. Including a 62 1/2" 965lb bull moose. IIRC I used a 275gr Hornady bullet. This was waaaaaay before there was a solid copper or even the Nosler Partitions.
Some of the deer that I killed up north were near 300lbs on the hoof. Now with some of the better bullets that come in 375cal I would pick the lightest solid copper Barnes in either TSX or even better TTSX available. I also killed several coyotes with my Contender in 375JDJ at close to 200yds with the very light bullets available back then. I installed a front 1/4" sling swivel stud on my gun and used the 9-13 inch Harris bipod. From prone or from the bench the legs would not collapse if I maintained my grip arms elbow locked.
The 375JDJ brass is super easy to make. One pass of the 444Marlin brass into a 375JDJ die and your done. I used Imperial sizing wax. I very seldom had to even trim to correct length with the proper lube.
I had a Leupold 4X pistol scope on my gun. It was ordered with a thick cross hair. Nowadays I probably would choose a 2-6X variable. The JDJ chambering shoots fairly flat at the <200yd ranges,especially with the lighter bullets. The Barnes line of bullets is all you would need for the biggest of hogs or deer,IMO.
There are several good powders that are used with this particular JDJ. As I recall my gun liked the case stuffed as full as possible. Being a single shot I also seated the bullets .010" off the lands for my fuller than full power loads. I also would put a light crimp on the bullet NOT in the cannelure.
Some years later I built up a 21" 375JDJ Contender rifle. Take a close look at this. It was really a fun gun. I gained another 200fps over the 14" bbl even with the heavy bullets.
You will absolutely love the 375JDJ. It is extremely versatile,accurate,and powerful. J.D. Jones has killed ALL African big game with this chambering. --- pruhdlr