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Extreme Cold Bore Shot Problem

farmer7

farmer7

Private
Full Member
Minuteman
Feb 28, 2013
55
1
Scotland, Highlands
I recently bought a new AR which suffers from extreme cold bore issues.

It groups pretty well averaging 0.7 MOA for 5 shots with some groups a lot better. But without fail the first shot of the day is hitting low by 3.5 inches at 100 yards with subsequent shots grouping together on zero. None of my other rifles suffer from cold bore problems or if they do its less than half an inch.

I have a ASE Utra CQBS supressor fitted, barrel is 18" semi-heavy 1 in 8". Fore end is a Samson Evo 12.37". Ammo is handloads using 73gr Berger LTB's.

Has anyone heard of such extreme shifts for cold bore? (Its cold bore, not a cold clean bore, I always fire a few foulers after cleaning).

Other than noting the impact of the first shot and correcting for it is there anything you can do to alleviate this in anyway? Is it likely to improve with a few more rounds through it?

I plan on using it for fox shooting and other long range varmints. Just cant quite believe it shifts so far for the first shot!

Any thoughts or opinions?

Thanks!
 
Try dry-firing with a more solid hold on the gun, with a little rearward pressure supported by your Natural Point of Aim/Position. Once you can call your dry-fire shots into the cone of error that is acceptable to you, go live.

There have been courses where half of the class was told to dry-fire before going live on Day 2 in the morning, while the other half went straight live. Grouping was night and day.

If you still see the 3.5" initial shot, then it is probably mechanical. That first shot, especially on a gasser, can really break up your position if it isn't solid.
 
Keep the gas system dry after cleaning, dry fire, don't over lube the bore, keep it as dry as possible but still protected. I think you will still have issues but this might help a bit.
 
My first thought would be its suppressor related. I'm curious too, if you've tested without it attached. If you've eliminated the suppressor, and human tendency/error, then maybe consider re-torquing the barrel nut.... Just thinking out loud.
 
Thanks for the input fellas. I dont believe it to be shooter error. I'm shooting prone with an Atlas and butt bag, could understand half an inch but 3.5" is such a massive shift at 100 yards. Its only ever the cold bore shot also.

I'm just heading out the door just now to test it without the supressor to see if that makes any difference. I'll let you know how it goes. Hopefully it could be something simple like the barrel nut torque! ( need to buy a wrench though!)

Has anyone any ideas how long you would have to leave the rifle to fire another cold bore shot? Its 35ºF here today, but last week it was a little warmer and left it 25 minutes but didnt get the shift, first round was on zero. What constitutes a cold bore shot? Would be nice to get more than one a day so I can test more variables!

Thanks for the help.
 
I'm going to add, I don't think the gas system is a problem as he is in the UK. It will be a manual action straight pull rifle.
 
Just back in after testing without the supressor, just using the compensator instead. The cold bore shot is now 2.5" low and 1.5" left with the remaining four rounds all in a cluster of .65 of an inch.

I waited 35 minutes (with bolt open with a cold breeze blowing down the barrel, rifle sitting on its bipod on the ground in snow) to fire another cold bore shot this time with the supressor fitted but all 5 shots grouped on zero!

This is driving me nuts! I dont know how long I'll have to wait to replicate the cold bore problem,2 hours, 6 hours, 24 hours......... its annoying as say for example I shot a fox at 250 yards but dialed in 3.5 MOA correction for the cold bore and killed it. Later on 2-3 hours later I see another its a gamble as to know whether to allow for it or not!

I could live with an inch but not 3.5".

I'm thinking I need a new barrel. Its a pity as it shoots nicely after the first shot.
 
Don't go throwing out the baby with the bath water yet... Since you eliminated it being the suppressor, I'm with Crosshair and thinking you need to remove, inspect and reinstall your barrel.
 
How are you loading the first round from the magazine? Its possible that the bullet seating depth is changing with cycling. Manually loading the case would explain why the first round is out of the group vs the rifle cycling the rest.

