Hello all,
I’m a noob to the forum and to ar’s. I have an bushmaster m4 a3 and want to change 3 things. I need some advice. Here is what I want to do:
1 - I want to remove the handle and gas block/sight in front and go withthe magpul mbus sights and later put a red dot in top. My question is what is best to replace the front block with? I have seen some that have a picatinny on to built in. That would fit my need for mountingthe front mbus . Is there any particular brand that is good or do you recomend somethig diffirent?
2-Im a lefty and want a lefty safety but haven’t seen one. Can the original lever just be flipped over or do i need to go with an ambidexterous system?
3-I already changed the rear plate behind the buffer tube so I could have a single point sling mount.I don’t like the blackhark single point sling plate , I’m looking at the magpul one . Any recomendations for that plate? I had a hell of a time getting that castle nut of and screwed it up. I ended up replacing it but I noticed that the threads on the buffer tube gut a little chews up. My question is how tight does this need to be and how do you do this without a problem. I saw a video on YouTube and itmade it look so easy. Butmine was a pain In the arse.I’ll be replacing the buffer tube and plate and I need this info to do it correcly this time . Any tips?
I know this is a lot of info but any input would be appreciated . I just want a pretty basic carbine and want to keep it lightweight. Thanks
You would be better off buying a new upper rather than switching out the Upper receiver and the gas block. This will be cheaper in the long run and result in a better weapon. Lurk around and you will find all the information you need to make an informed decision. (time saving hint: BCM)
Just use an ambi safety. There is no downside to being able to manipulate your safety from either side of the weapon.
The Magpul ASAP plate is Good to go. Get a castle nut wrench if you are replacing the receiver extension (buffer tube), it is a tool you can get for about $30 online. Someone more knowledgeable than me can tell you how tight it needs to be.
Oh, and welcome to the forum! Keep an open mind, dont take offense to anything, and go read all the stickys.
I second the motion of just replacing the upper. BCM or Colt are very high quality uppers that can’t be beat. They are, for all intents and purposes, an actual M4 upper that you would find on any GI carbine. You can get a BCM 16" M4 upper for around $450-$480. In my opinion, this investment will be well worth it in the long run. As far as a BUIS, I prefer Troy folding battle sites. They’re extremely durable and pretty sweet. Check 'em out if you get a chance.
I would just get an ambi selector switch, I don’t think you can switch it to the other side because the spring and spring detent that holds the selector switch in place wouldn’t line up with the hole it sits in on the selector switch anymore. Someone will correct me if I’m wrong.
It’s supposed to be difficult to remove because it’s not supposed to come off. I’ve never had a problem with threads getting chewed up so I’m not sure about that one. My UBR reciever extension had to be torqued to 35-39 pds. so I would imagine yours would have to be torqued to approx. the same. If you can’t do that, just get it as tight as you possible can by hand. Once again, someone correct me if I’m wrong. Just make sure you re-stake the castle nut when your done. I’ve never done that myself, I’ve just always taken it to a gunsmith so I know it’s done properly. Hopefully someone here can help you with that if you wanted to do it youself and had the necessary tools.
Thanks guys. So i think I may have written the first paragraph a little confusing. The handle is removable and it already has afaik buit in underneath. So really I just need to removed the front sight ladder/ gas block so when I get a red dot itwont be in the way. Do you still think I should replaced the whole upper?
If not what gas block should I replace the original with?
Has anyone tried replacing this ?
Also I did get the tool for the vastly nut and it was still a pain. Obj well guess that’s just how it is.
I agree with the recommendations you’ve gotten so far on the ambi-selector. If money is a consideration - and I’m assuming it is - you may try the directions for cutting down your front site and making your own low-profile gas block.
I followed the directions from another website - I haven’t been on this one long enough to see if it’s on here as well - but it didn’t take long using my Dremel tool. I was able to cut the site down and removed the bayonet lug and sling swivel while I was at it. I ground it down and painted it with a flat black paint.
I even showed it to some of our guys at the range and they thought I had bought it. It really came out pretty well. Didn’t cost me anything and it’s mostly covered by a free-float rail.
If you do cut down your front site you can mount the MBUS (front) on a rail if that’s the route you go.
No need to replace the whole upper. That front sight will not be in your way when you mount a Aimpoint or Eotech. As you’ll see many of us have that particular setup. The red dot will be above the front sight when you look through it. Also, if you were to replace your front sight with a railed gas block, Magpul warns against using their sights due to the heat buildup. There are many folding front sight/ gas blocks on the market. Bravocompanyusa.com sells a few of the better quality ones. Personally, I would just stick with your rear BUIS and the original front sight block.
If you have the standard 2-piece plastic handguards, you won’t be able to use the MBUS up front, even if you switch to a picatinny gas block. The sights are the right height to mount to a railed handguard that is flush with the top of the receiver, and picatinny gas blocks sit a little lower.
Unless you want to switch to a free floated handguard, I would stick with the standard gas block. If you change to a flip-up rear (MBUS rear will work for this) with an unmagnified optic in the future, you will still be able to use the optic with the standard gas block in place.
If you set up for a lower 1/3 co-witness with the Ampoint mount there really is no need to remove the fixed FSB. The front site base will be visible, but it’s not an issue, especially if you are shooting both eyes open with the red dot. (I close my off eye due to a dominance problem and it’s still not an issue with lower 1/3.)
A dremel and some filing/polishing will turn it into a low profile, but if you change your mind latter a new FSB is not user installable unless you are a machinist, ( AMHIK). Add a quality BUIS on the rear and you will be good to go.
Thanks for the sound advice guys. I have never personally looked down a red dot sight so i didnt know that the front sight would not obstruct my view. Thanks for clearing that up for me.