Re: Why is this happening?
....my guess = bedding issue + barrel heat..how fast are you shooting
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Speedy Gonzalez, noted shooter, gunsmith and recent inductee into the Benchrest Hall of Fame, offers these pearls of wisdom to help you eliminate vertical in your shot strings. Remember that vertical can result from myriad gear issues and gun-handling mistakes. Try to isolate one item at a time as you work to improve your groups.
MECHANICAL and HARDWARE ISSUES
• Barrel Weight--A lot of rifles are muzzle-heavy. Some rifles have too heavy a barrel and this causes vertical, especially when shooting free recoil. Basically the gun wants to tip forward. The remedy is to trim or flute the barrel, or add weight in the rear (if you can stay within weight limits).
• Unbalanced Rifle--If the rifle is not balanced, it does not recoil straight, and it will jump in the bags. If the rifle is built properly this will not happen. Clay Spencer calls this "recoil balancing", and he uses dual scales (front and rear) to ensure the rifle recoils properly.
• Firing Pin--A number of firing-pin issues can cause vertical. First, a firing pin spring that is either too weak or too strong will induce vertical problems. If you think this is the problem change springs and see what happens. Second, a firing pin that is not seated correctly in the bolt (in the cocked position) will cause poor ignition. Take the bolt out of rifle and look in the firing pin hole. If you cannot see the entire end of firing pin it has come out of the hole. Lastly, a firing pin dragging in bolt or shroud can cause vertical. Listen to the sound when you dry fire. If you don't hear the same sound each shot, something is wrong.
• Trigger--A trigger sear with excessive spring load can cause problems. To diagnose, with an UNLOADED gun, hold the trigger in firing position and push down on sear with your thumb. If it is hard to push down, this will cause vertical problems.
• Stock Flex--Some stocks are very flexible. This can cause vertical. There are ways to stiffen stocks, but sometimes replacement is the best answer.
• Reliability--ALL your bench equipment must work flawlessly. If it doesn't, get it fixed or get rid of it. We need all our attention on wind flags.
GUN HANDLING and BENCH TECHNIQUE
• Be Consistent--You can get vertical if your bench technique is not the same every shot. One common problem is putting your shoulder against the stock for one shot and not the next.
• Free Recoil--Free recoil shooters should be sure their rifle hits their shoulder squarely on recoil, not on the edge of their shoulder or the side of their arm.
• Head Position--Learn to keep your head down and follow-through after each shot. Stay relaxed and hold your position after breaking the shot.
• Eyes--Learn to shoot with both eyes open so you can see more of the conditions.
• Last Shot Laziness--If the 5th shot is a regular problem, you may be guilty of what I call "wishing the last shot in". This is a very common mistake. We just aim, pull the trigger, and do not worry about the wind flags. Note that in the photo above, the 5th shot was the highest in the group--probably because of fatigue or lack of concentration.
• Last Shot Low--I hear a lot of discussion about low shots in a group and apparently this occurs a lot on the 5th shot. If your 5th shot that goes out most of the time, you can bet you are doing something at the bench.
• Seating--When possible, bring your own stool so that you can sit comfortably, at a consistent height, every time you shoot.
LOAD TUNING
• Find the Sweet Spot--A load that is too light or too heavy can cause vertical problems. When you've tuned the load right, you should see a reduction in vertical. Even 0.1 grain may make a difference, as will small changes in seating depth.
• Primers--If you're getting vertical, and everything else looks fine, try another brand of primers. And remove the carbon from the primer pockets so the primers seat uniformly every time.
• Case Prep--When you chamfer the inside of your case necks make sure they are smooth enough that they don't peel jacket material off when you seat the bullet. Bullets with J4 Jackets (like Bergers) and Lapua Scenar bullets seem more prone to jacket scratching or tearing than Sierra bullets.
• Shell Holders--Keep shell holders clean, in both your press and priming tool. I have seen so much dirt/crud in shell holders that the cases end up get sized crooked because the rim is not square to the die.
• Water in Cases--I see people walking around with case necks turned up in the loading block. A lot of the time there is condensation dropping from the roof of your loading area. If one drop of water gets in a case you are in trouble. How many times have you had a bad low shot when it has been raining and you have been walking around with your cases turned up in your block?
BAGS and REST--VERY IMPORTANT
• Front Rest Wobble--You will get vertical if the top section of the front rest is loose. Unfortunately, a lot of rests have movement even when you tighten them as much as you can. This can cause unexplained shots.
• Rifle Angle--If the gun is not level, but rather angles down at muzzle end, the rifle will recoil up at butt-end, causing vertical. You may need to try different rear bags to get the set-up right.
• Front Bag Tension--Vertical can happen if the front sand bag grips the fore-arm too tightly. If, when you pull the rifle back by hand, the fore-arm feels like it is stuck in the bag, then the front bag's grip is too tight. Your rifle should move in evenly and smoothly in the sand bags, not jerk or chatter when you pull the gun back by hand.
• Sandbag Fill--A front sandbag that is too hard can induce vertical. Personally, I've have never had a rifle that will shoot consistently with a rock-hard front sandbag. It always causes vertical or other unexplained shots.
• If the channel between the Rear Bag's ears is not in line with the barrel, but is twisted left or right, this can affect recoil and vertical consistency. If the bag is off-axis quite a bit, you will get horizontal stringing.
SCOPE ISSUES
• Lock Rings--This year alone I have seen nine lock rings on scopes that are not tight. Guess what that does to your group? Make sure yours are tight.
• Big Tubes Need Tension--We've observed that some 30mm scope rings are not getting tight enough, and scopes are slipping in the rings under recoil. This will cause point of aim movement.
• Windage Bases--If you're using a conventional-style single dovetail with rear windage adjustment, make sure both sides of the windage screws are tight. This can induce both windage AND vertical issues since the rear ring is held down by the windage tension.
AWARENESS of CONDITIONS and READING WIND
• Basic Wind-Reading Rule--If you do not know how to read wind flags or are very inexperienced, try to shoot your group with the flags all going in one direction.
• Rate of Fire--The longer you wait between shots when a condition is changing, the more the condition change will affect your shots.
• Look Far and Wide--Learn to look at the whole field of flags, not just the row in front of you. Many times a change quite a ways out will cause shot to go out of your group well before that change shows up in front of your bench.
• Don't Fear the Wind--When you realize that the wind is your friend you will become a much better benchrest shooter. By this I mean that wind skills can separate you from other shooters who have equally good equipment. To learn how to read the wind, you must practice in challenging winds, not only in good conditions.
• Watch Wind Direction AND Velocity--Pay attention to angle changes on flags. Even though you see the same windspeed indicators, angle changes make a big difference in your groups.
• Watch While You Wait--Between courses of fire, whenever possible, watch conditions on the range. That way you will be aware of any changes in conditions since your last group and you will be mentally prepared for the new condition.
<span style="font-weight: bold">SPECIAL ADVICE for HUNTING RIFLES
• Clean That Barrel--Most hunting rifle barrels do not get cleaned enough. If you keep barrel clean it will shoot better for you. You should clean your barrel well after every 10 to 12 shots. If you're lazy, just use Wipe-Out.
• First Shot Inconsistency--Most hunting rifles will not put the first shot (after cleaning) with the subsequent shots. So, after cleaning, if you have a rifle that tosses that first shot high or wide, then shoot one fouling shot before going hunting or before you shoot for group.
• Barrel Heat--Thin-contour "sporter" barrels WILL change point of impact as they heat up. When testing loads for your hunting rifle, take your time and don't let the barrel get hot on you.</span>
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