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Posted: 9/28/2014 7:59:45 PM EDT
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Stag flat top upper with Diamondhead handguard and flip up Diamondhead BUIS
Leupold Mark AR scope with LaRue QR mount So if you mount a scope with the configuration described and if the scope cannot be mounted forward enough so that proper eye relief isn't provided (scope flip up caps hit folded down front BUIS) should I add a section of raised Picatinny rail to the top? I can mount the scope, but eye relief doesn't look adequate with normal cheek weld/nose near charging handle position. If I mount the scope one rail space further forward (close to ideal) I can't open the scope cap. Also, the rear scope objective rubs a bit on the rear BUIS. Make sense to add a Picatinny scope riser? Recommended brand? Thanks in advance. SD eta - like this? http://www.brownells.com/optics-mounting/rings-mounts-amp-bases/rifle-bases/scope-riser-prod54612.aspx or - http://www.opticsplanet.com/leapers-utg-0-5-low-profile-riser-mounts-for-rifles-with-picatinny-weaver-rail.html |
Can you post a photo? I have Leupold VX-R Patrol in a LaRue SPR mount and there is plenty of remaining forward adjustment range still left. The rear of my eyepiece is just about even with the rear of my charge handle for the cheek weld and eye relief that works for me, and could probably go forward two inches more, if I needed.
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Will do, but in my case the rear objective is really tight on the rear Diamonhead BUIS and not as far back as yours (scope cap just touches) and that seems too far back already to me. My rear objective ends about where the 'P' is on your Leupold. To get a clear scope field I have to move my cheek too far back (nose maybe 2" + back from charging handle).
Moving the scope forward one space on the rail would be perfect, but that's tight enough on the front sight (Stag 3H) that I can't flip open the front objective cap. Now, I could just slide the scope back on the rings a little (like yours) and get it to fit but again it's an eye relief issue and clearance to the rear BUIS. Where you have maybe 1/4" of clearance I have nearly 0" between the rear scope objective and the top of the rear BUIS. I think my rear objective may be a little larger too, the VX-R patrol lists at 1.6" and the same height is missing on the Leupold site, but your front objective is 1.8" and the Mark AR is 2.0". The scopes are exactly the same length. |
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I would probably get a different (longer) rail and move the front sight farther forward. Before using a riser mount I would replace the current mount with a LT-135 http://www.laruetactical.com/larue-tactical-sprm4-193-mount-qd-lt-135  |
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Quoted: The LT-135 would work if I could get LaRue to take back the LT-104. Can't move the front sight - sits on the railed gas block. You could probably put your LT-104 on the EE and find a used LT-135 for about the same price. Or offer it as a trade option in your listing. |
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Quoted:
The LT-135 would work if I could get LaRue to take back the LT-104. Can't move the front sight - sits on the railed gas block. I don't know if you can tell, but the LaRue SPR in the photo I posted above is the LT-135. It is 1.93" from centerline of the scope to the top of the rail, rather than 1.5." It is not farther forward, however. I needed that extra height because my face is longer and raising the scope up a little gave me a better cheek weld. I still can't understand where the interference is taking place on your setup. Is the Diamondhead rear BUIS really that much taller than most? Is your gas block mounted front sight fixed, or folding? A photo really would help to understand your problem. |
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Will take photo tomorrow. Diamondhead BUIS are folding. Face is "normal" ;o)
http://vtsupply.com/images/DMD1199_1.jpg |
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See if the photo helps. Yes, I can slide the scope in the mount, although it's very tight on the rear BUIS. I'd like to move it one space forward, but cannot open the cap. I could move it up then slide it back, but would I benefit from the taller La Rue mount?
http://i26.photobucket.com/albums/c135/silencedogood2/scope_zpsf3433dd2.jpg |
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I see. You needed the LT-135 for that rear backup. I see three choices, though there may be others.
1. Sell your LT-104 in EE and get an LT-135. You might even be able to trade even with someone with the 135 looking for a 104. 2. Replace the Diamondhead rear sight with a lower one. For many reasons, this is probably the best choice. Almost every rear BUIS is lower, and most will be stronger and more resistant to damage from impact. 3. Stack a 1/2" riser between your upper and your scope. This seems to be what you want, but may be the worst choice for many reasons. Stacking risers and mounts injects a series of variables that can produce unexpected problems with tolerances and opportunities for mount screw loosening and slot slippage. Using thread locker on the riser screws helps, but will not help if you run into problems with cumulative tolerance addition that might, for instance, cause you to lose a lot of elevation or windage range in your scope. I'd get a different rear backup and be done with it, keeping the scope height matching the cheek weld on your stock and letting you mount the stock the same way with your scope as you do with your irons. I speak from experience, having to run an LT-135 because of my rear sight and a somewhat larger eyepiece on my scope and using a flip up lens cap over it. I have a long face and get a better cheek weld that way, too, but it is different than my backups. I don't have a choice. You do. For most people it is better to keep them the same. |
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It looks as if your rear flip isn't going all the way down. If that's true try flipping the aperure to see if it will fold flat with the other aperture up. If it's not going all the way down that seems like the problem right there.
A) loose the rear flip cap. You really don't need it and it's the least important part of the system. If that's interfering with the BUIS, remove it. B) OR move the scope mount forward one notch and/or shift the scope forward / back in the rings until you find a spot where they don't interfere. |
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If you are referring to me the MBUS rear sight is all the way down and the scope is ideally placed for my cheek weld and the scope's sweet spot for eye relief. Also, the LaRue mount is all the way forward. There are no slots ahead of it on the receiver. I could move the scope forward in the mount, but would then have to resight it and would still have an eye relief distance greater than ideal. As to the rear lens cover, while it is not in the photo, I hunt with this rifle. In the rain. Sometimes, but rarely, snow or sleet. When hunting I need to have both ends of the scope covered under those conditions. LT-135 is the proper solution for me.
If you are referring to OP, I think he has explained why he can't move the scope forward (front lens cap interference with front sight). I may be mistaken, but I think his rear sight is known for being high and is probably all the way down. Given the length of the interference at the rear, removing the rear lens cap, even if he does not really need, it, might not be much help. They are worth a try, but I think the solution for OP might be to simply get a lower rear MBUIS and roll on, unless he is really wedded to the Diamonhead. |
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1. Why are you concerned with back up sights with a scoped rifle?
2. Why are you concerned with setting up your scope eye relief with a nose to charging handle position? 3. Why did you choose such a low scope mount? 4. They make a riser so you don't have to go through the hassle and added expense of getting the higher scope mount. |
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Quoted:
1. Why are you concerned with back up sights with a scoped rifle? Because I want to be able to shoot both, and the LaRue mount contributes to that. 2. Why are you concerned with setting up your scope eye relief with a nose to charging handle position? I'm just saying that eye relief with the pictured mounting position seems too far back to me in the scope position shown, and I cannot move the mount forward one notch (clearance on front cap). 3. Why did you choose such a low scope mount? I probably made a mistake - didn't measure working scope centerline vs. BUIS clearance. 4. They make a riser so you don't have to go through the hassle and added expense of getting the higher scope mount. Yes, but other posters don't seem to think that's the way to go, and I'm inclined to agree. |
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