Hello all!  I just purchased my first AR style gun.  I got a Bushmaster 5.56 Optics Ready setup.  My first accessories for it were the Magpul front grip, rails for the top and bottom of it, Magpul MBUS backup sights and an angled fore grip

My problem is that when I put it all together, the rear rail (the one that's part of the gun) is causing the sight to sit about 1/4 - 3/8" lower then the front.  First, I am not sure how to measure the risers.  From the top of the riser, all the way to the bottom is 3/4", the gun came with 2 of these, but when I put that on, the rear is now too high for the front.  I tried looking for rails, but everything I find online is being labeled a 1/2" riser.  Do I actually have 1/2" risers and I just don't know how they are measured?  If I do have 1/2" risers, are there any smaller?  I tried searching for 1/4" risers but did not have any luck with that.

I have uploaded 3 pictures to show my issues.  Before anyone asks, I moved the rear sight all the way forward to illustrate the height difference.

Can anyone help this AR noob?

EDIT: Removed pictures, they aren't needed anymore....

I own and a fan of the MOE stuff,but this front sight placement will not yield a stable mount for your front sight post. The Moe handguard while pretty rigid will move some left to right and your POA will suffer..
Might want to look into a quality quad-rail. While this is not ideal it will serve you better than the MOE..

There is a bit of play in my MOE handguards I can twist the handguard when holding the rifle and it moves a bit, and would not put a sight on it. I didn't even know you could put a rail on top of the MOE. I think you should rethink this approach.

that rifle is not meant for buis. your best bet will be to get a quality FF rail. since you have the cut down FSB if you want a drop in get one of the DD omegas, or get a VLTOR CASV-M with the front sight installed

personally i would get a larue 9" rail get a smith to install it for you and put your buis there

I'm, all for changing things, and doing this right, but I really can't spend another $300 on a new rail system.  I think I can return everything but the gun within either 30 or 90 days.  I went with this setup because I plan on putting some kind of scope, whether it be a red dot or ACOG style.

Is it possible to change the gas block to the stock AR type front sight, and go with the Magpul rear?  Do they make a fold down front sight?  I do not want to co-witness with the front if I get a scope, which is why I went with the parts I did.

If I return the front Magpul sight and the rail, I would save like $50, so for right now I would not want to spend much more then that.

I'm really kind of lost as to how to give myself a good working rifle, as inexpensive as I can (for now).  

I found this part on Cheaper Than Dirt, would this solve my problems?
http://www.cheaperthandirt.com/2GGG1297-1.html

I'm guessing you have a round cap under there.

Best bet...

http://www.aimsurplus.com/product.aspx?item=XTSRAIMRFD7BT00&name=Troy+Ind.+MRF+Drop+In+M4+Carbine+7%22+Battle+Rail&groupid=52


...or maybe...

http://www.cdnninvestments.com/arcalequrasy.html

I can handle $65.  I realize you always get what you pay for, so what am I "losing" by going with a $65 rail as opposed to a $200 or $300 rail?

American made materials and craftsmanship, and the chance the item will not work as advertised. UTG is Chinese, and the manufacturing consistancy is always in question when you go Chinese....unless you are getting a SKS :)

Oh yeah, I forgot about these.....

http://www.midwestindustriesinc.com/index.cfm?fuseaction=category.display&category_id=422&CFID=21433977&CFTOKEN=60190792


...probebly easier to install than the Troy drop in.

It seems I have some homework to do.  If I didn't want to change out the front grip, are any of the gas block mount options available on this rifle?  Do the gas mount options replace the existing gas block, or do they mount around it?

There are clamp on barrel rails, but they won;t be tall enough to get the front sight up. That barrel is either made for a free float, or someone chopped down the front sight tower.

you have one more option, get a smith to put a FSB on for you and remove the cut down one on there

OK, I loled...

Is this serious?

ETA - I guess this is serious.

Do this.

Take that rail off your MOE hand guards.

Have a gun smith remove your hacked gas block. Keep it for future use.

Have a smith install an F marked, regular FSB.

Sell the MBUS. They suck.

Get a quality ( Daniel Defense, Troy, etc.) rear site.

Profit!

