Large BC Differences — Due to Barrel Differences? 🤔

[ThomasT]

We live in an age of too much information, and we have too many things that interfere with shooting. My head hurts just reading this stuff. Regardless of the information indicated by the technology, even the technoids among us are going to validate their assumptions by shooting. So, why not just shoot? The goal of all this is to hit our target, and there is only one way to find out which pellets and tuning combination will do that in any given rifle. I'm old, and I guess I just like something simple, especially when it works.

Hello elh0102,

So very well stated, excellent .

ThomasT

 

[Franklink]

Well... I had hoped to put some time in on very specific tests before posting again but things have a way of interfering.
However... a new project has caused more questions ...
I built a special choked poly 177 to be cf wrapped for Franklink's Vet Standard . After some teething issues we were able to get it to him after the Utah match this last weekend . When he was able to install and test it... it was very good or at least adequately good in no wind conditions but horrible in windy conditions. At this point you're probably thinking "but it's a 177.. what do you expect ?". In that vein of thought, he breaks out the trusty USFT and what do you know, it shoots extremely well and a fraction of the wind deflection . Now the poly on the Vet was 1 in 17 and the USFT was 1 in 36 so MAYBE this has something to do with it but as I have 2 extremely good samples that are wonderful in the wind and are 1 in 17, I'm not convinced of the importance of the twist rate here.

Another thought as I was reading back through this thread... on the experiments at LD's place, all were tested on a USFT, so differences in obturation and pressure profiles would not have been a factor.

Soo... it's kind of bumped the research priority again. Hope to post some results this coming week.

Bob

The difference was PROFOUND.
Here are some ten shot groups taken @ 30 yards without much wind from the carbon fiber wrapped poly barrel in the .177 Vet. Circles are 5/16"

I shot another couple 10 shot groups on that row and the rows above and below it after I took this photo. All 15 or so ten-shot groups looked about like those 3 above (pretty decent).

Couple days later had the same gun out out while I had a thunderstorm coming in with a pretty stiff wind. Had to chase down my ballcap at one point when it was torn off my head by the wind. Had paper @ 30 yards again, and also at 55 yards. Groups at 30 yards were 2 inches vertical and 3 inches horizontal, simply huge for that distance, and not very predictable to the wind gusts. And only worse at 55 yards. Shots were impacting in an area roughly 4" high by 6" wide. The wind was absolutely ripping the shots horizontally. It wasn't fun. And it's rare for me to think any shooting isn't fun.

So I did exactly what Arzrover explained, got out the USFT to do a little comparison. My intent was to see what that miserable wind would do to shots fired from that gun. I could put em where I wanted without any issues, both @ 30 and 55 yards. The wind was of course affecting the shots, but drastically less than it was with the Veteran/1:17 twist poly gun. I could have easily kept the shots withim a field target kill zone appropriate for those distances (roughly an inch @ 30 and 2 inches @ 55).

Both guns shooting JSB 10.34s around 925fps. On that note, I had two different batches of JSBs and an FX branded batch out with me and I was switching back and forth with all three batches from gun to gun to rule out the USFT barrel preferring one of the batches more than the other. Same effect was seen from all 3 batches from either gun: amazing from the USFT, and abysmal from the Vet.

And the ballcap chasing was done when I was putting everything away, so the wind hadn't decreased or reduced in intensity from one gun to the other.

Frustrating thing here is how well the Vet barrel can do without wind versus how poorly it does with wind.

Quite the mystery. I'm very excited to see what Arzrover's research turns up.

 

[Camber314]

We live in an age of too much information, and we have too many things that interfere with shooting. My head hurts just reading this stuff. Regardless of the information indicated by the technology, even the technoids among us are going to validate their assumptions by shooting. So, why not just shoot? The goal of all this is to hit our target, and there is only one way to find out which pellets and tuning combination will do that in any given rifle. I'm old, and I guess I just like something simple, especially when it works.

Hello elh0102,

So very well stated, excellent .

ThomasT

I certainly agree with Mike, et al, that the only way to properly find out which combination works best is to go out and shoot and assess your direct results at the target.

But part of the fun at times is to analyze which variables will result in optimal performance. Guys like Bob and Cole and many others help us all forward when they start working these speculative scenarios and theories. When you're ready to demonstrate results, you just shoot. But the process of improvement over time can potentially be accelerated by trying to predict which of the many combinations might work best proactively. Sometimes it's fun to sit and try to analyze the variables, speculate which one is causing the results you are seeing, change one (or many) and retest.

I think both sides of this equation work, you just decide which side you want to be on during a given shooting day. Sometimes it's fun just to go out and shoot some stuff .

