How to correct drop?

[koppertop]

I hesitate to post in long range but figure my questions might fit better here than elsewhere even though I’m not shooting long range compared to most here. I’m looking for help correcting how many mils I dial at a given range.

So, I have a t3x 6.5cm with swfa 3-9, degreased and torqued all the dead cats. Im using the Shooter app. Im in CA and forced to shoot non-lead, right now I’m shooting the 124grain hammer hunter. It groups really well so for this season I’m sticking with it. I don’t own a chrono and don’t know the velocity. I read that hammer’s BC’s are notoriously optimistic.

I put out a target at 580 yards and dialed 3.1 mils per the shooter app . I shot five rounds and they were all low, with an average of 3.6 inches low. When I sight in at 100 I simply use the reticle to measure the needed correction and it works great. At 580 yards I obviously can’t see the bullet holes and don’t have a spotter with mil reticle. I’ve waded through a bunch of conflicting formulas for converting a certain number of inches at a given distance to mils. It seems like the “cheater” way would be adjust BC/velocity in the shooter app until the drop in inches given in the app is 3.6” more than currently.

Given that I don’t know either velocity or BC am I simply SOL? What’s the correct way to correct my correction? And yes, I’ll be shooting more to confirm.
Thanks!
KT

 

[omicron1792]

I hesitate to post in long range but figure my questions might fit better here than elsewhere even though I’m not shooting long range compared to most here. I’m looking for help correcting how many mils I dial at a given range.

So, I have a t3x 6.5cm with swfa 3-9, degreased and torqued all the dead cats. Im using the Shooter app. Im in CA and forced to shoot non-lead, right now I’m shooting the 124grain hammer hunter. It groups really well so for this season I’m sticking with it. I don’t own a chrono and don’t know the velocity. I read that hammer’s BC’s are notoriously optimistic.

I put out a target at 580 yards and dialed 3.1 mils per the shooter app . I shot five rounds and they were all low, with an average of 3.6 inches low. When I sight in at 100 I simply use the reticle to measure the needed correction and it works great. At 580 yards I obviously can’t see the bullet holes and don’t have a spotter with mil reticle. I’ve waded through a bunch of conflicting formulas for converting a certain number of inches at a given distance to mils. It seems like the “cheater” way would be adjust BC/velocity in the shooter app until the drop in inches given in the app is 3.6” more than currently.

Given that I don’t know either velocity or BC am I simply SOL? What’s the correct way to correct my correction? And yes, I’ll be shooting more to confirm.
Thanks!
KT

If you don’t know velocity then just change that in app to correct for 3.6 inches low at 580 yards.

That said 3 inches low at 600 yards ain’t bad

 

[BBob]

Adjust the velocity until it trues up.

 

[koppertop]

So if I adjust velocity in the app, and have a bunk BC given by hammer, does that fix my correction at all distances or only at the one I tested? Thanks for the input!

 

[BBob]

So if I adjust velocity in the app, and have a bunk BC given by hammer, does that fix my correction at all distances or only at the one I tested? Thanks for the input!

BC has far less affect than velocity. The rule of thumb is true with velocity up to 750 ish yards and then true BC at distances longer.

Punch some BC numbers in and see how little it changes things. Punch some velocity numbers in and see how much more it changes things than the BC. Pretty quick you'll see the picture.

does that fix my correction at all distances or only at the one I tested?

You need to test as far of a distance as you reliably can. If your zero is correct and you true at the furthest distance you can and if it is correct everything between those should be correct. Beyond that all bets are off.

 

[fuzzymarindave]

Head out to a public range and there is bound to be a friendly person there who will let you fire a couple rounds over their chronograph. Then use that number and change the stated BC to match your target splashes.

 

[DiabeticKripple]

you should be able to estimate your velocity based on your handloads and then i would true the BC so it matches with your actual drops on target.

 

[eric1115]

you should be able to estimate your velocity based on your handloads and then i would true the BC so it matches with your actual drops on target.

No way I would recommend that. Different rifles are going to run different speeds for same loads. Barrel length, throat, etc all make a difference. I've been 100+ fps different than book speeds. You need huge changes in BC to make up for a 100fps error in MV.

Going from 2700 to 2800 fps requires going from a .245 G7 to a .195 G7 to maintain same POI at 600.

OP, I'd recommend bumping BC down, they claim a .245 G7, maybe go to .230 and then true velocity based on drop. BC doesn't matter that much for trajectory at that range, so make a modest bump in the direction you know you need to go and call it good (until you get a chance to check it on someone else's chronograph).

 

[ztc92]

Are you aware of the “velocity calibration” function for MV in the shooter app? This should solve your problem as long as you can get a roughly accurate BC.

1) Choose the “extra” icon in top right (red arrow in screenshot)

2) Menu appears, choose “Velocity Calibration”

3) Enter your distance and the elevation dialed to hit the target.

4) Hit calculate

5) Choose “use MV”.

 

[Zork]

I hesitate to post in long range but figure my questions might fit better here than elsewhere even though I’m not shooting long range compared to most here. I’m looking for help correcting how many mils I dial at a given range.

So, I have a t3x 6.5cm with swfa 3-9, degreased and torqued all the dead cats. Im using the Shooter app. Im in CA and forced to shoot non-lead, right now I’m shooting the 124grain hammer hunter. It groups really well so for this season I’m sticking with it. I don’t own a chrono and don’t know the velocity. I read that hammer’s BC’s are notoriously optimistic.

