Switch scopes.

George

This might not be the culprit, but the rear guard screw has (by design) only 7.5 full turns before bottoming in the blind hole. Make sure you shorten the screw such that it reaches full torque setting by 6.5 turns - better yet 6.0 turns.

It may feel tight (bottomed in hole) and yet the action is not adequately supported.

Same scope? - have you checked those mounts and such?

I had a Burris that would do the same thing 1st group great (coupla different loads) - then all over the place - swapped scopes and all ok.

I am pulling my hair out with this problem, and hope someone might be able to help. I built a rifle for a customer in 243Win, MRC action, well known stock maker (to be explained later) 24 inch Krieger barrel #4 contour 9 twist.

I did all the work assembled the rifle,bedded it with marine-tex,let it cure 48 hrs, and started shooting, cleaning thoroughly between shots and letting the barrel cool completely. The first shot I ignored, the next 3 basically went thru the same hole. I didn't measure it but probably .1 or .2. Took the gun apart and sent the stock to be painted. Got the stock back put it together, started to zero and all of a sudden the group opened up to approx 1.75". Messed with everything,rechecked my work, cleaned everything, put it back together--still bad! Then I tried another barrel, another Krieger 3 contour 9 twist, reassembled and rebedded the action again. Now the gun fired a 5 shot group in the .4's about shot 7 or 8 it opened up to 1.5" again. I took everything apart checked my work, had a friend who was a gunsmith for 30 years check it and found nothing, put it back together, re-bedded it and shot again. Same exact results 4-5 good shots then it turned to sh--.

Talked to the stock maker and they had me send them the rifle, just talked to them and they restocked and rebedded the gun it fired 8-10 rounds fine then opened up, so the same problem from before. I quote "we are totally mystified we have no idea what is wrong" I talked with Jeff from MRC and he agrees that this is a strange one and also wants to look and see what they can find, so the gun will be on its way to them.

Conclusion, all shots from a COLD barrel, always cleaned and checked with bore scope, fired same exact loads all powder charges weighed, fired in a tunnel-no wind or change in conditions. It seems after bedding to shoot 4-10 rounds fine then goes bad. Anybody have any ideas? All of the manufacturers have been great and willing to help! I didn't mention the name of the stock maker because they have been more than good to me and went the extra mile, so I want to make it clear I am NOT blaming anybody just need help. Just added also rechecked the bases and 2 or 3 different scopes, and the stockmaker used even another scope>

What do you consider "proper torque setting"? I have exactly the same problem, neutral bedded shorter barrel, 21". Mine is in 338 WSM. Rear is pillar bedded and it's torqued to 40 in/lbs as is the front. The screw is NOT bottoming. I'm on the second Pac-Nor barrel now. Only thing I haven't done is free float the barrel but since it's a #2 contour I think it's too light for free floating. Going to try shims in the front based on what your saying here. That's about all that's left for me now. Two scopes have been Leupold 2.5X8's and the third one is going on this evening having just been returned by Leupold. They found nothing wrong.

Thanks for the input everybody, I will try to answer everybody here ! Rod I also thought about the screws and did shorten both screws, I also used dykem (sp)? on the end of the screws to check for bottoming. I also used different screws all the way from loose to 50" pounds. no change at all. Rod I do have a question for you, I am sending the gun to Jeff at MRC would you be willing to look at it with them, i almost called you to ask you about this I think you probably understand these actions,and bedding as well as anybody?
Matt, I bedded the rifle with the barrel free floated with probably and 1/8" gap between the barrel and stock, then bedded it tight about 3" forward of the action, then free floated with a pressure point at the end of the stock. I bedded the action with guide pins and surgical tubing. the second time I used the screws just snug.
Bob sorry to hear you have the same problem, I hope we find an answer, but I am glad to hear I'm not the only one I thought I was going CRAZY!!
One more thought the stock maker also got the same results with a different stock, and they have a VERY good reputation! Any more thoughts ?? PLEASE again thanks for the help Ed

Have you checked the headspace after you've fired a few rounds?? If it set back, this could cause some accuracy problems as well. Unlikely, but then again so are these problems that you're having too.

Stresses in the barrel could cause these problems too, but considering you've changed barrels out and you're still having the problem, the chances are unlikely that two barrels would suffer from the same problem.

The only common denominator is the receiver, hence the need for examining lug setback and headspace problems.

Was the barrel floated, or pressure bedded???

If pressure bedded, the stock could hold appropriate pressure for the first few shots, then move away from the barrel, releasing tension and causing the effects you describe. After the action is removed, the stock, if subjected to different weather conditions, could move back to it's original position, so when reassembly occurs you've gone back to square one with tight groups.

If the barrel was floated, ensure that it has ample clearance by painting on inletting black on the bottom of the barrel and reassemblying the rifle very carefully, then shooting again. If the barrel or stock is moving on heat up, remove material in the stock that's making contact.

It doesn't take much heat to cause a piece of steel the size of a barrel that's got a hole through it to move.

