One of the biggest advantages of the Garmin Xero chronograph is its so small and easy to use it justifies using every range session, which in turn gives you way more velocity data over time increases the accuracy of your handloads average velocity and ES/SD data, plus any random anomalies stand out...
Preface: an over winter project led me to swap rifle scopes around requiring me to rezero so off to the range I went.
The 1st weekend my first shot recorded an unusually low velocity that stood out. The rest of the loads were the usual expected velocity. I didn't think anything of it other than maybe I miscalculated my charge weight or something, I just kinda ignored it since it was so odd but scope zeroed. The next weekend I went back to get my actual drops out to 300yds, so I loaded up another 10 rounds or so and off to the range I went, again, the very first shot recorded was also unusually low and the shots after that quickly increased back to the usual. I could not think of any cause so again, I ignored the issue.
Over the week I decided to check my action screws and check the inside of my stock for rust or anything since this was used elk hunting in rough weather and a wood stock. This of course meant I will need to, again, check my zero... so I loaded up 20 rounds and off I go to the range. Once again, my very first shot was unusually low. The second shot sped up and the third shot was back to normal as well as all other shots after that within the usual velocity average.
Pondering this I decided to test cold bore velocity, it was a cold day but I put a barrel cooler in and let it run until the barrel was not just cooled off but very cold to the touch like the first shot was. But that velocity was normal. So, its not a cold bore issue.
The only thing now I can think of is its a clean bore issue.... I typically clean after every range session, so this would mean my first shot next time will always be a clean bore shot, and what I think is happening is it takes between 1 and 3 rounds to foul the bore and stabilize the velocity. Whats odd is the rifle shoots the group the same size regardless of fouling or barrel temp, the rifle is a "tack driver" (to me anyways) so while the rifle might not need a fouling shot it could mean that clean bores have less friction?
Has anyone experienced a change in velocity between a clean bore and a fouled bore?
Velocity data and notes:
Date - 1st shot velocity - average velocity of day (either 10 or 20rds average)
3/29 -2968 - 3018
3/22 - 2968 - 3025
3/9 - 2987 - 3016
notes: 25-06ai, 127gn Hammer, H1000 all the same charge weights.
Preface: an over winter project led me to swap rifle scopes around requiring me to rezero so off to the range I went.
The 1st weekend my first shot recorded an unusually low velocity that stood out. The rest of the loads were the usual expected velocity. I didn't think anything of it other than maybe I miscalculated my charge weight or something, I just kinda ignored it since it was so odd but scope zeroed. The next weekend I went back to get my actual drops out to 300yds, so I loaded up another 10 rounds or so and off to the range I went, again, the very first shot recorded was also unusually low and the shots after that quickly increased back to the usual. I could not think of any cause so again, I ignored the issue.
Over the week I decided to check my action screws and check the inside of my stock for rust or anything since this was used elk hunting in rough weather and a wood stock. This of course meant I will need to, again, check my zero... so I loaded up 20 rounds and off I go to the range. Once again, my very first shot was unusually low. The second shot sped up and the third shot was back to normal as well as all other shots after that within the usual velocity average.
Pondering this I decided to test cold bore velocity, it was a cold day but I put a barrel cooler in and let it run until the barrel was not just cooled off but very cold to the touch like the first shot was. But that velocity was normal. So, its not a cold bore issue.
The only thing now I can think of is its a clean bore issue.... I typically clean after every range session, so this would mean my first shot next time will always be a clean bore shot, and what I think is happening is it takes between 1 and 3 rounds to foul the bore and stabilize the velocity. Whats odd is the rifle shoots the group the same size regardless of fouling or barrel temp, the rifle is a "tack driver" (to me anyways) so while the rifle might not need a fouling shot it could mean that clean bores have less friction?
Has anyone experienced a change in velocity between a clean bore and a fouled bore?
Velocity data and notes:
Date - 1st shot velocity - average velocity of day (either 10 or 20rds average)
3/29 -2968 - 3018
3/22 - 2968 - 3025
3/9 - 2987 - 3016
notes: 25-06ai, 127gn Hammer, H1000 all the same charge weights.