I put out a target at 580 yards and dialed 3.1 mils per the shooter app . I shot five rounds and they were all low, with an average of 3.6 inches low. When I sight in at 100 I simply use the reticle to measure the needed correction and it works great. At 580 yards I obviously can’t see the bullet holes and don’t have a spotter with mil reticle. I’ve waded through a bunch of conflicting formulas for converting a certain number of inches at a given distance to mils. It seems like the “cheater” way would be adjust BC/velocity in the shooter app until the drop in inches given in the app is 3.6” more than currently.

Given that I don’t know either velocity or BC am I simply SOL? What’s the correct way to correct my correction? And yes, I’ll be shooting more to confirm.
Thanks!
KT

What mv were you using? What's the load?

 

[Lawnboi]

With an oddball hammer bullet, who knows what the BC acually is.

With any other known bullet, I wouldn’t be correcting anything at 580 yards. I’d be looking for problems in your system or your shot process.

 

[koppertop]

Thanks for the input everyone. I started with the hammers a couple years ago. Given what I know now I’d likely go a different direction. I likely will go a different direction once this season is over. Unfortunately will have to stay non lead.

My load is 40.0 grains of Varget. Multiple sources say it’s around 3000fps, including the guy I spoke with at hammer.

I previously shot it at 525 yards. And was hitting too low to be on paper (stupidly had smaller paper than ideal). I adjusted MV to 2950 and dialed 2.6 mil. This group averaged 3.9 inches low.

Given the group at 525 I bumped the MV down to 2900 when I shot at 580 (info in first post). I’m far from a ballistic whiz but know that garbage in equals garbage out…….not sure what I should be adjusting (if anything).

I guess the old stand by would be shoot a group every 100yds until I have it centered. Kinda spendy with hammers and I don’t feel like buying a heap more. Like I mentioned I’ll likely work up a load for a different non lead after this season.

Realistically I’ll be keeping my shots under 400 yards this year. Just trying to learn and figure stuff out.
Thanks!

 

[Lawnboi]

Get your hands on a chronograph and make it easy

 

[eric1115]

How many shots per group? It would be super easy if you're shooting 3 shot groups to have them not representing true center. If your zero is off by .1-.2 mil, and your 580 group is on one edge or the other of the true cone of fire, that could easily be all that discrepancy.

Edit: I see 5 shots for the 580 group. How many shots was your zero group, and is it dead on?

 

[SouthPaw]

I've loaded 5 or so rifles with the 124 hammer, including Tikka 6.5cms. The BC of that bullet generally waterlines at distance using .205-.208 G7 and velocity verified by multiple chronos.

 

[omicron1792]

Thanks for the input everyone. I started with the hammers a couple years ago. Given what I know now I’d likely go a different direction. I likely will go a different direction once this season is over. Unfortunately will have to stay non lead.

My load is 40.0 grains of Varget. Multiple sources say it’s around 3000fps, including the guy I spoke with at hammer.

I previously shot it at 525 yards. And was hitting too low to be on paper (stupidly had smaller paper than ideal). I adjusted MV to 2950 and dialed 2.6 mil. This group averaged 3.9 inches low.

Given the group at 525 I bumped the MV down to 2900 when I shot at 580 (info in first post). I’m far from a ballistic whiz but know that garbage in equals garbage out…….not sure what I should be adjusting (if anything).

I guess the old stand by would be shoot a group every 100yds until I have it centered. Kinda spendy with hammers and I don’t feel like buying a heap more. Like I mentioned I’ll likely work up a load for a different non lead after this season.

Realistically I’ll be keeping my shots under 400 yards this year. Just trying to learn and figure stuff out.
Thanks!

I find velocities vary all over the place. Without a chrono MV is your error point till proven otherwise.

 

[Zork]

Thanks for the input everyone. I started with the hammers a couple years ago. Given what I know now I’d likely go a different direction. I likely will go a different direction once this season is over. Unfortunately will have to stay non lead.

My load is 40.0 grains of Varget. Multiple sources say it’s around 3000fps, including the guy I spoke with at hammer.

I previously shot it at 525 yards. And was hitting too low to be on paper (stupidly had smaller paper than ideal). I adjusted MV to 2950 and dialed 2.6 mil. This group averaged 3.9 inches low.

Given the group at 525 I bumped the MV down to 2900 when I shot at 580 (info in first post). I’m far from a ballistic whiz but know that garbage in equals garbage out…….not sure what I should be adjusting (if anything).

I guess the old stand by would be shoot a group every 100yds until I have it centered. Kinda spendy with hammers and I don’t feel like buying a heap more. Like I mentioned I’ll likely work up a load for a different non lead after this season.

Realistically I’ll be keeping my shots under 400 yards this year. Just trying to learn and figure stuff out.
Thanks!

I'm shooting that load and round out of my tikka and have chrono'd mv at 2900. And my dope all lined up to 700 without ******* with bc.

 

[koppertop]

Thanks everyone! SouthPaw, thanks for the BC info. I’ll likely plug that into the app and see what velocity would be required to end up with what I’m seeing.

Zork-it sounds like you used the hammer provided bc and 2900 mv and everything lined up?

To clarify, I’m zeroed with a 10 round group.
Thanks again everyone.

 

[Zork]

Thanks everyone! SouthPaw, thanks for the BC info. I’ll likely plug that into the app and see what velocity would be required to end up with what I’m seeing.

Zork-it sounds like you used the hammer provided bc and 2900 mv and everything lined up?

To clarify, I’m zeroed with a 10 round group.
Thanks again everyone.

Correct. You should verify yourself but your results from your first go sound about right.

 

[wapitibob]

Get a good zero
Plug in estimated velocity and bc from mfg
Shoot at 600 and adjust velocity to match your drop
Go to 1000 and adjust bc to fine tune drops at distance

You don’t need a chrono, spend the money on powder and primers.