Paco knows someone else had to try necking up the 356 to 375...but no one has Improved it like he has. This is a fun article.....

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I made a mold that takes .375 diameter copper tubing for a 300+ grain jacketed/cast bullet (3/8" copper tubing)...and with 35 to 36 grains of Reloader #7 I get just under 2300 fps for over 3600 lbs of muzzle energy. That’s more muzzle energy than the best Speer load listed in their Reloading Manual #12 for the 30-06 and their 200 grain bullet! Almost 700 Ft. Lbs. better.

The down range ballistics for the 30-06 will be better with less bullet drop. Speer’s 200 grain Spire point runs well over .550 BC...where as I figure my .375/300 gr bullet runs around a .220 to 230 BC. But I find that with a three inch high point at 100 yards...my bullet drops 16 inches at 300 yards. It is on at 200 yards and down 9 inches at 250 yards.

And at 250 yards it still has more muzzle energy than a fully loaded commercial 44 mag round from a handgun! I just wanted to put it all into perspective for you...my drop figures are actual measurements from groups I fired. At an elevation of 1500 ft. And a temperature of 96 degrees...I use WW brass and WW mag/standard primers. I use very soft lead for the bullet core...and copper tubing that is used for plumbing. It comes in straight sections of a yard or so each. I can’t use the coiled type...can’t get the bend out of it completely even for short bullet lengths.....

My mainstay bullet comes from an old NEI mold. It was designed again for copper tubing and a spire rounded nose bullet...I cut a flat tip on them for the loading tube of the leveraction rifles. It was supposed to drop at 250 grains, but because I use very soft lead the drop closer to 265 grains. Again using ReL#7 I have a top load that’s very accurate at over 2470 fps...and almost 3600 ft. lbs. of energy at the muzzle. Drop figures did better than the 300 gr. because of the better shape and much better BC.

Winchester back around the turn of the century... before and after, produced ‘Gallery Molds’...multi cavity cuts....I have one that was manufactured in 1898, a seven cavity beauty. Bought it 25 years ago, at a gun show for $40...it drops 250 grain bullets....and I can make hundreds in no time. The bullet is very accurate...in both my .375s and from a Marlin 38-55. Cast shooting requires the right alloy for the pressure involved, the right powder, and the right sizing diameter for the bore involved. I use .379 for the 38-55 Marlin and .376 for the 375 WBB.

My accuracy load for the recut mold’s 300 grain plus jacketed bullet, is 36 grains of H335 it gives 2020 fps...and near one hole accuracy at fifty yards...only an inch and a half group at 100 yards, three and a half inch group at 200 yards and five inches at 250 yards....gads that’s good for peep sights.

This bullet was inserted into the butt...a very large butt at that...of a wild, open-range bull in 1982. This animal was really fouling up a number of Black Angus breeding cows that belonged to Stuart Anderson, the restaurant owner and pure beef cattle producer. I was asked to eliminate the problem.

At well over 125 yards I caught him sniffing around one of the breed cows.....The bullet cut his tail almost in half, going in...it ripped a four+ inch radial wound channel from the top of the hams to the front of the back legs (35 plus inches), then coned down to three inch radial thru to the back of the left lung along the bottom of it, and out the lower chest with a two inch exit.

The animal turned at the shot...surprised....suddenly put it’s head down and fell. Never gaining it’s feet again...the cattle scales topped it 1800 plus lbs....it’s the biggest critter I ever took with this round....but it shows what the 375 and the right reloads can do. That load gives just over 3000 lbs of muzzle energy.

I wrote the above words over a year and a half ago...I still have not changed my mind...with the right reloading to the pressure the .375 Win BB was designed for, with the right bullets and powders....this is a very powerful 20 inch barreled rifle. I have two of them. This one we just spoke of is an original Winchester before USRAC. The second one is also a top eject and it is a USRAC....I decided to se if I could put the little gun into the power range of the old cordite 375 H&H ammo I used in Africa in the late 1950s. Don’t go looking in your reloading manuals for 375 H&H velocities....I am speaking of cordite powder loads that were loaded down for hot African hunting....I have little knowledge of the velocities of that ammo...but I do know the English loads gave 2500+ fps with the 300 solids and a might more with the soft noses....giving 4160 ft. lbs of muzzle punch. Very respectable. And I took everything except Rhino with it.

A resounding NO! I call it lazy ballistics study. Hearing some idiot that doesn’t do his homework, and then they start repeating what he thinks without checking is lazy ballistics.

First because it takes more powder...your powder is going to burn longer, holding the top pressure longer, giving the bullet MORE velocity. Second, usually a change to a slightly slower powder in an improved case does even better than the standard powder for that case. Take for example the use of 3031 in the 30-30...the improved cases work so much better with a jump to the slower H335. At the same pressure the H335 gives 100 fps more in the standard case between 3031 and H335...in the Imp case your going to get 150 fps (still at 37000+ cup) more, with the 150 grain bullet. Standard case with H335 will give 2400 plus fps....the good Imp case will give 2550 fps....is it worth four to five more grains and the initial trouble of fire forming, buying new sizing dies, and rechambering???? For me it is well worth it.

So when I thought about improving the velocities of the 375BB in the W94BB leveraction I had to do a little research. I needed a case that was bigger in the body than the .410 base size of the .375 BB....but yet I couldn’t go much over the length of the 38-55 case length which is 2.085. I really thought about buying a 444 Winchester BB, a .375BB Win barrel, and chambering it for a 35 Remington Mag Imp. case necked up to .375 and have the cycling work done by a pro. That would obstensively give me a 375 Whelen Improved ballistics in a mod.94 BB Win Levergun. The velocity and power would be incredible. It would easily reach the old H&H ballistics. And I am still thinking about it...but it is going to be above my budget for awhile.

I thought about the .356 Win case...a rimmed 358 Winchester for the BB leveraction....but I wondered if it would be enough. Necking the 444 case down to .375 had some appeal...it’s a sixty-six water grain case. But that also would be some cycle work. I got a hold of a friend that is a math whizz. We sectioned a 358 case. He measured and fiddled, and figured and played, and said with the right length neck and blown out shoulder it would increase internal capacity and jump from 49 grains of water weight to 57+ grains of water weight. The 375 Win case is a 46 grain water weight holder. What would that come out to in powder? So I tried a standard 358 case in my 375BB...it would take minimal work for cycling....even I could do it.

I took one of my 35 Whelen ultra Imp cases (all these measurements are on fired cases.) And using STP oil, necked that dude to hold a .375 slug and back to 2.015 in length. It held 56+ grains of water. I redesigned my design for the 358 case...I opened the shoulder to .465 from .454....I pushed the shoulder forward shortening the neck length from .388 to .350, and gave the shoulder a sharp 40 degrees...I didn’t know what the final case fired in the new chamber would hold. Turned out to be 58 grains of water....remember that’s water not powder.

Top powder amount load in the .375 BB was 44 gr. with WW748 and a 200 grain jacketed bullet. Top load of WW748 under a 200 grain bullet in the .356BB is 50 grains...2000 fps for the .375BB load, and 2300+ fps for the 356BB load. Respectable jump.....my new case held 53.5 grains of 748 for a top load under a the 200 gr.375 bullet and gave over 2474 fps in a 20 inch barrel. A 474 fps jump over the .375BB. Just under my 358 Win Ruger bolt gun which gives over 2600 fps with the same weight .358 slug and 748. Was it worth it???? For me it was. Now the serious reloading and discovery begins...I’ll get back to you all......

p.s. A little work on the extractor and you can use 358 brass in the rechambered .375BB..