Question for AR Builders

[Jingles]

Ok the first thing to do is admit you don't know all the answers so I'm asking what might be a silly question for some but I Don't know so am asking those that do.
If a person has a complete lower assembly for a 5.56/223 is it possible to switch out the uppers between the 5.56 and say a 6.8 or 7.62 so that 1 lower would be enough for the other uppers so in essence have 3 different calibers to choose from depending on the game being pursued?

[chrisb]

Yes... but switching mags may be required.

Also with 7.62x39 you'll want to do a lot of research on getting reliable mags as they tend to have feeding issues due to cartridge dimensions.

[Jburke]

Yes... but switching mags may be required.

Also with 7.62x39 you'll want to do a lot of research on getting reliable mags as they tend to have feeding issues due to cartridge dimensions.

Just built an upper in 6.5 grendel and will be using the same lower.  Toss in a couple new mags and I was good to go.

[JohnVH]

same lower for any upper, but have to get a mag to work with the caliber your using. Thats why I dig AR's, it can be almost anything.

[carpsniperg2]

There is some cal that will switch and some that will not. If you have a ar-15 lower you can't run the 308 or 243 etc on that lower you have to go to the ar-10 lower to get into those cals. Also do not quote me on this but I am pretty sure you have to have a multi cal stamped lower to run different uppers. If it is stamped 5.56 only and you have a 6.8 or 6.5 on it I do not think that is legal to do, or at least that the way I understand it to be.

[Atroxus]

There is some cal that will switch and some that will not. If you have a ar-15 lower you can't run the 308 or 243 etc on that lower you have to go to the ar-10 lower to get into those cals. Also do not quote me on this but I am pretty sure you have to have a multi cal stamped lower to run different uppers. If it is stamped 5.56 only and you have a 6.8 or 6.5 on it I do not think that is legal to do, or at least that the way I understand it to be.

I never heard of the multi-cal stamp, so I am just tagging this to find out if someone else can confirm or refute this. 

[grundy53]

There is some cal that will switch and some that will not. If you have a ar-15 lower you can't run the 308 or 243 etc on that lower you have to go to the ar-10 lower to get into those cals. Also do not quote me on this but I am pretty sure you have to have a multi cal stamped lower to run different uppers. If it is stamped 5.56 only and you have a 6.8 or 6.5 on it I do not think that is legal to do, or at least that the way I understand it to be.

I never heard of the multi-cal stamp, so I am just tagging this to find out if someone else can confirm or refute this. 

If you buy a stripped lower it will be stamped "Cal: Multi". They do this since there are various calibers that can be built on the lower and they don't know which caliber is going to be used. Not to mention the fact that you can run multiple uppers on the same lower.

[BsB]

AFAIK its not illegal to change upper calibers. Lowers are good like previously stated to 6.5/6.8spc/7.62x39 and even .50 beowulf with different mags. Its only illegal if you put a barrel less than 16" on a lower receiver built originally as a rifle.

Sent from my Nexus 4 using Tapatalk 2

[carpsniperg2]

See some lowers are stamped just 5.56 not all are stamped multi when you buy a stripped lower.

If it is stamped only 5.56 on the lower and you run a differnt cal upper I am not sure if that is legal.

[Atroxus]

There is some cal that will switch and some that will not. If you have a ar-15 lower you can't run the 308 or 243 etc on that lower you have to go to the ar-10 lower to get into those cals. Also do not quote me on this but I am pretty sure you have to have a multi cal stamped lower to run different uppers. If it is stamped 5.56 only and you have a 6.8 or 6.5 on it I do not think that is legal to do, or at least that the way I understand it to be.

I never heard of the multi-cal stamp, so I am just tagging this to find out if someone else can confirm or refute this. 

If you buy a stripped lower it will be stamped "Cal: Multi". They do this since there are various calibers that can be built on the lower and they don't know which caliber is going to be used. Not to mention the fact that you can run multiple uppers on the same lower.

So is this a legal restriction if it is missing the stamp, or just a safety one? Like saying "Hey we only tested this lower with 5.56, so we are not going to mark it "Multi-Cal" that way we can't be sued if someone puts a .50 BMG upper on it and it explodes"?

[carpsniperg2]

Like I said I do not know the legal laws. For a person wanting to run different uppers I would think you would need a multi cal lower. If it's stamped 5.56 and has a 50bmg upper on it I am not sure if you could get into trouble on that. I have always went the safe way and got multi cal lowers.

[chrisb]

I really don't know that I've ever seen a lower not stamped "multi". I've got a factory built rifle and it even says "multi".

You'd probably be dealing with a much older lower if it were stamped with an actual caliber, unless there is some weird reason why they would do that in a ban state maybe.

[carpsniperg2]

That's my thoughts, there is some reason why they have some stamped 5.56 and others stamped multi. All the factory 223's I have bought have always been marked 5.56 on them. So it must have to do with something or every lower out there would be stamped multi.

[carpsniperg2]

She check this out.

http://www.gunbroker.com/Auction/ViewItem.aspx?Item=333037265

Marked 5.56 ONLY

http://www.gunbroker.com/Auction/ViewItem.aspx?Item=333244619

Marked muti

[grundy53]

She check this out.

http://www.gunbroker.com/Auction/ViewItem.aspx?Item=333037265

Marked 5.56 ONLY

http://www.gunbroker.com/Auction/ViewItem.aspx?Item=333244619

Marked muti

I'm thinking since it is on gunbroker.com someone stripped a factory built AR and sold it piece buy piece. I can't think of a reason why a company would stamp a stripped lower 5.56 unless they were using it to factory build a 5.56. I don't think those lowers would be as marketable.