New Armalite carbine question.

[brazosvet]

Just picked-up my new AR-10 A4CF with the rail gas block and flat-top reciever.  I would like to replace the gas block with a A2 front sight.  Is this difficult to do?  Will the finish on the barrel show marks where the gas block was attached?  I may want to change back later on if I decide to attach a scope, but for now I just want the iron sites and the gun to look like the infantry model.  I plan on adding the detachable carry handle for my rear site, and preferr the look of the A2 front over the clamp-on A2 style.

[Robocop1051]

Not 100% plug and play. But if you're willing to make sacrifices, it can be done a lot easier.

The A2 front sight requires two taper pin holes drilled through the bottom of the barrel. Not all barrel have these holes pre-drilled. In fact, if you don't have an A2 sight on your barrel now. I'll bet the holes aren't there at all.

Don't fret, there are still options. Armalite make a clamp on style A2 sight. I think there is even a bayonet lug option (<---Needs verification). ARMS makes a folding A2 sight that can clamp on as well. This is a little more expensive, but they are very well made, and you may never need to switch back to a railed block.

[brazosvet]

Hmmm....  Drilling holes in the bottom of the barrel doesn't sound like anything I want even a competent local gunsmith to do.  IMHO that is a factory only job.  Can anyone else verify if these holes are not already pre-placed when the barrels are made?  I wonder if all the barrels are made the same so the company doesn't have to pick a specific sight for the barrel produced.  An economy of scale thing.

[Jgun]

Perhaps someone with first hand knowledge will post to confirm this, but, from a manufacturing prospective, I believe that the most likely, and logical way that something like this would be done would be that the front sight (without any holes drilled in it) would be placed on the barrel using a jig or fixture of some type to locate it in the proper place and radial orientation, and then, either using a manual machine or CNC (if combined with other operations) will drill and ream the holes through both the front sight and the lower edge of the barrel. This is how they assemble AK's which are almost fully pinned/riveted together. It would be impractical to attempt to machine a crescent half hole on the bottom of the barrel and then try to get the holes drilled through the sight to try to line up. I would be shocked if you find those crescent relief cuts on the bottom of your barrel, unless it previously had the type of sight you want, already mounted. If I were you I'd go with one of those clamp on sights that Robocop posted.

[Retired JM]

Just picked-up my new AR-10 A4CF with the rail gas block and flat-top reciever.  I would like to replace the gas block with a A2 front sight.  Is this difficult to do?  Will the finish on the barrel show marks where the gas block was attached?  I may want to change back later on if I decide to attach a scope, but for now I just want the iron sites and the gun to look like the infantry model.  I plan on adding the detachable carry handle for my rear site, and preferr the look of the A2 front over the clamp-on A2 style.

Wouldn't this create a height issue between the front sight and rear? The removable carrying handle rear sight on the flattop is going to sit higher than the A2 front sight, which could create some elevation adjustment problems. Colt's answer for the M4 was to make a taller FSB. Before executing your plan, you might wanna contact Armalite and get their input.

[brazosvet]

Maybe so.  I may have wrongly assumed that the detachable carry handle would be the same height as the carry handle on the A2, so would line-up with the A2 front site when properly mounted on the barrel.  Prob. a good idea to check with the mfg. on this.

I really like Robocops first suggestion (clamp-on).  Looks right.  So back to my first question, would the barrel be marred from the removed gas block?

[edgecrusher]

maybe , maybe not. some high temp auto spray paint will be a good enough touch up for cheap, just take your hand guard off too before you hit it.

[Jgun]

The likelyhood is that YOU will be able to see some signs that the GB was changed, will anyone else, maybe,maybe not, depending on how meticules you are when removing the old one and installing the clamp on. inevitably,any surfaces where one of the GB's doesn't cover where the other was mounted, will show signs of the others mounting.

[392heminut]

As for the front sight/gas blocks that mount with tapered pins, I've done one by hand filing, but it takes patience and attention to detail. I filed the grooves by hand with a round chainsaw sharpening type file, which is a straight file, not tapered like a rat tail file. It involved quite a bit of installing and removing the gas block to check progress and I wouldn't recommend someone doing it who doesn't have experience in hand fitting gun parts as it could be easy to screw it up and get the sight misaligned. I've been building competition grade 1911's and doing hand checkering on them for years so it wasn't too much of a chore for me to do. If the issue comes up again though, I will probably just do as others have suggested here and get a clamp on sight/gas block.

[mrraley]

Why don't you go with the clamp on front sight?

http://www.armalite.com/ItemForm.aspx?item=EA5045&ReturnUrl=Categories.aspx?Category=b5d84597-3666-4326-89c9-15fac1afdf18

And the detachable carry handle...

http://www.armalite.com/ItemForm.aspx?item=EA5050&ReturnUrl=Categories.aspx?Category=b5d84597-3666-4326-89c9-15fac1afdf18

[Slash]

ArmaLite's clamp-on A2 FSB is a good piece.  I've used them on my personal guns.

A note on 'pinned' FSBs and gas blocks.  There is no standard for hole placement.  In fact it is rare that you could find two guns where you could swap the FSBs and have them fit/align correctly.  These are actually tapered holes.  You can't just drill them, they need to be reamed.  Any competent machinst/gunsmith can do the job, it's just a matter of having the right tools and the fixtures to hold the barrel.

[survivalshop]

They sell the tapered reamers at Midway ,now finding a jig or making one will be a challenge, but doable.

[brazosvet]

Thanks for all the advice on this.  I got to see the folding A2 sight from A.R.M.S. and was very impressed.  The quality is very good. I think I will go with that for the front sight. 

[Robocop1051]

<thumbsup>

They grew on me. I used to think, "why?"

After a while I just started liking them. Especially if you have a standard handguard.

I look forward to your pictures! <munch>

[brazosvet]

Pics soon to come.

[brazosvet]

Folding A2 style front sight is now installed.  Barrel is perfect under the gas block.  No scratches or marring.  I also went with the ARMS 40 L SP rear folding site.  Man that A2 front really looks cool.  Thanks for the advice on that.  I'll get some pics up soon.