Managed to get a few hrs in yesterday between the rains. Tested the 358 180's and the chambered just fine. Tried to do a water capacity check on new cases, but my scale just isn't sensitive enough. Maybe some other member here can check stock mag/max vs the 223 based brass. I am guessing there is less volume and therefore can't duplicate load data, even with the higher operating pressures.
Getting reports back from ARMax users getting 1" groups at 100 yds with H110, 2400, Lil Gun, and 296. We are trying to compile some load date with their input so we'll see how it goes. Sent Dave Manson a note today about a new reamer that is set up for head spacing on the cast mouth for the AR. I thinks he's already got that T-Shirt so hopefully we can update our set up. I could probably grind on mine but......
I am curious. You are working with a shortened case in an AR platform, Headspacing the cartridge on the case mouth like a .45 ACP. Since Starline has full-length brass available that has not been necked down, it seems that a full-length or nearly so .35 caliber cartridge using that brass would be feasible and would possibly bring .35 Remington power to the AR15 rifle. I know there have been rifles like this tried before, like the .400 Whelen. The problem with them was headspacing because there was no shoulder. That problem no longer seems to exist. There are lots of pistol and a few rifle cartridges that headspace on the case mouth - like the .351 Winchester. I would think the brass would need to be shortened a bit to allow for pointed or semi-pointed bullets to work in an AR magazine.
Looking at the image of the .357 magnum rimless and the .357 maximum rimless in the AR magazine begs the question, "Why not fill the front of the magazine with case?".
Post by paulsblackrifles on Aug 10, 2018 8:16:21 GMT -5
Great idea Jim22! But remember the case has to align with the barrel when the bolt is going froward. I'm not saying your idea can't work, just that one needs to look at the whole picture. I don't know what the answer is, I will trust the guy with the experience!
Hey Guys, thanks for posting! You are both right. Here is what we do to get these running: Technically the straight wall pistol rule for deer hunting is driving this demand. Some states however, do not allow anything but factory brass with a headstamp. Starline's basic 223 brass is long at 1.75+/-". Yes, it would do a fine full length round. I have not tried it yet just because I don't have enough time. The 357 ARMax is a bit short in a std AR mag, depending on bullet. We are using stock 357 Max reamers for our barrels. These reamers Do Not have a case mouth "shoulder". They are tapered. "So, how do you headspace?" you wonder..... For some strange reason (to be explained below) they work. We made a chamber gauge and cut the chamber to fit and (luckily) it has worked (so far). Main issue we have with the Max is case bulge at the base of the seated bullet with very heavy bullets. Wall thickness measure .010" - .011" and gives us just over the .379" diam spec. I measured what 38 spec cases I could find today and they all measure .011" - .012". 9mm and 45 LC were .012 and above. If anyone has 357 mag cases. please let me know your wall thicknesses. Even tho the ARMax wall measure the same, there is a bit of a bulge and, the stock Lee sizing die over sizes (smaller than required) and the case mouth expander over sizes the 223 basic brass. So we don't want to inside ream the basic brass, but that might be the answer. Now, the bulge also might be from a soft case and a roll crimp most die sets have.
The 357 ARMag is even worse, because its wall thickness (with the shorter case) does get thicker. Seating 158 gr bullets causes chambering issues. 125 grs are fine.
The good thing about all of that is that it makes a very tight chamber at the mouth of the case and allows it to "headspace" on the tapered junction. As I stated a few posts ago, if we keep this up, we'll get Dave to cut us a "acp" style reamer.
And, the folks at Starline offered when we first got into this (before the basic brass was available) to cut the rims off a run of 357 max brass. What nice people there. That would also take care of the friendly DNR folks about "stock" cases.
Now to make things more interesting, we also do a 358 ARMax. Our blank supplier has std 357 cal 1:20 twist blanks. The 358 cal blanks are suited for the 35 Remington, so we also make a 358 caliber version of the Maximum. This is a cast boolit machine and we've loaded up to 300gr hard cast. Now that will fill up the front of an AR mag! Plus to mention that standard 357 bullets are not designed to hit the velocities the ARMax will produce.
I'm also going to do a 9mm version (in our spare time)
Thanks to B whose been testing the 358 ARMax in 18" and 20". Commented that the 20" is shooting great, but the 18" just is not cutting it. These are both .358 cal barrels. Bullets have been from 180 - 250gr jacketed and cast. Went through the build sheets with B last week: We throated both barrels for the heavy cast bullets...… but, the 18" had a longer throat! Sent B the dims and asked him to check OAL and seating depths to the lands. Report back tonight: "Seated the 18" loads out and shoots like a champ!" I asked about OAL and relationship to lands so waiting on that reply, but: seat those bullets out! (and watch for pressure...)
By the way, the .357 magnum rimless you are experimenting with should make a wonderful conversion caliber for the M-1 Carbine. The case is the same length as the .30 carbine case. You might be limited to lighter weight bullets in order to fit in the magazine - or you'd have to seat deeper. I don't think the carbine's magazines would need much alteration. Of course they wouldn't hold as many cartridges because of increased diameter. That would turn the little carbine into a legit deer rifle... at least at reasonable ranges.
Hey Jim, Welcome! That definitely would be a nice rifle. Would have to take a hard look at the bolt to make sure it could be opened up for the .223 case and hold up to the pressure, but 357 Magnum should be doable...
Don't know about anyone else but I'd like one of those little carbines. I would rather have it on the M1-Carbine action than on an AR. Maybe 18 or 20 inch barrel. I once owned a surplus M1 Carbine. The .30 Carbine cartridge was too limiting so I sold it. Wish I had it back now. I'd think I still have what it would take to load for it... Carbide .357 die set and .223 shell holder. I liked the 5 round magazines because they didn't protrude too much right at the balance point, making it comfortable for one hand carry.
Here is an image of an M-1 Carbine bolt: Click to enlarge.
You know, the only difficult part of converting an M-1 Carbine would be getting the gas port right. Making it adjustable would help. The rifle could also be built without a gas port - as a straight-pull. Far as I can see the bolt and the barrel should be pretty easy. Is there any reason the .30 cal. barrel couldn't be rebored?
BTW... if you're having to ream the inside of .223 brass after it's cut down, maybe you should try starting with .300 Blackout brass. It's about 0.07" longer than the .357 Magnum brass. Necks are thin as well. Starline lists case length as 1.356-1.360". $70.00 for 250 cases.