You could also buy a cheap red dot to use until you save up for a free float....

http://www.opticsplanet.net/leatherwood-hi-lux-optics-1x30mm-red-dot-tactical-sight-es1x30tp.html

....should go nicely with you little riser there.

You don't need a "rail."

You need a front site base.

The MOE is fine, it's just not designed to be sturdy enough to mount a site on. Plus it shortens your site radius. That's bad.

Not sure if serious?

The wording seems sincere but the 1st post and foot pic make me go hmmmmmm...

If you are an AR noob and not a brilliantly subtle troll, then I would recommend ditching the chopped gas block and replacing it with the clamp on YHM folding front sight. They cost about $75 and you can do it yourself in about 20 minutes.

If I remember bravocompany has a Midwest 2 Piece FF rail sytem that will solve this too.. Cut the delta ring off put the rail on and you MagPul BUIS will work plus you have a FF rail. Iast time I checked they were $150 (on Sale)for the rail. Installing it is alot easier than ya think. just take your time. Better to spend more on a good rail than that over seas UTG crap. you will regret the cheap stuff in the end... Everyone has good replies in the end its your decision so chose wisely.

I'd do that, with a red dot sight from Primary Arms.  That would be the fastest, easiest method.  Their M4 clone includes the mount and runs on AA batteries.  I use one on my ST-22 trainer.  

Do not mount a front sight to the MOE handguards.  They are not designed for that (they have some wiggle which will prevent a consistent zero).  Similarly, any non-free floating rail or handguard will have the same problem of wiggle.

If you want to run a full set of BUIS, you'll need to
1) Install a free-floating handguard that has some kind of picatinny rail on top (the longer the better, for a longer sight radius)
or
2) Install a traditional FSB
or
3) Install a railed gas block.  You'll need a gas-block height front sight that isn't made of plastic for this.  YHM makes one, as do others.

1 and 3 you can do yourself.  #2 might require an AR-gunsmith (such as ADCO).

ARMS folding front sight.

Sorry to say, I am 100% serious and I am NOT trolling.

I really am brand new to this.  Before this purchase I owned an S&W MP15-22, a couple hand guns, and a 12ga Winchester.  On the .22 I put a red dot sight, and it came with the front grip with the rails on it.

I did take a look through all the picture threads with the cheap optics, backup optics, etc, and I have a slightly better idea on what to do.  I am reading as many threads on here as I can to pick up information.

A couple people here have mentioned a 'chopped up' front gas block.  I am not sure what that means, the gun is a brand new optics ready package.  I assure you I now regret going this route.

So pretty much, I need to return everything but the angled grip that I like, and go with a free floating rail?

When you say to go back to a traditional front sight, is this what you mean to purchase?
http://www.cheaperthandirt.com/2ARMS41BL-1.html

I pulled the front grip off and the 2 gas block halves are riveted together, so obviously I can't do anything with that on my own.

Look, I feel really stupid for trusting the salesman that helped me.  I assumed, incorrectly, that working for a big name company (Cheaper Than Dirt - McKinney) the guy would know what he was talking about.  I realize that everything I have done, short of buying the gun itself, was incorrect.  I want to fix my mistakes and have a good working setup.

Nothing wrong with being a newbie and asking questions. More research on the front end next time, though

To clarify: you can either A.) Remove the low-profile gas block you have now and install either a standard front sight base (fsb) or a gas block flip up front sight combo, or you can B) install a free float rail (many lengths/options avail.) and put your front mbus on that.

don't despair, lots of options for you. Good luck and welcome.

Eta: or you can say screw it and put a red dot sight (rds) on and forget irons.

You know, that's part of why I'm so pissed at myself.  I research purchases 1/10th the price of this, 10 times more in depth.  I thought I knew enough to just get started when obviously I should not have walked into the store.  But that's in the past now, I own this gun and can't do anything about that.



I have removed all parts and returned the gun to stock.  For now I will deal with not having the front grip the way I want it, and begin to look into the scope I was going to wait to put on in the future.  I am not so reliant on the functioning of this gun that I need to have backup sights, so maybe going right to an ACOG style scope would be the way to go.  That way I have a working gun that I can enjoy for now, and work on building up as I learn more.

