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Renron
02-21-2006, 10:16 AM
This is the first question I have asked on this site. I have used the search engine to a point where it needs an oil change now!:)
What is the purpose of the elevated rail? and why would I want one? specific sights/scopes? does it help in check to stock placement? How does it work with BUIS?
TIA
Ron

bu-bye
02-21-2006, 11:49 AM
This is the first question I have asked on this site. I have used the search engine to a point where it needs an oil change now!:)
What is the purpose of the elevated rail? and why would I want one? specific sights/scopes? does it help in check to stock placement? How does it work with BUIS?
TIA
Ron

Yes cheek placement would be the many reason. If you bring up your rifle to your sholder with your eyes closed then open them, you should to have a clear picture in your scope. ALWAYS make the rifle fit to your body! Never have it so you have to find the sweet spot on your scope. For an AR flat top upper, 1 inch riser plus low to mid rings seems to be the average. That is what I use.

As far as BUIS, If you have a scope you will need a quick detach mount for it otherwise your BUIS are usless unless you carry tools with your rifle all the time. IMO its not wise to plan on using tools when the SHTF. If you are using a Red Dot sight, you can run co-witness which means the irons sights can be used while looking through the red dots window. Some like the irons to be viewed in the center of the window and some like it in the lower section of the window. Different risers will give you different options. Again, its better to setup up your rifle around your body. If you plan to run with a red dot then set it up the way your body would use a red dot. Let the BUIS be what it is, a backup not your primary.

Matt-man
02-21-2006, 2:50 PM
Uh, putting backup iron sights of the standard height on the EOP means you'll need a front sight 3/4" taller than normal. Assuming you're talking about the RRA EOP, anyway.

http://www.rockriverarms.com/images/uveop.gif

maxicon
02-21-2006, 2:55 PM
A couple of other considerations for mounting traditional scopes, if you're thinking about that:

- Whatever riser and rings combo you use will need to get the scope high enough for the bell to clear the iron sights. This can be a problem with non-folding BUIS or with ones that are still high profile when they're folded.

- Depending on you and your scope, some scopes can't be mounted far enough forward on the AR's short flattop rail to give the right amount of eye relief. There are extended risers/rails available for this that give you a few more inches of rail forward of the receiver. You have to make sure extended rails will clear your handguards as well.

Neither of these is likely to be a problem with non-magnified scopes like red dots, or short magnified scopes like ACOGs, but the variations are infinite.

I'd recommend a standard flattop with risers, rather than a high-rise upper, as that gives the most flexibility. It is an extra connection point and another place to lose repeatability, but good (ie, expensive) mounts generally solve those problems.

max

SI-guru
02-21-2006, 3:55 PM
Neither my shooting skill nor my barrel is accurate enough to tell the difference but I believe both trijicon ACOG reticles and Leupold M3 BDC cams are adjusted to fixed height from barrel and also barrel length.
There are also CQB training that favors an elevated 1x optics. I am no operator so my guess is this favors transition between shooting from strong to weak side at corners without any cheek weld.

jmlivingston
02-21-2006, 4:42 PM
Whatever riser and rings combo you use will need to get the scope high enough for the bell to clear the iron sights. This can be a problem with non-folding BUIS or with ones that are still high profile when they're folded.


Which folding BUIS tend to be high profile and problematic? I'm looking to go with front and rear folders and will eventually want to be able to co-witness when I can afford the optics. I'm looking at the YHM right now, but it seems like the A.I.M. #40 gets lots of praise.

John

maxicon
02-21-2006, 6:16 PM
Many of them can be a problem with traditional scopes, especially 50 mm. The problem is finding the height above the rail before you buy one. You can fix it with a combination of rail height and ring height, but it can be tricky unless you know exactly what you want.

I've accumulated quite a collection of mounts, rings, and rails, mostly bought cheap on the ar15.com equipment exchange, but I'm a tinkerer.

The ARMS #40 is very popular, and they make a lower profile one to fit under scopes better - the #40L. I have an ARMS #38EX, which is an extended rail with a #40 built in, and the sight is too high for several of my scopes without going to high or extra-high rings or using a riser.

My problem is that I like to switch optics around a lot. I'll put a set of quick-release rings on a scope and try to switch it between a Mini14, an SU16, various ARs, a 10/22, etc, so I like to stick with medium rings. It's a problematic approach, for a variety of reasons, including mounting height, but I enjoy the challenge.

