AR A3 sight question

[wheelgun]

I visted both Four Seasons and Collecto'rs Gallery today. (Side comment - Hadn't been to Collectors since they moved. Was my first time at Four Seasons, and I have to say their store was much nicer. Collector's was kind of dingy and the guys there didn't seem to be very interested in customers. Four Seasons on the other hand was very active, the sales guys were attentive, friendly, and informative.)

Anyway, I was looking at an AR15 A3 at Collector's. I commented that I thought I could replace the A3 handle with a scope/optics, and the guy said "yeah, you can , but then the front sight would be in your way. If you want a scope you should go with a flat-top."

Can't the standard front sight be replaced by a gas tube block without a sight? Or what about a flip-down front sight?

 

[Moderator]

Can't the standard front sight be replaced by a gas tube block without a sight? Or what about a flip-down front sight?

Yes it can

 

[BIG DAVE]

If your gonna use telescopic optics the easiest thing to do would be to shave off the front site down to its base and use a Bushmaster modular fold up/down front sight that goes over a shaved standard base.If your using a red dot sight you still need a 1" riser to co witness the red dot to the front post in other words have the red dot sit right on the front post wich is the way it should be for a red dot.The ARMS #38 swan sleeve is excellent for this giving you the 1" you need and having the ARMS #40 back up rear sight built on.The whole unit goes over the existing rail on your flat top.Front sight bases are a bitch to get off even with the proper chuck.I have dremeled off or shaved off front sight bases down to the gas block with excellent results and is the easiest do it your self way.You could also send the upper to Yankee Hill Machine and they will install a fold down front sight block,I just would rather have a pinned in one than one with allen screws locking it down.You could also order the rifle that way from Bushmaster with the modular front sight already done or the different gas block with folding sight built on as YHM supplies Bushy with alot of their products.,check out their 25th aniversary carbine it has that set up in front.And yes collectors coin gallery is that way especially if your not from the north shore as I was told once in that shop is where most of his customers come from.Four seasons has the best selection of military type semi-autos anyway and will extend their layaway way past what others do as long as you make regular payments.Carl and the guys are great.

 

[cdkayak]

Before you shave the front sight, I would do a test mount with a scope and see if it really interferes. You may see a slight shadow but it may not be as much of an obstruction as you think.

I've seen all done. Personally I'd probably lean towards a flip-up if the existing sight proves to interfere, leaving the option of putting the carry handle back on if needed.

CD

 

[wheelgun]

Thanks all! I think I'll probably be going with a flattop.

 

[centermass181]

Before you shave the front sight, I would do a test mount with a scope and see if it really interferes. You may see a slight shadow but it may not be as much of an obstruction as you think.

I've seen all done. Personally I'd probably lean towards a flip-up if the existing sight proves to interfere, leaving the option of putting the carry handle back on if needed.

CD

+1

before you 'shave' anything off, slap yourself in the head. Its not a rubberband gun, for goodness sake.

 

[bpm990d]

In 1993 I had an opportunity to go to Australia with the USAR Combat Shooting team to compete in the AASAM (Australian Army Skill at Arms Matches). All of the team members shot optics (Trijicon TA01 ACOGs) on their rifles. Most with them attached to the top of the carrying handle. We found it difficult to shoot well with them attached that way. Not that it couldn’t be done, but it wasn’t consistently good shooting. I would have preferred to shoot iron sights given that setup.

However we did have a couple of guys shoot what we were unofficially calling A3 uppers (the correct designation now would be A4) with the ACOG directly attached to the rail with an ARMS throw mount. The front sight base was still in the field of view but it was nothing but a blur very low in the scope. One of the soldiers that had his rifle set up that way walked away (no one was even close if I remember correctly) with the individual championship, against several hundred of the very best shooters.

I wouldn't worry too much about the front sight unless your mount has the blur near the center of the reticule or it drives you crazy. On my rifle the bullet drop compensator in the ACOG goes down to 800M and the front sight blur is well below that.

If you have a conventional scope and you desire to shoot it in the prone position with a sling, you may have to use a rail extender to get the proper eye relief. If you are just shooting it from the bench or in some type of in the field application, you could get away with just a pair of rings. Don’t forget, the rings need to be pretty high depending on the bell of the scope.

I wouldn’t go cutting off the front sight. Just get a couple of punches a wrench and a rubber mallet and you can replace the front sight yourself for relatively cheap money. I have not used any of the dot sights, but my guess is that they would have problems with the front sight because of no magnification.

