I am picking up a Contender barrel inn .375 JDJ and I am looking for .375 JDJ Data with 250-grain Sierra Gameking. Anybody have a source of data?

Hornady reloading manual #8 and Hodgdon #27 has data for the T/C and there is quite a bit online. It's not hard to reload for but use the slightly faster burning powders for the shorter barrels.

It's NOT the most efficient cartridge around...748, H4895, 3031, H322, and Tac are in the ≈25% +/- category and AR-Comp gets close to 30%. My 26" 375 JDJ likes CFE233 for the same bullet, but likes the Speer 235 gr and 748 MUCH better at ≈2650-2700 fs but the efficiency is only ≈31% according to QL...maybe yes, maybe no...the targets will tell the tale.

Good Hunting

What is efficiency? When I am shooting a 375 that is the last thing I worry about. I have a 14 inch Contender; with a brake on it.
Hang on with both hands.

Efficiency takes MANY forms...the more efficient the better the powder burns, the higher the velo and possibly better accuracy...the same with an M.B...the more efficient it is the more it reduces the recoil impulses...and the easier it is to shoot...same with fast cars/motorcycles/etc...When I was racing I wanted a highly efficient engine/drive train AND body shape so I could kick the **** outta anyone that got in my way.

No difference for racing yachts or even fishing rigs or econoboxes.

When I work up loads for any rifle/pistol I want the highest efficiency in ALL the components...wasted, unburned powder is wasted energy just costing me money without any returns...

Way back in the bad old days I shot a lot of steel and always on the lookout for a "better mouse trap" that would slam the rams and not hammer me too much. I was swapping barrels in my XP-100's like I changed socks. I kept going up in caliber size. One guy at one match had an XP-100 in 458 WM that spit a flame 6-8 ft long out the barrel...THAT WAS TOTALLY INEFFICIENT... but the rams were knocked off the pedestals and sent spinning...it was outlawed very quickly at that range. I DIDN'T want ANY part of that nitemare, plus it wasn't braked and almost hit him in the head everytime he fired it from a lay-back shooting position.

I'm interested in efficiency for many reasons...more in some calibers...much less in others...using efficiency as an adjunct to the rest of the information always informs and not always of interest to all in this game.

I designed many of my M.B.'s to jet the gases upwards between 60° left and right of center-line with most of the larger ports on top pointing up...they do a very good job of reducing/redirecting gas recoil and keeping the muzzle down and don't kick up the dust.

Good Hunting

Have no interest in efficiency; just shooting cool rifles.
If you want total powder to energy efficiency, just shoot a 22 Long Rifle.

I have the Hornady reloading manual and can extrapolate the data from a 270-grain Hornady to a 250-grain Sierra, but would prefer tried and true data.

Right on...the 22 LR has served me well for a ton of years and kept the meat locker well stocked...you're taking my favorite observation away from me.

I have 3-375's including the JDJ and have tried(still have a couple boxes on the shelf) the 250 Sierra in all of them at one time or another and it has never failed to take whatever I shot at. I don't want to start a dust-up only to say what is "tried and true" in one rifle might be Banta-poo in another...but because it is a good bullet it usually does well in ANY rifle/pistol...all personal bias aside.

I'm not all that fond of this particular BT as far as seating is concerned, it needing a good crimp in mag fed rifles due to possible recoil problems...I use a taper crimper and a custom Lee FCD...but that is rifle/reloading dependent, in a pistol that isn't a real problem, the lower bearing surface area MIGHT help with velocity...only testing against a non-BT bullet would show any variance...and again...that is a lot of conjecture...hard to really test out in practice.

I think an early Speer manual also had some good data and comments on the JDJ...not sure...memory fading.

If you like that bullet then testing is the way to find out what's what...some of the newer powders might also be a way to go, after all it is just a ≈65-70 gr H20 case and how many other calibers fit into that category...

I use fireformed and trimmed 9.3x62 cases in my JDJ now due to higher case vol and I've tried 7,8, 9, 9.3 mm x 57, 35 Whelen and 30'06 cases as well - R-P, RWS, Lapua and Hornady...trimming/forming to fit the chamber length...all run ≈65-68 gr H2O, ≈100% load capacity. The Sierra GK #2950 runs at 2550 to 2650 fs with CFE223 and 748 in my 26" braked barrel...and 35 - 37% efficiency, burning almost All the powder by 25" - 98%...your 14" barrel does very well with the same powders...93% burn and 26% efficiency...and about 2300 fs velo according to QL which...that needs to be checked with a chrono to verify. QL shows high pressure with those powders and load volumes, but case life doesn't concur...15 reloads easy

Anyway...just received two PCP Hatsan 177 and 22 cal air rifles...time to go play.

Good Luck

Rats. I had a 14-inch Contender barrel in this caliber several years ago and shot the Speer 235 and the Sierra 250 and cannot find any trace of the data I had ...
It was indeed a "hang on tight" affair.

Bill. Those are the two bullets I plan to try in it.

Dave, any follow up on your JDJ?

None yet. I have everything I need to reload it and will probably try 225-grain starting loads backed off another couple of grains for the 235-grain bullets, and 270-grain load data for the 250s.

Tip:
Let your teenagers shoot it first.

I am expecting recoil to be “sporty.”

I've used a .375 JDJ Contender since it's inception. JD Jones, my good friend, developed most of his early JDJ calibers using AA 2520. His .375 load was 52.0 gr. AA2520 for the 250 gr. Sierra SPBT.
A friend of mine used it on eland, kudu, and gemsbok a few years ago.
I've shot a lot of deer and groundhogs with the .375 JDJ and the Sierra. It's very accurate and reasonably flat shooting.
The Sierra can be loaded a little hotter in the .375 JDJ ENCORE.
I've wanted a little more power in my big game hunts so I mostly use a .375/.285 XP-100. With the speed of the Sierra (2450 fps) in this gun it's fragile and comes apart.
Better bullets in the .375 Contender are 220 gr. Horn. FPs and 225 gr. Horn. SPs. I don't think either are made any more, but I have a big supply of both.
An important thing about the .375 Contender is NOT to "hotrod" it. It won't handle the pressure of an Encore or XP. Be careful with bonded bullets (Nos. ABs) and solid bullets (Xs, monolithics). Don't load them at levels of jacketed bullets of the same weight. Drop back 2-4 grains. A Contender frame can only handle 40,000 psi pressure.
Recoil of the .375 is noticeable, but far from being brutal.

Thank you, Larry.