Manually load up a few dummy rounds and cycle them, check to see if your COAL is changing. It might be a good idea to stagger live rounds and dummy rounds next time out to see if there is a difference in COAL with manually cycling vs. the rifle cycling. You may need a light crimp or more neck tension on your cases if this is the case.
 
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wareagle700 said:
How a e you loading the first round from the magazine? Its possible that the bullet seating depth is changing with cycling. Manually loading the case would explain why the first round is out of the group vs the rifle cycling the rest.

Manually load up a few dummy rounds and cycle them, check to see if your COAL is changing. It might be a good idea to stagger live rounds and dummy rounds next time out to see if there is a difference in COAL with manually cycling vs. the rifle cycling. You may need a light crimp or more neck tension on your cases if this is the case.
Click to expand...
All rounds are being fed by hand one at a time directly into the chamber and closed manually to try and keep all variables the same, has an external handle fitted to the bolt. Same for every round.

A picture of my 'castrated AR' :





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Something with you or the rifle is moving differently on the first shot. If the scope, mounts, and everything else is mounted correct and working properly, it's you. I seriously doubt it has anything to do with the bore being cold. If it did, your groups would open up considerably as it kept heating up.
 
wareagle700 said:
Something with you or the rifle is moving differently on the first shot. If the scope, mounts, and everything else is mounted correct and working properly, it's you. I seriously doubt it has anything to do with the bore being cold. If it did, your groups would open up considerably as it kept heating up.
Click to expand...
I'm not adverse to admitting fault of myself and could understand maybe half an inch or an inch at worst but nearly four inches at 100 yards? And it is only happening with this rifle, none of the others. All shots are prone of bipod with a butt bag as i shoot my other rifles. The barrel is hammer-forged and wondered about the possibility of some sort of stress when its stone cold?
 
Have someone else fire the "cold bore" shot. then get down behind it and shoot. Or, get up after every shot and then rebuild your position. No offense man, but you say you have a .7 Minute or better gun. You also are saying that this highly precise piece of gear has a "cold bore" shift of 3.5 minutes? That's a stretch. Do you have a vise you could put it in and shoot it? Everyone says semis have a voodoo about them. I just can't get on board with that. Honestly, (and I don't mean to question your shooting ability) look at your position.
 
Before you set up to shoot, fire the first round in the dirt (not from prone, not from the shoulder, not looking through the scope) or even better, let someone else fire it. Then, get down in position and set up for your "cold shooter" shot and 5 round group. Repeat and see if you see a pattern.
 
I am new here, but not to shooting and weapons.

I read your posts and look's like it's not you or the rifle, so only a couple of variables I can think of left.
1. Is the ammo and rifle stored at the same temperature? 10 degrees will affect some powder's performance, even if from the same batch.

2. It looks like a Vortex scope and if something is loose inside, a reticle can shift and the first vibration or shot can bring it back to zero, could be internal springs, or a number of other items.

3. Do the cold bore shots hit in the same general area of the target when fired each first time, if so the scope reticle could be shifting. I read you checked all the mounting hardware for the scope, so you should be good on that one, because just having .001 movement will affect accuracy and generally is associated with the mount.

Have you tried a simple box test to check scope function and see if it is tracking and holding zero.
When the gun was put together any idea what the temperature was, where this is going is as we all know metal shrinks when cold and expands when hot, if the rifle was put together in hot weather and you are shooting in the 30 degree cold weather, it maybe the barrel nut could require a torque check. Stranger things have happened, depending on who put it together.
 
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[MENTION=92838]AZ2000[/MENTION],
Your remedies might be valid here if we were talking about a smaller shift. 10 degrees will not move a shot 3.5 MOA. If a reticle is shifting on one round, then why would it automatically return to zero after the first round and then stay there and be good for the rest of the group? I have a feeling that the scope was not moved over any of this, maybe the OP can weigh in and verify. If it were a mount issue, he would NOT be getting a stated .7 MOA or better group after the initial "cold bore". Even if you compounded all of those issues, you would not produce what the OP is saying is happening. This is a common problem. I would wager that it is shooter and not the gun, as long as the reported .7 MOA groups are legit and from the same shooter.
Do some research on here about cold bore myths. It will blow your mind.
 
