I may be in the market for a RDIAS. What are the reputable ones to buy? I obviously prefer all steel one.

I had a John C. Benjamin (JCB) all-steel DIAS and it worked with every upper I tried and my Ceiner .22 conversion. So top marks there. I ultimately sold it b/c I didn't like having a conversion part that could fall out of the gun and found the need to move the full auto parts from receiver to receiver meant it wasn't as flexible as it seemed. I now have RR Colt guns, and I prefer them to the RDIAS.

Not many on the market at this time, so you may be waiting for a while (especially if you want an all steel as those are more infrequent than the LL's and aluminum DIAS's).

JCB here and no issues.

I don't believe you'd be at a disadvantage with an aluminum DIAS body. They are under practically no stress whatsoever. If for some reason one does break, it could be welded and repaired. I haven't heard of one breaking. Sear trips must be replaced rarely. They are unregulated.

 I also have a JCB I bought about 12 years ago.  I've had the trip replaced once so far, and it's going strong.  I have 3 lowers with the FA lower parts kits installed.  One is an AR pistol with a 4" barrel and a Ceiner kit.  FUN   My go to gun is a standard upper with a 11.5" barrel. 

I'm amazed at the prices I'm seeing on machinegunprices.com for these units.  What are you expecting to pay these days?

34k for the one sold last month.

Just about everyone I have seen in the last 6 months have been north of 30K

Then you don't want to know what I paid for mine, trust me.

I agree, you don't want to know what I paid for my M16's, I have three of them..

I got a $110 DIAS. 
It was a post sample. 

What's a RDIAS?

I'd agree with the poster above: Just not as easily moved from weapon to weapon as I'd hoped. Owned it for years but use my RR lowers almost exclusively with a myriad of uppers from 6945's and 6933's to 6940's and 6721's and, my favorite: Colt LMG uppers. Even though I have an ARES MCR, the LMG's with Beta C mags is much more fun/easy to run. YRWNV

On that note, can you run the MCR fullauto with a DIAS?

Yes, just have to get an auto bolt carrier if it didn't ship with one.

I also have 2 M16A1's, but the  auto sear was my first MG.    Funny thing is, I could put this on my keychain and pass through every TSA check in the country without a worry.

I know what you mean, the law as wrote is so stupid, I could go out to the shop and turn out quite a few of them in a very short time. I don't because I am a good boy!

I saw a guy at the LGS a couple of weeks ago, that had a necklace full of auto sears... I didn't even ask!

What does it say for "finnish" on your guy's form 4?
Mines a TGS (Tom's gun shop) and it says "Stainless"
I have wondered if the body is indeed stainless. I didnt rust when it got rained on for a day and put away dirty.

I think most are pretty good these days that come up for sale. For what they cost if they had issues along the way they were probably fixed or worked out by now. M60joe can work magic with them. When I bought my first one I saw a steel Hard Times Armory that looked pretty beat up I passed on. I bought a broadhead aluminum and it was flawless, dropped in every spec lower and ran great. I sold it to fund a few other projects including an engagement ring. I found a steel C Ray Systems end of last year I bought and it is at my local dealer waiting transfer to me. I had never heard of C Ray but before I bought it the seller had sent to M60Joe to replace the trip, spring, pin and make sure it was in spec. It has had thousands of rounds on it prior to that. I have read for steel the JCB, Billistics, and Norrell (stainless I think) were all great. I have read several folks including my own experience say the broadhead aluminums are great. Steel's command more money and no doubt would be easier to work on but I would not shy away from a good aluminum DIAS. Once you see how they work in the gun there is little to no stress on the body. I also read a thread a long time ago that back before the 86 ban the grades of steel used vs. aluminum may not be as great compared to would be used today. A modern sear would probably be made on a C&C machine out of tool steel and hardened but not sure any transferables were made that way. A few weeks ago there was a C Ray for sale on Subguns but not sure it is still available FYI.

This.
I'm looking for one that's very inexpensive (maybe with known problems), if any of you ever come across one. 

Our modern DIAS have CNC aluminum bodies and tool steel trips. I set the dimensions slightly oversize. It's easy/quick to file the aluminum bodies to fit snug in most any lower. I prefer them to stay in the lower, not on the upper's lug. They can be removed with just finger pressure once fitted correctly. I found one would swap easily between DPMS, Nodak, and one other brand lower.

What is obvious about all-steel?

Many DIAS are now approaching 35+ years old and there is no measurable difference in wear/functionality between a steel an Al one.

I paid under $50 in 1982.

At the bottom of page 293 of "The MAC Man" there is a copy of an ad from RPB COBRAY selling, among other items, AR-15 to M-16 Drop-in auto sears for $29.95 each or 10 for $175.00. RPB went out of business in April, 1982.

Just get whatever you can buy since they are so rare. They can all be modified to fit perfectly if needed. The two that I own are both steel, and are both individual Form 1 garage made ones from the 1980s, and they both run 100% with no shims or anything needed. In other words, the RDIAS does not have to be "name brand" to be perfect. Good luck on the hunt!

Wow, did they actually use the Lightning link metal and some how combine with a DIAS or just illegally reuse the same serial number on a newly made dias? I remember reading SWD also made RDIAS (aluminum) I think, so would presume those did not prefix with "AC" just to avoid confusion.

There was one for sale (briefly before the ad was pulled) on GunBroker about a year ago. It was a DIAS with a broken RLL body including the serial number nicely welded to the DIAS body. IIRC, at least some were made by the same group of dealers that were cutting SWD M11/9 serial number sections out of the M11/9s and welding them on newly made machinegun receivers. IIRC, the 2015 article that I read indicated that over 30 illegal machineguns so made by the group had been tracked down but more were suspected to be around.

MHO, YMMV, etc.

haha... I remember that, too.

Good info on steel vs. aluminum. Wondered about wear on the Al ones.

Prices? Wow. I guess my local dealer is not up to date on prices. He told me to expect 18-25k. Placed a WTB in Exchange so maybe someone with one lying around will let go of it.

Another C Ray Systems (steel) owner here. No problems with mine. I’ve kept it in the same Bushmaster lower since I purchased it but have checked fitting in a few lowers to make sure it was gtg.

I’ve had a steel broadhead RDIAS since 2007 and it’s been perfect through over 30K rounds in various lowers and calibers. I don’t think you can go wrong as long as you avoid a married DIAS or one is the aforementioned LC RDIAS.

My C3 had plastic bags full of DIAS that he couldnt GIVE AWAY in the 80s... Literally could not, so he gave them away FREE if you bought a short upper. He paid the tax.