Tell me what you know! I've thought about combining a phantom an or a Thumper too make a subsonic .50 in a semi package!
Last I heard they weren't making any more due to lack of a reliable supplier of brass. I have a dummy round I bought direct from Marty a couple years back. Maybe they got a supplier again, I don't know, but haven't heard the caliber mentioned for over a year. I do know you need a .308 magwell for the round to reach its full potential(won't work in AR15 magwell if using the BMG bullets IIRC.). Marty from Teppo Jutsu is a member here, I don't remember his user name though. Maybe he'll chime in on whether a barrel is available or not.
The cases are no longer being made so that is a very poor round to be building on. I have 350 for my .500 Phantom and there are no more to be had. Marty has abandoned the .500 Phantom and the Rhino series which were both based on the .500 Jeffrey case, shortened and the rim rebated. To make them look at $165 per 20. For my .470 Rhino I have to buy 20 cases from Jamison ($65) then spend $5 per case to have the heads turned. That's what happens when you play with wildcats, sometimes you get bitten.
When we did our bulk buy of .500 Phantom cases it took over two years to complete. The company who made them, started with an H and in Germany IIRC, would not give a delivery date, expected full payment up front, and needed a huge order. That was why Marty dropped both the .500 and Rhino cases; it was just too damned hard and expensive to get them to make the brass and all brass makers were pretty much the same: full payment up front, very large minimum orders, and no guaranteed delivery date.
It is a good thumper though. I am shooting the M33 ball bullet out of mine and getting between 900 fps (short loaded) and 1300 fps (long loaded) out of a 16 inch barrel. As it stands right now the M33 has to be loaded longer than the mag will hold so it must be single loaded but I have started working up a load with another powder that will allow me to seat to 2.800 length and run OK but the velocity is in the 900 fps range if QL is correct. I still need to lob a few over the chrono to verify if the rain will ever stop and the load needs some tweaking to see if it is going to lock the bolt back. Preliminary test have the bolt locking back half the time but feeding reliably with Re #7 powder. With short loaded M33 and H110 powder I could not get enough powder in the case to operate the action before running into pressure problems. Seating them long got enough powder to create enough gas to lock the bolt back but of course, round must be fed in one at a time.
With 600 gr. Woodleigh and 475 gr. LBT LFN GC bullets it does very well, sort of a semi-auto version of the .50 Alaskan giving velocities in the 1400 to 1600 fps range IIRC.
Last I heard from Marty he is no longer doing any .500 Phantom or Rhinos because of the lack of brass. I think he even has something like that on his web site.
Your better bet is to go with something based on a case that is readily available, like the RUM or WSM case. You won't be able to push them as fast as you can in the Phantom case but since you are wanting to stay subsonic you don't need that large a case anyway.
Why has no 1 tried making a 'new' bolt instead on the brass? After reviewing the thumper the wsm brass seems to be the way to travel! 1 problem DPMS will not sell you a SAUM bolt and Armalite doesn't have any left!
Kreiger will make the barrels!
I just need some bolts!
Yes, correct you are. DPMS has dropped the RSAUM lineup and are no longer making bolts. I had a couple of builds planned but that is on hold now. Good news though, Harrison at AR Performance is considering adding RSAUM bolts and barrel extensions to his lineup but I do not know if he will only be doing complete uppers or if he will be selling the bolts and barrel extensions separately.
There is no way to make a bolt that will accommodate the full size head of the .500 Jeffery case and work with the LR-308 platform or did you mean making RSAUM bolts?
The Saum bolt face is what I mean. I thought about lathing out a .308 bolt an I assume thats what DPMS did, but I don't have too compare too and not sure there is enough metal too do it. I have the means too reheat treat the bolt and I'm sure it could work if I got a bolt, but none the less that is the issue!
I think it would be a intresting project if I can get that part to work!
I think you would be OK machining it even if you do not heat threat. The LR-308 uses only one barrel extension for the .308 and its variations as well as the RSAUM so the bolts would be the same external dimensions also. My .338 Federal bolt looks just like the RSAUM bolts except the face is larger on the later. When Marty does the .458 SOCOM from standard 5.56 bolts he opens up the bolt face but they do not require re-heat treating so far as I know. The three .458 SOCOM bolts I have from him all look like they have been milled open and that's it. There is no indication that they have been reheat treated which would discolor the milled area someone. All of mine look like they just came off the mill and have held up just fine for many thousands of rounds. It is my understanding that the heat treating of the bolt lugs and face is not a surface treatment so opening it up will not hurt it unless you overheat it, which is easy enough to avoid. I have no idea if they RSAUM uses the same extractor as does the .308 but I cannot recall ever seeing an extractor sold separately for the RSAUM.