I just came back in after trying it again, same thing exactly, first shot 3.5" low following four on zero in a neat little cluster. They dont walk up the paper either its just one shot low all others grouping together. I've learnt it takes somewhere between 35minutes and 3.5 hours to re-create the problem!

AZ2000 said:
I am new here, but not to shooting and weapons.

I read your posts and look's like it's not you or the rifle, so only a couple of variables I can think of left.
1. Is the ammo and rifle stored at the same temperature? 10 degrees will affect some powder's performance, even if from the same batch. Yes all stored together. Powder is N140
2. It looks like a Vortex scope and if something is loose inside, a reticle can shift and the first vibration or shot can bring it back to zero, could be internal springs, or a number of other items. It is Vortex, I'll try another scope on it.
3. Do the cold bore shots hit in the same general area of the target when fired each first time, if so the scope reticle could be shifting. The cold bore shots are all hitting the same place, if I'd shot them all on the same target it would be right around a 1" group. read you checked all the mounting hardware for the scope, so you should be good on that one, because just having .001 movement, will affect accuracy and generally is associated with the mount.
Have you tried a simple box test to check scope function and see if it is tracking and holding zero. The scope was tracking perfectly at long range and dialing back and forth fine, haven't tried a box test since I got it. I'll check it out again. Thanks for the input
Click to expand...
 
0311 Hesco said:
[MENTION=92838]AZ2000[/MENTION],
Your remedies might be valid here if we were talking about a smaller shift. 10 degrees will not move a shot 3.5 MOA. If a reticle is shifting on one round, then why would it automatically return to zero after the first round and then stay there and be good for the rest of the group? I have a feeling that the scope was not moved over any of this, maybe the OP can weigh in and verify. Scope settings untouched If it were a mount issue, he would NOT be getting a stated .7 MOA or better group after the initial "cold bore". Even if you compounded all of those issues, you would not produce what the OP is saying is happening. This is a common problem. I would wager that it is shooter and not the gun, as long as the reported .7 MOA groups are legit and from the same shooter.
Do some research on here about cold bore myths. It will blow your mind.
Click to expand...

So far this is the best group its fired, but several others pretty similar. This was fired last weekend immediately after the first group with the cold bore shot out by - you guessed it, 3.5"!! I'm the only one who has fired this rifle, dont know anyone else round here with an interest in rifle shooting so getting another shooter is not handy. Its never 1 3/4", 2 1/2", 2 3/4" away, its consistently 3.2-3.7" or so.


 
Rig up a vise to hold it absolutely solid and shoot it. This is the only way you will be sure. I'm all but certain that this is cold shooter and not cold bore.
 
The majority of people, including myself suffer from "cold shooter" but 3.5" is a lot. I don't think he's cold, I think its the gun. I've seen a few guns before that were the same way. They are rare and in those guns the problem was never located either. Good luck, I hope you get it worked out.
 
I'm thinking possibly a new barrel. If it was "cold shooter" problems surely it would be evident with other rifles? Especially rifles with more recoil. I've honestly never had issues with any other rifle.
 
Do you have another scope and mount to try out? I wonder if the ADM mount is sliding on the picatinny. Then after your first shot goes back up against the front lug.
 
Cold shooter... Dry fire for 30 minutes then fire your shots for group. That the impacts do not walk up the paper, but immediately shifts to a tight group, points to the shooter. And, your experiment firing 2 "cold bore shots" followed by groups points to the shooter being the problem. The gun may have been cold for the second set of shots, but you were still warm.

Grab another rifle the next time you head to the range (preferably another ar type rifle). Shoot that one for 30 minutes then switch to the problematic rifle. Even money says your cold bore/shooter issue is gone...
 
farmer7 said:
I'm thinking possibly a new barrel. If it was "cold shooter" problems surely it would be evident with other rifles? Especially rifles with more recoil. I've honestly never had issues with any other rifle.
Click to expand...

