.458 WSM wildcat

[Hamburger Monster]

Little story on my .458 WSM wildcat build. It's was completed over 5 years ago so some of the details may be a little fuzzy

Ordered a custom barrel from McGowen. also acquired about 30 pieces of 300 WSM brass to play around with. Reloading and sizing dies made by Hornady. Had to fire form a few cases of brass and send it over so they can make the custom dies. Would have been nice if McGowan could have just sent me the chamber or reamer specs but they declined the request

for comparison. the .308/7.62x51 has about double the powder volume over the .223/5.56x45. the WSM cartridge has about 50% more powder then the .308/7.62.

after running some simulations on GRT between a few dozen cartridges and bullet weights it looks like a can get the best velocity vs energy from the 458 WSM over the other option

 

[Hamburger Monster]

in continuing this project I started modding the LR308 upper for a left side charging handle. it's a slick side so no forward assist. this could take it's place if needed. I also plan of capping the original charging handle hole in the back.

all done by hand with a lot of filing. drilling and tapping the bolt carrier wasn't too hard. lots of cutting oil and sharp bits and it went right through. one tap didn't want to cut the threads but a second one I found worked great.

 

[Hamburger Monster]

Some information on the build: Raw upper and lower that I anodized at home. barrel is mcgowen. custom chambered in 458 WSM. 16" with muzzle attachment. I don't plan on keeping that stock but it's what I have so until I get a replacement it will have to do. KAK bolt and carrier. haven't weighed it yet but it doesn't seem to be real heavy so it will likely kick hard. Currently set up as a single shot. Having trouble with the magazines not holding the rounds and can't get it to strip them out properly without the whole magazine unloading every round

 

[Hamburger Monster]

Here are the powders that the simulation says I can use. listed from best to worst

1. Accurate LT-30
2. Accurate 2230 / Ramshot X-Terminator (same stuff)
3. Accurate 2460
4. Hodgdon CFE-BLK

lower velocity but still safe pressure

5. H4198
6. IMR4227
7. H322
8. H4895
9. IMR4198
10. H335

Hodgdon 4895 is an interesting one as the pressure is only about 50k but still produces about 2000 ft/s. that's about 200 ft/s less then the top listings. but because of its 10k psi less pressure it may be a good one to fire form with along with practicing load development. a 105% compressed load just barely gets into the velocity of the top contenders but still at only 55k psi. almost fool proof

and, while LT-30 looks like it produces the best velocity, the confidence of the simulation is low due to the lack of real world pressure data tests on this powder. info is mostly just from the manufacturer's data with little to back it up.

Accurate 2230 has a lot of user data to back up the manufacturer charts. CFE-BLK is also one of these.

Accurate 2230 is the powder I ended up getting and using in the end

 

[Hamburger Monster]

Before I was able to get the dies. And to be able to fire form the brass, I made a homemade expanding button and used my vise to press it into a few cases and enlarge the necks. worked out pretty good. close enough to barely fit the chamber. now just load them up and fire form

photo: far left is 223/5.56, next one is your typical .308 and next right is an unaltered 300 WSM which I used to make all the other you see. plopped one of the 350 grain bullets into one to show you how big they are compared to the others

 

[Hamburger Monster]

went out to the national forest to shoot it and put a few down range. kicks like an angry mule. I'd say it feels like a 1.25 Oz. high brass 3.5" 12 gauge shotgun slugs. I shot the first few in my homemade rifle rest with a string so I could stand back. once I knew it was safe and didn't blow up the gun I shouldered at the bench. put about 12 more through the barrel.

Started with 60 grains. Worked up to 67.5 and zero signs of excessive pressure. Still have room to get it up to about 73 with a little compression if I wanted

took a few to find the steel target. once I was hitting it it was punching 3/4" holes in the 1/4" steel plate

I sent out some of these out for the fire formed brass to have some resizing dies made

I don't have a chronograph. Need to invest in one. But the simulation says these 350 grain bullets should be around 2400 fps at max powder load of 73 grains

 

[Hamburger Monster]

calculations show north of 4600 ft/lbs if loaded to max.

 

[Hamburger Monster]

Custom dies

 

[Hamburger Monster]

Swapped out the temporary stock for a PRS light and adjusted the scope to match the new length and get better eye relief

 

[Hamburger Monster]

Because the issue with not finding a magazine that works with WSM cartages, tried steel, Magpul and lancer and all won't feed and or dump all the rounds out with just a little bump, I pretty much gave up on it. I'm thinking about moving over to a bolt action with a custom barrel and just do single shot. I could also go with a longer barrel for even more velocity. Maybe 18 or 20 inch. See if I can get up to 2800 fps with 350 grain bullets.

But for now it's on the back burner because the price of powder. Primers are scarce and the brass seems almost non existent.

 

[Hamburger Monster]

Very short video of firing it

 

[AR15barrels]

Magazines are always the limiting factor when wildcatting in the AR platform.
When I made a few wildcats, the first thing I always did was test feeding of dummy cartridges.
If they could not be made to feed reliably, I passed on making dedicated chamber reamers and dies.
Feed testing can be done with a chamber in a barrel thats not to perfect dimensions as you are not actually firing the cases to test the cartridges getting out of the magazine and up into the chamber.

 

[Darqhelmet]

Very short video of firing it

Well that looked aggressive. haha