.358 Yeti For Cast AR 15 ?

[Wolfdog91]

So have been kicking around the idea of building a cast specific ar upper ( yeah I know not like I have enough pokers in the fire lol !) in something......off the wall .... A little on the weird side,but not too crazy. And in an AR configuration so I don't need ,well you know a lathe and all sorts of other gunsmithing tools. Well after I finally build a good 5.56 upper lol, anyway Mad Dog Weapons Systems has this deal called the .358 Yeti and along with the cool name ( gotta have the cool name am I right ? ) ,The parent cases are pretty easy to find it ,theirs a TON of various .358 dia molds it seems. Heck noe show 600+ options for .358 molds. Heres a quote and some screenshots from their website.

Some of you may know about this one, but for those that don't here's some info!

358 Yeti
The .358 Yeti is a mid-bore wildcat being developed for the AR-15 platform with the balance of speed and power in mind. It is based off plentiful 7.62x51 NATO brass shortened to 1.646" and resized to accommodate a .358 diameter projectile. The choice to use NATO brass for the parent case is because it has the thickest case wall, meaning that any other brass with the .473" head will be useable (i.e. .308, .243, 7mm-08, 6.5CM, etc). This gives the end user many sources for very affordable (and sometimes free) brass. The chamber has been designed with brass making in mind meaning there is no neck turning or reaming necessary. Simply chop the brass at the neck/ shoulder junction, run through a sizing die, final trim, and chamfer/ debur –much like the 277 Wolverine. Formed cases will hold 45-47g of h2o with a slight increase of capacity being gained once fired, but this round not one to be classified as “requiring fire-forming.”

The performance goals for this cartridge are to get a 180g projectile up to 2600fps from a 16"-18" barrel and a 200g to 2500fps. At those anticipated velocities, the 358 Yeti will generate more energy than the following calibers: 6.8 SPC, 300 Blackout, 450 Bushmaster, 458 SOCOM, 50 Beowulf, 35 Remington, and 6.5 Grendel (*up to 375 yards).


Useable projectiles are in the 180g-225g range with the option of lighter projectiles such as those for 38/357 and 9mm as well for inexpensive rounds for plinking. The 358 Yeti is designed to have optimal performance with projectiles in the 180-200g range such as the Speer Hotcor, Hornady interlock, and Hornady FTX. Some Barnes and Nosler offerings are also possible with the removal of the polymer ballistic tips. Additionally, 250g+ projectiles will be tested for subsonic performance.

A newly designed, strengthened bolt by Maxim Firearms will be utilized with a matching oversized extension. The bolt being used was initially designed for the 30 RAR at SAAMI pressures of 55,000 psi. This bolt will be machined with the smaller .473 bolt face as opposed to the .492 bolt face of the 30RAR, resulting in more material on the bolt, yielding slightly more strength. Loads will be pressure tested via pressure trace to ensure we are staying at or below 60k psi.



Latest progress:
Earlier this week I received the die that I had modified for forming 358 Yeti brass from my gunsmith. Now that I am able to form brass to the proper dimensions, I am able to get the last few measurements needed to complete the reamer print. Once those measurements are determined, I will send out for the reamer and gauges. When the reamers are delivered, I will then have the first 358 Yeti barrel chambered for my Savage. That's when the real fun begins!

Welcome to the beginning, fellas! Feel free to share ideas, ask questions, or just tag along for the ride. This is going to be fun!




Idk seems like something cool to play with. Is there suff that will do what it does already? I mean yeah probably but come on, .358 Yeti , if that doesn't scream crazy gun but / reloader I don't know what does lol ! Anyhow anyone mess with something like this ?

Sent from my motorola one 5G UW using Tapatalk

[BK7saum]

Having been loading the 358 winchester a little, I think the 358 Yeti ballistics may be very optimistic.

Hodgdon only gives 2500-2600 fps for the 358 winchester with a 180 and that is from a 26" barrel. The 200s are running 2464 to around 2600, again from a longer barrel.

Please post what your velocities are when you get up and running. I would really expect Yeti velocities to be about 200 fps below what they advertise, based upon reduced case capacity. Good luck. i have entertained building a Yeti in the AR15 and having a lightweight thumper. I currently have a 300 hamr in the 11.3" shorty and am liking it. But bigger would be better.