The op says this is a new AR and the other rifles are bolt guns. Differences in fit and operation are more likely the difference in performance ==> shooter problem.
 
Are you adjusting your sporran after the first shot changing your NPA? Laying prone I could see how it would get in the way.

Or perhaps a tail wind is giving a secondary non rifle related "cold bore" that causes you too become frigid rigid (constricted balloon knot syndrome) for the first shot but you relax for the remainder once you get used to the breeze up the kilt.

Sorry for the useless answer, I just love Scotland. I know your laws are tough. Good to see your making the most of what freedom is available to you. I hope you are shooting in a place where you can take advantage of that wide open, beautiful terrain and you get this figured out. Shame as your group looks great save for the issue with the cold bore.
 
Last edited:
AZ2000 said:
I am new here, but not to shooting and weapons.

I read your posts and look's like it's not you or the rifle, so only a couple of variables I can think of left.
1. Is the ammo and rifle stored at the same temperature? 10 degrees will affect some powder's performance, even if from the same batch.

2. It looks like a Vortex scope and if something is loose inside, a reticle can shift and the first vibration or shot can bring it back to zero, could be internal springs, or a number of other items.

3. Do the cold bore shots hit in the same general area of the target when fired each first time, if so the scope reticle could be shifting. I read you checked all the mounting hardware for the scope, so you should be good on that one, because just having .001 movement will affect accuracy and generally is associated with the mount.

Have you tried a simple box test to check scope function and see if it is tracking and holding zero.
When the gun was put together any idea what the temperature was, where this is going is as we all know metal shrinks when cold and expands when hot, if the rifle was put together in hot weather and you are shooting in the 30 degree cold weather, it maybe the barrel nut could require a torque check. Stranger things have happened, depending on who put it together.
Click to expand...

I agree with you.
 
hlee said:
The op says this is a new AR and the other rifles are bolt guns. Differences in fit and operation are more likely the difference in performance ==> shooter problem.
Click to expand...

The AR in question is effectively a single shot bolt action due to stupid govt rules banning semi auto rifles in the UK. Hence, there is NO real difference between the two. If the scope and mount are eliminated, I think you might have a rogue barrel on your hands. Good luck getting it squared away so you can squeak a few Reynards in. I used to spend many a happy day up in Glen Lyon culling hinds before I emigrated out here and funnily enough, the shooting is what I really miss about UK. Gun laws, politicians and high prices for many things, not so much......
 
All info below assumes you aren't cleaning the barrel between test sessions. Don't clean the barrel until you figure what the issue is or you are adding another dimension to your evaluation....

When you have a repeatable issue such as yours, the shooter isn't the problem. Unfortunately I know this to be fact due to issues I have had with my own rifles. Some of the guys on this board have been listening to those who believe that cold bore shift is a myth. Let me assure you it is not. Cold bore shift can be caused by a number of different things, all of which involve excess tolerance somewhere in the rifle. I have seen issues with undercut barrel tenon threads cause issues similar but less dramatic than yours. Undercut muzzle brake threads could also cause a similar issue but it would have to be a very severe tolerance issue. You are dealing with an semi-auto gas gun which opens the door to there being tolerance issues with the bolt/bolt carrier group as well. Because after shot number one the grouping stabilizes you can likely ignore the scope or scope mount. The fact that exactly the same scenario is occuring repeatedly means that the change in your component that is causing the problem is occuring exactly the same way each time. I have seen other issues cause cold bore shift but they would not be applicable to your rifle. The most likely cause is the barrel fit or bolt/bolt carrier fit. It is always some tolerance that is influenced by the heat created on the first shot. Steel suppressors often have a cold bore shift over the first 5 shots or so but you have already ruled that out. If you find that the barrel fit is the problem, you may be able to correct the isssue with teflon tape on the tenon threads. This isn't a perfect solution but I have seen it correct the problem and yield amazingly accurate results. Let us know what you figure out and I hope this information helps you or someone else.
 
