Also, concerning serial numbers. The serial number on a stripped lower does not indicate if it is a pistol or a rifle. When you buy it from a FFL, the ATF form 4473 that you fill out will list the lower as "other" because it is not a rifle or a pistol but is a receiver.

Ray pretty much nailed it. The only thing I have heard differently is that once you convert a pistol to a rifle it is always a rifle and if you have a barrel shorter than 16 inches overall it is now an SBR.

But an unfinished lower is neither a rifle or a pistol. I wouldn't own an upper than is shorter than rifle length without a pistol lower. That's a recipe for disaster.

When you purchase a lower from an FFL you can have them mark it as a pistol if you choose.

I wished I had known that when I bought my lower. I paid way too much to have a pistol marked lower. I could have saved about 100 bucks. On the lower.

Heck right now they have bushy lowers for under 50 bucks. If my go to FFL hadn't gone under I would buy a couple more.

I found documentation on the ATF website that said that if the lower was built originally as a pistol, it can be changed back and forth from pistol to rifle and back again. I am confused by what you said about having the FFL mark the lower as a pistol if you choose. Did you mean engraving "pistol" on the lower or checking off the pistol box on the ATF form 4473?

I am talking about the form 4473. Some people are more comfortable by having that done but I'm not sure it makes a difference.

Do you have a link or PDF from the ATF document? Everything I have ever seen says once its a rifle its always a rifle. They ahd some problems with pistols sold with longer barrels and stocks claiming that once the stock was put on it was now a rifle and if it was coverts back to a pistol it was now considered an SBR.

It would be great if I was wrong. The make or used to some great conversion carbine kits for 1911's and Glocks.

Some clarification

My newest setup for the piston AR.

What front sight is that.

Here is the link to ATF concerning pistols.

ATF

They are 45 deg off set buis GD. Here is a link, https://www.youtube.com/watch?v=4GZEdtJ_LgA

Mine are a different brand but he does a good explanation of why to use them.

Thanks Ray good to see it in writing I will be printing this off and saving a copy of it.

This afternoons project a little fiddly with the hand fitting but isn't everything gun smithing. LOL

Looking Good Greaser!