Weird times made me wanna build a pistol.  The only other I did was a 12" 7.62X39 from a stripped lower a few years ago.  

It fell in the creek.  

This one is a 10" and I am having gas tube length anxiety.  I've never asked a tech question here I don't think...

Anyway...when I was collecting cheap parts months ago (years?) I got a "pistol" length gas tube and a "mid" length gas tube.  Now that it's time to assemble, neither are correct.  My barrel is 10 1/2" in length (advertised and measured from rear of barrel extension to end of threads) and when installed (fully seated but without a barrel nut) onto my upper receiver, I measure 10" for gas tube length needed (accounting for depth into receiver to reach the gas key, depth into gas block to have the pin hole line up, and with the gas block hole lined up with the gas hole in the barrel).  The pistol tube I have is about 6 3/4".  The mid tube I have is about 11 7/8".  None of the "regular" sources for tubes actually list a length spec so it's tough to choose which one to buy.

I could shorten by "mid" tube but then the slight bubble type flare on it's rear end would be lost and I wonder if that would seal well with the gas key.  I guess I could have an oddball barrel not worth a crap because it was $60 new but it's a 10" 5.56X45 so the bullet won't be in there long.

I am an automotive technician with access to tubing and flaring tools and I have a Dremmel but this sounds tedious for a $11 part.

Am I making this too tough?  Sorry about the question that has likely been asked 35416541 times but the search function on this site is a PITA.

TIA

Carbine length has tube

Dang

I feel dumb

Right on brother

But why does a pistol need a carbine gas tube?

Guess that's what I get for having all mid length 16's...

Gas length and what the ATF considers a pistol are not related.

Technically you could have a "pistol" with any barrel/gas length.

10.3/10.5" barrels are most likely going to be carbine gas assuming we are talking a 223/556 barrel.

Related:

https://www.ar15.com/forums/AR-15/Is-it-a-requirement-to-use-a-rifle-buffer-with-a-rifle-length-gas-system-/118-761757/#i8237156

Gas port location has nothing to do with about anything other than gas tube length (one could argue handguard length as well).

Somehow I double posted.

common use barrels for 10.5 to 12.5 is all carbine, 13.x and up is usually midlength but a lot still make them in carbine still.

rifle length is usually 18+

Yup, although I’m considering a mid length 12.5 just to see how it shoots.

Your post has ZERO to do with the subject.

Where is the gas port located on your barrel? As in what distance from the end?