Here's a pic of one of my Fab 10s, with a YHM-9860 rear. In order to use my 40mm Leupold VX1 and 2 scopes with medium rings, I need the ARMS #05 riser mounted as shown. To mount my Mueller 50mm, it has to be in higher mounts (currently an Armalite 1 piece) for a yet a bit more height. Unfortunately, the ARMS #05 isn't Picatinny spec, and the Armalite doesn't fit very optimally.

http://www.maxicon.com/guns/fab10/fab10_2-1a.jpg

Some combos are very straightforward, like Eotechs, ACOGs, and other popular stuff. AR optics mounts are a bit of a jungle - once you get off the beaten path, you have to hack your own way. Best bet is to post "I'd like to mount X scope on a flattop with the Y BUIS - what will i need?", or something like that, here and at ar15.com.

Here's a post at arf.com with a ton of info on BUIS. It's amazing just how many options and variations there are.
http://www.ar15.com/forums/topic.html?b=3&f=18&t=206233

Unfortunately, with long-running pinned threads like this, lots of photos get broken over time - one downside of forums as archival media.

Here's another current thread on rear BUIS. There have been dozens of these over time, and you can spend many happy hours reading through them.
http://www.ar15.com/forums/topic.html?b=3&f=18&t=269420

max

Renron
02-22-2006, 8:52 AM
Thank you all for the input and info. It truly is a jungle of options when concidering optics and BUIS. I believe I will go with a standard "flat top" and purchase a raised platform as the configuration options are greater. Again thanks for taking the time to respond.
Ron

tenpercentfirearms
02-22-2006, 9:52 AM
Really there is no point in the EOP. With the EOP you just buy shorter rings and then never have the option of going lower again. Just get a standard A3 and then get higher rings. I like my Rock River Hi-Riser scope mount. As one other person has said though, the only thing is you really have to get that scope base far forward with the eye relief of my Leupold scope.

rkt88edmo
02-22-2006, 10:20 AM
I just scanned this topic and I don't think anyone mentioned it but, if you are going to use optics that weren't designed with an AR in mind (like any regular scope, not eotech/aimpoint/trijicon) you want a special AR mount that will place the scope farther FORWARD. If you put a scope and rings on top of a flat top you often end up with a cheekweld that is very different from the standard iron sight cheekweld. It isn't necessarily the rise that gets you, it is the cheekweld and eye relief.

This may not apply to you, so FYI.

Here is an example, the armalite one piece mount, I don't know what the latest and greatest mounts are, but this is just to give you visual of the above.

http://groups.msn.com/ThePennsylvaniaAR15ShootersSite/armalitereview.msnw

maxicon
02-22-2006, 3:31 PM
That Armalite 1 piece is the one I have my Mueller scope in right now. They were blowing them out in their winter sale a few years back for $35 or so in camo.

The only problem with them is they're a bit heavy, but they're very sturdy. Also, most BUIS folding rears won't fit under a traditional scope in one without a bit more height - you can see in the pic that there's not that much room under the rear bell.

FWIW, Armalite's having their annual winter clearance sale. No 1 piece mounts right now, but several 2 piece mounts for dirt cheap:

http://www.armalite.com/sales/specials/excess/Excess031008.htm

The EX0029, for instance, are big, solid 1" mounts that list for $89 and are selling for $30 on clearance. The equivalent 30mm mounts in camo are $31.

To see what they look like, download their 10 MB catalog here - http://www.armalite.com/sales/catalog/adobeCatalog/ArmaLiteCatalog10.pdf - and look on page 19.

I like these rings a lot - you just can't beat them for this price. Semi-quick release, solid as a rock, and a tight fit in a Picatinny rail, but not very compatible with Weaver rails.

max

SI-guru
02-22-2006, 5:21 PM
A continues rail platform like the LMT MRP or Troy MRF

http://www.troyind.com/images/mrf.jpg

with A.R.M.S. #22 L/M/H rings can set you up with any scope objective on any eye-relief.

Renron
03-12-2006, 5:44 PM
Thanks for all the great input guys. I was trying to learn as much as I can before my build up. I WILL buy a A3 style flattop for greater modification options.
Thanks
Ron