Today I installed a new Bushy M4 barrel on my carbine. I used a set of vise blocks that I got from Bushmaster, even wraped the barrel in a towel prior to inserting in the block, but still got marks on the barrel from the blocks. How do you install a barrel and avoid leaving the barrel looking like a hack gunsmith did the job?????

Try steel wool and CLP to get it off. Receiver blocks are a whole lot better, Brownells sell a good one.

MM419

First, you should've used a receiver block instead of the barrel blocks.  Bushmaster sells 'em.

If you have silver-colored marks on the barrel from the vise blocks, you can blacken them with Birchwood-Casey Aluminum Black and they'll blend in with the parkerizing on the barrel so you'd hardly notice them.

The sales rep from Bushmaster at the BRC last summer sold me the vise block specifically for installing barrels. But I see that the action block would probably eliminate the problem I am having. A little CLP and some steel wool cleaned it up though, it was metal from the vise block and not actual marring of the barrel metal.

Use vise jaws only for removing and installing muzzle brakes and flash hiders.  

For barrel installation, use the action block.

When you tighten the barrel nut onto the receiver with the barrel held in vise jaws, the force countering your torque on the barrel nut is concentrated on that little steel index pin of the barrel where it contacts the soft aluminum of the receiver.  Guess what happens?  The aluminum will dent and the sight will be canted unless you luck out and get alignment early.

Any marks on the barrel from removing or replacing a flash hider will be under the handguard and not show.

Ditto to what everyone else is saying, just get the receiver block, it makes life real easy.