Need help figuring out my grouping problem

Discussion in '7mm STW' started by abrian, Aug 5, 2014.

  1. abrian

    abrian Member

    Messages:
    19
    Joined:
    Apr 6, 2012
    Just finished building a new STW, im in a huge time crunch for a coveted Oregon antelope hunt in 10 days. I'm having trouble figuring out what the deal is and hoping someone can see something I'm not.

    Rig: Remington 700 7mm STW with Pacnor 26" barrel 1:9 twist, Vais brake, McMillan Game scout stock, Jewell trigger, Nightforce NXS 5-22, Nightforce rings and rail.

    The best powder/ammo combo is 73gr H4831 with Barnes 168gr LRX

    PROBLEM: at 100 yards I can shoot 4 out of 5 rounds 1/2 MOA, but 1 out of 5 is always a flier at least 2 inches off the group. All velocities are close to each other. Barrel is clean each time I shoot a new 5 set. No rhyme or reason on which shot is the flier either.

    ATTEMPTED FIXES: different powders(retumbo, h1000, & RL22), charges, bullets, different shooter, different rest, fowled barrel, factory ammo, checked tightness of rings and bases, checked action screws, barrel is bedded and floated, no over-pressure signs.

    Am I missing something obvious? I can't seem to shoot a group without having an unexplained flier. I didn't spend the time and money to build this thing to have to worry about a flier. Again I'm in a time crunch to use this thing in 10 days, yes I have other options, but I want to figure this gun out.

    Thoughts?
     
  2. Black67

    Black67 Well-Known Member

    Messages:
    172
    Joined:
    Feb 5, 2012
    For the cleaning, are you getting all of the copper out?

    How was the barrel broke in?

    For the loads used, what primer are you using? What other bullets have you tried? Have you tried different bullet seating depths?

    For the LRX 168gr, how do they look for the hole on the traget? Are they nice and round or oblonge?

    How long do you wait between shots? I usually wait about 1 minute with the one STW, as it has a heavy barrel. For my second STW, I will only do a 3 shot group due to it has a lighter barrel on it.

    Do you change the point of contact for the front rest?

    How is your breathing when you pull the trigger?

    How about the trigger, where is the poundage set?

    Just some other things to think about.

    Bill
     
  3. Lefty7mmstw

    Lefty7mmstw Well-Known Member

    Messages:
    4,292
    Joined:
    May 13, 2012
    watch your trigger control, bagging, and follow through. If 4 of 5 are coming in it's likely shooter error causing the last to be pulled from the group. If you have the chance, have someone watch to see if your pulled shots show up in the rifle coming off the bags awkwardly, etc.. That has helped me a lot with my rifle. I had a problem with my rifle similar to your problem; I was letting the rifle get jumpy on the bags and she wasn't recoiling straight back every time, but off to the side once on a while. If you are sure it isn't shooting technique, then I'd progress from there.

    I'd also check your rifle again from top to bottom to make sure you don't have something just "snug" as it'll also sometimes do what you are describing.

    If everything's buttoned up and tight, I'd run a new load run-up with a different primer. Inconsistent ignition causing vel. variation can cause fliers too.

    Black67has something too with the 168 being a long bullet-- if they are key-holing one could be diving out arbitrarily and spoiling your group. You'll have to go to a shorter/lighter bullet if that is happening.

    I don't think it'd bbl. break in or trigger #... I shoot factory triggers and rifles that are broken in by firing a box and cleaning and they do just fine without fliers.
     
  4. abrian

    abrian Member

    Messages:
    19
    Joined:
    Apr 6, 2012
    -Break in: I shot 1 and cleaned for 10. Shot 3 and cleaned for the next 30.
    -primers: Using CCI mag rifle, going to try Federal mag rifle.
    -cleaning: scrubbing with Hoppes 9 then patching 'til clean, then scrubbing with either Hollands witches brew or CR10 and patching 'til clean, 1 patch with alcohol, then an oil patch.
    -Other bullets: I've tried 160 Barnes TSX FB & Factory 160 Nosler AB
    -Holes: They are ripping the paper slightly, leading me to believe they are key-holing somewhat, the TSX loads were perfect little holes but a crappy group.
    -Rest: I am not changing the point of contact and my breathing seems controlled. To rule out human error I even shot off a lead-sled (Im not a fan of them) to assure it was a steady shot, same results. Had my buddy shoot off the bags, same result.
    -Trigger: its a Jewell set at a nice crisp 2.5 lbs
    -Time between shots: Im not waiting a particular time (prob atleast a min) after I see where I hit, jot down the chrono speed, reload, and find aim point. Its a #4 contour so not heavy, but doesn't seem to get very warm.

    A big thing I forgot to mention was, McMillan screwed up the barrel channel of the stock where it wouldn't fit well. My smith had to inlet it some to free it up. Its now bedded and free floated up to 3" in front of the recoil lug. Next time I shoot I'm going to check the free float before each shot.

