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Posted: 12/4/2011 6:50:22 PM EDT
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I know that a RDIAS can work in an AR-10, but the ATF takes a dim view to the practice since the DIAS was designed for an AR-15. While I don't agree with their view at least the ATF is showing some consistency ( FNC sear in a SCAR, HK sear in a UMP) but after seeing the Colt 901 I began to wonder about the legality of utilizing a sear in this lower. From the magazine well back toward the stock it's the same as an AR-15 and uses the same FCG and when the 7.62 upper is removed it will function with any milspec 5.56 pattern upper so I don't see this being any different than running a MGI lower. I know that the answer is that this is probably forbidden but at the very least it could make an interesting hypothetical conversation. What say the resident subject matter experts? Even if I can't run my sear in this I still want a SBR. Gun in question: http://www.coltsmfg.com/Catalog/ColtRifles/SP901.aspx Posted Via AR15.Com Mobile |
| RDIAS in an AR-10 is a no go. The sear trip isn't long enough to work. Also I think to the ATF it is considered a different weapon type. You are only allowed to use the RDIAS in an AR-15. The MGI lower is still an AR-15 lower, and it is a great lower for an RDIAS host. |
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I know the AR 10 needs a taller trip and I used to have a MGI lower but with the limited amount of info I have been able to find about the 901 is it is capeable of running both uppers with a GI autosear. So the existing trip in my DIAS should function in theory. Since an unmodified 5.56 upper will work and the FCG is the same as what is already in my current host lower why would this be forbidden?
Obviously I have no intent in writing the ATF as little good comes from that course of action but I still think it poses an interesting question on the extent of the versatility of a DIAS in an AR style weapon. Posted Via AR15.Com Mobile |
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Quoted:
I know the AR 10 needs a taller trip and I used to have a MGI lower but with the limited amount of info I have been able to find about the 901 is it is capeable of running both uppers with a GI autosear. So the existing trip in my DIAS should function in theory. Since an unmodified 5.56 upper will work and the FCG is the same as what is already in my current host lower why would this be forbidden? Obviously I have no intent in writing the ATF as little good comes from that course of action but I still think it poses an interesting question on the extent of the versatility of a DIAS in an AR style weapon. Posted Via AR15.Com Mobile I would be interested to see if it would work in a 901 as well. I've been wondering about that since I first saw them and the same AR10 questions went through my head. As much as I don't think it's a good idea, I'm sure that someone will write to ATF for "clarification" and we will have an idea of where they stand on it. Does the 901 use a standard M16 FCG or is it something else? Speaking of MGI, they originally had plans to make a .308 upper that fed from a G3 magwell IIRC. Of course that has yet to materialize and I can't even seem to get an AK74 magwell from them so... |
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The FCG is standard M-16 from what I can gather but the 7.62 bolt carrier likely follows the design of other AR-10 type guns. I think the key to this being ok is that it will run AR-15 uppers which no other AR-10 type rifle will do. I really don't see a functional difference between this rifle and the MGI. I actually just sold my MGI lower since they seemed to be going the way of the shrike with MGI's lack of available mag wells. I tried for several months to buy an AK-74 well but after several calls and emails the best answers I received was that they didn't have any and there wasn't an idea on if or when more would be made. I love the idea of running multiple calibers with my DIAS, but having a modular lower without spare mag wells is rather pointless. If a sear will run with a 901 it could be a great host and I would bet that an enterprising individual could fabricate magwell adapters for almost any mag that fits in a SR25 sized envelope. |
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The MGI lower is a very poor lower for a RDIAS host!
earlier MGI lowers had the SP1 style bump to support the DIAS side and were very good. Later MGI and current MGI no longer have that bump and thus may require shims on the side. Remember RDIAS were designed for Colt SP1 spec lowers. AND Colt uppers without the auto sear cutout. |
| Oh ok interesting, so this new rifle might work with a standard unmodified RDIAS? Well if it does then the ATF may consider it ok. I would be interested in this since I also have an RDIAS. I guess someone will just have to test it out to see if it actually works. |
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My take on this is this.....................................
