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I posted this on a couple other forums, but thought I might as well share it here too since a bunch of you guys are also handloading loonies.

I've been working for a couple months on a project to build a 35 caliber AR-15, and have reached a very successful result. I'm calling this one the 358 Herrett AR, and it duplicates the ballistics of a 35 Remington lever action rifle, but in a 16" AR15 platform. It also runs subsonic suppressed very well with heavy bullets. This round is basically a scaled-up 300 Blackout, using the same powders as the 300 for both subsonic and full throttle loads.

The concept is nothing new, the Russians did a 9x39, and others have built various wildcats by necking up the 6.8 SPC and 6.5 Grendel cases. My version uses 6.8 SPC brass and 357 Herrett dies, available from Hornady. The 357 Herrett chamber was cut 0.110" short to fit AR15 magazines, and the 6.8 brass allows it to run at much higher pressure than the old T/C Contender loads.

This round will run anything from light 9mm bullets up to heavy 250gr+ .358 bullets, but was designed around the 180-200gr bullets common in 35 Remington. The 16" barrel delivers a 180gr SP @ 2300 fps, retaining more power at 150 yards than a 5.56 at the muzzle. The 10.5" barrel is only slightly slower, since this case is very efficient like the 300 Blk.

This isn't a long range round with these fat heavy bullets; it's intended as a short-medium range hunting round that will handle large four legged animals better than other common AR15 rounds. The larger bore also allows subsonic bullets to be far more effective, with enough frontal area to hold large hollow points that actually expand at subsonic speeds.

Barrel blank
[Linked Image]

Partly finished 16" barrel, test fired before drilling the gas port
[Linked Image]

Completed rifle
[Linked Image]

300 Blk on left, 358 Herrett AR on right with 180gr full power and 255gr subsonic loads. You can see the similarity between the two cartridges.
[Linked Image]

A few bullets this round handles: 115gr 9mm, 200gr Hornady SP, 270gr solid
[Linked Image]

ARIC

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Sounds like the 358 MGP

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Yes, very similar to the MGP. I didn't know about the MGP until I was in the middle of this project already, but the end result is pretty close. The MGP has the shoulder a little farther forward, and uses proprietary dies. I set the shoulder on mine to be even with the base of the 200gr Hornady SP when seated at 2.300".

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I've thought about something similar, such as a .223/5.56 case blown out to use .358 bullets, seated to mag length. Like the Blackout, it could use the same bolts and magazines as a 5.56. Should be an effective round with good killing power.


"...the designer of the .270 Ingwe cartridge!..."

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very cool! Nice looking build as well. Its on an AR-10 frame correct??


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Looks like a standard AR15 platform to me.

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That's very neat!


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Thats a cool project.

I've never had an issue getting 300/221 bullets to expand subsonic.

I suspect you'll do fine with the 358 too.


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AR15 platform; in the AR10 I would just do the 358 Win.

I considered the 556 case blown out to 35 cal, but that's a straight wall case, basically a rimless 357 Max, and would have to headspace on the case mouth.

rost, what bullets are you getting to expand subsonic from the 300? I've done a lot of experimenting with 30 cal subsonic bullets, and the only bullets that will expand significantly use a large hollow point. Even round nose cast bullets with pure lead noses don't expand, unless they hit something hard. Maybe on bone, but not in meat. I do cast my own hollow point bullets for that, but the 35 cal just works better and easier.

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Originally Posted by Yondering

I considered the 556 case blown out to 35 cal, but that's a straight wall case, basically a rimless 357 Max, and would have to headspace on the case mouth.


I was considering building something like that too, but I understand that feeding & ejection are also problematic when you get that long of a straight wall in the AR.


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Originally Posted by Yondering
AR15 platform; in the AR10 I would just do the 358 Win.

I considered the 556 case blown out to 35 cal, but that's a straight wall case, basically a rimless 357 Max, and would have to headspace on the case mouth.

rost, what bullets are you getting to expand subsonic from the 300? I've done a lot of experimenting with 30 cal subsonic bullets, and the only bullets that will expand significantly use a large hollow point. Even round nose cast bullets with pure lead noses don't expand, unless they hit something hard. Maybe on bone, but not in meat. I do cast my own hollow point bullets for that, but the 35 cal just works better and easier.


194 Lehigh max expansion. I have a bag of them here that have all opened just like a barnes in my backstop, and I have one here at the computer that I shot into the chest of a buck and stopped in the hindquarter.

They are the best solution I've found and after about 20 animals with them, I wouldn't trade em for anything.


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one of the most intriguing aspects of the AR platform, is it's ability to be chambered in almost any cartridge.
Most of which are not needed, or wanted by more than a few folks, but then when did rifle loonies like us need REASONS for what we do? smile


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Pretty cool and would be legal for deer in Indiana. Let me borrow it a week in Nov and I'll let you know how it does... wink

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If anyone has a 35 Whelen M1 Garand I would be interested in hearing about it.
whelennut

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Whelen, I don't know of anyone, but all it is, the right port for the gas, and the right powder, I"d check into any of the custom M1 builders that have a top name, and I"m not even sure who that is these days.. I"m sure Roland Beaver is no more in business???

Its not magical, its simply don't over or under gas it and make sure you don't run powders/loads that would bend the op rod, and IIRC, maybe can get it supported somewhat by mods?


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Awesome! I'm a huge fan of the 35 cal and have wanted to someday do something on the AR platform. Should be great with cast bullets with the lead friendly 1-14 twist. I like the idea of using 357 Herret dies, used ones are a dime a dozen.

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Cast bullets were a big consideration for this one. I'm using the new Lee clone of the RCBS 200gr mold, as well as the Saeco 352 and my own heavy hollow point shown above. It does seem to be a good cast bullet round.

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Let's bring this up to the top for an update


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Still using both of these (16" and 10.5"); I'll see if I can dig up a pic of them in their current configurations. Any particular info you're interested in?
I've been shooting the 16" a bit with the 200gr FTX as well as the 180 Speer Hot Cor and 180 Hdy SS/PB. The 10.5" gets used exclusively suppressed and with my 255gr hollow point cast bullet.

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Originally Posted by tex_n_cal
I've thought about something similar, such as a .223/5.56 case blown out to use .358 bullets, seated to mag length. Like the Blackout, it could use the same bolts and magazines as a 5.56. Should be an effective round with good killing power.



Dang, I knew I had thought of the .350 Legend, years ago - there's the proof grin

Pity they apparently won't run in 5.56 magazines frown


"...the designer of the .270 Ingwe cartridge!..."

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