Good luck on your project.

Matt, Very good idea, and something I never considered, I will check it as soon as i get the gun back, and let you know. I may not have any hair left by the time I figure this out!!! Thanks Ed

Bob...problems with the 2.5 x 8 Vari-III almost drove me nuts. Leupold kept telling me nothing was wrong and after several trips back I gave up and put something else on the rifle ..... my problems went away.

I too have had that experience but then on this one I also tried a Burris that worked well on another rifle and it still did the same thing. I just reinstalled the scope from Leupold and shot today. Same thing. I just finished free floating this barrel and will try again Monday. Thanks.

Bob, I am willing to bet that fee floating your barrel won't help anything!! Am I right that your gun shot fine and then went south? What kind of stock do you have it in ? If you are interested in talking about this more please pm me Ed H

PMJI, but does the accurracy improve after re-bedding or re-barreling?

If the former, could the recoil lug have something to do with it?

If the latter I would have to think that when you, rebarrel you rechamber at correct headspce and then after 8-10 shots some setback may occur.

JMTCW

Rob, I have not checked the headspace, but will as soon as I get the gun back. The problem occured exactly the same when I re-barreled the gun AND when I just re-bedded it. All thoughts are appreciated,maybe somebody will come up with the answer!!!!!!!!!!

Quote:

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Insanity is doing the same thing over and over and expecting the outcome to be different!

Some possibilities:

1) I built a .243 with a 1938 type Turkish Mauser, Adams and Bennet bull barrel blank, and Pacific reamer, trued the action, glass bedded, trigger job, and lapped the lugs.

The first shot is a fouling shot, the next three holes are touching at 100 meters, and the fourth shot on, all groups are opened up to 3".

The cause was copper fouling. It was then two hours and many brushes to get the copper out. The bore and grooves had a cut every 1mm, which I speculate was caused by button chatter.

2) With other rifles, new brass was much more accurate than reloaded brass until I stopped using an expander ball in the resizing die.

3)So many times, so many rifles, trouble at the range turned out to be that one of the scope mount to receiver connections was slightly loose, undetectable with the scope and rings on the rifle.

4) Constant wind makes small groups, gusty wind makes big groups.

--
A society that teaches evolution as fact will breed a generation of atheists that will destroy the society. It is Darwinian.

Ed,

Is the problem consistent? or does it do it once and then you try something different? Is the action bedded tight around the recoil lug? Was the action completely trued?

It sounds like something is moving. I think checking the the headspace is a good idea. You might also check the barrel torque and maybe try going a little tighter. I have seen barrels shift when they heated up due to a crooked front receiver ring.

More information on my responses! thanks everybody I appreciate the help.
Clark I wiil answer yours first, as far a copper fouling, I was cleaning after every shot and checking for copper. The gunsmith at MRC had me check the bore with a bore scope for copper in the middle of the barrel where I couldn't see, and there was some copper. I started cleaning better and checked for copper with a scope every time to be sure, looking at the bore with a scope it appears to be fine, although it has been slow to "break in". I have been cleaning after every shot all the way through this.

As far as brass I used either all new brass or once fired brass, never mixing the batches. all of the brass from the same lot.

As far as bases and rings, I have also seen this sort of problem and I may still be missing something. I have changed bases, one set I fit to the action and lock tighted them down, even used lock tight on the scope rings. I've used different bases,rings, and scope with no change!

You will probalby hate me for this but NO WIND I have a tunnel I shoot in and the conditions are always exactly the same except for a small temperature change. Only problem is now I don't have any weather excuses.!

My fear is that I THINK I have thoroughly checked everything but maybe i can't see the forest for the trees

Idaho CTD The problem seems to change only when I re-bed the rifle or re-barrel it and bed it. On the recoil lug one time I bedded it totally tight with NO clearance. I normally bed with clearance in the front, sides and bottom of the recoil lug, which is how I did it the first time. I also tried bedding it with clearance down the sides of the action lengthwise in an attemp to maybe releive any pressure

action truing, I built an arbor trued the face of the action, trued the face of the bolt and the recoil lugs on the bolt, you cant get to the lugs in the action. I did not single point the threads in the action true to the center axis. As far as torque, I tried just good and snug (tight) and very tight. Tighten it till it strips and back it off a 1/4 turn right?? hehe All kidding aside I did try snug and good and tight, no change. thanks everybody Ed H





Insanity is doing the same thing over and over again and expecting the result to be different

Ed,



How loose (or tight) is the fit between the barrel threads and the receiver? How soft is the front receiver ring? Did you re-tighten the barrel after the groups opened up before removing and reinstalling?



I think you see where I am headed (thread fit between barrel and receiver, or soft receiver allowing loosening of fit after a few shots).

Jim

Jim I would say that I would rate the thread fit as very tight, to the point that it is almost too tight to thread on. Actually I thought I might be too tight causing some strees. As far as hardness I just assumed................yea I know! I can probably get access to a rockwell machine and will do that when I get the gun back, any thoughts on how hard it should be, about 40 rockwell c ?

