I ordered parts from RRA arms so I could swap out my front sight bases on two rifles that currently do not have the bayonet lugs.

Well, today I got the sight bases and I assumed they would be pre-drilled so all I would have to do is knock the pins out of the ones on the barrel now, remove them, slide these on and line up the holes and put the pins back in.  I guess nothing is that simple is it?

Now what?  This sucks.  I bought a barrel wrench to change out an upper, bought the correct punch set so I wouldn't ruin the roll pins and the sight base pins.  Didn't know I would need a drill press.

I feel your pain Brother!  I was in the same situation about 2 weeks ago myself.  I figured that I had a choice...do it myself and risk messing up a $20 FSB, or pay a decent 'smith an additional $25-$50 to install it for me.  Since I drink, gamble, use foul language, and hadn't committed any acts of stupidity lately, I decided to try it myself.  The 2 tricks are: to make a jig that holds the fsb completely solid and horizontal while drilling, and to measure VERY carefully.  (it took me 3 beers before I was satisfied with my measurements and more than a few whiskey shots to work up the courage to start drilling)  Mine came out GREAT, but I think it was more due to luck than any kind of skill.  (WECSOG 1988 graduate)


I would NOT try this again without some serious upgrades to my workshop equipment.  Call around and see what the local 'smiths are charging, then send your upper off to ADCO.  They'll probably beat any local prices and you're definately gonna get a quality, straight job done.

There is no standard to where the pin holes are drilled.  I think the factory guys that drill them may have been on their third or fourth beer as well.  You could take two like barrels, Colt, Bushmaster or whatever, remove both FSBs and neither will fit on the other barrel.  Some pins are high in the barrel, some low, some are drilled further back, others further forward.  

Colt45guy, if I were you, I'd buy a lottery ticket in the near future.  You luck is running good right now.

Quoted: the factory guys that drill them may have been on their third or fourth beer as well.

Dude, I know some guys down at Oly and you have no idea how close that quote is

Quoted: Dude, I know some guys down at Oly and you have no idea how close that quote is

That is not surprising!  They must employ the mentally challenged for the junk they make.

Quoted: Quoted: Dude, I know some guys down at Oly and you have no idea how close that quote is That is not surprising!  They must employ the mentally challenged for the junk they make.

Colt barrels are the same way.  Maybe the Colt guys are only on their second beer when they drill the FSBs at Colt.

Quoted: Colt barrels are the same way.  Maybe the Colt guys are only on their second beer when they drill the FSBs at Colt.

I don't mean the FSB holes.  I'm talking about their overall lack of any consistancy in production.

Well, I boxed up both my uppers and they are getting shipped to ADCO.  I'm not going to scew with this, I'll leave it to the professionals.  Live and learn.  The irony is I just got one of my uppers back from ADCO because I had them thread the barrel.  Plus I bought an upper receiver  form them which I just got so I could swap it on one of the uppers.  Now I have to send it all back to them.    They do the swap for $30. with customer supplied FSB.  I just didn't ask the right questions or I would have just sent them both in.  And yeah, I now have the tools(barrel wrench, receiver block) to do the receiver swap but I figured the hell with it, while they've got it, they might as well do it all.  Just wish I would have known about the FSB's from the start and I could have had this done a week ago.  Oh well, like I said, live and learn.  

Quoted: I ordered parts from RRA arms so I could swap out my front sight bases on two rifles that currently do not have the bayonet lugs. Well, today I got the sight bases and I assumed they would be pre-drilled so all I would have to do is knock the pins out of the ones on the barrel now, remove them, slide these on and line up the holes and put the pins back in.  I guess nothing is that simple is it? Now what?  This sucks.  I bought a barrel wrench to change out an upper, bought the correct punch set so I wouldn't ruin the roll pins and the sight base pins.  Didn't know I would need a drill press.

Yeah you did!  We tried to tell ya!

the front sights are not pre drilled, when a front sight is put on a barrel they use a jig, it drills and puts the front pins in, if you have steel  bar stock the same with  as your carry handel you can make a type of jig up put it threw the top of your carry handel and the top of your front sight ( the old one on the barrel" (stripp the front sight  post, detent, and spring)  so your centered "in line"  mark everthing  and true it to the old sight,  remove the  old sight slip on new sight bolt your jig on then start drilling use a very small drill at first  them move up in size you can see if your in the right spot  with the slots on the barrel  if your off your going to play Hel* zeroing the rifle  when your done      

Quoted: the front sights are not pre drilled, when a front sight is put on a barrel they use a jig, it drills and puts the front pins in, if you have steel  bar stock the same with  as your carry handel you can make a type of jig up put it threw the top of your carry handel and the top of your front sight ( the old one on the barrel" (stripp the front sight  post, detent, and spring)  so your centered "in line"  mark everthing  and true it to the old sight,  remove the  old sight slip on new sight bolt your jig on then start drilling use a very small drill at first  them move up in size you can see if your in the right spot  with the slots on the barrel  if your off your going to play Hel* zeroing the rifle  when your done

This is exaxctly why I sent them both to ADCO.  I hope they know how to do it the right way.  To invloved for my mechanical skill and lack of proper tools.

tagged...  

Not sure how I missed this before but here is a related thread:  

ar15.com/forums/topic.html?b=3&f=4&t=204939

I have never tried to do an undrilled gas block but I may need to figure it out to get a bayonet lug gas block on my AR-10...  I like the idea of using a small set screw to lock the FSB down and test fire and check the timing before I drill her...  The small screw isn't noticable afterwords...