Range Report 105 Hybrid BC? Impacting high

[Patty]

Backstory: I have been shooting 105 Hybrids out of my 6BR for a while now. I shot a 2 day match about a month ago, and day two I was consistently impacting high about .2 tenths. I quickly trued my velocity to 2905fps (from 2870fps) and got back on track. Shrugging it off as a barrel speed up or environmental change, i was curious, but didnt spend a lot of time on it because 105 Hybrids have always been spot on elevation wise with the Kestrel and AB custom curve I always use. A buddy of mine in the same squad had the exact same experience in this match.

Fast forward to this past Sunday: Got out to a friends property to check a load using the 112 barnes match burners, and brought some of my leftover 105 hybrid loads from the match i mentioned above. Target at 976 yards, magnetospeed attached (off barrel mount). I send a few using the 112 match burners, 8.1 Mils, dead center, Chrono says 2770 and BC is true at .320, great! Switch over to the Hybrids, send them, chrono reads as normal. 2870. impacts are .3 high. Kestrel calls for 8.1, actual was 7.9. Verified by following up with center hits using 7.9.

Moving on to 740 yard target, .2 high

410 yard target, .1 high.

So, going through my mental checklist of everything that could be going on. I am left with the BC, if I input a g7 of .286 on the hybrids or a speed of 2905, everything lines up. Whats going on? has anyone ever experienced this with 105 Hybrids?

 

[b6graham]

that velocity change is 1%

confirmed zero?

 

[Patty]

that velocity change is 1%

confirmed zero?

Confirmed zero, scope height over bore is also spot on. Mid match on that day 2 there was a 100 yard stage so I got to confirm zero right in the middle of seeing all these high impacts. Zero was good and has been since.

1% isn’t much but in a rifle that never shoots an SD of more than 4, that would be a lot.

 

[Olen_4504]

tagging in

i'm the buddy who also had the problem on day 2.

.3 high at 950yds - hitting plates high at closer ranges, trued to 2905 and shot the rest of the day no issues. also shot the 100yd card stage - zero was dead nuts on.


however - when I shot with Patrick at 976 last week - my dope was good. whereas he was still shooting high

 

[b6graham]

Confirmed zero, scope height over bore is also spot on. Mid match on that day 2 there was a 100 yard stage so I got to confirm zero right in the middle of seeing all these high impacts. Zero was good and has been since.

1% isn’t much but in a rifle that never shoots an SD of more than 4, that would be a lot.

could be the labradar being off 1% too but eh maybe not since you have prior chrono data

DA change that wasnt accounted for? or kestrel not picking it up? saw it a few times last weekend. kestrel/weatherflow saying da around -600, every weather station around -3k or so

 

[generalzip]

Dude I had the same problem! BR going 2900ish. At 947 yards I was .3-.4 high. I updated the atmosphere and put in a BC of .285 G7 velocity 2905 and it seemed to get me close within about .1 mil.

Granted my barrel was speeding up a bit while shooting but it def needed a higher BC. Not complaining. I'm thinking the newer lots of 105s may have a bit higher BC?

 

[Olen_4504]

Dude I had the same problem! BR going 2900ish. At 947 yards I was .3-.4 high. I updated the atmosphere and put in a BC of .285 G7 velocity 2905 and it seemed to get me close within about .1 mil.

Granted my barrel was speeding up a bit while shooting but it def needed a higher BC. Not complaining. I'm thinking the newer lots of 105s may have a bit higher BC?

this is what i'm thinking. .275 is a bit conservative on the lot of bullets we have. .278 gets me the 8.0mil i needed for 976yard.

patrick used .286 to get his 7.9 he needed.

another guy i'm talking to on IG also used .286 to get his dope correct at 900-1200yards

 

[b6graham]

well that'll make a lot of people happy...once they correct it

if it's in fact the new bullets

 

[lennyo3034]

I had the same problem using the AB custom curve.

For me, it turned out to be velocity. I thought I was at 3100, but turned out be 3160 when I switched from magnetospeed to labradar. At 3160, AB matches my actual drops perfectly.

 

[Sheldon N]

Yours true out with a higher BC than mine, and I"m pointing the hybrids too.

Sounds like you have an accurate velocity and have confirmed everything else, so the BC is what the BC is. If the BC works to get hits at distances on different days, different locations, different conditions, then I would just run it. Some barrels can give better BC than other barrels, even with the same bullet.

Think of this... if you have a smaller diameter bore that can compress the bullet shape and alter its ballistics. I've also seen BC degrade as a barrel gets firecracked and older. Jacket gets more torn up during firing, bullet doesn't fly as efficiently.

 

[jbailey]

what twist are you sending them at? There is a modest yet notable positive impact on BC at higher twist rates, or rather more correctly a negative impact at less than optimal twists, from yaw drag. So if Berger's data was collected using less than optimal twist, they could have under-reported it relative to your twist.

Most likely however your lot is slightly better than the lot that Berger tested. 0.286 vs 0.275 they are reporting is only 4% difference, within the tolerance range expected.

