What keeps a round from holding MOA

[LB]

<BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><HR>When I try to diganose a problem their is a process that I go threw steps to find out what may be the problem one of the most commom problems you find is that shooters are useing the wrong bullets for what the barrel is set up for varmint bullets out of heavy game barrels or heavy game bullets out of varmint barrels
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I'll agree with that, but the man says:
<BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><HR>I have several rifles that are good shooters. Sub MOA at 100, 200, about right on MOA at 300.
But by 400 they are way out.
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1)Excessively slow, bullets would be all over the place.

2)Excessively fast twist, the bullets would blow up, in flight.

Therefore, it does not appear that he is using an incorrect twist.

Good hunting. LB

 

[Mysticplayer]

Straydog, I would suggest you play with a ballistics program and see how much effect wind can have on your bullet.

At 400yds, you are trying to stay within a 4" group. However, a small variation in wind/conditions can move your bullet a few inches. Throw in a bit of shooter oops and voila, big groups.

With low power scopes, the reticle covers so much of your target that you can be off by an inch just by scope error alone. With scopes of poor resolution, it is hard to know where to put the blurr. Add that to all the other factors and I think you just solved your problem.

When I develop my LR loads I do it at 180 to 250yds. That's just the distance of my range but far enough to show if a load works or not. Wind is not a big factor and with some wind flags on calm days, I can predict which is gun or conditions.

I use a scope that allows me to see 1/16" at that range. Now I know where I am aiming.

I then take that load and start shooting at ranges out to 750yds at known rocks. With my earlier suggestions of better components including match primers, the shots are within the mechanical accuracy of the rifle, taking wind into account.

If I start spraying, I can usually find a load related problem or not reading the wind well enough. A good bullet launched straight, stays straight until mother nature moves it.

Jerry

 

[StrayDog]

Thanks everyone, it really helped getting feed back from experienced LR shooters.

 

[sdiehn]

I had graet luch with the 120 seirras out of a 1-9 kreiger same cartrige 25-06 the primers were fed GM and 4831 i am guessing that the 120`s need about 8.5

Just for giggles try some 100 grain match kings

Rember both of the other bullets are on the heavy side 160`s in 7mm just a guess the twist on that should be around 7.5 and the 270 with 130`s I would have to look up

 

[StrayDog]

After reading the posts from you guys, it sounds like most of my problems are most likely my techniques. I have only recently began shooting targets past 200, and this is with hunting scopes that top out at 9X.

My 6 shot 300 yard groups usually go between 2 3/4" to 3 1/4".

The 400 yard groups are going between 6" to 8".

This is with 25-06, 1-10 twist Douglas with a Hornady 120 HP.
And factory barrels of .270 Win with Barnes 130 TSX and a 7 RM with 160 Accubond.

None are heavy barrels, which might make a difference. But then again might not?

It just seemed weird that the accuracy would open up that much between 300 and 400.