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Posted: 6/13/2011 3:04:41 PM EDT
| What does oblong versus round groups indicate? |
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Quoted:
are you talking about groups or actual impact? If the bullet is making a oblong shape in the paper it is tumbling or "keyholing" and could mean your barrel is damaged or the round is unstable with the twist/velocity I'm not keyhole-ing. I saw the topic come up in another thread but I didn't want to hijack... Quoted:
oblong height wise or width wise ? We can discuss both. Quoted:
Stringing but you can't really say that based on one group. What are you shooting(gun/sights)? Using a sling? it could be any number of things such as inconsistent cheek weld, breath control, loos sling, loose sights, your position changing with teach shot... AR10. Scoped. At a bench. I was curious if it was related to the reloading process at all. But I wonder what exactly it can tell you about your shooting errors as well... |
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Quoted: AR10. Scoped. At a bench. I was curious if it was related to the reloading process at all. But I wonder what exactly it can tell you about your shooting errors as well... There are so many things that affect groups, if you don't see anything that stands out as a possible issue, you start working on one thing at a time. It could be your bench technique, how the gun rides the bags, cheekweld... Maybe your barrel is walking as it heats up. You might fire at a very slow rate, letting the barrel cool between shots and see if you still get the oblong groups. it can definitely be a reloading thing but if we're talking about vertical stringing, I don't think you're going to see that and say for certain what it is at short ranges(under 300 yards) unless you're a good shooter using a benchrest rifle. |
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An accurate rifle will shoot a nice round group with a tuned load, in no wind, with good technique, and so on.
Horizontal stringing is usually an indication of the effect of the wind, and something as simple as a piece of surveyor's tape hanging 1/4 to 1/3 to the target can help sort out what the wind is doing. But, it's important to pay attention at the spot where you're shooting from; feel the lightest breeze on your face or neck, check down range if there's something to watch, and pay attention to the terrain and buildings around you. Cross winds also affect vertical impact, via the gyroscopic precession of the bullet. A wind from the left blowing on a bullet rotating clockwise from the shooter's view point will impact the target low. Horizontal stringing can also be caused by poor bedding bearing up on a barrel, causing point of impact shifts as the barrel heats. Yanking the trigger can also cause the bullet to strike left or right. All of these are easily seen at 100 yards. Vertical stringing has several sources. An untuned load will throw bullets in a vertical line, the front rest or shooter's hold are a cause, and poor bedding or loose action screws can cause vertical stringing. Wind blowing directly at the shooter will cause the bullet to strike low and slightly left, and a wind directly from 6 o'clock will strike high and slightly right of center (bullet rotating clockwise). These effects are also easy to see at 100 yards, however a load that is tuned may not show stringing at 200 yards while scattering a little at 100 yards due to slow stabilization of the bullet. Our goal is to get as much vertical out of a load as possible; control what we can in order to minimize the effects of what we can't control, which is the wind. Here's a wind chart to study: Wind Chart . You'll see some of my shooting friends and the club where I shoot in the photos at that site. |
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