 

[Patty]

what twist are you sending them at? There is a modest yet notable positive impact on BC at higher twist rates, or rather more correctly a negative impact at less than optimal twists, from yaw drag. So if Berger's data was collected using less than optimal twist, they could have under-reported it relative to your twist.

Most likely however your lot is slightly better than the lot that Berger tested. 0.286 vs 0.275 they are reporting is only 4% difference, within the tolerance range expected.

It is a 7 twist, but for the first 500 of these 105 hybrids my custom curve was working just fine, it’s only lately (last 250 or so) that I’ve been impacting high.

 

[Patty]

could be the labradar being off 1% too but eh maybe not since you have prior chrono data

DA change that wasnt accounted for? or kestrel not picking it up? saw it a few times last weekend. kestrel/weatherflow saying da around -600, every weather station around -3k or so

Thought about that and double checked, however the 112's shot spot on using the same environmental data that was being used for the 105s.

 

[Bulldog Firearms]

Backstory: I have been shooting 105 Hybrids out of my 6BR for a while now. I shot a 2 day match about a month ago, and day two I was consistently impacting high about .2 tenths. I quickly trued my velocity to 2905fps (from 2870fps) and got back on track. Shrugging it off as a barrel speed up or environmental change, i was curious, but didnt spend a lot of time on it because 105 Hybrids have always been spot on elevation wise with the Kestrel and AB custom curve I always use. A buddy of mine in the same squad had the exact same experience in this match.

Fast forward to this past Sunday: Got out to a friends property to check a load using the 112 barnes match burners, and brought some of my leftover 105 hybrid loads from the match i mentioned above. Target at 976 yards, magnetospeed attached (off barrel mount). I send a few using the 112 match burners, 8.1 Mils, dead center, Chrono says 2770 and BC is true at .320, great! Switch over to the Hybrids, send them, chrono reads as normal. 2870. impacts are .3 high. Kestrel calls for 8.1, actual was 7.9. Verified by following up with center hits using 7.9.

Moving on to 740 yard target, .2 high

410 yard target, .1 high.

So, going through my mental checklist of everything that could be going on. I am left with the BC, if I input a g7 of .286 on the hybrids or a speed of 2905, everything lines up. Whats going on? has anyone ever experienced this with 105 Hybrids?

I know this is off subject, but what's your jump/jam for the 112?

 

[Patty]

I know this is off subject, but what's your jump/jam for the 112?

Started them at .025 off the lands and they seem happy there. Here’s the first group I shot with them at 976.

 

[steve123]

I'm assuming you have been using a recent batch of bullets?? I compared my 3 year old batch of 105 hybrids to a new batch I just bought, the new batch are .053 shorter BBTO and have a smaller meplat.

Seems like mine were hitting high at 1000-ish last weekend too but we were shooting into a large hill, with decent wind, and everyone was hitting high.

 

[generalzip]

When I was shooting at 950 it was maybe 5-6 mph winds mostly tail wind.

 

[Diver160651]

Backstory: I have been shooting 105 Hybrids out of my 6BR for a while now. I shot a 2 day match about a month ago, and day two I was consistently impacting high about .2 tenths. I quickly trued my velocity to 2905fps (from 2870fps) and got back on track. Shrugging it off as a barrel speed up or environmental change, i was curious, but didnt spend a lot of time on it because 105 Hybrids have always been spot on elevation wise with the Kestrel and AB custom curve I always use. A buddy of mine in the same squad had the exact same experience in this match.

Fast forward to this past Sunday: Got out to a friends property to check a load using the 112 barnes match burners, and brought some of my leftover 105 hybrid loads from the match i mentioned above. Target at 976 yards, magnetospeed attached (off barrel mount). I send a few using the 112 match burners, 8.1 Mils, dead center, Chrono says 2770 and BC is true at .320, great! Switch over to the Hybrids, send them, chrono reads as normal. 2870. impacts are .3 high. Kestrel calls for 8.1, actual was 7.9. Verified by following up with center hits using 7.9.

Moving on to 740 yard target, .2 high




So, going through my mental checklist of everything that could be going on. I am left with the BC, if I input a g7 of .286 on the hybrids or a speed of 2905, everything lines up. Whats going on? has anyone ever experienced this with 105 Hybrids?

You wrote <410 yard target, .1 high.>

At your speed and BC. I would absolutely true that 400 yard offset out with velocity BEFORE starting to crank BC. BC needs a huge value change at close range to impact the drop number, it needs time for the drag to slow the bullet and increase the drop over distance - at 2900 FPS the time to 400 is too fast and almost all gravity. That’s one of the reasons BCD drop reticles work with all kinds of bullets with same speed.

Sounds to me like your putting all your eggs in the BC basket and it is a combination.

The issue with tuning the BC too much is rather wired because it will usually work ok in the supersonic range with fairly decent BC bullets, but if that bullet is pushed to far, you’ll get a weird curve. The curve might have your 300, 400, 500 a hair high, then lineup pretty good to just past 1k and then start falling very low if you push it really far. This is super apparent if you’re shooting ELR with full near to far vetted dope. Of course, many people aren’t shooting ELR or using complete 100y out dope, so the “get away” with over cranking BCs.

