357AR

[j427x]

Originally Posted by moleman

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.

i wouldn't think a 24" barrel would be much help, i figure a 16"-18" would probably get about all there is to get driving one of those 180 grain slugs. ironically this is "just right" for an AR-15!

[1biggun]

HMMM THOSE 147 GRAIN LOADS LOOK PRETTY GOOD ALSO AND THERE A HELL OF A LOT FASTER THAN A 300BO OR X39. NOT SURE THE AR CAN TAKE THOSE PRESSURES LISTED IN THE RELOADING LINK THOUGH. INTERESTING ROUND THOSE LIGHT BULLETS REALLY HAUL ASS.

[moleman]

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.

[moleman]

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)

[j427x]

next you'll have to make a 357AK to complete the set!--LOL!

[1biggun]

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

[moleman]

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.

[mtdew]

moleman does it again! u da man!

[moleman]

Thanks mtdew! It continues to be a fun build, and I can't wait to see how it performs on deer.

[1biggun]

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.