Which rifle for a DIAS

[jhco]

While attending a gathering, and discussing guns, the subject of auto sears came up. The consensus of one party was that all you needed was an AR15, any AR15, drop in an auto sear and it becomes a M16. My knowledge on these is lacking, however, I offered the opinion that it might need to be a Pre-Ban AR. So my questions are: What type of AR will accept drop in auto sear? If its pre ban only then are they currently manufacturing any the are to pre ban specs? Can any AR be milled or modified to accept a DIAS?

P.S. I am fully aware that the alteration of a fire arm to full auto would have repercussions unless it's tax stamped and or registered as a class 3. The question is for hypothetical and conversational/ informational purposes only.

 

[yugorpk]

Theres all kinds that will accept the DIAS but its not as easy as dropping one in. You need the M16 FCG and of course the bolt carrier needs to have the right back end and it often needs to get tuned to the sear to get the timing right. Then, when you take the sear out youve got a lower with M16 parts in it that can't stay that way as it will fire commercial ammo full auto a lot of times with the hammer riding the carrier forward.

In any case with everyone and their brother contracting out AR-15 3 position lowers these days its almost easier to ask which ones don't have the shelf to place the DIAS on. Most modern receivers have the cutout but some, like Andersons don't make it quite deep enough. Also, you don't need to mod or stamp or "class 3" the weapon itself. The DIAS is the part that is registered. You don't need to mark the host gun at all. You just need to plunk down the $20K or whatever it is those things go for these days, do your paperwork and tune your gun to the sear. I still think lightning links are a more practical idea.

 

[jhco]

Ok, so let say that the person assuming that any ar will take a DIAS has a rock river car15 lower. Would a DIAS assumedly work in his lower if timed properly, while using a M16 bcg?? Is it as simple as drop in and shoot if a M16 bcg is used in this rifle? How is timing achieved?

 

[yugorpk]

Timing the carrier just means having to take a little metal from the carrier ( and maybe add metal ) to trip the hammer ( through the DIAS when the bolt closes all the way) Sometimes they are good to go right out of the get go but often there is a timing adjustment you'll have to make. They used to make and probably still do a chunk of metal that bolted to the bottom of a semi carrier that you could use to time the sear without having to buy a M16 carrier.

Pretty sure the Rock river ledge is too high . They can be cut down to be sure but but you should be able to find a compatible receiver under $100. That expense will be the least of your expenses.

 

[Aaron Baker]

Do a little Google searching on the topic of "high shelf" versus "low shelf" lower receivers. The area that yugorpk is talking about is the "shelf" behind the FCG pocket in an AR lower--the little ledge in the area of the rear takedown pin. To accept a RDIAS, you need a lower with a "low shelf" in that area.

There's a few options for that. First, you can buy a "preban" Colt AR15. The "green label" Colts are a low shelf lower. But that's not necessary, because as yugorpk points out, there's new manufacture options as well. I believe that Spike's Tactical makes a low shelf lower receiver.

I believe, however, that most newly manufactured lower receivers are "high shelf." So picking a random lower and assuming an RDIAS will drop in is probably wrong. I don't know whether Rock River Arms lowers are high or low shelf.

You can have that area milled out by a machine shop on the lower receiver of your choice, but given that a new stripped lower from almost any manufacturer is cheap, you might as well buy one that's "low shelf."

As yugorpk points out, the RDIAS is the biggest cost.

Aaron

 

[yugorpk]

I just looked at a few of mine. Out of 7 lowers the only ones that will accept a DIAS are from Bushmaster, Mega, Stoner Arms and Aero. Stoner being milled from billet and the best machined/looking of them all. I should pick up another Stoner lower. They're local and make ( or pay someone to make ) a good lower..

SIG M400, Rogue Defense, and Anderson will not accept a DIAS

 

[Elkins45]

still think lightning links are a more practical idea.

I just Googled lightning link. Apparently there are less than 500 in the registry, they bend or wear out, and even with these obvious flaws they are still $8K.

I'm thinking bumpfire or a BMF activator are more my budget--bet that still won't buy the ammo. Full auto remains a rich man's game.

 

[yugorpk]

Machine Guns are a great investment. They have no practical value but neither does a lot of stuff. $20K+ for a sear will allow you to shoot it until you are tired of shooting full auto and then sell it for more than you paid for it. Its FREE. Think of the $20K+ as a fully refundable deposit.

Having said that the slidefires do work very well. The trigger activator gizmos not so much.

 

[Jim K]

A note on the DIAS. In the period after the law was changed to make a DIAS itself a machinegun and before the change took effect, many companies rushed to make as many of the devices as they could so they could be sold without paperwork. (In theory, it is illegal to install them, but that is beside the point here.)

The problem is that very many of those DIAS's were of poor quality material that won't hold up to much firing before wearing out or breaking. Many folks have sunk a lot of money into a DIAS (registered or not), installed it (legally or not), then had it give up the ghost in less than a full magazine. And they can't be repaired or duplicated by the owner; the only way to continue to have a DIAS is to buy another one.

Jim

 

[yugorpk]

If its a registered DIAS it can be repaired by a 02/07 manufacturer and its legal to install in any AR.
I think you are referring to the pre 82 DIAS that were installed in registered receiver AR's prior to 1982. Those are not legal to install in post 82 guns ( or pre 82 non registered receiver guns ) and as they wear out the receiver should be converted to actual sears if they havent all been already. Suppress on used to sell those for $150 a pop and advertised for years in the SGN but I havent seen them for sale in 15 years or so. They did have a very narrow subset of guns they were legal to go into but thats not what people bought them for. Its a myth that they were manufactured prior to 82 and held somewhere and sold off over the years. They were manufactured for years AFTER the 86 ban as legal replacement parts for the pre 82 guns and were not considered MG's unto themselves until a much later ATF ruling. They had steel sears and aluminum bodies and were well machined. Suppress on sold a boatload of them and probably not one of them went into registered receiver guns.