 

[lte82]

It is a 7 twist, but for the first 500 of these 105 hybrids my custom curve was working just fine, it’s only lately (last 250 or so) that I’ve been impacting high.

Im shooting the latest lot that shipped in January, and they trued up to somewhere in the .280-.285 range at 2840 fps.

 

[generalzip]

Even my lots from late last year are truing to the same around .285ish 7.5 twist bart

 

[TackDriver2]

this is what i'm thinking. .275 is a bit conservative on the lot of bullets we have. .278 gets me the 8.0mil i needed for 976yard.

patrick used .286 to get his 7.9 he needed.

another guy i'm talking to on IG also used .286 to get his dope correct at 900-1200yards

When I tested the same bullet with my 6 BR at 705 yards, I was shooting about 12 inches low even though my Strelok Pro says 16.4 MOA, but I used 18 if I could remember. Should I drop the BC value to get it correct? The BC input is .275
I'm ditching the Strelok Pro anyway, my new Kestrel 5700 is coming next week.

 

[lte82]

When I tested the same bullet with my 6 BR at 705 yards, I was shooting about 12 inches low even though my Strelok Pro says 16.4 MOA, but I used 18 if I could remember. Should I drop the BC value to get it correct? The BC input is .275
I'm ditching the Strelok Pro anyway, my new Kestrel 5700 is coming next week.

Verify that your zero, scope height, and velocity are correct. Also verify firing direction, as east vs west can net a .2 mil difference at 1000. 12” low at 700 is .5 mil, and there is no way your BC is off by *that* much if you plugged in .275. Something or a combination of things is off.

 

[TackDriver2]

Verify that your zero, scope height, and velocity are correct. Also verify firing direction, as east vs west can net a .2 mil difference at 1000. 12” low at 700 is .5 mil, and there is no way your BC is off by *that* much if you plugged in .275. Something or a combination of things is off.

I did check everything last time, the scope height, velocity and my zero. Velocity was checked on two chronographs and spot on with 3 fps ES. I'll recheck the scope height again.
Does increasing scope height increase your elevation or the other way around?

 

[lte82]

I did check everything last time, the scope height, velocity and my zero. Velocity was checked on two chronographs and spot on with 3 fps ES. I'll recheck the scope height again.
Does increasing scope height increase your elevation or the other way around?

raising scope height lowers required elevation.

Tweak your BC to get the data to line up. If it’s less then .265-.270 then something else is wrong. Can you reverify distance of the target?

 

[TackDriver2]

raising scope height lowers required elevation.

Tweak your BC to get the data to line up. If it’s less then .265-.270 then something else is wrong. Can you reverify distance of the target?

I did recheck the scope height and its spot on. Yes, the target was verified at 705 yards. If I lower the BC to .250, then its spot on, but its too much BC drop to justify why I'm getting that kind of drop. Even the velocity is spot on too. It's driving me nuts or is that Strelok Pro the issue on calculations?

 

[lte82]

I don’t know to be honest. List your scope height, velocity, and firing direction. I’ll run it through the kestrel later today and see what it comes up with. Maybe screenshot your strelok inputs as well. 10% BC is a lot to be off.

I’m assuming atmospherics are input correctly as well? Where are you located?

 

[TackDriver2]

I don’t know to be honest. List your scope height, velocity, and firing direction. I’ll run it through the kestrel later today and see what it comes up with. Maybe screenshot your strelok inputs as well. 10% BC is a lot to be off.

I’m assuming atmospherics are input correctly as well? Where are you located?

Scope height - 2.12
Velocity - 2825 fps
Firing direction to the East with 20 mph southeast wind
Location is south Texas - 33' elevation
Temp - 85 degrees / humidity 65%
As for atmospherics, please define for me if above is not enough. I sent some images. Thanks

 

[b6graham]

go run it your data through the Berger ballistic calculator and see what you get

did it quick with your data

says 16moa roughly

weigh topography doing something with that 20mph wind?

mirage?

 

[TackDriver2]

go run it your data through the Berger ballistic calculator and see what you get

did it quick with your data

says 16moa roughly

weigh topography doing something with that 20mph wind?

mirage?

Checked as well, its 16 MOA on Berger website and yes there was mirage. Wind was from 3 o clock about 20 mph

 

[b6graham]

checked geoballistics

i get 16.4 with a DA of 0 for atmospherics and the rest of your data

i blame mirage at this point.

or hitting high on plate

 

[Changed]

Have you tested your scope? Have you shot a tall target test and verified the function and error?

Finally, have you plugged the actual bullet length into your solver?

I know you have plenty of experience shooting and probably know this; your interface with the rifle greatly influences where your shots go. For example, I have a bad habit of pressing my shoulder forward into the buttpad rather than pulling the rifle into my clavicle. Doing so pushes my shots high.