On the retightening of the barrel I never checked that, and I do see where you are going with this, that just might be the answer! Thanks Ed H

Could the scope base screws be bottoming out in the
holes before the base gets completely tight? Either
screws too long or holes not drilled & tapped deep
enough & getting snug but not solid? Hope you figure
it out! I've got an SS SA MRC & have had no problems
at all.

Good Luck, Bruce

Just throwing darts here Ed, but could it be a bad batch of MarineTex that is breaking down and compressing after the first 8-10 shots?

Have you chronographed the rounds? If not it might tell if you were getting bad ignition or something. Maybe there is a burr or something inside the bolt that keeping you from getting consistant ignition. Long shot but easy to check.....DJ

Rob I thought about the marine-tex, and the possibility that it could be soft. Just before I gave up and sent the stock to the stock builder, I ground out all of the marine-tex and replaced it with acraglass. I didn't notice any improvement by doing that!

DJ I have been chronographing most of the rounds and generally checking for huge changes. To be honest I haven't been watching this very closely, but it is a good thought! From now on I will pay attention, you know how it is when you get on a certain mind set ! Thanks all Ed H

oulufinn,

What's your opinion of the fit and finish of your MRC action? Dan says mine is finally "staged" and that it should be going out the door very soon. Too bad I have only just recently moved to Nevada from Virginia; I have to establish residency by playing Switch for 90 days before I can buy or take receipt of any gun bought through a dealer or transferring agent. Mine is SS, LA and LH Magnum. Fernley is the place to shoot: there is a dry lakebed just 4.5 miles from my house. It's about 200 or more acres and the desert surrounds it totally. The Oregon border is 150 miles to the North, so no need to worry about where the bullets come down. The bottom of the lake is strewn with all kinds of junk at which to shoot and 4-wheelers go nuts out there after a rain. Great fun!!

Rootbeer,

I am very happy with the fit & finish. It's a SS SA RH
in 25-284. I had MRC do the barreled action in a blasted
matte finish. Initial accuracy is under an inch & should
do better with some load development & a trigger tweak.
Good luck getting your project finished, Bruce

We've always believed 60-65 in/lb was a better number. But then that is with ProBed 2000, which is a fairly stout compound when fully cured (48hrs). The problem stated was with a rifle that shoots very good for 5-6 rounds only. This sounds suspiciously like it's coming loose in the stock.

BTW, we've had a rifle or two over the years that wouldn't shoot pressure bedded. We try floating (very little clearance - like .005-006in). If that shows improvement, we give it a little more. If not, full length bedding - with ProBed 2000. One of these methods has worked on all but one rifle - that one got a new barrel.

The receiver should be Rc 40-44. The bolt a bit harder.

Early actions had a tight thread specification, this was opened up a little bit early in 2003.

Is it just the barreled action at MRC, or the entire rifle? This is a short action, yes? I'd be tempted to drop it in one of our Red Mist test stocks and shoot a box of ammo to see what happens. Curiosity.

Thanks Rod. This SA action is bedded in Marine Tex which is also pretty hard. It's torqued at 40-45 in/lbs. It's on its second barrel now and third scope. No change with any of those. It shot well initially with the first barrel then went steadily down hill. The frustrating part is that it will occasionally shoot astounding groups one being the smallest I've ever shot with any 338, it was .175", but the next time out that load shot almost 3" and it's never been close again. Same with other loads. Often there are two shots in one hole and the other at random locations around the clock, and it's always random, sometimes the first is out and the next two in or two togther and the last one out. No pattern. The barrel was originally bedded neutral. Shims under fore end made no change. Last week I relieved the barrel .020" or so to float it and it shot horribly, some as wide as 6". Bedded the fore end with 10# pressure and it's back to its old habits, still not good but better than floated. I relieved the bedding at the flat behind the trigger group thinking that might be acting as a recoil lug and not letting the real one do it's job, but it made absolutely no difference. The only common denominator now IS the action. Oh! I also replaced the firing pin spring because of dramatic velocity variations occasionally, which was likely the propellant I was trying. No change.

Any other ideas would sure be welcome.

Well, there are a hundred questions that come to mind. Borescopes, powder types, brass runout, so on and so forth. Assuming all of those have been thought about. We have a 338 WSM just starting in the test cycle now. We've had three problem childs so far this year. One, a 30-06, I gave up on for a while, an then tried full-length bedding. It went from 1.5" best with 150gr bullets to .6" with everything. The other one was a .338-06 that would do 3 nice and tight and then throw the last two every time. That was powder. RL15 pulled it to consistant five in .80". The 300win was 4.0in no matter what. But, the clue was in the barrel. A tight patch on a jag felt a series of knotholes when pushed through the barrel. The borescope showed nothing. Ditched the barrel and the one went immediately to .80".

Try sending email to my home address, and we'll talk this one over a bit. I don't get on here as much as I used to because of time constraints. Maybe there's a clue somewhere.

rod@mountainofdreams.com