I have a JP Enterprises upper, an older Grade 1 upper, that I've been shooting for about 4 years.
Back when flattop accurized uppers were starting to get real popular, JP Enterprises was one of the first to do it with style while also delivering on performance. I bought mine back when I wasn't quite as knowledable about how easy it is to build an accurate AR15. On one hand I couldn't be more satisfied in the rifle I have, it's served very well and it's accurate averaging around 3/4 inch for 10 shot groups at 100 yards(with rather simple handloads). But on the other hand, it was kinda the model of "what I wanted, before I knew what I wanted" sort of thing. Lots of decisions that I made back then I may have done differently if I had the experience I have now.
For instance, I'm not 100% sure who's barrel I have whether it's a total custom make or if it's from one of the more recognized makers and then I also don't know precisely what chamber I have nor how it's throated. You can call them up and get a certain amount of information from them but it's not nearly as much a custom process as if somebody were to have a Compass Lake upper built or have George Gardner of GA Precision build one up where you have choices of reamers for the chamber, choices of contours, or choices several twist rates or rifling patterns.
JP Enterprises supposedly offered their uppers with Mike Rock 5R barrels at one time, now THERE is a reason for going with a maker if they offer the Mike Rock barrels and chamber them correctly.
My rifle weighs in at friggin 15 pounds unloaded.... Now a LOT of that was planned, I wanted a light recoiling rifle and by gawd I got it, this thing from a stable position allows for the shooter to spot all shots no matter what the range and recoil is extremely mild. Makes for a great varmint rifle when shooting from a single position for long periods of time but it makes a crappy walking gun. Much of the mild recoil is due to the weight but even with a 24inch barrel the JP brake is helping out, I CANNOT STRESS THIS ENOUGH THOUGH, REQUEST TO HAVE A REMOVABLE MUZZLE BRAKE WITH NON-STANARD THREADS! It is near impossible to clean the muzzle crown of your rifle if that brake is installed permanently, in fact I went through the trouble of torquing that muzzle brake off of my barrel so that I could clean the 2+ years of carbon fouling off my muzzle. Really mangled the finish of the brake too but I got it off(was on there with red LockTite), I've tested accuracy with and without the muzzle brake and the point of impact and group size change is minimal between when the brake is installed and uninstalled. Go with a removable brake for sure and have them send a thread protector with it. There are times that the JP brake is more than just a pain, sometimes it's downright punishing because it is SO loud. It redirects MUCH of the muzzle blast back at the shooter and in 4+ years of owning the rifle I have fired it without hearing protection exactly 2 times. Once was sorta deliberate and after that I said I would never again fire it without hearing protection, the 2nd time was an honest mistake when I removed one cup of my hearing protection to listen to what a mumbling friend was saying then I forgot to place it back over my ear.
Now long story short, everyone and their grandmother are putting out accurized uppers these days. MANY of the uppers out there can offer performance similar to if not equal to that of the JP Enterprises upper while doing it for slightly less to significantly less. But sometimes a person has got to admit that style plays a little bit of a role in what causes a person to choose one upper over another. If it comes down to all your choices being equal in price and in accuracy capabilities then typically all that is left is deciding on which style you like more.
Here's my squirrel killing beast....
[url]http://home.bak.rr.com/varmintcong/jpar/jpar.html[/url]
I used a DPMS stainless steel lower in my build up to help off set some of the weight of the long bull barrel. The paracord wrapping is there for 2 primary reasons, one was for insulation from those stupid black aluminum handguards which soak up the heat of the sun during summer or get DARN cold during winter. The other reason for the paracord was for additional texture, the 1/2 twists line up right along the joints of the fingers making for a comfortable grip, plus I managed to make a flat "pinch point" for the thumb and index fingers so that I could get a repeatable hold each and every time.
If I had it to do over again, or when I goto replace this upper after shooting out the barrel, I'll probably go 100% custom with something like an upper from Scott Medesha or similarly qualified knowledable builder. Just because I've advanced far enough to know where I'd do something different, the JP Enterprises rifle has been a GREAT rifle though considering it was my first step into the world of accurized long range firearms and was great to learn and even make mistakes with. For the 750 or so I spent for the upper assembly, it has been a decent upper assembly while maybe being a bit more expensive than some others.