Wildcatting the .356 Winchester Case


Staff member
Wildcatting the .356 Winchester Case

Back in 1993, I called my friend JD Jones at SSK Industries to discuss the possibility of doing a wildcat cartridge. I was interested in doing a .338 wildcat, specifically tailored for a 12” Contender. .338 because of the (then) new 200 grain Ballistic Tip, and the 200 Speer and 200 Hornady FP, all of which had reputations for expanding well at Contender velocities. The 200 Hornady SP and 250 Nosler Partition were also of interest, but were more of an unknown to me (at the time). I had decided on using the .356 Winchester case through a fairly simple process – JD had already designed the .338 Woodswalker (based on the smaller 8.15x46R case) for optimum performance from a 10” Contender, and the .338 JDJ wildcat (based on the .444 Marlin case) for maximum performance from a 14” Contender, so I selected the .356 Winchester case because it was a strong, rimmed case, with a case capacity intermediate between these two. I figured that JD knew more about wildcatting the Contender than just about anybody else, and if his two .338 wildcats worked well in their respective barrel lengths, that a .338 based on the .356 Winchester case should be right at home in a 12” Contender. I asked him for guidance on twist rate and throating. His response was simple and direct – 1 in 10” twist was standard in .338, no need to change that, and as far as throat went he asked me what was the heaviest bullet I intended to use? I told him the 250 Partition, but that I would like to play around with the 275 Speer semi-spitzer just for giggles, but that I wasn’t sure if I could push it fast enough to make it expand. He said probably not, and that he recommended cutting the throat such that the 250 Partition could be seated even with the base of the neck. I agreed that that sounded sensible, thanked him for his guidance, and placed the order.

.338 GEF in 12" Contender

I knew from the outset that for a cartridge the diameter of the .30-06/.308 family of cartridges that pressures needed to be limited to no more than about 40,000 psi peak pressure or it would produce too much back-thrust for the Contender frame. The problem is, I wasn’t really sure how I was going to go about doing that. I had a good understanding of the theory, but kind of a shaky grasp on the practice. Fortunately, I had a telephone, and wasn’t afraid to call JD. Load development began and was proceeding fairly smoothly. I called JD with a couple of questions, and to ask him if he thought I could push things a little bit harder, say another 100 fps or so. I got a stern and unequivocal “No!” from him. We reviewed my Powley Computer calculations, and he agreed that 40,000 psi peak pressure was a sensible limit for the .338 GEF (the name I had given to the .338/.356 wildcat). And then he gave me a very simple, and very useful piece of advice that made the rest of load development straightforward and easy. He told me that both the .308 and .358 Winchester cartridges had extensive pressure tested handloading data available (I knew that), and he told me to review that data, specifically looking at heavy for caliber bullet weights (i.e. 180s for the .308 and 250s for the .358), and to look for powders that were volume (not pressure) limited, where a lightly compressed load produced pressures at or below my chosen pressure ceiling. In this case, 4350 fit that role perfectly. JD then told me to work up loads with 4350 using my preferred 200 grain bullet (in this case the Nosler BT), working up to a lightly compressed load, and to monitor velocity and case expansion as I worked up. Cross reference this velocity with the results from the Powley Computer to make sure nothing weird is going on, then use this velocity and case expansion as a ceiling as I worked up loads with other powders. This method worked superbly, and I was able to safely push 200s at 2100 fps, 225s at 2000 fps, and 250s at 1900 fps, with sub-MOA accuracy. Slow powders (e.g. H380, 4350, etc.) tend to work the best. I am happy to report that 25+ years down the road, I have had zero problems with .338 GEF Contender. I have used the .338 GEF to take pronghorn antelope, white-tailed deer, mule deer, feral hogs, a Corsican ram, and a variety of varmints. JD has taught me many things over the years (not just on this project), and I will be forever grateful for his guidance. Good teachers are a blessing indeed.

Just for the record, my favorite jacketed bullet load for the .338 GEF Contender is the 200 grain Nosler Ballistic Tip, loaded over 48.0 grains of H380 for excellent accuracy and 2100 fps. They have always expanded beautifully for me, and I have never recovered one. The 200 grain Hornady SP is a bit harder, and shoots through 350 lb hogs with ease, and I even ran one lengthwise, on the diagonal (i.e. entered left shoulder, exited right hip), on a large mule deer doe. Penetration to spare!

