Iron sights for DPMS LR-308 w/Lo-pro upper?

[RifleShooter]

I have a DPMS LR-308 with their Lo-pro smooth sided upper. Since the upper has a rail that, according to DPMS, is 0.310" higher than their standard rail, that puts the gas block rail 0.310" below the receiver rail.

With the height differential established, I thought it would be easy to find a set of backup iron sights that would work for this configuration. Well, I am having no luck, as most manufacturers of sights do not have any dimensions listed for their parts. I even emailed a couple asking for information. GG&G says they don't have anything for that height, which is fair enough. YHM, on the other hand, told me that, although I would be able to use a standard AR-15 rear sight, that NO AR-15 front sight would work on a .308! Well, that must be news to DPMS, as they clearly state in their FAQ on the website that 'any standard AR-15 sights will work on the LR-308 series rifles'. Hmm.

None of the information I have found to this point has answered my question. Are there sights that will work on a high railed upper with a gas block mounted front sight?

Thanks for any help you can provide. This information must be out there, but if it is, my Google-fu must be very much weaker than normal.

Arnie, aka ImaShooter

imashooter at verizon dot net

[bigbrowndog]

short answer is NO, but you can take a YHM 1/2" riser block and place it on the gas block and get a set to work. or you could try the troy industries Micro rear sight that is made for high railed receivers, the problem is that it does not have elev. controls

Trapr

[Big Bore]

I had the same problem. You are S.O.L.

You will need to change out upper receivers for a A3 type, then you can use any standard sight.

[Jadeslade]

That seems so strange-is that because it is assumed you will use a scope?

[Big Bore]

That seems so strange-is that because it is assumed you will use a scope?

Correct. I bought mine and then realized it was not going to work with irons so it now has a scope on it full time. I may still get an A3 upper and change it out.

[RifleShooter]

Thanks for the replies. It is annoying, but I will have optics on the rifle, so I will live. However, I feel compelled to understand the problem. I understand that normally sights are designed to be installed on the same plane, yes? So in that case if you had a continuous rail from the receiver to the front of the rifle, you would have no issues. I have also seen front sights designed to be installed on a gas block that is not the same height as the receiver, as well as sights made to mount on handguard rails. Yankee Hill has three different heights of front sights, although they will not give me information on their dimensions. So, if there are sights designed to work when installed at different heights, what exactly is the problem?

As I understand it, you want a line from the front sight pin to the rear sight aperture to be parallel to the bore. That means if you have a height differential between the mounting position of the front and rear, you need to adjust for that in order to line up the sights correctly. That in theory can be done by raising the mounting position, as would be done using a riser, or by having a taller front or shorter rear sight. So, in my limited understanding, should it not be as simple as adjusting the height of one or the other, or possibly both? Also, what would be the result of having the sights mismatched? Obviously any elevation adjustments on the rear sight would be off, but would there be any other problems created by having sights that are not parallel?

I have been shooting for a long time, but the guns I had either had factory sights or optics, and when I got optics(years ago) I didn't have much choice in mounting height, or anything else for that matter. Now I am getting into previously unexplored territory, and while I am fascinated by all the potential combinations and permutations, it is a bit intimidating. That is why I am asking you guys who know everything about everything. Well, almost.

Thanks so much!

Arnie

[smokshwn]

The problem that you seem to miss is that all the sights you speak of are made to different dimensions to compensate for the height difference when either mounting the FRONT sight on the gas block or the rail on a handguard. None of them address the rear sight being mounted on a raised rail at the rear.

With respect to the setup you have there is no solution available unless you want to have someone either mill you a rail for the front gas block that elevates the front site .301 or you mill the receiver to lower the rear site .301.

The much more simple solution is to get an A3 receiver and swap out parts or sell your upper to someone who wants to run optics and buy a similar upper with the A3 receiver.

[RifleShooter]

The problem that you seem to miss is that all the sights you speak of are made to different dimensions to compensate for the height difference when either mounting the FRONT sight on the gas block or the rail on a handguard. None of them address the rear sight being mounted on a raised rail at the rear.

Yes, I understand, the raised rail on the receiver is the problem. Now let me ask a more basic question.

If I were to mount a set of sights on an AR-type rifle, how would I be able to tell whether they were going to work correctly? And what issues would be created by sights that were not correctly matched in terms of height?

Thanks for your patience. If I frustrate you too much, feel free to ignore me.

