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357AR

20K views 77 replies 14 participants last post by  moleman 
#1 · (Edited)
Here is what I've been working on this past winter with a lot of imput with several members over at weaponsguild. An ar15 based off of a 357 maximum rimless loaded to 223 pressures. I started with a home made chamber reamer (because standard 357max reamers won't work) and a 357 test barrel and once I got the bugs worked out I sectioned the test barrel and bought a Green Mountain blank to turn down. I haven't run it over a chronograph yet, but I was able to go above what Quickload shows for a 158gr bullet @ 2250fps without any signs of high pressure. I'm currently working up loads for 180gr bullets. Here's a few pics.
 

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#2 ·
Damn that looks good Mole.
 
#3 ·
Thanks 2nd! It was a fun build. Hopefully I'll get a chance to try it out on a deer this year. I also plan on turning the left over barrel blank into a pistol upper chambered for it as well once I finish a 80% lower so I have a pistol lower. I still should be able to get near 2000fps with 158gr bullets and a 9.5" barrel.
 
#5 ·
I was looking around for info on this build 6-8 months ago before i went 300 black out. Is there a reference web site on ar 357's??
Nope! I found info about making a rimless 357 mag, but the only info I could find about a 357 max rimless in an AR15 was that "it can't be done" because of the length :lol: The length was actually only a minor problem. I have two threads about the build concept and actual builds at weaponsguild. I tried using modified 357 max brass at first, but soon found out that they aren't a good canidate because although the web is higher on the max case the case wall is thinner since it is meant to be completely inside the chamber except for the rim, where the 223 case has a slightly shorter web with noticably thicker walls to handle the case sticking an 1/8" out or so. Once that was decided upon I did stick with the 357 max case length which gives you a very close case capacity to a 357 maximum. Mad Machinist suggested 357AR for a name and it stuck. I suppose it does sound better than 357 MoleMan Magnum :biggrin:
I found info on 357 maximum loaded to 223 pressures in strong actions with longer barrels which gave me hope of a real deer thumper which I think I've obtained. I haven't started playing around with powders and have been using 2400 and should be able to increase the velocity a bit switching to 296 or H110. I'm still working on 180gr loads, but the Hornady 180gr SP SSP Interlock looks to be very good. I was able to get blunt 158gr SJHP bullets to feed well and also 200gr rn bullets, but the pointy 180gr hornadys feed smoother. The 357 Maximum is a hot round, but the pressure is limited because not all of the firearms chambered for it (like revolvers) are strong enough to handle the increased pressure. The AR15 is meant for higher chamber pressures and since it has a larger bore diameter the pressure drops off faster than a 223. Modifying 223 cases was an issue at first, but I've figured out how to bump the cases up to straight wall with acceptable case losses which is bound to happen with that dramatic of a change in diameter.
 

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#7 ·
j427x, this is basically a hot 357 max even though the cases are formed from a 223 case the case capacity is within 1/10th of a grain of water between a modified remington 223 case and a remington 357 max case which is less than some cases will vary between brands. 357 max dies and reloading data can be used, and you can work up loads hotter than what the max stops at in the reloading books although some tc data is close. Look through the reloading data and velocities on this site and the links to load work-ups if you have time 357 Remington Maximum Loading Data
Check out the velocitys listed, but keep in mind it is with a 24" barrel. I don't know how much of an advantage the extra length gives him since the majority of the velocity is acheived in the first 10" at which point the velocity arc isn't as great. Here's a quickload graph Zebdeming made for my test barrel which was 17". I ran out of 158 gr bullets and moved on to .358" 180gr bullets which I started getting signs of increased pressure at 20.5gr- 21.0gr, so I backed down to 20.0gr in the test barrel which was a generic 9mm/38 bore diameter. My new barrel is a .358" blank with a 1-14" twist since I plan on mostly shooting bullets 158gr and heavier.
 

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#8 ·
wow--2400ft-lbs from a 180gr@ 2,400!

looks to be an impressive 200-300m round-- if you want to shoot big game with an AR this could be the ticket.

i had thought about going with a 35 rem bullets for such a project once. i keep getting side tracked.

right now i am building another 1911--LOL i got to check to see in the 223 brass will fit--!-LOL!
 
#9 ·
Interesting huh? I don't plan on ever putting a 24" barrel on an ar, but even taking a couple hundred fps off for a shorter barrel is still nothing to sneeze at. The pressure graph above is for Alliant 2400 which is a good powder, but isn't the best choice for this round if you're wanting more velocity. I picked up some 158gr XTP so I will try them out as well.
 
#10 ·
INTERESTING looks like you put a lot of work into developing it. it should do well on deer.

a littel off topic but I have turned a barrel tuned for a 358 win AK47. wanted the same thing heavier bullet with good speed. if I was confined to a ar length magwell id be really interested in you round. I have a 223 ak that the barrel is not the best and that would be a cool barrel swap only round for it. HMMMMMMM

your round would likely be good loaded subsonic as well. the round is kind of like the 9mmx39 just a little smaller.

