338 Edge goes from 0.4 MOA to 2.0 MOA with same load?

Discussion in 'Long Range Hunting & Shooting' started by midgetorama32, Mar 5, 2010.

  1. midgetorama32

    midgetorama32 Well-Known Member

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    About a month ago, I picked up my 338 Edge from my gunsmith to break in the barrel and do a little load development. I bedded the action and was able to get some 0.400”-ish groups at 110 yards with the 92gr H-1000, 300 SMK load with the bullets about 0.010” off the lands. They were shooting about 2800 fps. I took the gun back to have it bead blasted and machined for the bigger Wyatt’s magazine. I picked it up again and just got back from shooting it today.

    The load that initially gave me the ½” groups has now opened up to nearly 2” at the same 110 yard distance. Velocity is the same. I switched out the EGW base with a Nightforce base and aside from that, I didn’t change anything.

    The gun is a 700 Remington in and HS precision stock. NXS 5.5-22 X 56 scope with NF rings. One thing I noticed is that the stock fits much more tightly in the recoil lug area than it did before the bead blasting. Does bead blasting “swell” the metal a bit? My gunsmith is out of the state for the next two weeks so I thought I’d try a post here in the mean time.

    Any other areas to potentially look?

    Thanks!
     
  2. midwesthunter

    midwesthunter Well-Known Member

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    Check ur action screws. Does the action feel like it has to be forced in? Your action screws should go in very east till it bottoms out on bottom of stock then should only take about a half turn to proper torque
     
  3. midgetorama32

    midgetorama32 Well-Known Member

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    Yes. Much more than before the bead-blasting.
     
  4. dirtball

    dirtball Well-Known Member

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    A couple of thoughts, some thing changed either when the bead blasting was done OR when the the machining was done for the Wyatts. Did the same smith that did the original work do the machining for the Wyatts? Was the barrel removed to work on the action? If so was the same tool used to align the recoil lug when the barrel was reinstalled? If not this could be your problem, it would not make any difference in a "factory" inlet but if you bedded it with some sort of epoxy and the recoil lug is not aligned EXACTLY like it was originally, it will not fit properly.
    Dave
     
  5. Michael Eichele

    Michael Eichele Well-Known Member

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    You mentioned that you changed scope bases. Did you put a one or two piece base on it?

    If it is a two piece, then take off your scope and loosen the rear two screws. If you look closely, when you loosen and tighten the screws, you may see the base flex up and down to conform to the action when being tightened and raise when the pressure is released. If you can detect even the slightest movement, it is more than enough to put stress on the action and scope when the scope is tightened down to the base. When you get this stress, accuracy is impossible to attain. If that is the case, you will need to 'bed' your base for a stress free fit of the scope.
     
  6. davewilson

    davewilson Well-Known Member

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    i would agree with everything said so far. and i would also think that the bedding could possibly need redone. you've changed the surface of what goes against the bedding. one itsy bitsy high spot can change a good bedding.
     
  7. midgetorama32

    midgetorama32 Well-Known Member

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    Here is what I have found so far...

    There is a lot of residual compound in the recoil lug area. With the fresh bead blasted surface it's very easy to see contact points. The contact on the recoil lug is twisting the action horizontally in the stock so that the right side on the back of the receiver and the barrel shank on the left hand side show major signs of contact against the bedding compound since the bead blast finish has been polished off.

    I removed some of it last night and its quite a bit better. I just need to go buy a very small chisel to finish the job. I'm not sure what happened because he uses a jig that aligns the recoil lug. I plan on checking the scope base too. It's a 20 MOA 1 piece base.

    Oh well. It will be a while before I can go shoot it again.

    Thanks for the advice.
     
  8. Broz

    Broz Well-Known Member

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    I agree with all that has been posted also.

    Was the crown of the muzzle blasted? If so I would consider a recrown job.

    Jeff
     
  9. Fiftydriver

    Fiftydriver Official LRH Sponsor

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    Interesting case. Some very good points have been brought up.

    The Bead Blasting should have made no effect on the rifles accuracy as far as the rifles fit to the bedding. I say this because every rifle I build for customers, around 80 to 100 yearly, every one is bedded prior to bead blast finished the metal surfaces. Simply put, it will not make any difference. If the barreled receiver is tighter going into the bedding, its for another reason, not the bead blasting because the blasting will actually remove a minute amount of steel. The blast media actually cuts the surface of the steel which is why it changes appearance. It in no way increases in size unless your smith is using gravel for blast media.

