Hi All.

I have a 14.5 pinned M4gery.  I purchased an Aero 16" M4 carbine barrel to replace it so I can swap muzzle devices.

I just realized that the barrel is not drilled to accept the FSB that I was going to take off the old barrel.

What are my options?

Is it possible to have a clamp style block with flip up front?  The upper has already been changed to a flat top.

Is so, can I still use the Magpul plastic hand guard?

Cheaper at Gunpartscorp.

True if they are still in stock. You have to be careful though because there is two listings..one is for the clamp on and one is for the taper pinned version, they do not tell you which is which in the description.

But yeah op, you have several options from easiest to more involved.

Option 1 - Clamp on/set screw etc. FSB, either fixed or folding. Their are a few options out there but I would suggest a clamp on type; the A.R.M.S #41-B sights are badass, give that classic FSB look when deployed or can be stowed folded and out of the way. The clamp on version is as easy as it gets to install. There is also a pinnable version that is as complicated to install as any other virgin pinnable FSB/GB (not impossible, but much easier to fetch up).

Option 2 - Have a new FSB drilled, taper reamed and pinned to the barrel. If you do not have the skill set or tooling to do this there are gunsmiths and machinists who can do it for you (ADCO and Retro Arms off the top of my head). Going with a new FSB and a virgin barrel should be much cheaper than trying to reuse the old FSB or reusing a barrel that  previously had a pinned FSB installed.

Option 3 - Reuse old FSB. This would be the most difficult, time consuming and likely the most expensive option if paying someone to do the work for you. You would likely have to find the exact center of the previously drilled and taper reamed hole, drill across the barrel without the bit deflecting off of the round barrel (likely use an end mill to mill a flat first) and then slowly open up the drilled channel to match the taper of the existing FSB..without going overboard or enlarging the tapered holes. It can be done, but you will either have to be skilled or pay someone who is to do it right. Honestly I would only suggest going this route if it was some rare clone correct FSB.

Thank you All.

I am thinking I may sell the barrel as new in wrapper.  I paid$160 for it.

I can pick up a barreled upper from Aero for $350.  Plug and play.

The barrel plus adco install would be $290 plus shipping...

You can also use a Yankee Hill Machine flip up sight / gas block combo.  They run about 75 bucks, clamp on install, compatible with standard front handguards or a variety of free float rails.  It's nice that the sight flips down, and a little less expensive than an ARM's mount.

INFO

Cool, but from experience that is not accurate. One part number is for the pinned version, one is for the clamp on. I dont recall which is which, the good news is you can get both at Numrich for less than the price of one nearly anywhere else so my buddy wasnt complaining and ended up with two lol. He was pleasantly suprised by receiving the pinned version since they are hard to find right now and ended up ordering the other part No. to get the clamp on version.

Does anyone make a clamp on like that with a standard front sight and not a folder?

JP does, but it's an adjustable gas block.

If you want a FSB, it's best to have the barrel drilled for a pinned FSB. There are jigs, but they are not perfect. It's not something the average person or gunsmith can tackle.

Yeah JP is the only non folding, traditionally styled, true clamp on (aka not set screw) FSB I am aware of that is currently availible. RRA used to make a nice non adjustable one but they have been discontinued for sometime.