358 Razorback

[lar45]

Hi everybody. Sorry, I got a little long winded here.

So there I was... Sitting in my deer stand watching all the button bucks walk by, wishing something shootable would show up... And I thought to myself, self I need a new gun for shooting Hogs. Well, not like I really "need" a new gun, but a guy Needs to have a project every now and then to keep the creative juices flowing and all. Right?
Anyway I had thought about the 358 Yeti, but it uses a cu$tom reamer, cu$tom dies, and an unobtainium cu$tom bolt and extension for the AR15 platform. So I thought about using a stock reamer and dies for the 358 Winchester and just running it in far enough for a max length case and still be able to use 180-200gn bullets. I'm not interested in shooting subsonic with super heavy bullets, so make the case as long as possible for max case capacity and still fit in an AR 15 magazine.
So I pull out my phone and start ordering supplies. Midway had Hornady 200gn FTX and Interlock, but the Speer 180 FN was no where to be found. I also ordered some Lee 358 Win dies, plus an extra 358 Win sizer die. A few days later Midway got in some Speer 358-180FN, but they had a limit of 2 every 14 days, so I clicked buy it now before they all disappeared. About an hour later I thought I'd try to place a second order, but they were sold out.
So a couple weeks later I get home from Deer camp and start mocking up cases. I chopped off a 308 case lubed with Imperial wax and stuffed it up into a 358 sizing die with the expander/decapping stem removed. I used the shell holder extension from a Lee bullet sizing set to run the whole case up into the die. Then I used a 5/16" punch and a small hammer to tap the case back out. I measured the noses of the bullets and the inside of an AR15 magazine. The metal 450 Bushmaster mags measure 2.300" inside, so I set my COAL to 2.290", did some math and came up with a max case length of 1.660". I ran the case through the trimmer, deburred and tried to seat a bullet. I could only screw the seater stem down so far so the bullets were about half seated. I pulled out the grinder with a cutoff wheel and chopped about 3/8" off the bottom of the sizer and seater dies, then cleaned them up on the buffer wheel. Now I could seat the bullets.



The cast bullets are the Lee 200 and my Fat35(265gn)

I stuffed them into some magazines and it looks like they will work.
A quick measurement with the calipers showed the necks were way too fat. So I ordered a 35 cal pilot for the Hornady neck turner. A couple days later Midway delivers again. I turned the necks for a thickness of .015" and they looked great.
I contacted a few AR barrel makers and found Deadshot Barrels in Oregon that said they would make me a barrel if I could supply them with a case and bolt to headspace on. Back to Midway for a 450 Bushmaster bolt...
I shipped them a couple of cases and the bolt on Dec 20th, they said 5-10 weeks lead time, so now I'm waiting...
While I was waiting I searched PSA and saw they had a special run of Boar Hunter 15 lowers in stock, so I had to have one of those...




Now the lower is all put together.


With a little help from you guys, it looks like Winchester and Hornady have the most case capacity in 308 Winchester. So I ordered some of those to compare with LC and RP brass.
My formed cases hold 45.8gns of H20. So now it time to setup a new cartridge in Quickload...
It looks like RL-7 is going to be the powder with a max pressure of 47kpsi. (I looked at bolt thrust numbers from several existing cartridges, It looks like most are running around 8000 lbs, so divide by the area of a .470" case head and you get a little over 46kpsi. I ordered the 9310 bolt which is supposed to be 7% stronger, which comes out to a little over 49k, so I'll try 47k and see what happens.)
I should be able to get 2340fps with the 180 Speer and 2150 with the 200gn Hornady's, from an 18.5" barrel.
If I can compress RL-10X, I might be able to do 2400 and 2180.

Look what Mrs. Claus wrapped up for me this year.

a Sightmark digital IR Scope for shooting Hogs at night!

2 weeks have passed so I was able to order another 2 boxes of Speer 180s.

So what haven't I thought about?