Given my interest in cast bullets, it was only a matter of time before I felt the urge to work up some cast bullet loads in the .338 GEF, and then hunt with them. I quickly learned that cast bullets sized .340” shot better than those sized .338”, and that the 1 in 10” twist of the barrel limited good cast bullet accuracy to about 1700 fps. Once again, slow powders seem to work the best (in this case 4350 and 4831), and accuracy with select loads runs under 2 MOA. I designed a 235 grain GC-FP using Mountain Molds online design spreadsheet, and Dan made me a beautiful bullet mould. It shoots very well (5 shots into less than 1” at 50 yards) with 44.5 grains of 4350 for 1700 fps. I used this bullet to take a 325 lb boar feral hog several years ago. Unfortunately, I had cast these bullets from a fairly hard alloy, so the first shot (a raking shot, base of the left side ribs, up to the right shoulder) didn’t expand at all. This shot would have ultimately proven fatal, but the boar was still on his feet, and making an escape through the nearby creek. I snapped off a second shot as the boar started up the far side creek bank. Wood shards flew everywhere, the boar collapsed, and then slid backwards back down into the creek. Turns out there was a low-hanging dead tree branch that my shot hit and the bullet started to tumble, then hit the boar in the middle of the ribs, entering sideways, and became a tumbling buzzsaw through the lungs and liver. I think this bullet has significant potential, but it needs to be cast softer (BHN of 10 or 11) instead of how hard I was shooting them (BHN about 16), especially given that in this cartridge/gun it is limited to 1700 fps.

338 GEF with Ideal 338320 HP.jpg
.338 GEF with cast bullets (338320 HP)

I had much better results using a 246 grain Lyman 33889 HP in the .338 GEF. In this case, I got best accuracy using 46.5 grains of H4831 for right at 1600 fps (which is about as fast as I like to push cast HPs). Once again, 5-shot groups at 50 yards were just under an inch. In this case, expansion was found to be excellent. This combination has been used to take a 250 lb feral boar, a large mule deer doe, and a nice Corsican ram. In each case, expansion was positive, the 33889 HP exited, and the animal was dropped quickly and humanely. Not a long range proposition, but all of these shots came at 50 yards or less (I would be comfortable taking shots out to 100-125 yards with this load).

I was describing this project to my shooting buddy Dave, and he listened politely and then asked, “Why did you neck it down?” I explained about the desire to use soft .338 bullets (NBT, Hornady FP, Speer SP, etc.), and he looked at me with a quizzical expression and said, “What? They don’t make any soft .35 caliber jacketed bullets?” Well, yeah….. and then we talked about the 180 grain Hornady SSP bullet, the 180 grain Speer FP, the various 200 grain RNs, etc. Then he asked, “What twist did they use in the .35 Remington?” And I said that historically the .35 Remington had been fitted with 1 in 16” twist barrels, but that I thought that T/C had used 1 in 14” for their .35 Remington barrels (which turned out to be correct). So then he asked me, “Wouldn’t that be more cast bullet friendly than the 1 in 10” twist you used in your .338?”

Sigh…..he’s right, you know.

So now Dave got all worked up, and started asking me a bunch of questions about pressures, and factory ammo, and chamber dimensions, etc. When we left things, he was going to push the shoulder back about .020” to keep .356 Winchester factory ammo from fully chambering, since it was loaded to higher pressures than a Contender should be asked to digest. He told me he was going to go do some homework, but he thought this .35 caliber project had some merit.

That was the last I heard about it. About a year later Dave died. Turns out he had indeed done his homework, and more. He had bought a chambering reamer that had .002” to .003” clearances, and used it to chamber a 14” stainless T/C Hunter barrel. He had stamped the barrel “.356 TCE” (for Thompson-Center-Ewer, following the lead of Wes Ugalde and the TCU cartridges). He had bought a set of .356 Winchester reloading dies, and ground off the bottom little bit of the sizer die (I assumed he had done this so he could use the factory dies to push the shoulder back). He had mounted a T/C scope on the barrel using his very cleverly designed rings that required no base to attach to the barrel, resulting in the scope being notably lower and farther forward, and leaving the hammer spur unencumbered and easily accessible. And he had laid in quite a supply of .356 Winchester brass, and the Hornady 180 grain SSP bullet. I found his field notes and preliminary load data, and found that he had done a fair amount of work with the 180 grain and 200 grain jacketed bullets. I found his fired cases and quickly discovered that he had tossed the idea of pushing the shoulder back, and had cut the full .356 Winchester chamber (just with tighter tolerances than they used on the leverguns). I don’t know what his thought process was for making this decision, but I was pleased because it meant that the pressure tested loading data for the .356 Winchester was now directly pertinent to this chamber.

