The AR-10 and the SWD Lightning Link

[Quarterbore]

Following is a collection of posts that I had posted on ARFCOM. I am woried that the post there will drop off their server so I am reposting it here where I can make sure I have it...

Here is the original thread: http://ar15.com/forums/topic.html?b=...896&page=1

Posted :: 6/4/2004 12:08:50 AM

After a rather long waite my Registered Lightning Link is transfered and I picked it up yesterday from Howard Block here is SE PA (Thanks Howard!). I dry fit the link in my Post-Ban Bushmaster with my Colt SP1 Carriers and my 5.56 and 7.62x39 uppers plus my 9mm upper with my 9mm Bolt that is already setup for the link. The timing of the link seems perfect with all three bolt/carrier/uppers and every thing seems to work fine... Now I just need a trip to the range

Well, I had mentioned this prospect in the past and now that I have the link and I have an AR-10 Carbine that is on it's way from another member's out of state FFL it is time to revisit the prospect of using the Lightning Link in the AR-10

I know that the AR-10 receiver is longer then the AR-15 receiver and I also know the AR-10 carrier will need to be modified. From there, I simply mill the AR-10 carrier to trip the link at the proper time for a full-auto AR-10 Carbine.

The Lightning link would still be the Machinegun and it is working the same way it always did and when the link is removed the AR-10 would still be a semi-auto rifle. The Lightning link is the machinegun and the AR-15 is just a part added to the link. An AR-10 would be just a different part added to the link and the both the AR-15 and AR-10 would be ran by the link in the same way as the link was originally intended to run.

I need to dig out my Eagle Arms AR-10 over the weekend and drop the link into the receiver and perhaps get some photos and drawings about how I may try this but I wanted some oppinions from the very knowledgable here about if this is a project that has a chance of working. I am also curious if there is a snowballs chance in hell the BATFE wouldn't agree with my logic described in the paragraph above?

Somebody stop me if I did a little too much day dreaming while waiting for the transfer to get done! Yea, I already have a great system and I really need to get a 300 Whisper Upper done but the thought of a full-auto battle rifle just sounds like something I have to try as well....

[Quarterbore]

Well, to be honest I need to "Bulk Down" as I think I am pushing 240 these days and I am 6'2" and spent many a fine day of my youth working on my Grandparents and Uncle's farms tossing livestock and haybails around... still, full auto 308s are not fun... no contest here!

Sorry for the delay tonight getting the pics up! I thought my "peanut" (my 3-mo old daughter) was going to stay up all night!!!

I dug out the AR-10 and Bushmaster and compared them... This is going to be EASY IMHO!!! The relative distances between the AR-15 and the AR-10 FCG parts to the rear take down pin looks to be the same! Yes, they look to be very close with the only difference being the larger diameter rear takedown pin in the AR-10!

Following are the photos...

Eagle Arms AR-10 - KAC trigger on Left
Bushmaster AR-15 w/ AR-15 FCG and 9mm hammer on Right







Oh yea, my link does have a serial number... it was just "touched up" after the photos were taken...

You will note that my Bushmaster has the standard Bushmaster AR-15 FCG installed while my AR-10 has the KAC 2-stage trigger group. The LL will never work with the KAC trigger but my KAC trigger is just raw perfection where it sits so I only sat the link on top of the KAC unit for comparision! When I get the new AR-10 which is on it's way (I hope) I will get pics with a standard FCG installed.

Now, note that the lower should not require any fitting as near as I can tell! The two things that may be necessary is a custom disconnector to allow me to time the link for the AR-10 mainly due to the larger rear takedown pin (may be possible to notch the original) plus do a major milling of the understide of the AR-10 carrier. Otherwise, this looks just too easy!

Please don't tell me I am the first person to look at this as this really looks easy and I don't see why a DIAS would be a problem either for the same reasons! I just always assumed the rear takedown was further to the rear relative to the FCG pins but that doesn't look to be the case....

Oh well, it's 1AM here and my two older kids have been asleap for hours and I promised them a trip to see the USS New Jersey tomorrow morning.... Hope this helps and I will post more pics when I get the AR-10 Carbine that I would like to use the link in!

[Quarterbore]

<center><table width=85% border=0><tr><td width=100% class=textBody><hr height=1px color=black noshade>Originally Posted By David_Hineline:
I don't know what kind of photo magic you have pulled but with my AR10 it was quite obvious the distance from the rear take down lug to where the fire control componants was quite a bit furthere. .

[>:/] Hmmm [>:/] The second AR-10 I have on the way is an Armalite but I can't believe my lower would be different then others? When I get the new AR-0 Carbine I can slide pins through the FCG holes of the Armalite and Bushmaster Receivers and see if that shows things better but no trick photos here[:O)]

<center><table width=85% border=0><tr><td width=100% class=textBody><hr height=1px color=black noshade>The rear take down lug would not fit into the smaller lug channel of the DIAS, plus there is no clearance under the AR10rear lug to the shelf floor in the lower receiver. .

Now, I didn't measure the lug or fit things so perhaps you are correct here! Given the larger rear takedown it would be logical the rear takedown lug would be larger. It wouldn't affect the Link too much but the DIAS could be an issue and I sure woudn't want to modify a DIAS to use with an AR-10 (M-16 more fun plus may not be enough DIAS body to allow milling for AR-10 lug). Oh as for depth of the shelf vs lug depth, here again without fitting I can't tell if it will be a problem yet. If depth is an issue this will be a simple fix to lower that surface inside the lower on the mill[:E].


<center><table width=85% border=0><tr><td width=100% class=textBody><hr height=1px color=black noshade>Plus the cutting off of the bolt carrier changes the dynamics of the operation of the gun, You will need to find a way to put that weight back on or the bolt will be opening too soon.

I thought of that as well and if the 9mm Bolt works through the addition of a tungsten core then the same could be done with an AR-10 bolt if needed. Following is my 9mm Bolt for use with the LL and this would be a pretty exact comparison, or so I would think...

quarterbore.com/ar15m16/9mmupper/9mm_a_34.JPG

Like I said, I really want the new rifle to arive before I do much else but this looking like a project that may just work and work easier then I thought....[8P]

[Quarterbore]

Posted :: 6/22/2004 9:47:05 PM

The new AR-10 is still on it's way[:/]

www.jobrelatedstuff.com/forums/topic.html?b=7&f=120&t=209814

As for the pictures of the BAR-10, vs the AR-10. the AR-10 will be much easier to use with the LL then the BAR-10. Compare the two pics that follow...



and



Note that the rear pivot in the AR-10 is in the same location in the AR-15 and AR-10 relative to the FCG pins. Now, notice how much further to the rear the AR-10 take down lug is. What this means is that the BAR-10 would require some type of new pivot added, which I believe is quite possible, while the AR-10 should be able to be used with the link pivoting on the rear takedown pin.

Also, M60Howard here on the forums has offered to work with me on the milling and I am likely going to take him up on the offer so we can get this done. I just don't want to pull my Eagle a part but if this AR-10 carbine doesn't get here soon I may just pull my KAC 2-stage and start working with the lower on hand especially now that I have an M16A2 FCG on hand to use with the AR-10 to allow me selective fire....

[Quarterbore]

Posted :: 7/5/2004 6:36:08 PM

I finally managed to get an Armalite single stage trigger for the AR-10 to fit the link into the AR-10. The results look very good but there will need to be some milling! The first problem is that the larger opening for the FCG does not come to the rear far enough to allow the Lightning Link to sit up against the disconnect, much less trip it, when the hammer is caught by the disconect. See the folloiwng photo:


Larger version: quarterbore.com/images/qbi_ar10_ll_huge.jpg

This problem can be solved by milling the receiver to the wider diameter as shown with the pencil marks on the lower.

The second problem is that the larger rear takedown pin and subsequent larger rear takedown lug on the AR-10 does not allow enough room under the lug for the link to fit into the lower. In addition, the selector of the AR-10 is at the same height of the shelf of the AR-10 so I do not think that it will be desirable to try and mill the shelf on the AR-10 to make it fit. Instead, I think I will simply remove some material from the bottom of the rear takedown lug on the upper receiver to allow the link to fit under it.

The third issue I am expecting to have with the lower is in the rear portion of the lower as the rear takedown lug goes almost to the radus cut towards the buffer tube. I wouldn't need to mill this to the rear much to give me the slack I need or I could evaluate milling the rear portion of the takedown lug.

As for the bolt carrier, obviously I need to get the lower to function with the link before worrying about the carrier becomes important. With the LL, you can manually work the link to trip the disconnect without an upper on it and I need to be able to do the same with the AR-10 lower to make sure the mods to the carrier will be correct for the timing of the link.

This still looks like a very great project! As an aside, I managed to get a M16A2 burst kit and dremel and grind it so I have a select fire kit for the Bushmaster AR-15 and the she is golden for the 9mm, 223, and 7.62x39 uppers. By using the M16A2 hammer and cutting off and rounding the rear half of the hammer (removing the hook) it works fine even with the 9mm bolt. Thanks for those that care to share with me as I slowely work on this!