In response
pmclaine said:
Are you adjusting your sporran after the first shot changing your NPA? Laying prone I could see how it would get in the way. I always swing my sporran to the side when shooting prone. :D

Or perhaps a tail wind is giving a secondary non rifle related "cold bore" that causes you too become frigid rigid (constricted balloon knot syndrome) for the first shot but you relax for the remainder once you get used to the breeze up the kilt. Wind was head on so think it not an issue!

Sorry for the useless answer, I just love Scotland. I know your laws are tough. Good to see your making the most of what freedom is available to you. I hope you are shooting in a place where you can take advantage of that wide open, beautiful terrain and you get this figured out. Shame as your group looks great save for the issue with the cold bore. I am lucky enough to be way out of any towns or cities, I'm surrounded by heather, grouse, red deer and a Whisky distillery on my doorstep! Thanks for your useful suggestions all the same! ;)
Click to expand...

0311 Hesco said:
Rig up a vise to hold it absolutely solid and shoot it. This is the only way you will be sure. I'm all but certain that this is cold shooter and not cold bore.Thank you but I'm all but certain its not cold shooter, if it was I'd happily admit it if it helped this problem go away!
Click to expand...

the gman said:
The AR in question is effectively a single shot bolt action due to stupid govt rules banning semi auto rifles in the UK. Hence, there is NO real difference between the two. If the scope and mount are eliminated, I think you might have a rogue barrel on your hands. Good luck getting it squared away so you can squeak a few Reynards in. I used to spend many a happy day up in Glen Lyon culling hinds before I emigrated out here and funnily enough, the shooting is what I really miss about UK. Gun laws, politicians and high prices for many things, not so much...... Thanks for your support, hopefully get it sorted soon! Glen Lyon is beautiful, been down there a few times, also shoot at Blair Atholl range on occasion fairly nearby goes out to 1200 yards, I live about an hour north in the Tomatin area. I hear you about politicians and gun laws though.....
Click to expand...

TxShooter63 said:
All info below assumes you aren't cleaning the barrel between test sessions. Don't clean the barrel until you figure what the issue is or you are adding another dimension to your evaluation.... I haven't cleaned the barrel at all during this testing.

When you have a repeatable issue such as yours, the shooter isn't the problem. Unfortunately I know this to be fact due to issues I have had with my own rifles. Some of the guys on this board have been listening to those who believe that cold bore shift is a myth. Let me assure you it is not. Cold bore shift can be caused by a number of different things, all of which involve excess tolerance somewhere in the rifle. I have seen issues with undercut barrel tenon threads cause issues similar but less dramatic than yours. Undercut muzzle brake threads could also cause a similar issue but it would have to be a very severe tolerance issue. You are dealing with an semi-auto gas gun which opens the door to there being tolerance issues with the bolt/bolt carrier group as well. Because after shot number one the grouping stabilizes you can likely ignore the scope or scope mount. The fact that exactly the same scenario is occuring repeatedly means that the change in your component that is causing the problem is occuring exactly the same way each time. I have seen other issues cause cold bore shift but they would not be applicable to your rifle. The most likely cause is the barrel fit or bolt/bolt carrier fit. It is always some tolerance that is influenced by the heat created on the first shot. Steel suppressors often have a cold bore shift over the first 5 shots or so but you have already ruled that out. If you find that the barrel fit is the problem, you may be able to correct the isssue with teflon tape on the tenon threads. This isn't a perfect solution but I have seen it correct the problem and yield amazingly accurate results. Let us know what you figure out and I hope this information helps you or someone else. Just for your information its not a gas gun due to our stupid gun laws, unfortunately.

Is there anyway for me to know if it is the barrel or bolt/bolt carrier fit? The rifle was put together by one of the most respected AR builders in the UK, unfortunately about 600 miles away! I'm very happy pulling guns apart and am quite competent in most simple tasks. Is it worth buying a vice block and barrel wrench and removing and re-torquing it? When you say the tenon threads what exactly do you mean? Is the AR barrel held in only by the barrel nut?

