Last week when the thread came up about the repeatability of Larue mounts, it prompted me to do my own little experimenting with the mounts to see, for myself,
what I already believed to be true.  I shared the results with the fine folks here in Larueville. I also thought it would be interesting to see how consistent the
PredatOBR is when broken down and re-assembled.  I have an 18" & 14.5" PredatOBR.  I chose to use the 18" rifle for the test gun. This rifle is one of the Rifle
Gear rifles that had Field Grade barrels.  I have put roughly 500 rounds through this rifle since I received it late last year.  The rifle with field grade barrel
is accurate, typically shooting in the 3/4 MOA area.  I feel that this barrel has lost a slight notch in consistency over the time I have owned it.  The rifle will
still shoot 3/4 MOA, just not all day like it did in the beginning.  For whatever reason some groups will open up with 3 or 4 bullets going 1/2-3/4 MOA and 1 or 2 bullets opening up the group.  I noticed that this started after @400 rounds.  Possibly this is something that has to do with the Field Grade stamping, a small kink that Larue was working on when barrels started getting lined out.  That's just an assumption, and the rifle is still more accurate than most, and I am very happy with it, field grade barrel and all. Here are typical groups from this rifle.



As I said the rifle is an 18" PredatOBR with Field Grade barrel.

Scope used was Leupold MK6 1-6 CMR Reticle in a ADM Recon Mount.   (IMO a low powered scope for this test, but adequate)

Surefire SOCOM Brake

Handloaded Ammunition

41.7g H4895

175 Berger OTM



I fired a 5 shot control group. On the target below it is diamond #1.  This group started out to be the smallest group I have shot to date in this particular rifle, on par with my OBR, and as I stated above the rifle spit one out with shot #5 falling 1/2 MOA outside the group opening it up to a 3/4 MOA control group.  I then proceeded to take the rifle down completely and re-assembled it and fired the first shot at diamond #2.  I continued this sequence for every shot for the next 4 shot at diamond #2.  I then did the same process again for diamond #3.  








RESULTS:

Control group:  .734

Group1: 1.075  .341 difference from control

Group2: 1.031  .297 difference from control

You can see by the groups that the approximate center of both test groups fell roughly 1 1/4-1 1/2 up and left of POA.  The difference in size of each test group has a change of less 1/2 MOA and closer to 1/4 MOA.  IMO incredible consistency for a rifle to have its barrel removed and replaced every shot.  It is interesting to see that there is obviously some vertical in the groups.  I have no opinion on the cause of this but I would be interested in any opinions out there.  I numbered the shots on the target so one can see the difference between each shot.  

Next I wanted to shoot for change in POI for 6 shots.  One shot on each diamond to better be able to visualize any change in POI for each dis-assembly/assembly.  The results of this were just as impressive as the above results.  Shot #5 fell outside what appeared to be the average by a margin. #5 was the only bullet that fell more than 1/2 MOA from the POA. Even with this the results were still fantastic.  I will update this thread with a test target just like this one, shot with the same rifle and the barrel never removed.  I did not have enough ammunition to do this that day. I feel like that would give a better idea of any change, however small, is being realized from taking the rifle down each time.  



My apologies for the wait, there were hogs that needed killing this weekend and other stuff......I will say that although my tests are rudimentary at best, the results were stellar and I believe fairly definitive that one can be comfortable taking down their PredatOBR and knowing that it will still hit where they are shooting when it is re-assembled. Hats off to you and your craftsmen Larue. Now about those sloppy RATS.........................................

Quoted:

Good point to bring up, and it may very well have been 1/2 min left,for actual zero.  POA was of course the center of the diamond, that said I made adjustments and fired at tgt #1 and that was assumed zero. with POA still the center of the diamond..... .2MRAD clicks makes it difficult to absoloutely zero on a particular spot.

ETA: Studying the actual target a bit more and based on the average center of all the shots as a single group, the true zero is most likely 1/4 MOA possibly 1/2

MOA left of POA which just makes this example more fantastic.    

