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Posted: 10/21/2017 3:56:51 PM EDT
I have seen some non-definitive discussions on using a RDIAS in a AR type in .308.  Some folks believe it is illegal to run a RDIAS in a 308.  

Set the 308 question aside for the moment.

What about a 9mm?  What about a 300 blk?

There are a ton of uppers in many calibers that will sit right down on an AR lower with the RDIAS installed and run perfectly.  No modifications to an AR lower at all.  So if a 308 is illegal, why isn't a 9mm illegal.  Or a 300?

Sure like to see something with NFA technical branch letterhead.
Link Posted: 10/21/2017 5:52:48 PM EDT
[#1]
I was under the impression it was kosher to use them with any caliber as long as its not being used in a gun different from what it was registered for. Like a HK sear can be used in any similar HK platform in whatever caliber despire it only being registered in 223 or 9mm, but not in a different gun like a SCAR even if it would work. Same for SBR's and silencers that have a caliber they are "registered" in.
Link Posted: 10/21/2017 6:29:18 PM EDT
[#2]
Thanks for the reply.  

I don't think anyone questions the HK sear in any caliber.  I frankly wonder why there is a "dispute" or question regarding the AR RDIAS.  But quite a few reasonably knowledgeable people think that the RDIAS can only run a 5.56 legally.  Even in the arcane NFA tech branch world, that seems odd.
Link Posted: 10/21/2017 8:23:27 PM EDT
[#3]
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Quoted:
Thanks for the reply.  

I don't think anyone questions the HK sear in any caliber.  I frankly wonder why there is a "dispute" or question regarding the AR RDIAS.  But quite a few reasonably knowledgeable people think that the RDIAS can only run a 5.56 legally.  Even in the arcane NFA tech branch world, that seems odd.
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I don't believe that is correct.
Link Posted: 10/21/2017 8:37:21 PM EDT
[#4]
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Quoted:


I don't believe that is correct.
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Not sure what part you don't think is correct.  Elaborate please.
Link Posted: 10/21/2017 10:06:43 PM EDT
[#5]
My understanding is that as long as the rdias is in an ar15 (the gun it was designed for), you are good to go. .308 is not an ar15, thus, the rdias can't be used to convert it legally. Same for an fnc sear.
Link Posted: 10/21/2017 11:10:58 PM EDT
[#6]
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Quoted:


Not sure what part you don't think is correct.  Elaborate please.
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As far as I have known, if you have an upper, no matter caliber and it is an AR15 upper it can be put on a legal registered lower or be used on a gun with a legal RDIAS or Lightening Link in it, so any of the many different calibers is legal to use with those parts.  An AR10 upper will not fit on an AR15 lower.
Link Posted: 10/22/2017 9:38:14 AM EDT
[#7]
Thanks.  That is the concept I am going to proceed with.
Link Posted: 10/22/2017 10:13:11 AM EDT
[#8]
People are using their RDIAS on the Colt 901 with both 5.56/7.26 uppers with no problem.

Supposedly there is an "ATF Determination" letter that OK's it (RDIAS) with both calibers on the 901 platform.

901 information .................

Archived SUBGUNS.COM discussion .......
Link Posted: 10/23/2017 6:02:46 PM EDT
[#9]
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Quoted:
But quite a few reasonably knowledgeable people think that the RDIAS can only run a 5.56 legally.
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Can you name one? I have been doing this for 30 years and have never met a reasonably knowledgeable person who believes that.
Link Posted: 10/24/2017 12:52:24 AM EDT
[#10]
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Quoted:
People are using their RDIAS on the Colt 901 with both 5.56/7.26 uppers with no problem.

Supposedly there is an "ATF Determination" letter that OK's it (RDIAS) with both calibers on the 901 platform.

901 information .................

Archived SUBGUNS.COM discussion .......
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There is a tech branch letter from 2014 approving the use of a DIAS in a LE901 as I have a copy.

User xm15e2s requested the determination and received the reply.

https://www.ar15.com/forums/armory/RDIAS-in-COLT-901-UPDATE-/23-433964/

I asked him for a  copy of the letter and he provided it to me under terms not to share it or repost it.

Unfortunately xm15e2s has pretty much disappeared from the site and has not logged on for 3+ years.   A handful of folks have come to me asking for a copy, I direct them to him, and he then never replies to IM or email.  I don't know if he died or just moved on from the hobby/community.

If somebody knows how to get in touch with him, maybe they can get him to finally publically post it.
Link Posted: 10/24/2017 1:13:59 AM EDT
[#11]
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Quoted:

There is a tech branch letter from 2014 approving the use of a DIAS in a LE901 as I have a copy.
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The problem with letters not addressed to you, is you never know if they have been rescinded, and even if they are addressed to you, most folks do not follow Appeals Courts, so it could have been overruled and you have no knowledge of it.
Link Posted: 10/24/2017 1:44:12 AM EDT
[#12]
As said, if a determination letter is not addressed to you, or a company you own/run, the letter is no good and should not be relied on for much more than a book mark or picking your teeth with.
Link Posted: 10/24/2017 2:47:05 AM EDT
[#13]
Troll thread

Caliber listed is the original manufactured configuration. Nothing more. The design was not altered.
Any suppressor can be used for any round that will fit through the hole. The design was not altered.
You could not increase the opening for a larger caliber than originally manufactured without another tax stamp.
The difference is what encloses or holds the offending parts that make the design either quiet or pew, pew, pew!
Except with RDIAS the ATF was left with a problem. How to classify? They chose to basically make them their own designated MG. Although you could run into an RDIAS that is mated to a receiver.
Link Posted: 10/24/2017 11:54:28 AM EDT
[#14]
Hey,  somebody stated that there was supposedly a letter out there.  I just answered in the affirmative, that yes there was an approval letter at one point a couple years back and I have a copy as proof vs. internet hearsay.  I make no affirmation of current legality as stated it is quite possible that the letter was modified or rescinded, etc.

