Ive got a good line on a colt 1x7 20" HBAR, can this be turned into an M4 barrel? If not maybe Ill just trade it off.

I don't think you can do that easily because of your front sight. However, instead of making it an M4, why don't you consider to make it a 18" SPR or 16" dissipator. Those two types of rifles don't give you the look of M4 but the power and ease of handling.

Yes - you'd still have the two pin cuts, plus the gas port hole, which would be right at the 12" - 13" mark.

I am shortening a 20" HBAR blank to 16" right now, but this BBL has no sight cuts/holes.

The M4 contour would probably not be cost-effective in the long run. You'd need to re-finish it, plus mount the front sight again, and locate & drill the gas port hole, then pin the sight base...blah...

Try a Sale/Trade posting in the Equipment Exchange.

Is the gas hole and pin locations on the 20" barrel beyond 14.5"? If so I dont see the big problem in drilling a couple new holes.

No. The gas port hole is exactly at 13.5", measuring from the very rear end of the barrel. The rear pin is just about 1/8" behind that, with the front pin 1.5" ahead of the rear pin.

(I measure 13 1/8" from the bolt face to the gas port hole, on 20" barrel).

You could make a 3" long fake suppressor, internally threaded full length, thread the end of the barrel where the holes/cuts are, and cover all that stuff...And then make it permanent...

Lotta work...makes me tired just thinking about it all...

Looks like it wont work. Thanks for the info guys. Hmm maybe an spr clone, or Ill just trade it off. Thanks for the help.

If you have a lathe, and like to watch chips fly, then this is a worthwhile modification (shortening 20" to 16" or less).

I have seen new mil-spec 20" HBAR barrels for ~$50...

Thanks again.