Arnie

[bigbrowndog]

I have used the same rifle set up you mention, please read post#2 it can be made to work it is just not optimum.

if you wanted to run iron sights on the rifle you should have purchased the A3 receiver which is the standard flat top upper and will work with a standard gas block.

Trapr

but then I do not really shoot 308 rifles much!!!

Edited May 16, 2010 by bigbrowndog

[smokshwn]

If the receiver rail is not elevated and you have the proper sight to either mount to the gasblock or the forearm, the sights will work correctly. It should be clearly delineated in the sight information ie.

this one listed as a forearm sight http://www.brownells.com/.aspx/pid=24933/Product/FOREARM_FRONT_SLIP_SIGHT

or this same sight listed as a gasblock sight http://www.brownells.com/.aspx/pid=21358/Product/GAS_BLOCK_FRONT_FLIP_SIGHT

as stated above to my knowledge noone (other than Troy Ind.) makes a rear sight that is outside milspec with respect to sight height.

This is assuming you are talking about sights which represent some semblance of practicality not diopter target sights.

Edited May 16, 2010 by smokshwn

[P.E. Kelley]

This was my solution before flat top uppers were

available for the LR-308.

Worked well for me.

Patrick

[RiggerJJ]

What about a front sight system that is adjustable in height? I used one of these on my AR-22 and it works well;

http://www.brownells.com/.aspx/pid=7919/Product/COMPETITION_BARREL_BAND

JP also has a adjustable height front sight that will mount to a railed gas block;

http://www.jprifles.com/1.6.4.php

use a adjustable heigth front sight and a standard rear...I'm not sure however that these will make up the difference, but they might. Have you tried calling DPMS?

jj

[smokshwn]

BigBore may shed more light on this but I believe he called and asked JP about their front sight and it did not have enough adjustability to work.

The barrel band looks like it may work but at $120 + $65 for the sight housing you can easily buy the A3 receiver outright an not have the headache.

[Big Bore]

I actually bought and tried the JP adjustable front globe sight and it did not have enough adjustment to make it work. It was quite a while ago and I beleive it did not have enough adjustment to bring the point of impact low enough.

I looked at the Lipski ( http://www.brownells...ION_BARREL_BAND )it might work, it looks like it has more adjustment. But it was more expensive and I hate buying a bunch of parts that may or amy not work.

By the way I have a JP adjustable front sight lying in a drawer gathering dust.

[RiggerJJ]

I actually bought and tried the JP adjustable front globe sight and it did not have enough adjustment to make it work. It was quite a while ago and I beleive it did not have enough adjustment to bring the point of impact low enough.

I looked at the Lipski ( http://www.brownells...ION_BARREL_BAND )it might work, it looks like it has more adjustment. But it was more expensive and I hate buying a bunch of parts that may or amy not work.

By the way I have a JP adjustable front sight lying in a drawer gathering dust.

I'd be glad to do some measuring on my Lipski front sight system and report back to you if you would like...

jj

[Big Bore]

I actually bought and tried the JP adjustable front globe sight and it did not have enough adjustment to make it work. It was quite a while ago and I beleive it did not have enough adjustment to bring the point of impact low enough.

I looked at the Lipski ( http://www.brownells...ION_BARREL_BAND )it might work, it looks like it has more adjustment. But it was more expensive and I hate buying a bunch of parts that may or amy not work.

By the way I have a JP adjustable front sight lying in a drawer gathering dust.

I'd be glad to do some measuring on my Lipski front sight system and report back to you if you would like...

jj

Thanks for the offer but this rifle will keep a scope until I can fund a standard A3 upper.

See you in August.

Scott

[RifleShooter]

Thanks to everyone for all the input. I finally got a reply from DPMS, which I will paste below:

Any front sight that is made for a gas block will work.

Thanks,

Mark Imholte | Customer Service

DPMS Firearms, LLC

So there we have it. Apparently the height differential is the same as the height differential on a standard height A3 upper, as neither gas block rail is the same height as their corresponding upper rails. The higher than standard rail is accompanied by a higher than standard gas block. The only issue appears to be the fact that the rails are higher, thus possibly causing problems aligning your eye to the sights. I got a response to an email I sent to Troy Industries indicating that the Micro Battlesight set would not work, as they are designed for same-height rails. I don't know of any other lower than normal rear sights.

I put a set of sights on the rifle, with a Matech rear and a Yankee Hill gas block front sight, to see how they looked. They appear to be in the same plane, which would support the information from DPMS, both on their web site and in my email. How would I be able to tell if the sights were aligned correctly in relation to each other?

Arnie