Brian

 

[BIG DAVE]

First off the proper use of say an aimpoint you want to see the fron sight to properly co witness the sight,ACOGs are also not a problem because its a 4x anyway and with the proper height yes you will only see a small portion of the sight in the optic...but lets say you want to use the rifle as a sniper type set up and your gonna mount a 3 to 9 X50 optic then your gonna need the front sight to not get in the way at all and have a clear sight plane...an optic like that mounted too high and you wont get the proper cheak weld to stock...getting a punch and hammer to pop out the pins is not as easy as it sounds..I build custom uppers for the small inner circle of clients who come to me and beleive me it can be a royal pain in the ass and thats with using the proper fixture to hold the FSB in when trying to punch out pins.Also any time the gas block is replaced you have to get one with the set screws because all FSBs even from the same manufacturer can be off by thousandths of an inch as the holes are not drilled until the base is on the barrel so the base and barrel get drilled at the same time.So Aimpoints and ACOGs are combat sights meant to be used with seeing alot or a little of the FSB.If you have a varmint or sniper set up your gonna need a clear plane and that requires no FSB in the way.Its easier to shave it off and get a modular fold down that goes over the base then having to send it out to be modified or better yet order it that way from the factory as can be done from Bushmaster.Yes its not a rubber band gun but with 15 years of AR experience and 10 of that building them up and tearing them down I know how cetain optics can be with seeing the sight and sometimes its all in what a person can afford to do.Front sight bases are not easily replaced because as I said they do not come predrilled as this is done after its put on a barrel.Without the proper tools to measure to make sure the holes you drill will line up with the half circle cuts on the barrel is almost impossible to get correctly.There is a reason manufacturers dont drill those holes until its on the barrel and there can be minute variances even from the same manufacturer.If you do that yourself you will need an undrilled barrel and front sight bases..standard ones will come undrilled as well.Its the only way to do it correctly.Unless you have the right fixture to lay the FSB in a rubber mallet,punch and wrench will not do it.You will need at least a 16 oz hammer because when you wack the pin if its not a strong true hit with some hammer weight behind it you will flaten the pins head and then it will have to drilled out to remove as the are taperd pins..thats why you hit them left to right or in the direction the pivot pins open.

 

[bpm990d]

BIG DAVE,

What you said about front sight bases is true. I have received factory rifles that had as many as 15 clicks of windage on the rear sight. They obviously goofed installing the barrel assembly and or front sight base. I’m not sure what the TM says about acceptance or serviceability, but I didn’t feel it would have been bad for a combat rifle. I wanted to use it for over the course shooting and had a concern about running out of windage at the longer distances. At that time the heavy bullets were 69gr Sierras and I almost did have a problem once.

I agree with you about what a pain they can be to fit one back onto a rifle. What more reason to keep it. If he ever wants to go back to using it in the original configuration it wouldn’t be a bad thing to have in the junk box.

If some kind of bolt on/flip up FSB is desired, then any potential windage problem can be taken care of with a careful purchase. Worse case scenario you will have to crank the windage on the rear sight. Not the end of the world as long as they have windage.

YMMV

Brian

 

[BIG DAVE]

