someone educate me please

[LORD of WAR]

sear block vs no sear block
small push pin vs large push pin
mag fence
blue label and green label

im lookin to buy a preban lower and these terms keep coming up and i have no idea what they mean

the one i may make a move on is a colt sporter lightweight with sear block and small front push pin...what does that mean? will i be able to mate it with a RRA upper?

 

[dreppucci007]

The only part I really know of is the Blue Label vs. Green Label...

The Green Label is referring to Colt's preban rifle boxes...They had a green label on the side telling you the model, etc. The newer ones have a blue label, hence the Blue Label terminology.

 

[Moderator]

http://www.gunsnet.net/forums/archive/index.php/t-127066.html

"sear block" is a square hunk of aluminum that they placed in the back of the lower receiver that extends up into the lower part of the upper receiver.......so that a M16 bolt carrier couldn't be used, or a auto sear couldn't be installed.....as for bad, it really isn't "bad" it's just something COLT did to discourage folks from making their weapon a select fire one. there really is no mandate for it to be in the rifle, they did it as policy. the only thing about those blocks, is that you will have to have a AR bolt carrier that is completely milled out of the bottom so it will pass the block......you can't use a half milled out AR bolt carrier that other makers have. you can if you want to mill the "sear block"out.

AFAIK older models such as the SP used the large push pin.
http://www.fulton-armory.com/CombiningColtLowers-withStandardUppers.pdf

Note that “large pin” in this case refers to the front, pivot pin hole.
You can determine if your receiver is a “large pin” type if its front, pivot pin hole is larger (0.315”) than its rear, takedown pin hole (0.250”).

AFAIK, Full "fence" around mag release button was designed to protect from accidental magazine release. I have been told it also stiffens the receiver as well. I don't have a source for that.
Fence

No Fence

 

[sdavid]

Nothing to really add that hasn’t been posted other than I am 1/3 of the way through my first AR-15 build.

With the small hole pivot pin you should be able to mate an RRA or Stag upper to the lower. Bring the lower with you when you go to look for an upper to see how well it will fit. That is my plan for the next show in Marlboro.