Thanks for any help in the matter.
Click to expand...

Thank for all the replies and help everyone, I'm just trying to get to the bottom of this. To clarify the shift on cold bore is entirely consistent. Just a bit extreme at 3.5"!!
 
I'm assuming it's a sgc, have you called Bob?

Sent from my GT-I9100 using Tapatalk
 
It wouldn't do you any good to take anything apart unless you have the ability to measure the fit and know the accepted standards. My experience is with bolt guns but the cause will be the same, excess tolerance that dimishes with heating of some part of the rifle. Best to ship or take it back to the builder and let them sort it out. You may save alot of time and heartache by getting back to them.
 
If the rifle was built by a fully competent builder as you say, you might want to give him a call personally. Nobody will know more about it than him.

I'm now thinking it is the scope as was mentioned above by [MENTION=92838]AZ2000[/MENTION]. Try swapping a different scope on top and see if that removes the issue. You may be experiencing some scope lash where the erector springs stick a bit. Do a box test, try spinning your elevation through the cycle before shooting, and don't store your rifle with the elevation all the way down.

Again, thinking out loud here...
 
t140 said:
Do you have another scope and mount to try out? I wonder if the ADM mount is sliding on the picatinny. Then after your first shot goes back up against the front lug.
Click to expand...

I'm thinking the same thing.

I have to tighten down my ADM mounts to the point that I can't remove them by hand. If I don't, my POI will shift depending on bore angle, cheek weld pressure, and where I put my support hand.

Before you replace your barrel, tighten the nuts on your mount by at least an eighth turn. If it's then too tight to remove by hand, I've found that needle nose pliers wrapped in duct tape are useful.
 
I had this same issue with a rifle one time. It would randomly toss rounds. Its the qd mount. I will bet you lunch if you mount the scope in a set of rings, use a torque wrench, the problem will evaporate.

If you can isolate the mount then you can focus on tightening up the levers and fixing the problem. Try a set of rings first. I had my barrel recrowned before I figured out it was the qd mount I was using.
 
Redmanss said:
If the rifle was built by a fully competent builder as you say, you might want to give him a call personally. Nobody will know more about it than him.

I'm now thinking it is the scope as was mentioned above by [MENTION=92838]AZ2000[/MENTION]. Try swapping a different scope on top and see if that removes the issue. You may be experiencing some scope lash where the erector springs stick a bit. Do a box test, try spinning your elevation through the cycle before shooting, and don't store your rifle with the elevation all the way down.

Again, thinking out loud here...
Click to expand...

WaveNature said:
I'm thinking the same thing.

I have to tighten down my ADM mounts to the point that I can't remove them by hand. If I don't, my POI will shift depending on bore angle, cheek weld pressure, and where I put my support hand.

Before you replace your barrel, tighten the nuts on your mount by at least an eighth turn. If it's then too tight to remove by hand, I've found that needle nose pliers wrapped in duct tape are useful.
Click to expand...

LawnMM said:
I had this same issue with a rifle one time. It would randomly toss rounds. Its the qd mount. I will bet you lunch if you mount the scope in a set of rings, use a torque wrench, the problem will evaporate.

If you can isolate the mount then you can focus on tightening up the levers and fixing the problem. Try a set of rings first. I had my barrel recrowned before I figured out it was the qd mount I was using.
Click to expand...
I hope you're right guys, that would make me feel pretty stupid but happy if it sorted the problem!

The only mount that I have that would allow me to mount any of my scopes on an AR15 is a Burris PEPR QD,I dont have any extra high rings, but even if it threw a shot too its surely highly unlikely it would be by the same amount???

As I said I hope you're right but the thing that gets me is its every single time by the same amount when I first get to the firing point and take the first shot. Surely the mount wouldn't do that? I'm very happy to be proven wrong though! I'll try and get that done today and report back. Thanks again.
 