NICE WORK.
 
#13 ·
Thanks 1biggun, this build has kept me busy this past winter and should keep me busy well into the summer. I was a little skeptical about the strength of the ar15 bolt/barrel extension for this use at first, but the bolt thrust and chamber pressures are the same as the 223. I think that it doesn't hurt that the pressure drops off a lot faster in the larger bore. If the computer model is correct with 60k psi for the load listed, the brass and primers still looked good. Right now I'm still working with 158gr and 180gr bullets and Alliant 2400 which I also plan on using for the 140gr and 200gr bullets. When that is done I'll switch powders and start over. Oddly I got the first sign of increased pressure with the 180gr bullets with a charge very close to the 158gr loading. Not terrible or flat, I could just tell the edges of the primers were a little less curved that the .5gr loading before it so I stopped and backed down a little. I'll have to work the 158gr bullets back up also as I was using a 25year old box of 158gr sjhp hornadys that are no longer produced.
j427x, I'm right there with you on the barrel length. My test barrel was a 17" and the new barrel is 18.5" total with barrel extension. You can see in the pressure/velocity chart that the velocity isn't really climbing that much per inch at 17" as say before 10". I have a 9" piece of the blank left that I plan on making a pistol barrel out of.
 
#14 ·
Once I figured out I was going to attempt this build I needed a barrel and a chamber reamer since a standard 357 max reamer won't work as this round headspaces on the case mouth and a max reamer has a coned throat since it is a rimmed round. I searched the web and measured 357 max cartridges and figured out a chamber drawing to try. I don't have an indexer, but I needed a way to index several flutes into a reamer blank. What I used was a piece of hex steel that was formerly a plumb bob. I faced it off and bored a hole in the center and added a set screw. I also needed a way to support the end of it so I made a little tailstock to hold one end while the other end was held in the mill vise. I turned a reamer blank and mounted it in my plum bob indexer. There is a fancy formula about how to lay out the flutes in a reamer that basically came down to .007" below centerline for the depths of cuts. It was cold when I made the reamers and if you look close you can see the mill vise frosting up again (I'd already cleaned it off once) while I was using it. I messed up the heat treating of my first reamer and made it too soft, but the second one worked. When I went to chamber my second barrel I found that my first reamer wouldn't work due to differences in bore diameters. So I made a second reamer for the second barrel and made a piloted 60 degree center cutter while I was at it. 357 Max headspace gauges also won't work, so I made a set of those also. Here's some reamer pics
(the ejector and extrator were removed from the bolt for the headspacing, but I find the carrier makes the bolt easier to line up correctly for headspacing)
 

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#16 ·
OK THE GUN WAS IMPRESSIVE BUT IM MORE IMPRESSED WITH THE FACT YOU MADE YOUR OWN REAMER.

WHILE WORKING ON THE NOW ON HOLD 444 RIMLESS MARLIN I SPOKE TO A GUY WHO HAD MADE A SIMULAR ROUND THAT ALSO HEAD SPACED ON THE CASE MOUTH. HE SIMPLY USED THE 444 MARLIN REAMER AND THEN RAN IN A SEPERATE REAMER THAT CUT A SQUARED OFF FACE IN PLACE OF THE BEVEL THAT THE 444 REAMER HAD MADE. HE WAS USING CUT DOWN 30-06 BRAS LIKE i PLANED ON AND JUST TRIMMED HIS BRASS TO FIT HIS CHAMBER. IM PLANING ON DOING THIS ON MINE.
I WONDER IF A FACTORY 357 MAX REAMER AND SPERATE EASY TO MAKE OR BUY REAMER THAT JUST CUT A WAY THE BEVEL WOULD WORK???? THIS COULD EASLY MADE FROM A DRILL BIT OR END MILL GROUND TO TAKE A PILOT OR EVEN A DRILL BIT GROIUND FLAT ON THE END AND GROUND ON THE SIDES TO FIT THE CHAMBER. YOU ONLY NEED TO FACE OFF A FEW THOUSANDS HERE TO REMOVE THE BEVEL. DO YOU HAVE TO TRIM THE 223 BRASS AT ALL????

next you'll have to make a 357AK to complete the set!--LOL!
IT WOULD BE A EASY BUILD ON A 223 AK. i KNOW MY BULGYBOLT ROMMY TRUNION HAS HELD UP TO TONS OF HOT 223 LOADS THAT LITTERALY PIERCE THE PRIMERS AND FLATTEN THEM AS WELL AS SHOW THE EXTRACER CUT IN THE BOLT FACE IN THE BRASS. IM BETTING THERE AT AROUND 65,000 PSI. (IM BACKING THEM DOWN FOR THIS YEAR BTW)

I WONDER WHAT THE X39 CASE BLOWN OUT STRAIGHT WOULD BE?? A 41 CAL VERSION ON A X39 CASE WOULD BE SLICK AND ON A AR YOU WOULD NOT HAVE ISSUES FROM A TAPERED ROUND LIKE THE 7.62X39 HAS AS THE ROUND WOULD NOW BE STRAIGHT. THUS NO CURVED MAG NEEDED. SEEMS LIKE I LOOKED AT THIS A FEW YEARS BACK. A X39 BOLT AND YOU MIGHT BE ABLE TO DO A 41 CAL AR ??????

