The Accurate Reloading Forums
point of impact

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21 April 2003, 04:42
<toto>
point of impact
I loaded 6 identical 7x57 loads. The first two cut each the third I thought I pulled off a little still it was just one half left and high. I let the barrel cool. The next threeshots were one and three quaters higher than the first three. I had cleaned the barrel before shooting but fired one round before fireing the groups. By the way I'm using Speer 160gr bt. Any explanation will be appreciated. Thanks. fws
21 April 2003, 04:53
Jameister
we will all be guessing, but it is most likely that your hold point on the forearm, or what ever you were resting it on, were not exactly the same for each. Muzzle jump for the second group would be higher if your hold points were either tighter or placed at a different point on the stock.

Also possible that you placed the loaded rounds in the sun? hot powder burns faster.

nice shooting anyway!!
21 April 2003, 05:08
<toto>
Jameister I appreciate your guesstimation. I was shooting on sand bags. The rifle is bed all the way to the end of the forearm. The shells were in a plastic holder and it is cloudy and had just stopped raining. Like you said we could guess, but I was hoping with everything being equal their might be a more discriminating reason. Thanks. fws
22 April 2003, 03:32
BLR7 (Texas Cactus Shooter)
I have seen this same thing happen when breaking in a new barrel, cleaning after every 5 rounds
would bring the POI back down with suceeding shots. My theory is that as the first few rounds
leave deposits of copper and powder residue in the barrel, more resistance (fowling) occurs and
the succeeding shots are timed to a slightly different barrel harmonic. I noticed this phenomena would disappear after about 3-5 shots
without cleaning. I think this is the reason a
lot of hunters will sight in their rifles the day
before season and leave the barrel fowled during
hunting season. This is especially noticeable
when developing handloads that are not burning
the powder efficiently causing excessive fowling.
This is just my theory about what I have seen! BLR7 [Cool]
22 April 2003, 19:01
shootaway
I think point of impact will have slight play because of fouling.
23 April 2003, 04:16
Hcliff
Is this the first session with the gun? Or is this something that just happened with this bullet? A wet, oiled barrel with through shoots different that a fouled barrel. What I would do is shoot more and see if the barrel settles down. Or try different ammo. The stock could also be shifting with the weather you had if it was a wood stock. The moist air could be swelling it (since it just rained) and the shots are being pulled off. Let us know

Hcliff
23 April 2003, 07:54
BLR7 (Texas Cactus Shooter)
You might try shooting at a closer range target,
say 50 yds and see if this upward trend continues.
If so the problem is probably not the shooter.
Many times shooter errors are magnified as distance increases to the target. BLR7.
23 April 2003, 17:08
shootaway
I agree with Hcliff on the stock swelling.I forgot to mention that.
23 April 2003, 19:31
Gatehouse
DO it a few times...

See where the first three impact. Taht is where you should check your zero. The first one out of a barrel is the most important, the second and third are almost as important.

Don't go hunting with a perfectly clean bore. Foul it with a couple of shots, check the zero while doing so.

Then go hunting and don't worry about it. An inch up won't makie much of a difference on big game until you get out to really long distances...