 

[qball]

@Franklink

Is it possible to setup both of your guns side by side locked in so they can fire at the same time? That’s way you can see the BC/wind drift difference, it is really hard to tell when shooting them at different sessions as the wind never stay the same so side by side and pull trigger at the same time at the same target would be the only way to tell……excuse to get a shooting buddy over for some scientific “testing”.


I have seen small difference in wind drift between barrels but not as big as your experiment plus poly usually do well, so would love to see the side by side comparison.

To muddy the water up a bit more you need to compare same barrel with different twist rate as I see that making a difference too. Then both of them zero at say 20 yards do they have the same POI vertically without wind?

 

[Macros]

This one is fascinating.
Any updates to be had yet?
Just picked up a labradar myself to fine tune the BCs I am using with my various guns and hopefully squeeze that little bit more out of them. I guess I'm firmly in the techno/data camp, but you can't use a labradar without actually shooting, so no loss of fun for me there.

 

[Arzrover]

I did test 13 rifles in 177 with the same pellet at as close of velocity as practical and have the data somewhat organized but not quite ready to post. My LabRadar was a nightmare to clean up the shot strings with and would have taken some extensive Excel work to do it without it.
There were a couple of surprises but overall, the polygonal barrels gave higher bc's than the standard rifled barrel.
One interesting thing that has been noted before is that my USFT was running 923 avg when I recorded the first 25 shots so I did an additional 10 shots on a different string with it running 890. The bc went up by a significant amount.
For the 25 shot strings, I also held same poa to see if there were visual indications of the bc advantages. That seemed less definite as not all rifles preferred that particular pellet.
I also reached out to LabRadar about the pos software and as expected, they just essentially blew me off.
Trying to figure out a direction from here. It's interesting that 4 of the top 10 were direct insertion style with no bolt and one of those was an RN10 with 8.4s at 850 and standard rifled barrel compared to all the others with 10.3s around 900.
So that's a little preview anyway.
Bob

 

[Centercut]

Very interesting... Slight change in topic, but for the LabRadar I've found that using the V0 as the starting point can give erratic BC measurements because the "zero" speed sometimes isn't consistent (how far from the barrel is V0?). I've found it best when calculating BCs, say for FT guns at 50 yards, or high power guns at 100 yards, to set the initial yardage at 10 yards and the end yardage as 50 or 100 yards so the differential is 40 or 90 yards. The LabRadar seems to give more consistent BCs when done this way...

 

[Centercut]

The difference was PROFOUND.
Here are some ten shot groups taken @ 30 yards without much wind from the carbon fiber wrapped poly barrel in the .177 Vet. Circles are 5/16"View attachment 285568
I shot another couple 10 shot groups on that row and the rows above and below it after I took this photo. All 15 or so ten-shot groups looked about like those 3 above (pretty decent).

Couple days later had the same gun out out while I had a thunderstorm coming in with a pretty stiff wind. Had to chase down my ballcap at one point when it was torn off my head by the wind. Had paper @ 30 yards again, and also at 55 yards. Groups at 30 yards were 2 inches vertical and 3 inches horizontal, simply huge for that distance, and not very predictable to the wind gusts. And only worse at 55 yards. Shots were impacting in an area roughly 4" high by 6" wide. The wind was absolutely ripping the shots horizontally. It wasn't fun. And it's rare for me to think any shooting isn't fun.

So I did exactly what Arzrover explained, got out the USFT to do a little comparison. My intent was to see what that miserable wind would do to shots fired from that gun. I could put em where I wanted without any issues, both @ 30 and 55 yards. The wind was of course affecting the shots, but drastically less than it was with the Veteran/1:17 twist poly gun. I could have easily kept the shots withim a field target kill zone appropriate for those distances (roughly an inch @ 30 and 2 inches @ 55).

Both guns shooting JSB 10.34s around 925fps. On that note, I had two different batches of JSBs and an FX branded batch out with me and I was switching back and forth with all three batches from gun to gun to rule out the USFT barrel preferring one of the batches more than the other. Same effect was seen from all 3 batches from either gun: amazing from the USFT, and abysmal from the Vet.

And the ballcap chasing was done when I was putting everything away, so the wind hadn't decreased or reduced in intensity from one gun to the other.

Frustrating thing here is how well the Vet barrel can do without wind versus how poorly it does with wind.

Quite the mystery. I'm very excited to see what Arzrover's research turns up.

Very interesting Cole... I had a .177 Brocock Bantam a few years back, and tried the 10.34 JSB at "High" power which was 925 to 930 fps. Mediocre at best, half dollar or worse at 50 yards. Then I moved the power knob/switch? to "Medium", which was about 905 to 910 fps and the difference was night and day. Easily ten shots inside a dime at 50 yards. These were in LDs tunnel, so I didn't get to check how wind vs. speed worked out, but accuracy was much different only lowering the speed 25 fps.