I just purchased a 20" stainless heavy barrel that has a diameter of .7470 at the gas tube hole, and a YHM low profile gas block. The gas block wont slide up to the gas hole. Any one know the diameter of that gas block? and how tight is a gas block normally when slid onto a barrel? this is my first build so i have never put one on before. Thanks in advance

their catalog does not list the diameter.  some of the others are .625 or .75.  so it must be .625 if it doestnt fit.  measure with calipers for sure.  the specter is also low profile, offered in both diameters, and is removable with muzzle device.

hmmm. i guess im buying another one. Any one want a brand new gas block?

If your barrel is .747 and the gas block is close, you need to measure the ID.  Size on size will be a light press (plastic hammer) fit and it should go on.  If the gas block is actually smaller, you could take it to an automotive machine shop and have them hone it on their piston pin hone.  You don't want a sloppy fit.  It should be snug.

Quoted: I just purchased a 20" stainless heavy barrel that has a diameter of .7470 at the gas tube hole, and a YHM low profile gas block. The gas block wont slide up to the gas hole. Any one know the diameter of that gas block? and how tight is a gas block normally when slid onto a barrel? this is my first build so i have never put one on before. Thanks in advance

Are you sure of the 0.747" measurement?
I think you may be measuring across where the hole is.
The gas block seat should be 0.7498" (measure with micrometers, don't trust calipers)
Now, most 3/4" gas blocks will measure from 0.751" to 0.752"
They usually slide right on.

Front sight bases are right at 0.750", probably reamed to size, so they are mighty snug.
YHM gas blocks also seem to run tight, just add grease/oil and tap it on with a nylon faced hammer.
A tight fit is good, keeps the gas from leaking out...

Randall Rausch
www.ar15barrels.com

if it were a .625 gas block i dont think it would have even slid onto the muzzle of a heavy bbl.



clean both mating surfaces