Take a hard look at the QD mount. We ran a test this summer and found very few that would actually hold a zero. POI shift was the norm. Interesting that it is the same error each time. Perplexing? We use solid mounts now and have eliminated the "loose mount" issue.
 
Guys it appears that the scope or mount was to blame, I fitted a different scope in the Burris PEPR mount and bore-sighted it and put it on the target this morning and got a great little 5 shot group with no flier. I repeated it 5 hours later with the same result - no flier!

I'm quite delighted and thanks for all the replies especially the people who suggested the mount/scope. What I cant quite understand is how it happened every single time on arrival at my target on the first shot and the first shot was out by the same distance. But afterward the rifle would print nice tight groups similar to that above but always on zero. All I can think is something was moving on the short 1/2 mile journey in the 4x4 to the target.

When fitting the ADM mount I fitted it according to the instructions, i.e. levers closed with very firm pressure and all screws torqued to spec. I know I could turn the nuts another 1/8th turn and really force them closed, not to bothered about opening them by hand.

The scope has always performed perfectly in the past year dialing back and forth accurately.

What do you kind folks recommend to find the problem, turn the nuts another 1/8th turn and force the levers down and retest and take it from there?

Sorry for the long boring thread now for something so simple! Hopefully it can help someone else with a similar problem though.
 
What about buying some cheap rings? They may not be great, but won't have a very repeatable 3.5 inch.

Sent from my GT-I9100 using Tapatalk
 
The problem with rings is its quite a big scope and I'm 6'2" so I need the scope forward on some cantilever arrangement like the ADM. Plus I'd hate to give up on the ADM, its a nice mount!
 
The cantilever will be the sticking point to prevent cheap rings.

Sent from my GT-I9100 using Tapatalk
 
Farmer, If we are voting:), I would try the 1/8th of a turn, push the scope forward against the rail and set the locks. Depending on what type of steel the cross bolts are made they may stretch after they have been on awhile, or they may not. I have a QD mount similar to yours and had to do the same thing, but also carry a small screw driver to use for unlocking the cam levers if I need to remove the scope. So far no problems.
 
Go Larue for a QD cantilever mount if that's the style of mount you want. But you can try turning the nuts another 1/8 turn on the ADM first if you don't want to spend the money.

As for the problem - the mount probably slid to the rear lug while it was in the safe, riding in the car, etc.
 
Did you have the mount pushed forward into the rail when you torqued/screwed it down? The front of the rail acts as a recoil lug for the mount, and if not buttressed against it the mount can move during the first shot, either working itself loose or binding itself up from a looser state. It wouldn't explain the shift necessarily if the rifle was sedentary between groups experiencing the 3.5" poi shift, but who knows, maybe.
 
Good to hear you've finally found the source of the problem, and now it's easy to come up with the solution. Try tightening the mount screws if that will work, or remove and retorque the caps as well (or both). Cheapest solution first of course.

On the thread I linked to above, the OP was told by ADM to tighten all the bottom screws first on the rings, then torque the top screws. This goes against the star technique we're all used to, but I can see the reasoning for it. Worth a shot if you haven't already tried it.

If that doesn't work... For a mount, find yourself a cantilever one piece mount that is not QD, such as the Nightforce Unimount, Badger Ordnance, or other similar styles. SPUHR if you really want to go all out, or AAD Mount if you want a tank. I'm not aware of what kind of availability you have in your country, but I'm sure you can come up with something. A solid mount pushed forward on the recoil lug and torqued properly will serve you very well.

Another option is an extended riser rail like the Badger Ordnance one, and traditional rings on top of it. Again, not sure what you might have available there. Riser rail, 22 MOA | Badger Ordnance

I'll add that I personally dislike QD mounts and see little purpose in them outside a battlefield (and hardly any on). Solid mounts in the traditional style probably serves 90% of the shooters' needs out there, and the other 10% have scope ADD... :D
 
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FisherT&C
Fouling shots?
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Wyo_Jo
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