Remembering what JD had taught me years ago, I sat down and reviewed the pressure tested loading data, except that this time there was no need to bracket with larger and smaller calibers, I could use data for this exact cartridge. I could have just started with 4350 and started from Ground Zero (like I did with the .338 GEF), but this time, I had previous experience to work with -- I knew that from a 12” barrel, the .338 was safe with 200 grain jacketed bullets at 2100 fps and 250s at 1900 fps. In moving from the .338 to the .356 cartridge, the expansion ratio would be more favorable, the shift from jacketed bullets in the .338 to cast in the .356 would lower pressures, as would the slower rifling twist (1 in 14” vs. 1 in 10”). Plus, the 14” Hunter barrel is in reality a 13” barrel plus a muzzle brake (as opposed to the 12” MNP barrel used in the .338). All of these factors support the conclusion that 200 grain cast bullets should be safe at 2100 fps, and 250 grain cast bullets should be safe at 1900+ fps in the .356 TCE Contender (with suitable choice of powder, of course). Also based on prior experience with a variety of cartridges (both wildcat and factory), I knew that both Re 15 and Acc. Arms 2520 are very well suited for loads such as these, so that’s where I started. After working up loads at temperatures ranging from pleasantly cool, to downright hot, my bottom-line is simple -- for this particular cartridge in the Contender platform, shooting cast bullets, my preferred powder choice is Re 15.

200 cast (Lee GC-FP) – 47.0 grains Re 15 for 2100 fps

245 cast (SAECO GC-FP) – 44.0 grains Re 15 for 1930 fps

180 Hornady SSP – 48.0 grains Re 15 for 2150 fps

For 2520 in the .356 TCE, reduce these maximum loads 2.0 grains.

356 TCE and 200 Lee and 245 Saeco.jpg
.356 TCE with 200 grain Lee and 245 grain SAECO cast bullet.

Several years ago, I sent a single cavity Ideal 358318 off to my friend Erik Ohlen and had him convert it to drop HPs. At the same time, I also had him make a second HP pin so that I could make cup point bullets from that mould. The cup point bullets drop from the mould blocks at 242 grains (BHN of 11-12), and checked/lubed they run about 250 grains. ~1900 fps is faster than I generally want to push a cast HP (for anything that I want to eat, anyway), but a 250 grain .35 caliber cup point should hit like the hammer of Thor at that speed.

356 TCE and cast bullets.jpg
.356 TCE loaded with the (l-r) 200 grain Lee GCFP, Ideal 358318 HP, and the 358318 Cup Point (the last two from a mould modified by Erik Ohlen).

The 200 cast will be my general purpose load for the .356 TCE, and the 245/250 load will be for larger animals, and/or shorter ranges (e.g. black timber elk load). Previous experience with the Hornady 180 SSP has shown it to be an excellent deer bullet at this velocity (as is the Speer 180 FP).

1 in 14” twist is fast enough to push longer heavier bullets accurately, should I choose to do so. I have moulds for both the 286 grain Lyman 358009 and the 280 grain Lyman 358009 HP, as well as the 275 grain NEI GC-FP. From the .338 GEF, I learned that I could push the Speer 275 grain semi-spitzer 1600-1700 fps, so I suspect that I can get similar velocities with these bullets (which coincidentally is about as fast as I like to push cast HPs, anyway). Sounds like this project just grew a new phase to keep me busy this winter…

At this point, the .338 GEF is going to be relegated to use with jacketed bullets (primarily the 200 NBT), and the .356 TCE is going to be used primarily with cast bullets (and occasionally with the Hornady 180 SSP).

Using cases that were designed for routine operation at 52,000 psi, and keeping pressures under 40,000 psi, and shooting them in a chamber that has .002” to .003” clearances, I expect this brass is going to last forever (which is a good thing because .356 Winchester brass isn’t terribly common today).

Wildcatting is fun!
Last edited: