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Most folks are aware that M1A and Armscorp receivers have extra wide base rails on the right side. Back when, we thought this was a good feature on commercial receivers because it presents more surface area for glass bedding. Now days, with fewer NM rifles being built, it's not that important. Most receiver makers today make their rails close to mil spec. I've checked a few and found that SAI is still making their rail about .205" wide. Bula receivers are running about .145". Compare this with a Winchester GI receiver at .163". One LRB I checked was .174" (very early production).

So much for keeping things standard. Anyway, the issue I've run into isn't that they are all different, it's that the wide rails do not lend themselves well to installing a dummy selector kit. At least when the full length connector rod is used. The rod runs down the left side of the receiver rail and hooks in front of the op rod which activates the connector assembly.
Wide rails displace the rod further away from the receiver and sometimes completely outside of the stock and out of contact with the op rod. They can be installed, but it can be ugly and the stock may be damaged by the modifications required to install the selector assembly. Something to think about if you have a rifle with a wide rail.

I don't recommend installing a complete dummy connector assembly on SAI or Armscorp receivers.
 

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Ted, thanks for posting this. I have been able to use a full dummy kit with my SAIs and USGI wood stocks, but sometimes it’s a lot of tedious work to get it right. I agree that a somewhat thinner rail would be better for the reproduction rifles equipped with fake selector switches.

I think a real issue is SAGE chassis and an SAI receiver. No flexibility with aluminum and no room for the connector rod. I think if I do a SAGE chassis with my extra SAI receiver I’ll have to use the selector switch with just the very rear end of the connector rod. (Only about 1” horizontally). The full connector rod appears to be a no-go on a SAGE chassis.

I’m curious about what others have done to mimic the military rifle with a faux switch, as the vast majority of SAGE chassis rilfes I see so not have anything in the selector cut out area.
 

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Ted, what are the GWLA receivers miking at and how consistent are their rail widths??? -Lloyd BEERCHUG1
 
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Ted, what are the GWLA receivers miking at and how consistent are their rail widths??? -Lloyd BEERCHUG1
I measured one of my GunWorks and it fell in between 163-168 damn near spot on USGI specs at least according to Winchester.

I love me some GunWorks of Alabama receivers.

REN GI2
 

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I did fit one to an Armscorp receiver, took some doing but it looked fine to my eye. I ended up taking it off when informed that it was technically a machine gun part violation here in WA state. I later went back and screwed just the round button back into the stock at the selector cut out just to fill some of the hole. I figure if anyone gives me any guff about it, its two screws and gone.
 

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Add Fulton to the list of receivers with the wide rail. At .303 it is the widest in my herd.
I have installed Hawk's kits on most of them. Just have to move the rear base slightly outboard for the ones with the wide rails.
Nice thing about moving it outboard is that it removes the necessity of clipping the nub on the auto trigger/sear for clearance.
Others checked.
Win USGI .1625
GWLA .184
Bula .184

[URL=https://s1180.photobucket.com/user/nf1e/media/IMG_2488_zps5ujcmxqp.jpg.html][/URL]
 

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There is a thread in the M14 FORUM where I gave all the specs to install /modify the connector arms for wide rail receivers. The connector arm has to be extensively modified but will give the same basic appearance when installed.

This is the widest rail receiver the Fulton Armory ,actually the wide rails offer advantages over USGI spec.The flat contact surface of the Fulton Armory is over double the size of USGI .This is why they make them that way.

No cant to op rod
Nearly impossible for dismounts during fire
More bedding surfaces
More consistent lock up
Less wear to camming track in op rod from uneven roller contact.

 

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My contention has been that the addition of one of Hawk's kits can actually assist in the stability of an op rod on a commercial receiver with a close to USGI spec rail. This is done, I believe, by the slight pressure asserted on the outboard side to the op rod by the vertical part of the connector rod, tending to keep the operating rod in more of a plumb position during cycling as it would have on a USGI rifle.
Functionally , I think, Hawk's kits have added to the repeatable accuracy on some of my rifles. This does add another point that needs lubrication.

[URL=https://s1180.photobucket.com/user/nf1e/media/IMG_2489_zpsauqnmk2t.jpg.html][/URL]
 

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It has always been my understanding that SAI went to the wider rails in order to take advantage of all the used USGI operating rods that became available in the 1990's. These oprods had slightly worn tabs.

On a similar note, they also had 4 different receiver lengths, to take advantage of all the USGI barrels that now needed SAAMI .308 spec headspace.
 

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It has always been my understanding that SAI went to the wider rails in order to take advantage of all the used USGI operating rods that became available in the 1990's. These oprods had slightly worn tabs.

On a similar note, they also had 4 different receiver lengths, to take advantage of all the USGI barrels that now needed SAAMI .308 spec headspace.
I think originally is was to prohibit normal use of the connector arm. The ability to use worn op rods was a added bonus.
 

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Iron Worker, can you post the thread you mentioned regarding connector rod modifications? I can’t find it. I think it would a lot to this thread. Thanks.

FWIW, I suspect the wider rail was done to make the receiver stronger and provide more bedding surface. After all, the original inventors of the M1A perceived a market niche for civilians to have a semi-auto M14 type rifle to compete with in the Service Rifle competitions. All such rifles were of course glass-bedded by the early 1970s, hence my theory re the wider rail.
 
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