Trying to make a XM177 clone and my barrel needs a sight?  Should I call Double star and see if they will drill one of theirs?

Noooooooooooooooooooooooooooooooooooooooooooooo LOL....the taper pin holes are drilled after the FSB is installed on the barrel.....if yer barrel is already drilled and you don't have the original FSB you'll need to pin the existing holes and then cut the pins and smooth them down restoring the barrel to a solid....then install the sight and drill new holes ....ream and set the taper pins.

What about buying one of the replacements, then drill and tap the bottom with set screws.  Or should I just go to an after market gas block and add a front sight.

BTW - Thanks, I wondered how they did that.

you still need to do the above for set screws.  set crews need a flat spot to hold properly and the described repair is how you get good metal to mill the flat spot or dimple.  ADCO will properly install a new undrilled front sight tower on a barrel that already had taper pins in it.  they have it listed on their website.  anything else will just look like ass and probably won't hold properly for the long term.  YMMV

advntrjnky

It might look like ass if you do it.........but I know a lot of people capable of doing the job who are garage builders......If you have acess to a small lathe and at minimum a decent drill press......you can do it yourself......just lightly set a pair of taper pins in the existing barrel.....then either turn the pins down or cut with a dremel cut of wheel and file smooth.....or dress down with the same dremel you cut it off with and a small stone......tap the hole under the sling swivel for an 8-32 set screw.....make a cardbopard box and fill with plaster and press the fsb into it with saran wrap between the base and plaster........let dry....now you have a base for drilling the holes.....you can use taper pins.....but you'll nee a reamer....or you can use 1/8 spring pins......I prefer the taper pins.....but spring pins will work fine.

6-32 taper point set screws also workl well if you want to do a set screw base.......and with the taper point....no need to dimple the barrel....the original AR45 upper I built has a set screw base and it hasn't shifted through almost 18,000 rounds and quite a few years bouncing around in the back of my truck

too funny.... you need to learn reading comprehension  we are basicaly saying the same thing.  I meant that he needs to do the repair before the set screws, not that the set screw/ screws would look like ass.  I learned this the usual way...by doing it wrong first.  I D&T'd a FSB for set screws and did exactly what the OP wanted....just to run them up to the barrel.  However, the set screws usually end up right where the old taper pin holes are and they do not get a good enough bite to last under use.  the edges of the old holes ended up peening down and the FSB loosens up over time.  So, long story short i learned you need to repair the old taper pin grooves in the barrel to do it right......which ever way you want to do the final install (taper pin or set screw).  IIRC ADCO's repair technique lines up the FSB with the old taper pin holes in the barrel and they then use a slightly oversize reamer to make sure all is perfectly lined up.  If you're patient you could do the ADCO method at home as well.  Brownells sells the oversize taper pin reamer and pins.....you just need to do some accurate measuring.

advntrjnky

Thank team. Great info from all of you. Looks like the previous owner of the barrel filled the grooves with JB weld to give the set screws something to bite into. I think, I'm going to look for another base and try to pin it on first, I'll call Double star next week and see if they have a take off.  If that doesn't work, I might fill the holes and start over.  I've got a Tig, so I could probably fill with a softer metal.  At least I have a few options.  The rail clamp on gas block being the last. Thanks again and Happy Thanksgiving.

good luck!  let us know how it goes.  any way you can post a picture of what you have so we can completely understand what you are playing with?

advntrjnky

I'd be VERY judicious with the Tig.......use it to tack pins in...full fill welding could possibly warp the barrel.......

and  advntrjnky.....guess my somewhat warped sense of humor didn't translate in the post no offense intended.....was just kidding around.....

now worries! it did....I tried to be funny back, guess I'm not that good at it either.    I thought the emoticons were supposed to work better than that

advntrjnyk

we have one (emoticon ) over on weapons guild that is rolling on the floor laughing....and one giving a thumbs up.......wish they had those here.....