SORRY FOR THE CAPS I WAS ON THE GENERAL DISCUSSION FORUM TO LONG TONIGHT LOL
 
#17 ·
The standard 357 max reamer and a chucking reamer had come up in the weaponsguild thread, but I decided against it. From the front of the casemouth to the begining of the rifling is tapered on the max reamer. You'd have to short chamber by .4" or so and ream this distance to get the round to headspace, then recut the leade into the rifling with another reamer. It could be done with a custom grind reamer though. I figured a custom grind reamer =$$$ on a project I wasn't sure if it would work so I made my own. It took me two tries to make the first reamer and three tries to make the second one. Luckily the mistakes while making the second reamer were early on. There is definately a learning curve making a reamer and they get easier as you make them. No one step in making the reamers is hard by themselves, but they add up and there can be no mistakes.

I've had loads flatten 223 primers as well, but I've been conservative in reloading the 357AR and stopped at the very first sign and backed down. No flattened primer, no cratering and no brass flowing into the ejector hole. I figure the round is already performing better than I would of expected so there is no need to push it.

As far as a 357 in an AK, I was looking at expanding a 5.45x39 case before modifying the 223 cases. I still might make that round as well. Of course there's always the 9x39 too.

Some of the reasons I went with the setup I did was that I can use standard 357max reloading dies and not have to get or make a custom set....again custom =$. Also I can use 357 max data if I want and work up loads from there, so I'm not totally out there on my own as far as load development.
 
#20 ·
Some of the reasons I went with the setup I did was that I can use standard 357max reloading dies and not have to get or make a custom set....again custom =$. Also I can use 357 max data if I want and work up loads from there, so I'm not totally out there on my own as far as load development.
GOOD POINT NO DIES FOR A X39 BLOWN OUT STRAIGHT.
 
#21 ·
If I get around to making the 357-5.45x39 round I most likely will make an undersized chamber reamer and make a sizing die, or try to modify a 5.45 die set. Either way it's a lot more work than using off the shelf die sets. Here's a pic of the five 357 reamer attemps including the screw ups. The top reamer is a 3-flute that I tempered too much and ended up too soft. The 2nd down is the reamer I chambered my test barrel with which was a 357 1-20" twist with a .346" bore and .356" groove diameter. The 3rd reamer down I feed in the wrong amount and knew it right away so I just used it as practice. The 4th reamer blank down I snagged the cross feed knob on my jacket pocket which caused it to feed in slightly and leave a mark on the begining of the rifling leade. The bottem reamer is the one I used to chamber the finished rifle in the pic which has a 1-14" twist, .350" bore and .358" groove diameter. A 1-20" barrel is supposed to stablize up to 160gr, and some 180s but not all. I wanted to shoot mainly 160-200gr so I went with the 1-14" twist. The headspace gauges were also easy to make for a straightwall case. I only made a go and no-go gauge since I'm chambering a new barrel. If the bolt ever closes on the no-go I'll make a field gauge. The bullets next to the gauges are top sierra 200gr rn, middle hornady 180gr psp, bottem hornady 158gr sjhp.
 

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#23 ·
I finally got a chance to go and shoot the upper at paper. I kept the cheap red dot on the upper so this isn't really an accuracy test as much as it was a functioning test since the dot covered the target. My first impression firing from a bench was that it kicks more than a 223, but not a whole lot more. I'll need to work on the feed ramps a little as it isn't feeding as well as my test barrel was. I'll just have to look at the test barrel extension and modify this a little more like that one. The red dot was also a little low which caused me to have to contort in order to see the dot. I have a riser mount somewhere to bring it up to a more comfortable heigth. I'll also have to dig around to find what extra scopes I have laying around to see what kink of accuracy I'm getting. The 180gr feed well, but I was having trouble with the 158gr feeding smoothly. It shouldn't take much to get it feeding like the test barrel was though. My helper also was throwing a few 22s my way :ak47:
 

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#25 ·
No short stroking, the stubby 158s weren't sliding up the feed ramps smoothly. I was a little more conservative with the feed ramps on this barrel than I was on the test barrel. I just need to change the angle on the feed ramps a bit more and it should feed the 158's just as well as the test barrel did. The test barrel initially did the same thing until I got the angles right. I probably won't get to work on this barrel again until next week. I'll also have to load up some ammo since I shot it all off.
 
#27 ·
Thanks mtdew! Still a few things to figure out and finalize first though. If everything does work out well , there might also be some premade 357AR brass available for those barrels!
 
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