Interesting observation

[Varmint Hunter]

In my endless effort to find the perfect load I observed something interesting.

I loaded 9 rounds of several different loads to be tested. This would allow me to fire 3 - 3 shot groups of each load. I shot the groups in a round robin fashion.
First group of load #1 - then first group of load #2 - then first load of #3 and so on. Eventually I'd get back to load #1 again to retest that load. This would allow the groups to be fired under different bore conditions.

I fired 6 fouling loads the day before the tests began. Everything was chronographed with the Garmin.

The two things that I noticed were:
1. Velocity of each load continued to rise throughout the testing - not dramatically but noticeable
2. Fouling conditions definitely affected group size. Virtually all the loads shot the tightest groups on a relatively clean but fouled bore. Groups did open as the barrel accumulated more fouling.

FWIW - I was shooting a custom 6.5PRC with a 23.5" Bartlein carbon bbl.

 

[HSmithTX]

Interesting, how much did the velocity go up and how much did the groups open up?

 

[VinceMule]

Wind conditions change. The atmosphere heats up from morning till noon.

Wind has more to do with group size than most would ever like to imagine, yet few if any ever put out a wind flag. If you do not have a wind flag, you are shooting blind.

This is all I will say for now.

 

[memtb]

In my endless effort to find the perfect load I observed something interesting.

I loaded 9 rounds of several different loads to be tested. This would allow me to fire 3 - 3 shot groups of each load. I shot the groups in a round robin fashion.
First group of load #1 - then first group of load #2 - then first load of #3 and so on. Eventually I'd get back to load #1 again to retest that load. This would allow the groups to be fired under different bore conditions.

I fired 6 fouling loads the day before the tests began. Everything was chronographed with the Garmin.

The two things that I noticed were:
1. Velocity of each load continued to rise throughout the testing - not dramatically but noticeable
2. Fouling conditions definitely affected group size. Virtually all the loads shot the tightest groups on a relatively clean but fouled bore. Groups did open as the barrel accumulated more fouling.

FWIW - I was shooting a custom 6.5PRC with a 23.5" Bartlein carbon bbl.

I wonder if my groups would improve if I cleaned my rifle occasionally! memtb

 

[memtb]

Wind conditions change. The atmosphere heats up from morning till noon.

Wind has more to do with group size than most would ever like to imagine, yet few if any ever put out a wind flag. If you do not have a wind flag, you are shooting blind.

This is all I will say for now.

Thankfully, the wind rarely blows here. And as I rarely shoot…..I can choose the days with "zero" wind for load development.

"Wind Flags"! I step outside, drop a chicken feather, if it sticks in the dust at my feet …… It's a good day for shoot'n! memtb

 

[Varmint Hunter]

Wind conditions change. The atmosphere heats up from morning till noon.

Wind has more to do with group size than most would ever like to imagine, yet few if any ever put out a wind flag. If you do not have a wind flag, you are shooting blind.

This is all I will say for now.

Fortunately, it was a dead calm day with no wind or heat mirage to speak of. Our club has wind flags out that are permanently mounted. We have flags at 200yds-300yds and 400yds. I was shooting at 400yds.

I rotated three guns and never shot with a hot gun. It was 50deg when I started shooting. I use a cordless mattress inflator with a surgical hose to blow ambient air through the barrel between shots 2 and 3, and then the rifle is set back into the rack while I slap steel with other rifles. Barrels are barely warm to the touch when I shoot the next 3-shot group.

On average - I'd say that velocities increased about 20fps from the first group of any particular load to the last. They increased incrementally from the first to the last.

 

[memtb]

Fortunately, it was a dead calm day with no wind or heat mirage to speak of. Our club has wind flags out that are permanently mounted. We have flags at 200yds-300yds and 400yds. I was shooting at 400yds.

I rotated three guns and never shot with a hot gun. It was 50deg when I started shooting. I use a cordless mattress inflator with a surgical hose to blow ambient air through the barrel between shots 2 and 3, and then the rifle is set back into the rack while I slap steel with other rifles. Barrels are barely warm to the touch when I shoot the next 3-shot group.

On average - I'd say that velocities increased about 20fps from the first group of any particular load to the last. They increased incrementally from the first to the last.

I think that a steel ring when heated, shows an increase in hole diameter. Perhaps the barrel interior diameter is getting "slightly" larger….giving less drag/resistance in the bore! memtb

 

[Varmint Hunter]

I think that a steel ring when heated, shows an increase in hole diameter. Perhaps the barrel interior diameter is getting "slightly" larger….giving less drag/resistance in the bore! memtb

While that may be true, the tests were conducted with (essentially) cool barrels. Besides - a slightly larger bore would have reduced friction that could result in less pressure and reduced velocity. I think the bores got slightly tighter as fouling built. However, a Bartlein bbl should be smooth enough to resist fouling.

 

[Beluebow]

What increments were your three test loads?

Round count on the barrel?

 

[Varmint Hunter]

What increments were your three test loads?

Round count on the barrel?

Loads were not incremental. I was testing proven loads with various powders to determine which was best overall.
Barrel has about 500 easy rounds on it.

 

[Phil Rizzo]

I have tried 2 other manufacturers since my last Bartlein was installed, out of 3 I had in service.

Without getting too specific I can assure you of this Paison, I'm not going back.

Never owned a CFW Bartlein, these were SS. But I know of at least 2 that were returned because of QC issues, acknowledged and replaced. Eventually…