Bonecollector & I have been talking about this: chrono'ing a lower or stagnant velocity with more powder. 'BC shared a load work-up where he is seeing this.
I too may now be seeing this as well, and wanted to start a topic on this phenomena to see what the reloading brain trust can come up with as possible causes?
We've found threads on other forums, that are more reloading and shooting oriented, that show others have experienced this drop in velocity with increased charge. In all those threads, there are experienced folks weighing in saying that it is impossible and that they have never heard of this happening. Others talk about each barrel and gun having different max load points, that may differ from the test lab's gun's max load used to develop the recipe, and that this loss in velocity could be a pressure sign, or indicative of unburned powder. Often, the variability of the chrono is brought out as the culprit.
In the previous thread last week, I shared a great group I got using a faster powder from a 9 shot ladder test. The last 4 heaviest charges nearly cut each other in an area almost smaller than a penny at 100 yards. Fellas, that was the most accurate I have shot, or seen that gun shoot. In the joy of that experience, I may have missed a major velocity problem that I hastily attributed to changing light conditions screwing with the chrono.
Here are the velocities I recorded last week-1st number is the charge of AA4350:
51.6=2,596 51.9=2,596 52.2=ERR1 52.5=2,683 52.8=2,754 53.1=ERR 53.4=2,805 53.7=2,704(? Sun) 54.0=2,486(? Sun)
The "? Sun" were notes I jotted down to show my doubts of the validity of the measurements.
These were shot in order of lowest to highest charge. Since the last 4 cut the same hole, I figured 53.7 was a good charge out of that last set to go to print with.
Fast fwd to this past Friday at the range. My buddy was there with his chrono as well. He has a magneto model that straps to the muzzle-its non optical and we have seen it correlate well to my Shooting Chrony; when I take care to position it past the muzzle blast and align it well-which anymore I always do.
We measured 9 shots Friday loaded at 53.7 gr AA4350 that averaged ~ 2,660 on both chronos while I was tweaking the scope in. The scope and group tweaked in with no trouble. But what about that velocity? [emoji21]
I figured last week, the low speed meas at 53.7 was due to issues with strong shadows/variable sun-since up to 53.4 gr it did show an increasing trend in speed.
Chrono issues? For this past Friday, I don't think so. We have two sets of measurements with two instruments using completely different speed sensing methods. This just doesn't seem to make sense, other than it shows some similarities to last week's speed measurements. Either I misloaded the cartridges or something else is at play here.
Any ideas or shared experience with this is greatly appreciated. I will go to the range again and shoot a set of the 53.7 gr, and also now the 53.4 gr, to see what I get.
The gun was cleaned conventionally a couple of weeks ago; it has 27 rounds through it since then. I got copper fouling cleaner today and will be giving it a very thorough cleaning before hitting the range.
Regards,
Sent from my SAMSUNG-SGH-I337Z using Tapatalk
I too may now be seeing this as well, and wanted to start a topic on this phenomena to see what the reloading brain trust can come up with as possible causes?
We've found threads on other forums, that are more reloading and shooting oriented, that show others have experienced this drop in velocity with increased charge. In all those threads, there are experienced folks weighing in saying that it is impossible and that they have never heard of this happening. Others talk about each barrel and gun having different max load points, that may differ from the test lab's gun's max load used to develop the recipe, and that this loss in velocity could be a pressure sign, or indicative of unburned powder. Often, the variability of the chrono is brought out as the culprit.
In the previous thread last week, I shared a great group I got using a faster powder from a 9 shot ladder test. The last 4 heaviest charges nearly cut each other in an area almost smaller than a penny at 100 yards. Fellas, that was the most accurate I have shot, or seen that gun shoot. In the joy of that experience, I may have missed a major velocity problem that I hastily attributed to changing light conditions screwing with the chrono.
Here are the velocities I recorded last week-1st number is the charge of AA4350:
51.6=2,596 51.9=2,596 52.2=ERR1 52.5=2,683 52.8=2,754 53.1=ERR 53.4=2,805 53.7=2,704(? Sun) 54.0=2,486(? Sun)
The "? Sun" were notes I jotted down to show my doubts of the validity of the measurements.
These were shot in order of lowest to highest charge. Since the last 4 cut the same hole, I figured 53.7 was a good charge out of that last set to go to print with.
Fast fwd to this past Friday at the range. My buddy was there with his chrono as well. He has a magneto model that straps to the muzzle-its non optical and we have seen it correlate well to my Shooting Chrony; when I take care to position it past the muzzle blast and align it well-which anymore I always do.
We measured 9 shots Friday loaded at 53.7 gr AA4350 that averaged ~ 2,660 on both chronos while I was tweaking the scope in. The scope and group tweaked in with no trouble. But what about that velocity? [emoji21]
I figured last week, the low speed meas at 53.7 was due to issues with strong shadows/variable sun-since up to 53.4 gr it did show an increasing trend in speed.
Chrono issues? For this past Friday, I don't think so. We have two sets of measurements with two instruments using completely different speed sensing methods. This just doesn't seem to make sense, other than it shows some similarities to last week's speed measurements. Either I misloaded the cartridges or something else is at play here.
Any ideas or shared experience with this is greatly appreciated. I will go to the range again and shoot a set of the 53.7 gr, and also now the 53.4 gr, to see what I get.
The gun was cleaned conventionally a couple of weeks ago; it has 27 rounds through it since then. I got copper fouling cleaner today and will be giving it a very thorough cleaning before hitting the range.
Regards,
Sent from my SAMSUNG-SGH-I337Z using Tapatalk
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