[Texas by God]

Sending it to me?


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[dverna]

A very interesting project!!! I like calibers that can be made from readily available cases. I have thought about a .35 cal in one of the AR's to shoot cast rifle bullets and could not justify the cost. But we don't have hogs here...yet.

Are two jacketed bullets different and that is why they are seated differently?

[lar45]

The 180 Speer and 200 Hornady are the jacketed rounds. the 180 Speer has a slightly shorter nose.

[Fitz]

Is the 450 bushmaster and a 308 have the same size head ?

[lar45]

Is the 450 bushmaster and a 308 have the same size head ?

Yes, .473"
The 450 Bushmaster was based on cut down 284 Win cases.

[lar45]

I almost forgot,
Anderson Arms Big Bore Upper


Odin Works R2 M-LOK Handguard


Aero Precision Low Profile Adjustable Gas Block

[sukivel]

I have been wanting to shorten a .308 case and rebore it in .358 for an AR for a while now! Lots of ideas other guys have done, and I do like yours.

I’ll be watching this one!


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[Tripplebeards]

Sweet! An ar with close to 35 Rem velocities! Looks fun!

[wolfwing]

Nice project!!
I hit the easy button and went the 358 Yeti route. I haven't milled my lower yet, so it is not together. 6.5x47 Lapua brass is the deluxe way of making brass, but 6 GT is cheaper. I went the GT route.

[lar45]

The Yeti is definitely the better way to go. You can run much higher pressures and get higher velocities as well. I'm just a little late to the party.

[lar45]

I got the dust cover Lazer etched.

[lar45]

Got an email from Deadshot Barrels, my barrel is finished and shipping today.

[376Steyr]

May I suggest you look at Hodgdon BLK CFE as a powder choice? I love Reloder 7, but it has been almost impossible to find recently.

[405grain]

lar45: i think that your bolt thrust calculations may be in error. To start with, the surface area that is used in calculating bolt thrust is the inside of the base of the cartridge case (the area where the gas pressure is acting against), not the head of the case. For seeing how to properly calculate bolt thrust see this webpage: https://riflebarrels.com/a-look-at-bolt-lug-strength/

The inside diameter of a 308 based cartridge case is .385" (not .470"). Using the formula: area (pi x radius squared) times psi = bolt thrust, we would get 3.1416 X .1925 squared [.037056], multiplied by 47,000 psi = 5471 lbs of bolt thrust. Please double check my math as this is just some calculation from a random dude off the internet, but I think that you've got your calculation off by over 2500 lbs.

[lar45]

Okay, so if we go off of the inside of the case for bolt thrust numbers.
The 450 Bushmaster uses a .452" bullet and runs at 38.5kpsi = 6178 pounds of thrust
The .308 cases inside measurement of .385", run the math gives 53,068psi for the same bolt thrust.
I wish I had some Socom cases to cut and measure for comparison.

[lar45]

I made a case trimming jig to hold and cut off my 308 cases.
It's a straight rip off of the Squirrel Daddy 300BO jig, just scaled up to hold the 308 instead of a 223.
I did most of the exterior shaping with the best sander, so it needs cleaned up a little, but it works.

[lar45]

Well the rifle is done. Now I'm on to load development...



It shows some promise.
This is the 200FTX with the tip pulled off, loaded with 1680, almost 2350fps

[Texas by God]

What brand of bolt are you using for the .473” case head?


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[lar45]

I've been working on load work ups, RL10X kind of petered out, so I switched to 1680 and it woke right up.
I pulled the tips off of the 200ftx so I could get them closer to the lands.
Top load with 1680 yielded 2391fps. And a group around 1.25"
The Speer 358 180 went 2571fps, but the groups weren't as good.
I think I might try CFE-BLK next.

I'll have to check my receipts for where the bolt came from. I think it was from Midway, don't remember the brand. I know it's made of 9310 vs Carpenter.