[44Blam]

I'm just sayin'... I'm shooting a 174 grain Hornady ELD projectile in 308 pretty much maxed out at about 2450 fps. I do question the performance goals for the cartridge...

[Fitz]

Give that Yeti a try with cast and you will be hooked, AR-15 or the pre-fit savage barrel both perform great , just think what the 308x 1 1/2 done with the 308 thats what the 358 yeti does with the 358 win.

[megasupermagnum]

I'm shooting a 308 with 180gr bullet at 2550 fps in a 22" barrel, and that's not even a max load. You can get closer to 2650 fps with powders like RE17, but I don't think those kinds of loads are great for a semi auto. In my 18" barrel M1A similar loads are about 100 fps slower. So you are really topped out about 2500 fps with a 180 gr. I doubt your 358 Yetti will beat that.

My opinion is you are wasting your time. Just get an AR10 in 358 winchester.

[Fitz]

I'm shooting a 308 with 180gr bullet at 2550 fps in a 22" barrel, and that's not even a max load. You can get closer to 2650 fps with powders like RE17, but I don't think those kinds of loads are great for a semi auto.

My opinion is you are wasting your time. Just get an AR10 in 358 winchester.

are we talking cast bullets or jacketed

[megasupermagnum]

are we talking cast bullets or jacketed

Does it matter? I don't think he is going to get 2600 fps with a 180gr in a sub 18" barrel in the 358 Yeti. A 358 Winchester at least stands a chance. Accuracy at that level is another discussion. Hopefully he can source a 1:16 twist barrel.

[Fitz]

if it isn't cast it ain't squat , remember this is a CAST BOOLIT group , what everyone can do with a 308 is child's play it what can you do with a cast boolit that will impress the people here.

[P Flados]

I briefly considered the Yeti before I settled on the 357AR Max.

Any AR-15 set up to run rounds based on the 308 is pushing the platform. Special high strength bolts are required. The folks that play the wildcat game at Mad Dog also seem to be willing to push their stuff pretty hard.

The Yeti as a cast boolit gun is probably "overkill' if run hard, but I would say it is worth considering if run on the easy side. If you go for performance about the same as or a little more than 350L (closer to the new 360BM), pressures will be well below max and performance should be "good enough".

I have no idea if there is any extra effort needed for getting magazines to work well with the Yeti rounds. However, the bottle neck round makes the chamber entry larger than the 350L which should help with feeding. The bottleneck round also and makes it a lot easier to maintain good headspace. Getting brass for conversion should be easy.

Cost for the "custom grade" barrel and the reloading dies will be steep, but you should get top quality. Again, you will pay extra for the special bolt.

This one is pretty close to a 35 Rem "tweaked" to fit the AR-15 platform. Less case capacity, but higher allowed pressure to make up for it.

[Fitz]

I briefly considered the Yeti before I settled on the 357AR Max.

Any AR-15 set up to run rounds based on the 308 is pushing the platform. Special high strength bolts are required. The folks that play the wildcat game at Mad Dog also seem to be willing to push their stuff pretty hard.

The Yeti as a cast boolit gun is probably "overkill' if run hard, but I would say it is worth considering if run on the easy side. If you go for performance about the same as or a little more than 350L (closer to the new 360BM), pressures will be well below max and performance should be "good enough".

I have no idea if there is any extra effort needed for getting magazines to work well with the Yeti rounds. However, the bottle neck round makes the chamber entry larger than the 350L which should help with feeding. The bottleneck round also and makes it a lot easier to maintain good headspace. Getting brass for conversion should be easy.

Cost for the "custom grade" barrel and the reloading dies will be steep, but you should get top quality. Again, you will pay extra for the special bolt.

This one is pretty close to a 35 Rem "tweaked" to fit the AR-15 platform. Less case capacity, but higher allowed pressure to make up for it.

