I own an almost new 375 winchester Big Bore. Where I live it is impossible to find factory ammunition or the reloading components. I have the bullet mould 250 gr. The cases I use fireformed 30-30 win. Primers are large pistol. Propellant is the real problem. I use IMR 800X, which is the only available gunpowder here. I want to use the gun on Jaguars which is considered a pest in these latitudes. The distance would be from 50 to 80 meters. Please any advice would be welcome.

I own an almost new 375 winchester Big Bore. Where I live it is impossible to find factory ammunition or the reloading components. I have the bullet mould 250 gr. The cases I use fireformed 30-30 win. Primers are large pistol. Propellant is the real problem. I use IMR 800X, which is the only available gunpowder here. I want to use the gun on Jaguars which is considered a pest in these latitudes. The distance would be from 50 to 80 meters. Please any advice would be welcome..

250 home cast bullets, 800x powder and large pistol primers are OK for fireforming 30-30 brass in your .375 Winchester, but you are going to need the proper powders and primers for full powder Jag medicine. The proper powders are the medium burning rifle powders like H322, H335, AA2015BR, N133, IMR3031, W748, IMR or H 4198, and Reloader 7 (NOT Accurate Arms No. 7).

Also, you need a large rifle primer like CCI-200 or Federal 210 for the .375. The pistol primer is not going to be hot enough to effect proper powder ignition.

Using fireformed 30-30 brass is ok if you do not go to the wall (52,000 CUP) with your loads. I much prefer the thicker walls of .375 Winchester brass for top loads.

For bullets, try the Sierra 200gr. JFP or the Hornady 220gr. JFP. My favorite is the 375 Winchester beartoothbullets.com 250 grain cast LFN GC bullet. You can order 100 sized to .377" for $15.75 plus freight.

Additional info.

If all you have is 800X and WLP primers to shoot Jaguars with, you probably want to contact a member of this forum who has done very extensive research on using pistol powders for reduced loads in rifles. It is very dangerous, so be very carefull and aviod double powder charges. Safe velocity is probably going to be in the 1000 to 1200 fps range, but the old 38-55 killed a many of deer (and men) at these velocities with a 255 grain lead slug.

His user name is gmusial and his web site is www.gmdr.com . He lists several .375 Winchester loads using pistol powders but none with 800X. He has always been willing and able to accurately address any reloading question.

I agree with what Nitro's told you.
I'll add one thing: IME, the single best powder for the 375 Winchester is AA1680.
My second choice would be Reloder 7, third choice one of the 4198's.
But 1680 definitely exceeds the others in full power loads with rifle primers.

If you want you can make your own jacketed bullets quite easily with some of the equiptment you already posess. One of my friends on another forum, makes bullets for his 38-55 this way and uses a lube sizer to make them proper. He cut the lube grooves out of a mold and then cuts 3/8 dia copper tubing to length using an arrow cutter and places them in the mold and pours them full of soft lead. Sizes them using a spray lube. Your powder would be a problem and I would for all intents try to find a fast burning rifle powder to get more bang for your money. If you can get some H110 or W296 mag pistol powder a good starting load would be around 18gns. This powder works well in the smaller capacity cases from .303 on down. I used to shoot a load of 18gns in a .243 win and it would group well a 200 yds. I also used 18gns in a 30-30 win using 110gn round nose intended for the 30 carbine and it was accurate in my levergun. The only reason I suggest the two powders above is they are twins and as such will tell you the 18gn 30-30 load used to be published by Winchester in their small reloading handout books years ago, don't know why they dropped using 296 as a load recommendation. Good luck.