    So what will cause the accuracy problem, well, reading over your post I see several issues that MAY cause problems. I will go over each. Something happened and changed from when you broke in your barrel to when you get the rifle back. Lets look over what has changed:

    1. Bead blasting. I have said it should not effect fit to the stock and that is true. If the stock is tighter, you need to make sure nothing has changed on the barreled receiver such as the smith pulling the barrel for bead blasting and then reinstalling the barrel and the recoil lug is not indexed the same as before. Other then that, the real issue is if the muzzle crown was blasted. I never, EVER blast the muzzle of my rifles. A burr small enough that you can not even see it will destroy accuracy. Bead blasting the muzzle will be very hard on accuracy. If the bore was not plugged and the blast media actually got inside the bore under pressure, your pretty much screwed without removing that last part of the muzzle and recrowning but I am sure your smith would not do something like that or he has no business being called a smith. That would be a really rookie mistake.

    2. Scope base. Make for damn sure that the front receiver screw is not contacting the barrel threads. To do so, loosen all base screws just enough so that the base moves easily then screw the front base screw down until you feel resistance. The rail base should be solid. If there is any movement at all with the base, your front receiver screw is contacting the barrel threads and this can also cause some serious accuracy issues. Sand off some length of the front screw until it bottoms out and does not contact the barrel threads in any way. The NF base is a huge improvement over the other rail, make sure recoil lug on the rail base is contacting the receiver properly also, THis screw situation can occur with 1 or 2 piece bases. This problem ususally shows up if the receiver has been properly accurized because the receiver thread diameter has been increased but it can happen with a standard receiver as well just because of screws that are a bit longer then normal.

    3. Wyatts magazine box. If its the internal mag box that used a Rem 700 BDL floorplate, you have to make damn sure that the magazine box is free floating between the receiver and the floorplate. You should be able to open the hinged floorplate and reach inside with a couple fingers and be able to move the internal mag box some both on the front and rear of the mag box. If it will not move easily, its binding between the receiver and floorplate and you are not getting a solid hold on the receiver screws holding the receiver down into the bedding. This can cause SERIOUS accuracy problems. Also, make sure that the feed lips on the mag box are not contacting the bolt, if they are, they need to be shortened.

    4. Check to make sure that there is plenty of clearance between the bolt nose and the barrel bolt nose recess in the barrel. If there is any debris in this area that is contacting the bolt nose when close you will again get accuracy problems. Make sure this area is clean and free of any foreign objects. This area should be machined so there is around 15 thou clearance between the bolt nose and barrel so there is not alot of clearance but if it does not have this clearance you will have accuracy problems.

    I would be surpised if its not one of these things. A rifle just does not shoot sub 1/2 moa and then turn into a 2 moa rifle without something being obviously wrong. The trick is to find the problem and correct it as it can be very suttle at times to find the problem.
     
  10. midgetorama32

    midgetorama32 Well-Known Member

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    Thanks very much Fiftydriver for that post.

    I played it with it some more last night and here is what I have found so far...

    1. Some how, some of the bedding compound "repositioned" itself in the lug area when the action was out. I used Devcon and can only think that I may have not mixed enough and some of the compound that didn't have enough hardener finally began to set up. When removing it, I could have sworn it was still a little bit gooey in one area. The recoil lug has been completely relieved now on all sides except the back.

    2. This is what concerns me most. I layed the action in and tightened it down slowly, when the front action screw was tightened, I could visually see it pulling the action down further into the stock. Using a dial indicator, it told me the action was moving another 0.020" as the screw was being tightened. At this point I got ticked off thinking I had to re-bed it so I took the scope off. When I loosened the front screw again, I got no deflection at all. This was with the NF base still screwed on. I stuck the scope back on and again I had 0.020" of deflection.

    I read somewhere that NF rings didn't require lapping so I never lapped them or even thought about it. However, when I used an alignment tool, the rings were way out of whack. I lapped the heck out of them and the problem went away. No idea why it wasn't a problem with the EGW base unless it's because it's not nearly as rigid as this NF base and wasn't stressing the action as much when the rings were tightened down.

