I just started loading and shooting my 470 NE BSS Searcy for a cow ele hunt next July. My Woodleigh solids were an inch apart at 50 yards with 103 gr IMR4831. So far so good. Since I shoot mostly softs, I loaded up a bunch over 106 gr, a load that shot pretty well in the past. They were shooting wide, about 4 inches. Also, the point of impact was 2-3 inches low at 50 yards for both loads.
Velocity was about 2130 for the solids, about 2050 with the softs. In the past about 2150 fps in summer shooting with the softs.
I am prone to blame the ambient temperature, which was about 45 F. It's getting cold here in SoDak.
I'm just wondering what other's experiences have been like with temperature changes and velocity/regulation. Most of my shooting has been done in warmer weather.

quote:

Originally posted by Marty:
I just started loading and shooting my 470 NE BSS Searcy for a cow ele hunt next July. My Woodleigh solids were an inch apart at 50 yards with 103 gr IMR4831. So far so good. Since I shoot mostly softs, I loaded up a bunch over 106 gr, a load that shot pretty well in the past. They were shooting wide, about 4 inches. Also, the point of impact was 2-3 inches low at 50 yards for both loads.
Velocity was about 2130 for the solids, about 2050 with the softs. In the past about 2150 fps in summer shooting with the softs.
I am prone to blame the ambient temperature, which was about 45 F. It's getting cold here in SoDak.
I'm just wondering what other's experiences have been like with temperature changes and velocity/regulation. Most of my shooting has been done in warmer weather.

Marty are your shots shooting wide, or are they crossing? The speed you quote is right in the ball park, but if they are crossing, and shooting low, that usually means they too fast! That, to me, would not seem to be the case with the temprature being considerably lower than when you worked up that load.

When a rifle shoot "WIDE", and "HIGH" it useually means the velocity is too slow, and I would think which would be the case with the cold weather. SHOOTING WIDE,(rt barrel hitting on the rt, left barrel hitting on the left) and LOW does not compute, that usually will hit high! Crossing,(lft barrel hitting on rt, and rt barrel hitting on lft) and low does.

I believe apart. The right barrel placed two shots about two inches low and right, the left barrel two shots low and left. The left and right and right pairs were about an inch across.
I have a 7mm front sight, which will raise POI a bit from the 8mm sight on the gun, but am really more concerned with regulation at this point.
Your point about the POI going up with shooting apart makes good sense, I should have thought of that. Since this load has worked for me in the past, I need to look for other variables.
The elevation change could also be explained by the LASIK surgery I had a few weeks ago changing my sight picture. It's sharper now, the fiber optic front sight looks smaller and sharper, effectively making it aim a tad lower.
Do you think 80fps slower velocity could make the softs shoot that much wider?

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I just started loading and shooting my 470 NE BSS Searcy for a cow ele hunt next July.

If it were I .... I would quit screwing around shooting softs. Is it an elephant gun or not? I sometimes wonder how anyone can see well enough at 50 yards to consistently differentiate an inch with open sights. More power to you.

I would want the same load shooting the same bullet every time I pulled the trigger. In that way I would know where it is shooting and two inch groups at 50 yards is a dream come true for elephant hunting. And then it is a 1 inch group at 25 yards.

But then there are different strokes for different folks.

You mention that 106grs of 4831 shot well in the past. Was it with a different lot of powder? I have noticed more difference between lots of powder, especially 4831, than different temps.

I suggest when you find a powder your gun likes buy a 5 or 8lb jug work up your loads with that lot and you'll be set for a while.

It seems to me that anything that makes a significant difference in the MV of a load which shot well previously at a different velocity will change the pattern the double rifle shoots with both barrels. In your case, I would think that the lower velocity increases the barrel time, causing the barrels to rotate away from each other more with the slower load. Thus the barrels shoot wider of one another than they did when the bullets left the barrel sooner.

Whether this is due to a change in temperature, or is due to the use of a different lot of powder, the effect will be the same. IF you can SAFELY increase the MV of those bullets back to the speed you were getting previously, I suspect the barrels will again shoot as they did earlier, when the temperature was higher. BUT, when you go hunting, the hotter weather may (if this effect is due to temperature, and not the powder!) make the barrels "cross" at that time...

quote:

Originally posted by Marty:
I'm just wondering what other's experiences have been like with temperature changes and velocity/regulation. Most of my shooting has been done in warmer weather.

As you've just learned first-hand, outside temperature does have an effect on the velocity and POI. 10-degrees won't make a noticable difference, but a 45-degree swing will.

I reccomend that your load development be done to match the temperatures where you plan on hunting.

quote:

Originally posted by Marty:
I believe apart. The right barrel placed two shots about two inches low and right, the left barrel two shots low and left. The left and right and right pairs were about an inch across.
I have a 7mm front sight, which will raise POI a bit from the 8mm sight on the gun, but am really more concerned with regulation at this point.
Your point about the POI going up with shooting apart makes good sense, I should have thought of that. Since this load has worked for me in the past, I need to look for other variables.
The elevation change could also be explained by the LASIK surgery I had a few weeks ago changing my sight picture. It's sharper now, the fiber optic front sight looks smaller and sharper, effectively making it aim a tad lower.
Do you think 80fps slower velocity could make the softs shoot that much wider?

Marty,
Welcome to the often frustrating world of variables and double rifles.
I think if nothing in your load has changed ie same lot of powder, primers ect. I think the temperature is the culprit in making it shoot apart.
Congratulations on your Lasic surgery. You might try the 7mm front sight and see if it helps. I would also try a couple more grains of powder for my “Winter†loads and see if that brings them together. When it warms up You can go back to the load that worked in warmer weather.
Bill

I reported on temperature testing with H4831 in a .470 with 500gr Woodleighs earlier in the summer.

Over a 60* F temp range, we were getting a 1.6fps/degree F change (all of the same lot) and a constant term of 32fps (think of this as SD)

Theoretically this shouldn't change from lot-to-lot but every variable in the equation is subject to change with a new lot and actual testing is required.