A thread on here last week about the repeatability of Larue removable scope mounts prompted me to do some testing.  Let me preface this with the admission that I am just a guy that has a passion for the best of the best when it comes to all things firearm related. For me, the most important factor in all firearms, is accuracy and precision, regardless of what it costs.  There are many high priced weapon platforms, scopes...etc. that I have bought and sold or do not use because they don't fit my needs accuracy and precision wise.  That does not make these products bad, everyone has their expectations and use for a product, for my use and needs these did not prove themselves to be what I want. Let me also say I am by no means a formally instructed , white coat wearing, lab product vetting type of any sort. Point is I am sure that there are better ways to test these mounts but this is how I did it and in my mind it seems to have been a feasibly relevant test. On to the good stuff.

As some here that may have seen in previous posts of mine, I have what is IMO, an extraordinarily accurate 18" OBR.  A rifle that shots far better than 1/2 MOA, 1/4 MOA is closer to the average, every time it spits a projectile out. The perfect platform to test any optic, mount etc.  If this rifle does not shoot it is the fault of something other than the rifle itself.

Test Rifle:

Larue 2012 yr model 18" OBR

Nightforce NXS 5.5-22x56 scope.

TBA Supressor

Handloaded Ammunition 175g Berger OTM


Mount Tested:

Laure LT112 PSR20,  this is the 20 MOA mount.  






This rifle has had somewhere around 1000 rounds shot out of it.  The only scope it has ever worn is this nightforce scope.  This LT112 mount has been on the rifle for roughly 500 of those rounds.  I changed to the 20 MOA LT112 to get more distance out of the scope.  1300 yards was max using the full adjustment range and the reticle with the previous LT111.  The LT112 got me to 95 MOA of adjustment which gets me wayyyy out there.

In the past when I have seen comments criticizing Larue mounts there is talk of "slide marks" on the underside of the mount, where it has slid back and forth under recoil. I will agree that this is a highly likely scenario with a mount that is NOT adjusted properly.  In the next picture you will see that this mount with over 500 rounds, has no sign of slide marks.  In fact you will see the oil dots where the rail contacts the mount and they are pristine where they ride the rail. This photo was taken after firing the first 3 shots as the test control target.  





I have also seen comments criticizing Larue mounts that if the mount was tight enough to keep from sliding then the levers would tear up the rail.  I do not remove the scope from this rifle very often, maybe it has been off 10-15 times over the period of 500 rounds.  After I was done shooting this test and had removed and remounted the scope 8 times, I took this photo of the rail.  There is no damage or distortion to the rail.  There are several spots where the Anodizing has been marred, which IMO is a non issue and not what I would call damage.



Now the meat.  It has been well documented here with load development in this rifle how well it will shoot.  I shot a 3 round control group to compare the next two targets to.  I know there are people here that require 76 round groups to agree anything is proven, give me a pass here, a 5 round test group would have just made the final results boring, trust me.  For the test I had a single target with 6 aiming points, I only used the top row of 3.  The first group on the left, is the control group.  For the next group I removed the scope, took pictures of the underside of the LT112 (posted above) Fired one round, removed scope, fired another, removed scope and fired another, for a 3 round group.  The next target I did the same, starting by removing the scope and re mounting and then shot a 5 shot group with the same remove/shoot procedure.  



1. control group size:  .264

2. 3 shot group size:  .341  (Removed/mounted every shot)

3. 5 shot group size   .344  (Removed/mounted every shot)

In my opinion I would say this is a fairly revealing test.  With these results it is hard to dispute that the Larue mount, when properly adjusted, will return to zero in an amazingly consistent manner.  Going in to this I had assumed that the results would be great but I honestly did not think it would be this consistent.  I figured if there was less then 1/2 MOA movement then I was happy and the test was a success.  If this rifle still shot MOA with a 5 shot remove/mount group I thought that would be excellent results. I am sure these results are no news to the folks at Larue, Mark and Mark are likely saying, "told you sumbitches".......  I am a fan of Larue products because they work, they are quality engineered and executed and last but not least they reside in the greatest country known to man......................TEXAS