    I am considering bedding the base as well.

    3. The muzzle brake has a teeny little imperfection at the crown. It's just barely visible to the naked eye. It is something that I sure wouldn't have thought would make an impact on accuracy, but I guess it's something that needs to be addressed. When my smith gets back, I'll have him re-machine it.

    Hopefully, all of this will get me back on track.

    Thanks again.
     
  11. Michael Eichele

    Michael Eichele Well-Known Member

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    I think you are on the right track bedding your base to your action. Something you will want to keep in mind is that if your rings were not lined up and you lapped the heck out of them, then when you bed the base to the action, you will either have to re-lap the rings or start over with new rings. Once you bed the base, it will be straight which will make your rings which are now conformed to a crooked base, crooked again when mounted on a straight base.

    A base that is attached to an imporperly machined receiver in and of its self will not put enough stress on the action to seriously affect accuracy albiet it does not help. What really screws up your accuracy is when you torque a ridged scope tube to a base that is not properly fitted. This is evident by attaching a base and watching it flex and conform to the action, installing quick release rings where you dont have enough strength in your fingers to tighten them to the point of stressing anything. The rifle will shoot just fine. It is when you put a high quality set of rings on the scope and tighten them with a wrench that you will stress the scope and action to the point of diminished accuracy.

    I went through the exact same thing recently. I bedded the base, lapped the rings and problem solved.

    Also, you mentioned the crown on your muzzle break. While it is important to have a good crown on the brake, it is not nearly as critical as the crown on the end of the actual barrel. At least in my opinion.
     
  12. Fiftydriver

    Fiftydriver Official LRH Sponsor

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    You are seeing the joys of working with any factory receiver. They are all finished by hand. By that I mean that they are polished on a buffing wheel by hand and as such its very common to see receivers be wildly different from one to another as far as scope rail fit. Once you figure all the machining and time involved in getting a Rem 700 completely up and running for building a precision rifle on, a custom receiver looks alot more attractive in the end and in most cases not all that more expensive if any more at all.

    M.E. right, if you bed the rail base, you will need to lap the rings again. If you lapped on them alot, and you do it again, make sure that you have enough clamping force left on the rings, if not, you can have the bottom side of the top rings milled to take 20 thou off for more clamping action. With a heavy scope this is critical to have proper clamping power.

    With the bedding, if you have soft spots anywhere in the bedding, I would rebed the stock simply because if there is one soft spot, there WILL be others. Did you pillar bed the stock or just skim bed it?

    On the muzzle brake crown. As long as this does not touch the bullet as it passes through the brake, it will not effect accuracy in any way. I have tested this extensively to prove it and had SEVERELY marked up muzzle brakes shoot every bit as well as a perfectly clean crown on the muzzle brake. Its the crown on the actual barrel muzzle that is critical and MUST be free of any burr visiable or not.

    Back to the rail base issue. I would recommend going away from a one piece base in your situation to be honest. Obviously your receiver is dramatically out of spec if your getting 20 thou in flex when mounting the scope. I would bed a two piece NF set of bases, then install your rings, lap then to 100% contact and then mount your scope. This will eliminate any possible flex or stress to the receiver and just as important to the scope. Bedding a one piece base will also work but bedding compound is no where near as strong as steel and over time, I have seen some bedded rails start to have the bedding break down over time and cause problems. Generally this only occurs in severe cases where there is alot of bedding compound under the rail, for instance where the rear bridge is completely supported by bedding compound only.

    I still prefer steel to steel contact with bedding compound filling in around the contact points. A base completely supported by bedding compound just makes me nervous.

    Hope you get things figured out.
     
  13. midgetorama32

    midgetorama32 Well-Known Member

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    If I end up re-bedding it, what is the best way to go about it? Do I need to remove the old stuff somehow?

    I wish I would have thought about the ring lapping after I bedded the rail.
     
  14. Fiftydriver

    Fiftydriver Official LRH Sponsor

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    I like to remove at least 1/16" of the bedding compound at all contact points of the bedding to the receiver. Preferably it should be removed completely if there is a potential for soft spots but if its removed back to stock material behind the recoil lug and around both receiver screw supports you should be fine.