bpm ,definately 15 clicks is alot some times that can be from an over tightened nut that moves the barrel if the indexing pin dosent fit snug.Its a softer metal and can be squished to a point where there is play in the upper receivers notch and the barrel rotates and is not straight causing the rear sight to be adjusted as you describe.Some times the notch can be out of spec although ive never seen a widened notch that was a factory defect,more of a pin problem then people open up the notch and try to shim it..thats a bad move.Usualy if the barrel is straight but the FSB is canted..a sometimes problem with Bushmaster barrel assemblies the windage will most often have to be adjusted as far in either direction as it will go.With just 15 clicks Id say the barrel might have been tourqued on too tight causing a sqished index pin or even a sheared pin causing movement in the notch.Even when installing a barrel the index pin should be snug with no play.You put the receiver on the barrel ,line up the pin with the notch and using a rubber malet tap the rear of the receicer forward to make the notch meet the pin minimizing pin damage.I give the pin 2 very light taps with the malet on its top just to make sure as the pin can as I said easily be damaged or come out of its hole on the barrels extension if not properly treated.If this happens the pin itself can be replaced.15 clicks although alot wouldnt be considered extreme but im a perfectionist and it would drive me nuts but still acceptable.Its when you run out of windage adjustments left or right wich usualy means a canted FSB wich can some times be fixed by a few wacks with the rubber malet although id take out the taper pins a realign.A trick I like to use is to install the gas tube in the base and back it on the barrel that way you can use the tube as a level line.Doing it so many times I can eye ball it another but more time consuming way would be to use a pice of string from the rear arperture to the front post although some times that canted angle can be caused from holes drilled through the FSB and barrel that are not straight to begin with becase the FSB was not checked for being straight before drilling.In this case the barrel is no good and needs to be replaced.And one thing about Bushmaster is that they have great customer service.My advice iif this ever is experienced on a new out of the box rifle..dont mess with it and send the upper back to them from the get go if its determined that its canted.Tolerances on uppers can also vary.Ive noticed some key hole marked uppers when you put on the barrel through the uppers opening its not tight but smoothe with no play.On FK marked uppers Ive used the barrel goes on nice and snug when its put on and tolerances tighter then some other uppers ive used.Colt made uppers too are nice and snug so I assume thats the way they should be..nothing wrong with one not so snug you might with those just have to tourque tighter thats all.After you do enough of them it becomes more of a feel thing.Ive had to tourque barrels to the 80lb maximum and some to 40 or 50..also you do enough barrel changes to an upper and after a while it can loosen up from the constant tightening/loosening.Experience will eventualy bless you with the "feel" for it.Thats why you tighten and loosen a couple of times before final tightening.I also use a very light coat of high temperature grease on the uppers threads.Grease is used not to make tightening easy but to make loosening easy.If no grease is used the nut can fuse to the threads making loosning very,very difficult.Remeber metal expands when hot and grease keeps it workable.The TM says to use disulfide grease but a good quality high temp grease will work as well.

 

[bpm990d]

BIG DAVE,

Unless the rifle is a total POS, I’d almost never send it back. If I did send it to them I wouldn’t want it back! I’m more concerned that they (the factory) would screw it up even worse or fix something that isn’t broken. I’m much happier with decent parts and putting together the pieces I want. The rifle I told you about is a Hartford mule that was gutted for it’s parts. It’s just the way I want it now.

I don’t know for sure what the problem was, but I suspect an over torque on the barrel nut. My FSB is now secured with a set screw and Locktight 640. Not what I would recommend for any rifle for serious purposes, but just fine for a competition rifle. I haven't had an opportunity to deal with Bushmaster customer service. They sold me some real junk once and I've never looked back. At some point I'll come full circle.

Brian

 

[BIG DAVE]

My Bushies are 1992 models back when they were cranking out maybe 15 to 20 thousand a year at that point.Locktite will do well red is tough the green way tough and both need a a propane torch so soften up for removal.I agree on an overtorqued barrel.When I was at braintree a few years back I met a kid who had a brand new Bushmaster 20" govt profiled barrel.Never fired the first shot he took the rifle shot but nothing happened no rearward movement of the carrier..nothing.He manualy ejeted and rechamberd..boom same thing.I go over and tell him seems to be a gas problem..its new so I figured maybe an improperly staked on carrier key..another thing besides canted bases,over tourqed barrels and purple hued receivers Bushmaster is famous for.After everything was in order with the "brain" of the rifle I said lets take a look at the FSB maybe there is gas loss there.....low and behold some idiot I dont know how installed the gas tube upside down.My question was they are supposed to test fire the upper with 5 shots..obviously some didnt or the problem would have been picked up there or the dealer may have assembled the rifle himself.I made it right for him right on the spot.He later told me he called Bushmaster and they told him it was factory assembled..so it wasnt the dealer..it was them the company that told me when I aplied for a job many moons ago that they dont hire assemblers with out military armorer experience...thank god I wasnt going into harms way with that guy as a unit armorer..tough way to find out your self loader is now a bolt action.

 

[bpm990d]

I'm not surprised at all. I had a buddy that got a rifle from a very famous builder. It came with a test target and everything. He took it to the range and found out that the barrel blank was short chambered...just the way it came from Krieger. :-|

I didn't think BFI test fired their stuff. I may be wrong, but the pace is pretty small. Maybe they fire them into a tank of water or somthing. I never did get a chance to see past the nasty woman at the front desk that buzzed everyone in. No real loss. I wouldn't piss on them if they were on fire, and I like them better than Colt.

Brian

 

[BIG DAVE]

The customer service rep said they do but with that situation its debatable.Its like with their flat top models..they know the rifles wont zero without the taller .040 higher front post so instead of just using an F marked FSB on their flat tops they ship with a regualr post and then will send the higher one after they get a complaint..hell just get it right from the get go...ye I like em better than colt to.