Hot weather and cast ammo

[jhalcott]

How much difference SHOULD I expect in accuracy from ammo loaded and tested in January/February. Then shot again in 85 degree weather six to 8 months later?
I shot some 35 Whelen ammo today Aug 30 2007 and got patterns of about 8 to 10" at 100 yards. Another load using the same bullet(358315) but a different powder shot about 4" groups at 100 yards. That load went about 2-2 1/2" in Feb.
A 6mm load with J words went over 1". Maybe PART of the problem is ME, but I'm interested in the other part/s of the accuracy.

[stocker]

jh: two possibilities come to mind. First the lube may be breaking down in the hotter weather. Second , depending on what powder you used you may have seen an increase in pressure due to the heat that simply was excessive for the alloy/hardness in the boolits. As another powder tightened the group what were the comparative velocities? I have chrono'd velocity differences of 150fps using the same loads in winter and summer. If you can supply lube and load data it may become clearer to the forum.

[Bass Ackward]

jh,

Stocker called it.

If you stay with cast level loads you probably won't see much. If you stay with hard bullets you may not see as much. But if you developed a load combo on the edge for your rifle and bullet hardness in cold weather, then what you experienced is certainly common to my stuff. In cold weather lube can be added to the list.

And visa versa too by the way, on the temperature.

[Lloyd Smale]

lube contamination can be a big problem in hot weather. Ive loaded cast in the winter with tumble lube and have shot it in the hot summer and tend to get quite a few squib loads. Sometimes it will be hard to tell by the sound or recoil but using a chronograph will show your. Even conventionaly lubed bullets can do it. Especially if you dont wipe your bases or the base of your bullet extends down into the powder. I use to go crazy and load coffee cans full of 38s using a lee 105 tumble lubed. Its about my only use for tumble lube. Just had to much trouble with them after sitting so i keep it to one can at a time now.

[jhalcott]

The inaccurate powder was IMR 3931 while the more accurate one was Varget! both loads were chronoed in COLDER temps and ran about 2000 fps Muzzle velocity. With the inaccuracy I'm getting NOW I fear for the chronograph if I test the hot weather velocity. MAYBE I could put he ammo in the fridge and carry it to the range in an insulated box. BUT that would not help the barrel!

[stocker]

jh: I've just completed a sight in check with both my Whelen's in preparation for moose season. I've been using 40/IMR 4895, the 358009 Lyman boolit and Lars' Carnauba red lube. I also use Lyman 358318 using the same componentsThe combination has given me no problems maintaining excellent accuracy throughout the year. Mind you, when the temps go over 80F up here we retire to a position closely adjacent to an air conditioner outlet. Don't get enough of those temperatures to ever become accustomed tp it.

[HCL]

Just a thought, but you mentioned IMR 3931 and Varget, with Varget not giving you the differences.
Varget is an extreme powder; it is one in a group that was specifically designed to give consistent pressures/velocities with varying temperatures, ie the difference between Hot summer and Cold winter. (They work extremely well!)
The lube thing very well could be the problem; however I would take a look at the powders.
Amazing what differences you can get with a few deg in Temp, especially if your loads are close to the edge of max or min.
Anyhow, hope this helps.
Mike

[John Boy]

How much difference SHOULD I expect in accuracy from ammo loaded and tested in January/February. Then shot again in 85 degree weather six to 8 months later?
IMHO, at 100 yards ... the differences in temperature had nothing to due with the difference in size groups. If you were shooting at longer distances, then Yes. The Relative Humidity would be a factor.

I'd look towards the ballistics side - not the weather

[ReAX222]

Very good info. 1000 pistol rounds doesn't last me more than a month and as soon as my .401 top punch arrives, I'll be loading for my .40. Any forseable issues I should be aware of as Florida starts to cool off and warm up and cool off for the next few months?

[shotstring]

Any given load at longer distances is subject to variances due to temperature, not just cast. The real persnickety 1000 yard shooters often keep their ammo in a small cooler until it is loaded into the rifle just prior to the shot. As Bass said, with cast you can add lube to the mix of things that can affect accuracy. But I have found for me that handgun ballistics are very forgiving. Weighing cases and bullets or a host of other things you would do with long distance rifle just don't make much sense with handgun rounds. Even powder fluctuations don't have as much of an influence as I would have thought.

However, storing ammuntion with cast bullets for years that have run the gamut of heat/cold fluctuations over and over again have DEFINITELY made my stored cast handgun ammuntion far less accurate than it was in the weeks following its creation. What used to be competition ammo is now plinker ammo.

[jhalcott]

I pored over my load book and found out a SMALL error on MY part! The 3031 loads were FIRE FORMING ROUNDS. I shot them at 50 yards in jan/Feb not 100.!
There is STILL a difference in the size of the groups I expected to get. In cold weather I got 2 1/2" groups with Varget @ 100 yards and about 3+" with IMR 3031. Saturday in 85 degree heat I got about 4" with Varget and roughly 8+" with 3031 AT 100 YARDS. Maybe the cataract removal surgery worked better than I thought.

[Bass Ackward]

JH,

I shot my 35 again yesterday. My winter loading with a 250 grain bullet is 47.5 grains of RL15. It shoots .... sub MOA below 40 degrees. Above 70 like yesterday, it was 4".

But take my summer time loading of 45 grains of RL15 and accuracy comes right back to sub MOA with the same bullets. This is sub MOA down to about 50 degrees, but drops velocity to only about 2000 fps in the cold.

Now if I hardened my bullets or accepted a lower accuracy standard, this would not be as pronounced, but this is a hunting rifle and hunting loads that I stupidly obsess over. I manage to win a few bucks with it every fall from the .... un-educated. :grin:

[jhalcott]

I really looked for a leading problem when I cleaned the gun. I guess from Bass's comment ,It is just a load thing. Even the 6mm load went twice it's normal size.
thanks all for the replies.