Temperature Sensitive or load sensitive?

N

nonliberal

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This is touched on in another thread, but I thought it was a good general question that doesn't have to relate to my issue. In general, would you say that a certain powder is temperature sensitive or a load with that powder is more sensitive? For example, you have a load in the top velocity node that the case allows that shoots well from 30*to 95*, but after 95* it has a sharp spike and velocity goes up over 100fps and the group splatters like a shotgun.

1. Would you say that it is a sensitive powder and chase the tune by lowering the charge?
2. Would you say that the node in the top velocity range has a narrower window and is more prone to pressure spikes and try a lower node?
3. Would you say the powder is too finicky and look for a powder that may be a touch slower but possibly more forgiving?
4.Would you make an attempt to keep the ammo and gun cool between relays and hope it allows you to continue use of your pet load?

I'm trying to keep it as a general question, but if examples are needed I would give my current example: 30br with H4198 extreme. In the temperature ranges mentioned I can see a slight advantage with 4198 in groups over H322, but the 4198 hits that near 100*spike and goes crazy. The H322 is about 120 fps slower than the 4198 but I don't see the spike. I don't know if it's because of less pressure in the case or if its because 4198 is more sensitive? They are both called Extreme powders.
 
I would note the point at which the need for load adjustment was needed, how much and what kind of change was needed to bring it back into tune, and switch loads when conditions got to that point.

Years back, my first bench gun was a tight necked .222, that I loaded for at the range, and on those days when it would go from warm in the morning to flat out hot later in the day, I knew from experience that if I did not reduce my charge of 748 to the appropriate setting for the increase in temperature, that paper would appear between my bullet holes, and that it would disappear when the load was made right for the conditions. In my experience, in the summer, only two loads were needed to handle the temperature swings that I was experiencing.

It seems to me that if the temperature range is wide enough, and you are not using a turner, that trying to find an all day load is more than likely a waste of time.
 
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Thanks guys. I am shooting over a chrono. I just ran a test. I have VERY light wind conditions today and 100* outside.
I left my rifle and all loading equipment in the shop today with the door open so the temps would be the same as outdoors in the shade.

Using H4198 velocities were again 100 fps over what they are at 60-90*, (It seems like the velocity doesn't creep up as much as it just makes a jump when the temps are 95+) Anyway, The velocity was up and accuracy was off like the charge was too hot. It took 1.1 grains to get the velocity down to the original speed and groups got tighter again.

Next I used a known load of H322 that I also developed in the 70-80* range. Those velocities were up as well but only 55fps instead of 100fps. However, even though the speeds were up, accuracy didn't fall off. I guess they were still within the window?

On a cool day the 4198 load seems a touch more accurate and is 100fps faster, but it is obviously less forgiving than the H322 in my situation. I guess I either need to go exclusive with 322 and give up just a tad bit of accuracy for a more consistent load, or just keep the 4198 load for early spring and fall?

Boyd, This is a 30 caliber if that makes any difference in my approach?
 
Back to the original intent of thee thread though, would you guys say that load ranges or powders are the cause of sensitivity issues and how would you cope?
 
Boyd Allen said:
has anyone tried this one.
http://wideners.com/itemdetail.cfm?item_id=10000090&dir=278|283|1013
Click to expand...

Boyd, Jerry Sharrett did some extensive testing, and found it very close to IMR-4198. I don't believe he'll mind my posting this, written to me in an email 12/26/10:

Last Spring I tested a batch of powder (10,000#) that Stan Widener had just bought that was made in Switzerland for NATO that was supposed to be like 4198. I tested it against the three lots of IMR4198 and the one lot of H4198 I had on hand. This powder tested exactly like the IMR lots. Wideners just started jugging it and selling it about 2-3 months ago.

The powder, SPP210 is about $120/jug. Just as I got it loaded in the 6-40 Tyger, the weather turned to crap!!! So I'm waiting for some reasonable conditions. It will not go over well for the Culver-dumping shooters since it is long grained like the original IMR4198. Since I use a Chargemaster it doesn't bother me.
Click to expand...

You might ask him for a more recent evaluation...
 
What has the biggest effect on velocity due to temps? Is it the outside air temp, barrel temp (not including letting a round cook), ammo temp?

If I wanted to use my regular load in hot weather (due to preloading) would I try to keep the ammo cool, super cool the barrel between relays, or just be out of luck because its the outside air temps that are killing me? I hope to test it this weekend, but you guys may know the answer already?
 
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