    Thanks for the help so far. Any other thoughts with my answers above?
     
  5. Black67

    Black67 Well-Known Member

    Messages:
    172
    Joined:
    Feb 5, 2012
    For you handloads, do you know how much jump you have to the lands?

    For the Federals, if you can get the 215 Mag Gold Match, they are the most consisant. They are well liked with the 7mm STW group.

    Checking the barrel channel is a good idea. The barrel might also like some light pressure near the end of the forend. I have seen that before.

    Bill
     
  6. trebark

    trebark Well-Known Member

    Messages:
    3,475
    Joined:
    Jan 16, 2008
    This sounds like a bedding issue. Pull your action out of the stock and inspect the bedding. There could be something putting pressure on the action or barrel. Having bedding 3" in front of the recoil lug seem rather far but shouldn't be a problem if the end of the bedding is a clean line and not a jagged edge. When you put the action back in the stock, check to make sure your action screws are torqued properly and that your barrel is floating the way it should.

    Alternatively, you could have a bad barrel. I recently rebarreled a rifle and went through everything you're doing. I went to extremes and had someone else load ammo and shoot the rifle. Never could figure out the problem. The resolution was to replace the barrel and magically the rifle shot bugholes after that.
     
  7. C.O. Shooter

    C.O. Shooter Well-Known Member

    Messages:
    1,806
    Joined:
    Jul 20, 2011
    Can you post pics of your groups?

    Where are your action screws torqued at? 45-65#?

    How many rounds down your barrel?

    Try cleaning for carbon, not copper.
     
  8. eshorebwhntr

    eshorebwhntr Well-Known Member

    Messages:
    339
    Joined:
    Apr 11, 2009
    Check the bedding for inconsistency. Check that the action screws are torqued, not just tightened randomly.

    Try to verify the concentricity of your brass necks. If its a wild flier and the gun is an otherwise shooter then the flier could be chambering funny and the bullet could be leaving the case more out of true centerline than the other 4 that grouped seemingly well. Make sure the chamber and neck/throat area is very clean in addition to your barrel each time you scrub it out.

    I know you said your chronograph is giving you good numbers but maybe try shooting a 4-5 shot group at 400-450 to back it up (ie. prove there is minimal vertical stringing stemming from high SDs/ESs). Do it on paper as opposed to steel if possible so you can again check for bullet stabilization. I like a pallet covered with butcher paper and an orange circle in the middle. This also will give you a warm-fuzzy on how accurate your drop chart is (if you're using one).

    Good luck. I hope you get something that you're happy with for your hunt.
     
  9. abrian

    abrian Member

    Messages:
    19
    Joined:
    Apr 6, 2012
    Not sure what they are torqued at, I will check. There are probably 60 down the barrel so far.

    I'll try to put up some group pics
     
  10. abrian

    abrian Member

    Messages:
    19
    Joined:
    Apr 6, 2012
    I'm done with this thing for a while. Checked everything I know how with same results. Gonna use my ultra mag for the antelope hunt, and try again when I'm not so frustrated and short on time. Thanks for everyone's input.
     

    Attached Files:

  11. barnesuser28

    barnesuser28 Well-Known Member

    Messages:
    2,808
    Joined:
    Mar 2, 2012
    I had this problem with a 220 swift, it was caused from inconsistent bipod preload and a high point in the barrel channel of the stock. If the bipod wasnt preloaded enough, the stock would touch the barrel, throwing the shot.
     
  12. FearNoWind

    FearNoWind Well-Known Member

    Messages:
    2,319
    Joined:
    Jul 10, 2012
    Lots of good ideas here. Those long scenar bullets can be pretty temperamental with high sensitivity to rate of twist, MV and CTOB. My gut tells me that, even though your bullet is rated at 1:9 or faster, the bullet is too light. I ran the data over Don Miller's formula and it falls waaay short of minimum Sg.
    First thing I'd check beyond that is the torque on the action and the free float clearance. A dollar bill passed under the barrel isn't enough in many cases, especially with synthetic stocks. Two thicknesses of 20# bond is a better gauge and if you have any bedding compound in front of the recoil lug get rid of it. Free float means "free float" not part of the barrel free floated.
    On the subject of shooter input, if I were experiencing in competition what you show on your target I would certainly look at rear bag. Don't know if you're using rear bag or not - but if you are you might want to look there. Take it out of the equation and use your hand (fist) in place of it.
    Cheek weld can create a similar problem as can shoulder position/pressure or shifting of body position behind the rifle.

    Good luck ...............
     
  13. JGRJR

    JGRJR Member

    Messages:
    16
    Joined:
    Jul 19, 2013
    Not sure if I saw this information. Does the flyer occur randomly or is it always at the end of the five shot group?

    From your description of the stock work you might be experiencing some stock pressure as the rifle heats.

    If the flyer is random I would agree it might be a bullet stabilization issue. It might be both.

    Good luck on your hunt.