Need help, first shot high!

[Power]

Been loading for my new Tikka and had a pretty good night at the range. Been trying to get a load dialed in and think I'm pretty close. Problem is I shot 2 groups of 5 and the first shot is hitting high, with a cold barrel, and then as the barrel heats up the rest of the group is really good.

Anyone see this happen before? Are there any remedies to try? I'm shooting a 7mm Rem. Mag. with 160g Partition reloads on top of IMR 4831 pushing along around 3,000 fps.

Thanks for the help.

[Cabin4]

Is your fist shot high or are the follow up shots low ??

To me, I would count the first shot as 'the" shot with a cold bbl. If this is a hunting rifle, you will be shooting with a cold and clean bbl.

As it has been explained to me, both powder residue and bbl heat can/will cause the pattern to move. As the bbl heats up it will contract, tightening up the bore and thus moving the groups.

I could be wrong, but this is how I would react to this if you beileve the ammo is correct and stable.

[richp41]

This is a real common, normal occurence out of a clean, cold barrel and is the reason why nearly all match shooters fire one or more fouling shots. Rifles that shoot all bullets to the same POA after cleaning are pretty rare.

[Graybeard]

Here is the group made by the first three shots from my Remington M700 LSS Mtn. Rifle in .30-06 this morning after I thoroughly cleaned it. No fouling shots were fired.



I had just finished firing several groups with various loads all using Barnes X bullets in 150, 165 and 180 grains. Wanted to start with clean barrel for conventional bullets.

Yup this is the rifle with the little pencil thin barrel that heats up too hot to touch by the end of three shots. Don't matter tho. It is bedded right and just keeps on stacking them in there.

BTW the Barnes loads ALL OF THEM were horrible. I am giving up on Barnes bullets in rifles. I'll have a list of all I have on the Classifieds Forum in the next few days at seriously reduced prices if anyone is interested.

GB

[Iowegan]

I suspect it is the temperature sensitivity of your powder. All powders burn faster when temperature increases (warm chamber, ammo left in the sun, etc.). Faster burn rates increase velocity and chamber pressure. I use 4831 and have had very good results but 4831 and other IMR powders are the most temperature sensitive powders on the market. I started using Varget in 223 and 22-250 for that very reason. It's burn rate is very consistant across a wide temperature range. Varget is not well suited for a 7mm Mag but other Hodgdon powders such as H1000 (70.0g) will work well. Your loads are a bit on the hot side. Factory velocity for a 160g bullet is 2950 fps.
If you don't want to change powders, let the barrel cool down for several minutes after each shot then load the cartridge seconds before you shoot. As stated above, you want "first shot" accuracy.
If you have a Speer reloading manual, they discuss powder temperature sensitivity and have some charts showing results.

[Loader 3009]

A local gun store used to run a shooting contest where the prize was $500.  It cost you $10 to enter.  You got ONE shot at an egg, standing on end, at a distance of 300 yards.  I am told that in three years time there was only one winner.

There is a moral to this story............

[Cabin4]

Here's a few things I was told by a good friend who is 64 and a life long shooter, reloader and hunter. This guy was a superior marksman in the military and has the medals to proove it. Again, this is what he told me and I do it. I would like to know what some of the other experianced reloaders/shooter think.

I  addition to letting the barrel cool down, lightly tap the primer end of the cartridge on the bench. Note lightly. This will reseat the powder if it has for some reason packed or shifted to one side. Do this every time when shooting for groups and your assured the best possability for the same burn rate. If the powder has shifted in the cartridge on one and not another, those bullets will fly differant. Also, do not load a round into a hot chamber and let it sit. Load em one at a time after the barrel has cooled down. "Cooking" the cartridge in a hot chamber will also change the burn and thus the flight.

Seems to all make sence from a "cause and effect" standpoint.

[jhalcott]

sounds like a near max load. Try dropping back a little and work back up with a different primer.Also check your bedding.More fliers are caused by bad bedding than you think. I had a Rem. 700 7 mag that loved 4350 and 4831. It did not care what bullet I used as long as either of those powders were used.  jh
 ps it WAS glass bedded!