357 ar any ideas

[milsurpcollector1970]

[Moleman-]

Looking at how the case is hanging up take a look at the transition from the bevel to the chamber wall. I've gone to using a 3/32 radius bit to cut the bevel and always polish the bevel and transition. Yours looks too sharp. Also see if the base is hanging up on the ejector pin and if so it may need a slight bevel to it so the cases slip over it easier. What angle did you cut the bevel at? What bullet are you using and what is the COL? I'll get some pics up later this afternoon.

[rancher1913]

357 mag ar -------------want one. post photos when done please.

[Moleman-]

Here's a couple pics of the two types of feed ramps I've tried. The first was just opening up an M4 extension (black upper) with a 3/8" ball end mill (this first one I used a dremmel). The second type (tan upper) the same M4 extension was just put in a dividing head at the same angle and the trough formed by continuing the feed ramp cut until they were connected. There was still a little bit of the bottom lug left on this one, but it was ground off as it had no strength and was sharp. The ramps continue into the upper receiver like an M4 does. In the pic of the bare upper before it was gunkoted FDE you can see an area just below the extension opening where the ramp was extended. There are also two types of chamber mouth bevels. The first one uses a standard 30 degree taper (had to do it again I'd use 35 degree) and the transition from bevel to chamber wall beveled and polished. The second one (tan upper) was made with a 3/32 corner rounding end mill and polished. Both styles of extensions and chamber mouth bevels work. Another thought. On some of the Pmags I've had to remove a tiny bit of the top front edge as the cases were teetering on that and being forced to the top of the chamber.

[acoop101]

So is this basically a straight walled 223? What kind of velocity are you getting?

Sent from my XT1565 using Tapatalk

[Moleman-]

So is this basically a straight walled 223? What kind of velocity are you getting?

Sent from my XT1565 using Tapatalk

It's basically a rimless 357Max from 223 cases and run at 223 pressures. The bullets in the pic are Hornady 180gr SSP. 24gr W296 (safe in my guns don't know about yours) at 2.235" COL with a water capacity of 34.8gr quickload guestimate is 2119 fps at 52,454 Kpsi for a 15.5" barrel. No way to verify pressure, but the magneto speed average was 2140 fps (rounded up from 2139.66-). Tan rifle is my sons 15.5" and the one on the candy bowl is my 18".

[milsurpcollector1970]

I was able to get to almost chamber a round by trimming the front of a magazine

I was using some fmj 125 .357 bullets and some 115 gr 9mm rn

Neither worked well

I am going to set it aside for a while and work on my 6.5 grendel

I also have a direct impingement 45 acp that I would like to turn into a 460 Rowland

That will be my big bore hunting round

Dan
I appreciate all your help. It was very nice of you to take those photos to help me.

I wish you were closer I would love to look over your shoulder when you are doing your gunsmithing/machining

[Moleman-]

Did your feed ramp extend down into the upper a little bit similar to how an M4 does? Are there any marks on the cases from the chamber? dug through my dummy rounds and found one that jammed because the feed ramp was too sharp. Can't get a good pic of it for some reason but it has a little smiley cut into it. I'll try again in the daylight. On the beveled chambers I've blended the bevel/chamber junction and polished it with red compound and a felt drum in a dremel while spinning it in the lathe. On the radiused chambers I just polish the radius and bottom 3/16" of the chamber. I think you're close to getting it to feed. Here's the 44x1.6 mag I was talking about.

[Moleman-]

Was doing a little cleaning in the garage and found a pistol barrel I'd set aside 2 years ago or so. It was with the last batch of extensions I modified including the one on my sons gun. It is a Teflon coated M4 extension and I forgot who the maker was. Looking at the pics you can see the edges of the M4 feed ramps as they still have the silver Teflon coating on them and mainly the bottom lug area was milled on and is parkerized. There was a bit of the bottom lug left, but it was ground off since it wouldn't actually do anything and was sharp. The chamber mouth was cut with a 3/32" radius bit and was test fired before Parkerizing. It hasn't been mounted or fired since. It offers a little bit better picture of what the extension and chamber mouth looks like over one mounted in an upper.