I bet Colt will have a sear block in this SP901 lower, being a unmilled portion blocking a RDIAS, just like every new Colt AR lower has. To use your RDIAS in this SP901 a person would have to mill out that sear block. ATF will say no you cant do that on this specific SP901 lower! ATF doesnt really care if you remove the sear block in a Colt AR lower since the RDIAS is designed for the AR anyway. ATF view is that use are just returning the AR lower to normal semi auto specs similar to millions of other makers AR semi lowers. BUT in the case of this SP901 lower, it cant be said that removing the sear block is just returning it to a config of all other lowers of its kind BECAUSE there is no other lowers of its kind by other makers that didnt use a sear block. Since you are modifying the SP901 lower I bet ATF will say no. ATF needs a reason to stop people from using their RDIAS in this SP901 and I bet they pull this exact reason out of their ass! It may also occur that ATF says you can no longer remove the sear block in a Colt AR because ATF will need to level the logic in any ruling they make against SP901 block removal. NOW...............If Colt doesnt add a sear block, I would think there is great possibility to use your RDIAS with approval. |
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Quoted:
My take on this is this..................................... I bet Colt will have a sear block in this SP901 lower, being a unmilled portion blocking a RDIAS, just like every new Colt AR lower has. To use your RDIAS in this SP901 a person would have to mill out that sear block. ATF will say no you cant do that on this specific SP901 lower! ATF doesnt really care if you remove the sear block in a Colt AR lower since the RDIAS is designed for the AR anyway. ATF view is that use are just returning the AR lower to normal semi auto specs similar to millions of other makers AR semi lowers. BUT in the case of this SP901 lower, it cant be said that removing the sear block is just returning it to a config of all other lowers of its kind BECAUSE there is no other lowers of its kind by other makers that didnt use a sear block. Since you are modifying the SP901 lower I bet ATF will say no. ATF needs a reason to stop people from using their RDIAS in this SP901 and I bet they pull this exact reason out of their ass! It may also occur that ATF says you can no longer remove the sear block in a Colt AR because ATF will need to level the logic in any ruling they make against SP901 block removal. NOW...............If Colt doesnt add a sear block, I would think there is great possibility to use your RDIAS with approval. I disagree. If this receiver will accept a standard AR-15/M16 upper then it is in the same family of firearms IMHO. The one thing in the linked page I didn't see is how a magwell adapter for use with standard uppers would work. My limited understanding is that use of a DIAS with the AR 10 isn't allowed (as stated above) is that a standard .223 upper won't work with the AR10 lower, so they are not the same family. As far as modifying the lower, if the SP901 is in the same family, I can't see where there would be any issue with machining out the sear area for DIAS use. As Tony says, YMMV. Scott P.S. For me personally, while adding another caliber for my DIAS, would be cool, but I've never found full auto .308 to be "fun". Add a Beta C and 100 rds of .308 and you best be eating your Wheaties if you want to shoot that off hand. The G-3 and FN FAL that I've shot off hand in full auto where very muzzle heavy. Once I pulled the trigger, they went from muzzle heavy to climbing quite rapidly. I'm sure shortening up the barrel would help that, but you'd get into the same problems as with .223 short barrels only more so. Plus you'd get into the noise and concussion like a HK 51. Good luck with the project. Let us know how you make out. |
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The ability to use standard uppers was also what led me to believe this may be ok. The larger dimensions of the mag well and the possability of other caliber and magazine conversions is what appeals to me.
I used to have a HK91 that I used with my sear and while I could control it the gun felt like shooting a pogo stick. I have shot a few other auto 308's and the AR10 was the most controllable for me. The M14 is probably the only MG that I have no interest in shooting again. After the second round it turned into an artillery piece and out of the 6 guns I had in my armory I could only keep 3 running reliably. I wouldn't put many rounds through it if it works out, but it could be fun now and then. Sorta like a tamer HK51K. Posted Via AR15.Com Mobile |
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Did you guys notice that a standard AR upper must be fitted with some kind of extension adapter the extends the length of the AR front lug so it will reach the SP901 front lower push pin?
Anyone have pics on that feature? Full auto with .a shoulder fired 308 is a total waste and beats you to a pulp, BUT it would still be super cool to have one!. With a high quality Steel RDIAS reaching 15K right now, think about adding 2-3K to its value if its allowed to be used in the SP901. |
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Quoted:
Wait.... an FNC sear will work in a SCAR!?  
(i've never touched a scar and never seen a FNC sear) 
- Clint FNC sears can work in SCAR's but the ATF said no. However the FCG while similar is not interchangeable between weapon types so I can understand their decision. That doesn't mean I agree with it but at least it's in line with some other rulings. Posted Via AR15.Com Mobile |
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