This last weekend I finally got around to doing some chronograph work on some (relatively) new loads I made last February. To make sure the chronograph was all set up correctly I fired some old rounds that weren’t marked but I was pretty sure what they were. The mean velocity should verify or disprove my hypothesis as well as do the function check on my chronograph setup.
The mean velocity was 3507.92 fps. I looked up the last time I had reloaded and chronographed the ammo. I last reloaded that bullet in April of 2001 and chronographed them using the same gun in May of 2001. The mean velocity from over 18 years ago was 3506 fps.
The ammo (and gun!) aged better than I expected. I like Varget powder even more than I did before.
Stories abound, of firing 60 – 90 year-old ammo with no issues. I’ve fired a number of 50 BMG rounds loaded with Cordite in the 1940s. But actual “before and after” chrono results are a completely different, and almost unrelated issue. “Does it work?” and “Does it work exactly the same?” are two different questions. Very good.
Of course you’d have to test it in the same firearm using the same chronograph in the same conditions at the same distance from the muzzle and have accurate, definite records, and probably talk about the storage conditions and their variations during the time period in question, and likely some other things that I haven’t thought of, to be scientific. Most people, in my experience, can never get more than one or two of those things consistent, if any, at both ends of the test.
Nonetheless, people will never stop asking, “How long can I leave it loaded?” Probably the best response is; “How long do you expect your great great great grandchildren to live?”
And all this, as I recall, after Hornady or was it Hodgdon, gave us dire warnings of the out-gassing of powder which could alter its characteristics considerably?
Then again, maybe the fact that you got essentially the same number is more of a fluke, or anomaly, than getting averages that are barely within 50 fps on two consecutive days.
Changing bullet lots, having the same stock number, I’ve had one lot fit perfectly and another lot fail to even chamber at all, so a minor velocity variance could certainly result from using more than one lot overlapping within your sample. I imagine that could go for primers, powder and cases too.
This was all ammo loaded 18+ years ago measuring the same as it did shortly after it was loaded. So everything was from the same lot and was sealed in a brass cartridge. I found another instance where I chronographed the same load, again 18+ years ago. The mean velocity was 3497 fps. Not quite as close, but it close enough to be make it being a fluke very unlikely.
It’s true the chronographs used where not the same. But I always use Modern Ballistics to interpolate back to the muzzle using the atmospheric conditions so it is a true muzzle velocity and should be independent of the distance to the chronograph. And since the powder is Varget temperature variation should be almost very low. Storage conditions would be expected to affect the aging. In this case nothing special was done. The ammo was mostly at “room temperature” but the room sometimes got relatively hot like in the high 80s. But not for extended durations. Cold conditions were occasionally experienced but this generally slows down changes.
The out gassing issue seems unlikely to apply in a cartridge with a bullet which is firmly gripped by the cartridge neck.
It’s an astonishing result to me.
Me too.
Same chronograph or different chronograph isn’t really the issue. The issue is stability / reproducibility of the chronograph results. Ideally, you’d know both the random error and the calibration drift of your chronograph; those are the data you need to decide whether two measurements are “the same”. When dealing with two instruments, the question is the same except now you’d want to ask “calibration error” rather than “calibration drift”.
Of course, if you can determine the calibration error (either drift or between instruments), you can compensate for it.
Good to hear. I got me some Varget about to be loaded in my 308!
This brings to question whether any of the powder or ammo companies have bothered to do any similar long term testing of product? I know that they keep some samples from various lots for testing purposes (exemplars), but how long do they keep any of it on hand? I would imagine that storage space would eventually become a problem, if they kept it forever.
If outgassing is the issue, why would it be a concern for a closed container where pressure would soon reach equilibrium and prevent further outgassing? This should be the same for powder kept in an unopened container and only be a concern if you left the powder in your powder measure for an extended period of time. Furthermore, ambient atmospheric conditions would be the concern in that case with warmer temperatures and lower humidity increasing the rate.