I just got a barrel assy from Fulton.  The front site base has the 4 screw windage set up but the M4gery barrel isn't milled.  I know a lot of the competition front site bases are loctited on and there are a lot of differnt types of Loctite.  What is the best Loctite compound for this application?

I'd try blue before anything else.  If it doesn't hold, then go with something stronger.

RC/609, I have a large bottle my sis gave me from when her place of employ would change/rotate stock.  It is a shaft locking compound. 242 and 271 or worthless compared to this stuff.

Find a large industrial Loctite supplier/distributor to locate this product. If I had a way to get a small spoonfull, I'd send it, unless I have a tiny tube that is empty, as I used to get all kinds of Loctite/Permatex products when she used to work. Got some tubes of Prussian Blue to get rid of.....

Odiedog,
I have used Loctite frequently in the automotive business. I have used loctite on my firearms for mounting scope bases only to date.
I have used 242 blue for my mounts, which is removeable. 262 red is a permanent loctite and requires heat and muscle for removal. I think the 271 red is for studs and bearings.
Most important thing about using Loctite is to remove all oil and grease from both threads. Auto brake cleaner works great, just dont get the brake cleaner on any plastics or paint as it could cause damage. I believe that the Loctite is an anerobic compound, it sets up with the absense of oxygen. Keep the bottle or tube of loctite clean as the container "breathes".
You can purchase small tubes of loctite at your local auto parts store.

Dan

Hmmmmmmmm!  

Never heard of using Loctite to attach a major component such as a front site base to a barrel.  Why don't you use the traditional means such as taper pins, roll pins, setscrews, or clamp-on FSB's such as Armalite's??  

Barrels can get very hot and heat and Loctite don't go well together.

Fulton sent the barrel with a FSB with the 4 screws aleady drilled and tapped. They didn't mill the flats on the barrel though.  Go figure. I'll probably get the flats milled on.  I was going  to use the Loctite for backup.  I used to work in a machine shop 20 years ago and couldn't recall which of the loctite compounds  worked best or if any new compounds were out.  I have heard of a few good AR gunsmiths using Loctite to supplement the screws.

Thanks for the feedback.  Steve