H4895 Temp Changes
- Thread starter Terry
- Start date
HMMM! I was under the impression that the "Extreme" powders were temp stable! WOW! Was I wrong or was I wrong! Seriously, the ONLY powders I have found that really are VERY temp stable are the new Alliant powders, RL-16 and RL-23. They really are temp stable! Some IMR powders are pretty stable too, like 8208XBR, IMR 4895 and IMR 7828. They are not as stable as the new Alliant powders but they are just about like the "Extreme" powders..
He loaded this for World Open so i would bet money it is the same lot of everything. The only thing that changed is, it got hot out. The two days of heat and humidity was draining. After lunch each day it got really bad.
Testing years ago, I got 50 fps with a 20 degree spread in a Dasher with Varget. Same day, same components with all from the same lot. This was at the same range as Terry just shot this from. Matt
Terry
Gold $$ Contributor
No change in the components.
When Hodgon first began shipping Varget to the consumer market in very early 1995, I acquired a good quantity to give it a whirl in my Palma rifle (155's) and a .223 NRA Match Rifle (80 JLK's) at 600yds. Once loads were developed, I fired a 10-shot string over the chrono and onto paper, in a rapid cadence. An 11th round was allowed to cook in the chamber for 60 seconds and then was fired onto paper, through the chrono.
With both calibers, the 11th round fell within the extreme spread of the prior 10 shots and the elevation of the impact fell within the existing 10-shot groups.
Did that same test with H4895 in the 308 only circa 2001. Same result.
That 1 minute baking time in the chamber after 10 shots will far exceed the ambient temperature change found anywhere on earth.
With both calibers, the 11th round fell within the extreme spread of the prior 10 shots and the elevation of the impact fell within the existing 10-shot groups.
Did that same test with H4895 in the 308 only circa 2001. Same result.
That 1 minute baking time in the chamber after 10 shots will far exceed the ambient temperature change found anywhere on earth.
I believe you have no reason to lie. I just have never experienced anything like that with Hodgen powders in 35 years of reloading with them.
I use the same loads in several of my rifles, with the temps swinging from 80 degrees in August, to 0 degrees in February. The most I have ever seen in that range is 15-20 fps. I have chronographed them, because I have seen an inch of elevation impact change, at 400 to 600 yards in the cold winter temps.
But, 50 fps with a 20 degree temp change has me wondering...as I'm sure it does you...if there couldn't be something else going on.
I use the same loads in several of my rifles, with the temps swinging from 80 degrees in August, to 0 degrees in February. The most I have ever seen in that range is 15-20 fps. I have chronographed them, because I have seen an inch of elevation impact change, at 400 to 600 yards in the cold winter temps.
But, 50 fps with a 20 degree temp change has me wondering...as I'm sure it does you...if there couldn't be something else going on.
Terry
Gold $$ Contributor
No changes to anything. Did not clean the gun.
XTR
F-TR obssessed shooting junkie
Mr. Ten X you might be surprised how much the cooking heats, or doesn't heat, the powder. Yea, the brass will heat up. I was talking with a Brit at the FCWC in 2013, seems Mr. Chambers was doing some research on that actual topic. He installed a sensor in the center of the powder column in a 308 and popped the otherwise loaded round into a hot chamber. I don't recall now his exact findings, but in general he found that you need to cook one for a lot longer than I ever have to get a significant elevation in temperature in the core of the powder. The powder seems to be a pretty poor conductor of heat.
You read it on the interwebz, so take it for what it's worth.
You read it on the interwebz, so take it for what it's worth.
urbanrifleman
Site $$ Sponsor
It is NOT the powder. It is the air density. Thinner air the bullet goes faster and the pressure goes up. Plain and simple.
Ned Ludd
Silver $$ Contributor
The powder in the center of the cartridge itself doesn't need to become hot. A significant amount of powder burns in the first 6"-8" of barrel outside the case. If the barrel is screaming hot, whether from shooting or simply laying in the sun, the apparent powder burn rate will increase whether the cartridge started out cool or not.
What did this spread look like on the target ? I use H4895 for many loads,never had a problem I could blame on the powder...not for lack of trying .
Terry
Gold $$ Contributor
All velocities measured at the muzzle.
Terry
Gold $$ Contributor
Barrel kept in the shade. First two sighters were at this speed. 2-3 sighters and 10 record rounds.
If it was the case of speed up from barrel heat, your string would of got faster as the string went along. Your lab radar would of showed that. Matt
I for one believe you, and am not sure why guys are making you defend your findings.
Why not try duplicate the test to determine if it was an anomaly or normal. I had a dasher that sped up 20fps from start of my session, to the end. It was 85deg when we started, and 85 when done, I chrono'd 5, shot 55 rds, chrono'd my last 5 rds.
I assumed the new Proof barrel may have sped up, I shot the same load the next day and it was not faster. The temp of the ammo was warmer, as it sat in direct sunlight and was considerably warmer than ambient temps. I know enough to keep my ammo shaded, and that day a young kid was shooting the gun and in charge of the bullets,lol. I was chief spotter. As for affects downrange, I did not see any. Dopes were still spot on with the kestrel.
Ned Ludd
Silver $$ Contributor
I was merely pointing out a known effect of barrel heat on powder burn rate and velocity in response to XTR's statement regarding chamber heating up brass, but not the powder it contained. I was not in any way suggesting your rifle heated up in the sun.
FWIW - I think it's unfortunate you felt the need to state you had no reason lie. Nor do I think you should you be forced to "defend your findings" as Milo stated just above, merely for posting what you observed. I have no reason not to believe you observed and recorded exactly what you said you did.
Nonetheless, the implication from your original post, which was reinforced by a few subsequent responses, is that Hodgdon powders are somehow defective, or at the very least, that Hodgdon has made misleading claims regarding the temperature-sensitivity of their powders. My response (and I believe those of a few others) was simply to point out that I had not had similar experiences with Hodgdon powders, which I think is completely fair given the tone of your original post. I've used H4895 and Varget for years under some pretty significant temperature swings and never seen velocity changes even remotely similar to what you described. So I think it is also completely fair to point out there are potentially other explanations and/or contributing factors for the effect you observed, rather than simply to reach the unreasonable conclusion that Hodgdon powders in general exhibit poor temperature sensitivity. Further, you really have no way of knowing whether some other manufacturer's powder wouldn't have exhibited even worse behavior under the exact same conditions.
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