Cheaper Than Dirt are scumbags, namely for the "Save -51%" nonsense back after the '08 election.  Don't send them another dime.

This is a standard FSB.  It attaches to the barrel using pins.  Your gas block is basically a commercial version of a "chopped" A2 FSB.  Nothing wrong with it, and many folks like them because they are very secure and allow you to use many different free float tubes.

Chances are your gas block is pinned on, not riveted.  If so, those pins need to be drifted out using a drift punch and a BFH.  Then you can install a gas block like this, which uses set screws, or like this, which clamps on.  If you get a new gas block, be sure to measure the diameter of the barrel at the gas port and buy the proper size block.  It's *probably* a .750", but it could be different.  

This might be a better solution as it gives you the gas block, front sight, and sling swivel all in one bolt on unit.  

One problem you may encounter is that the area under your existing gas block is not parkerized.  In that case, the replacement block would have to be large enough to cover the unfinished area.

Paying a smith to do all of this will drive the price up too.  If you check your hometown forum, you might find someone local with the tools to help you out.  



A free float handguard would solve the problem too, but would cost a bit more.  Something like a Samson Evolution would work well and would be very easy to install.  You'd remove your MOE handguards, cut off the delta ring with a dremel, attach the Evo barrel nut bushings (snap into place over the existing barrel nut), slide the handguard over the barrel, and then tighten the handguard.  The Evo has a continuous top rail that would work perfectly with the MBUS.

Sell the MOE handguards to recover some of the cost.  Attach your foregrip to the Evo.

Thanks for the wealth of information and taking the time to grab me examples, it helped tremendously.  I had seen that Yankee Hill setup last night and bookmarked it because it looked very interesting.  It seemed to solve all my problems, except obviously for having it installed.  That small piece of rail on the bottom, is that what people are talking about when the refer to a bayonet lug to attach a bayonet knife?

I should be able to return all the accessories to the store and get a refund.  If they try to give me a problem, I assure you I will raise hell because everything the salesman told me was a flat out lie.  At this point, if I could, I would even return the rifle and buy somewhere else.

I am going to keep browsing this site like I am doing, and will try to figure out what I want to do before spending another $1.

wow...

That is not how BUIS are designed to be used at all, in order to use them you will need to get a FF rail system and mount them as designed.  Or get a replacement gas block with a built in flip up BUIS

You're welcome.  

Yes, on the Yankee Hill and on standard A2 FSB, that chunk of metal on the bottom is the bayonet lug.  Standard bayonets won't fit on a 16" barrel with carbine gas.  You need either a 14.5" with carbine gas or a 16" with a mid-length gas system.  Bayonets are good for scaring the sheep and that's about it.  There are some accessories that will mount to the bayonet lug - I think some bipods do and some light mounts do.


It's not a terrible rifle you have, but it's designed for optics, not irons.  My first AR was a Stag 3, their version of the ORC, except the Stag had a railed gas block so I could add a front sight easily.

If/when you're ready for a FF rail, check out the Samson Evolution.  I used one on my last build, a 3-gun rifle.  On a carbine like yours, installation would be very, very easy - just cut the delta ring off and you're set.  The Evo uses the stock OEM barrel nut.  Many other FF rails use proprietary barrel nuts which generally require stripping the barrel for install.  The 11" and 12.37" models will cover your gas block and give you plenty of space to mount a folding front sight.  You then can add small sections of rail to accommodate a foregrip, light, or bipod, rather than having a full set of quad rails.  


Since it sounds like you're on a budget, check out the Equipment Exchange.  You might find a relatively inexpensive red dot to tide you over.  A Primary Arms red dot will get your carbine into a usable configuration, but it will also introduce you to red dot sights.  Most people like them, but they're not for everyone.  If you hate it, you're only out $100 for a Primary Arms sight rather than $400 for an Aimpoint.  You won't take a huge hit selling a used Primary Arms sight either.

Can't you just get a front sight that sits on the gas block?  I had a flip-up on mine, but they make ones for the low pro gas blocks too.

His gas block is just a shaved fsb.

Ooooh.  I was thinking it was a short rail top one like my DPMS was.