However, I also don’t fully subscribe to the idea that tech branch letters unless directly addressed to the end user are completely worthless either.

The industry at large highly relies upon tech branch letters to provide guidance for legality and they provide direction as to the ATFs thinking at least at that time.  It is not practical for every end user to write the ATF for their own letter, nor do I suspect that ATF wants to write thousands of replies to the exact same question.

Take the KNS letter for a lightning link protector.  The 10+ year old ATF letter stating their protector is legal to use isn’t addressed to any individual end user.  Yet virtually everyone relies upon a letter not addressed to them to provide for legality.    

I see no addition legal safe harbor for the end users just because the original tech letter was written to a “manufacturer” telling them it was legal to sell at that time vs. relying upon a letter written to an individual covering the exact same situation.  

Folks rely upon tech branch determination letters not specifically addressed to them all the time for slidefires, braces, shockwave’s, digital triggers, and the myriad of other products that slide right up to the line of legality without tipping over.   There are individuals here who are building “semi-auto” M60s utilizing legal determination letters written to guy who has been dead for years, lots of folks who make their own personal bump stocks, etc.

Could you be prosecuted relying somebody else’s letter….sure.    Could you be prosecuted even if you have your own letter….I believe you could be.  Just because the ATF wrote you a determination letter years ago doesn’t mean that they didn’t change their mind and decide to make an example out of you if you garnered their attention somehow.

That said, in my opinion, the odds of being prosecuted are reduced if you hold a tech branch letter be it addressed to your or somebody else (manufacturer or individual).  Is it better if its addressed to you personally…sure.  However, I don’t think there are a whole lot of district attorney’s out there that would waste their time and resources to take a case to a jury with a tech branch stating the behavior is legal unless there are some other mitigating circumstances.

Honestly, if you want a completely risk free hobby than collecting and shooting NFA firearms probably isn’t for you.   There are a host of federal and state laws to contend with not to mention a venerable booby trap of potential historical and technical pedigree issues for the guns themselves.

Issues such as receivers that have been replaced post 86, receivers that may have been “over-repaired”, receivers that have been illegally remarked (HK93 to HK53), sears that have become unmarried from their host, sears married to drilled receivers post 86 (like AKs and FNCs), Stenling conversions, anybody who owns a suppressor with a replacement tube that isn’t original or a historical repair no longer considered kosher, anybody who owns an extra dead-air wipe, etc..   If the ATF wanted to be an asshole they could probably find some technical violation for a lot of NFA owners out there.

If you want to feel extra safe write the ATF a letter asking for your own DIAS in 901 ruling.    The challenge here is that in my personal experience the ATF doesn’t answer the vast majority of the letter written to the tech branch.  I think I have personally written the tech branch about 4 or 5 times over the past 15+ years and they have never once responded back to me including my own personal LE901 determination question letter.
Link Posted: 10/24/2017 12:08:33 PM EDT
[#15]
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Quoted:
As said, if a determination letter is not addressed to you, or a company you own/run, the letter is no good and should not be relied on for much more than a book mark or picking your teeth with.
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14th amendment provides equal protection of the law, so the opinion of the letter applies to all, regardless of who it is addressed to.

Anyone have a letter saying it is ok to have a sear cut upper? How about a f/a carrier? f/a firing pin? No? Well you do not need one as prior rulings apply to you.
Link Posted: 10/24/2017 12:27:37 PM EDT
[#16]
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Quoted:


14th amendment provides equal protection of the law, so the opinion of the letter applies to all, regardless of who it is addressed to.

Anyone have a letter saying it is ok to have a sear cut upper? How about a f/a carrier? f/a firing pin? No? Well you do not need one as prior rulings apply to you.
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In theory I agree.  

In my years of dealing with the various branches of the Federal Government, it is not always true.  I really wish that was the way that it always worked.

The biggest problem with the BATF is they are not always consistent in their determinations and/or actions, once such incident earlier this year showed that when the fake sear hole engraving situation came up.
Link Posted: 10/24/2017 12:43:47 PM EDT
[#17]
I think as long as you don't have to modify the RDIAS to work, then it's legal to use. Like it's not legal in a regular AR-10 because you would need a longer trip to work correctly. But in the Colt 901 which has AR-15 control group the RDIAS can work with no modifications. As long as it's plug and play I see no reason why it wouldn't be legal. You can use whatever calibers you want. I really like .22lr/9mm/5.56mm the best. I wouldn't mind doing a 45acp AR-15 also. Or maybe a 7.62x39mm as well. I like 300BLK a lot for semi-auto, but it's not my favorite for full-auto, kind of sluggish and expensive to feed. 
Link Posted: 10/24/2017 9:07:28 PM EDT
[#18]
Thanks for the opinions folks.  I appreciate the effort placed in the detailed posts.

I have a Colt 901 purchased because of what you guys added to my thought processes.
Link Posted: 10/25/2017 8:52:58 PM EDT
[#19]
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Quoted:
My understanding is that as long as the rdias is in an ar15 (the gun it was designed for), you are good to go. .308 is not an ar15, thus, the rdias can't be used to convert it legally. Same for an fnc sear.
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Correct
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