The AR-15 barrel comes with a special bolt designed to handle the pressure of 60,000 psi , but when you take it to that level your primer pockets don't last but a couple of firings .And running CFE-BLK or shooter world Blackout on a full case you do get some good velocity but as you said things are working hard , Now as a cast bullet gun running for accuracy the AR-15 has no trouble pushing a 250 gr. bullet at 1600 fps and has the knock down power you need for tough critters , and the Savage bolt gun I had Bruce at Mad dog add some extra throat for shooting a 280 to a 310 gr. paper patched bullet at around 1600 fps and so far every thing from deer ,Hogs and even a 500 lb Red stag have not made it farther than 30 yards and most drop in their tracks.

[lar45]

The 358 Yeti sounds like a great idea. Should be an absolute hammer on Hogs.
Like was mentioned, I would definitely check to see what barrel twist rates are available if you are going to be running cast.
Most AR-10 platforms are very HEAVY compared to the AR-15. That's the biggest reason that I have stuck with the AR-15s. I just don't want to pack a 10# gun around.

[Fitz]

The 358 Yeti sounds like a great idea. Should be an absolute hammer on Hogs.
Like was mentioned, I would definitely check to see what barrel twist rates are available if you are going to be running cast.
Most AR-10 platforms are very HEAVY compared to the AR-15. That's the biggest reason that I have stuck with the AR-15s. I just don't want to pack a 10# gun around.

r

both my yetis are 1-14 twist the AR-15 is a 18in. and the savage is a 16 in.

[milsurpcollector1970]

What are you using for a magazine? Many of those wildcats are cool but for me getting them to run through a magazine was the problem.

[Fitz]

What are you using for a magazine? Many of those wildcats are cool but for me getting them to run through a magazine was the problem.

450 bushmaster works with just bending the feed lips slightly , just e.nough to hold the rounds in place

[Tonto]

I was traveling down the Yeti path. Even got dies and formed a bunch of brass. Just couldn’t go $400 for a barrel and bolt given what complete uppers were/still are selling for. I got a 350 Legend and am quite happy. I’d gladly shed the dies, formed and finished brass. I still have the 375 itch though.

[RJM52]

Sounds interesting if one wants a .358 running on an AR15 platform...

To me, .35s are big game hunting rifles. When rifle hunting, have been using .350s almost exclusively since 1990... .350 Rem. Mag., .358 Winchester and .35 Remington...

One of the guns is a Ruger Frontier in .358 with a 16.5" barrel... With the 220 Speer velocity is around 2300 fps...one is REALY going to have to push hard to get 2600 from a 16.5"...

And bullet expansion, forget it on deer or lighter... .35s are really tough. I've gone to the MP220 cast HP for the .358...no longer have a .35 Rem...

Good luck and please keep us posted...

Bob

[FMpreacher]

This is not something I would ever do but I like to hear other people's adventures with wildcat .358s. I am a dyed in the wool 35 cal fan and have a fair amount of experience with both the 35Remington and the 358Winchester and their effects on whitetail deer. Good luck and keep us in the loop!

[Outer Rondacker]

Awful nice pictures of bullets. Didnt see any cast bullets in them. Like FMpreacher said I too am a dying 35 cal fan and like to see what is being done with it on other setups. Honestly hate the AR thing but to each their own. I hope to see more of your project.

[dogmower]

I just built a 358 win upper for my AR-10 and picked up a 350 legend upper for the AR-15. Really beginning to appreciate the 35 caliber in semiautomatic, and of course still love the 35 remington. The 358 yeti sounds intriguing. Keep us posted

[Idaho Sharpshooter]

At the risk of seeming to: "rain on your parade...", may I just suggest a standard 358 Winchester in an AR-10 like dogmower. I got a Wilson Combat 16.5" barrel and used AERO Precision's Enhanced Upper/Lower/Hand guard set. There is a ton of 358 Win brass out there, and it is C-H-E-A-P. No issue forming, I just run the case thru my 358W FL sizing die, and square the case mouth. MagPul offers 20 and 25 round mags. NOE has a great 250gr RN mould, and if you powder coat you can get over 2250fps as safe pressures.

For me, a way to judge pressure is how far it throws the empties, and in how small a pile. It also helps finding the brass. Reinventing the wheel is always fun, if cost and time are not issues. Me, at age 73 I want to spend more time shooting, not case forming.

Rich
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