[ 08-18-2003, 01:07: Message edited by: simdow ]

H4350 is one of Hodgdons extreem powders and shouldn`t be affected too badly by a temp change. You don`t say but is the load near or at max?

One other thought, could the cold ammo frost up from the humidity in the air unnoticed while in the chamber?? I don`t know for sure that a bit of frost could raise pressure notably, but it`s something to consider.

Flattened primers are not necessarily an indicator of high pressure. You stated that you placed the cases in the freezer but you did not put the gun in the freezer. Thus, there was a temperature difference between cartridge and chamber. The cold cartridges went into the chamber and, if it as humid where you are as where I am, there was sufficient moisture condensation in that small period of time to lubricate the case and increase breach thrust causing the flattened primers, et al. When they "thawed" they no longer had condensation and you no longer had "any signs of pressure" (other than the bullet went down range). When you hunt both ammo and rifle are exposed to the same temperatures. It doesn't take water dripping off the case to "lube" the case in this way. Water being non-compressible can do this with a very thin film of condensation. However, it might give you pause as to how your ammo is loaded if you hunt in wet weather...

You are not, IMO, using the proper indicators for "measuring" pressure. The only viable indicator most reloaders can use for excessive pressure is the Ken Waters method (unless you have a strain gauge).

Your theory on the brass shrinkage causing excessive headspace is not supported by the expansion ratio for cartridge brass. Perhaps you can get one-thousandth of an inch from 110 degrees to -40, but I doubt it. Headspace problems haven't occured in .30-30 cartridges in M94 rifles used in the jungle and then taken north of 40 (110 to -40 degrees F), why would they occur in your rifle in what was probably a range of 90 to 25 degrees F)?

Further, as said by another poster, H4350 is NOT overly sensitive to temperature extremes and pressures would have been LESS at the lower temp, not more.

Well, that's my $.02.

Very interesting problem... I have no firm answer, but will speculate with the rest.

If you're seeing brass extrusion into the ejector, you definitely have too much pressure. If another load is not doing this, it is producing lower pressure.

I think the condensation theory has quite a bit of merit. A tiny bit of moisture on the outside could make a big difference.

Another possibility is the behavior of the powder itself. The Hodgdon powder is treated to give a lower temperature coefficient than other powders. How well this works is a function of charge weight and case capacity. In some cases it works very well, and in others, not at all. It may well be that the reduced charge and extreme cold produce unexpected results with that powder.

Aahhhh.... one more speculation.

Reduced loads of slow burning powders do have a tendency to produce extreme pressures. Ackley wrote quite a bit about this. As powder temperature decreases, it burning rate becomes slower. So by freezing the bejabbers out of your cartridge, you render the powder slower, and subject extreme pressure spikes.

Did you mean to say 130 gr. and not 140 gr., my book shows 52 gr. h4350 as a max load and 53.0 gr. IMR4350 max load for the 140 gr. spt sp.

BOY DO I FEEL LIKE AN IDIOT!!!

bobw, after reading your last post I went and checked my data, and I wish I could lie about this but I can't.

I used H450 data with H4350 powder, what a stupid careless mistake. That put me at 2 gr. over max according to my book, so on top of freezing the rounds I was in a bad place to start with. I have never done this before and hopefully will not make a mistake like this again.

The results I posted are still correct in that The cases showed very little marking until I froze them.

HObie, in responce to your post it is very humid here and yes they did frost, I even wiped off the frost on the first one before I shot it. So I guess if you add the frost and the condensation to my dangerous BRAIN FART it results in a very bad place that I feel extremely fortunate to not have anything worse happen.

I will back up and start over and call myself lucky

Thanks for the help

I was down that way, near Clyde, a couple of weeks back and it was nice but rained on us and the dew was very heavy in the morning. I thought it might have been.

I can see that using the wrong data would have produced problems. However, we were all working on the assumption that you hadn't made THAT particular mistake because it was so obvious that that mistake is the most likely to occur. You might have not even loaded every case the same, how the heck are we supposed to know. Anyway, lubing a case always exacerbates the situation, no matter how that comes about.