I load Sako pre garcia Forester in .243 winchester with 100 grain hornady flat based inteloc bullets and 38 grains of IMR 4350 to a COL of 2.045 inches (seated to the cannelure). The gun shoots a 1 inch group and it is zeroed to hit dead on at 100 as the scope is an old Leupold 2 x 7 VariX II and 150 yard shots are the most I think about in regards to shooting a deer with the gun. I had zeroed the gun with this load back in March and even plinked bottle caps and other small targets at 100 yards as it shoots to Point of Aim. This weekend after not doing anything to the gun with the same run of ammunition it shot a nice 1 inch group but 3 inches above point of aim! It was 95 degrees out and I am wondering if IMR 4350 is heat sensitive and if it would make this much difference? If its not the IMR4350, I need a new scope...

I shoot a load of 39.1 gr. IMR4350 with a 100gr. Speer. I ran into the same thing the other day and it was a spot about 3/4" long right on the end of my stock rubbing my barrel. I have had this gun for around 20 yrs. and this was a first for me.
Steve

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It was 95 degrees out and I am wondering if IMR 4350 is heat sensitive and if it would make this much difference? If its not the IMR4350, I need a new scope...

I'd think that if the scope was bad you'd be getting lousy groups.....eh?

I seriously doubt that the 3" shift is related to the choice of powder either.....

All powders are sensitive to heat over about 70 F. The ones advertized as insensitive are better with lower temps then higher. I use IMR4350 in my `06 and 7-08 and never have seen a POI change of more then a inch or so though over a temp induced swing from 10-15 f to 90-95F in either of them.

I would check the velocity for pressure changes, although I personally suspect the stock. Changes in humidity can cause the stock to warp and change POI. The change can be at the fore end or in the action bedding itself. A quick check with another trusted scope will rule the one you have out if it is the problem.

this old Sako is not free floated, and I hate to do anything to it. If it shoots reasonable groups, but higher maybe it is the high summer humidity.

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Originally posted by Jimmy P Coaltrain:
this old Sako is not free floated, and I hate to do anything to it. If it shoots reasonable groups, but higher maybe it is the high summer humidity.

I think your right, more the stock and weather, then a powder problem.

I had a similar experience last year. Bought an old 700ADL in .30-06. It shot fairly well so I tried some handloading. Found a very accurate load but when I checked zero before deer season, the point of impact was 2" lower. Still had a fantastic group, but it was, relatively speaking, 2" low.

I had chalked this up to the Reloder 19 I was using and the 50+ degree lower temperature. There was also much less humidity. However, the wood stock contacts the barrel for its full length, so maybe I am wrong. But I too don't want to mess with the stock or bedding because it shoots so well.

Do we just have to live with this problem?

LWD

I think it is reasonable to assume that it is the warmer temperatures. What I do if testing a load in cooler temperatures is to allow the last cartridge to sit in the chamber for several minutes after firing a series which warms the cartridge up, simulating warmer ambient temperatures. Most time the bullet POI(point of impact) is inches higher.