Adjusting a known load

[Gregor.Samsa]

I rarely get to shoot at extended range so yesterday was a great opportunity to stretch it out to 1000 yards. I shot a load I'v been working on that was in the middle of a node, had great accuracy at 1-300 yards and very good ES/SD. The load's velocity is an average 2715 fps when i developed it about 4 months ago. Yesterday, I pretty much shot mediocre at best up to 900 and fell apart at 1000 but that was mostly my fault due to my lack of experience. What I did notice however is that this load was way off of my theoretical dope (run on both Strelok and JBM which were very close) and required much more elevation than anticipated once got to 400. I confirmed actual dope and reverse calculated the velocity to be in the 2600 fps range. When I developed the load the temperature was in the high 80's and yesterday was in the low 60's so I'd imagine that that accounts for some of the velocity loss.

So getting to the point, should I continue with this load and now confirmed dope or should I try to increase powder to bump the velocity back up to the 2700 fps node where the harmonics are presumably happy in my rifle? I'm hoping to get off of load development and practice more but also want to practice with my best foot forward.

Some specifics of said cartridge:
6.5CM
Hornady 1X fired brass, bumped .002", annealed, trimmed 1.195" .002" NT, full length sized and mandrel expanded
210M primers
41.5 g H4350
140 ELDM
.035" jump

Thank you for the advice!

 

[Lunchbox27]

Powder/bullets from the same lots you developed it with? Do you know anyone with a chrono?

 

[Gregor.Samsa]

Yes same jug of powder and bullets same batch. I chronoed using a magnetospeed sporter. Thanks

 

[Reload10]

I'd double check your atmospheric conditions as well as test the scopes tracking.

 

[TheOfficeT-Rex]

This is normal.

You will almost always have to 'true' your ballistics software to match what happens on the range. We do this by adjusting muzzle velocity and BC. There's a great thread on it here.

Don't chase your tail with load development. Take your actual dope, adjust your calculator, and go shoot.

 

[Gregor.Samsa]

I'd double check your atmospheric conditions as well as test the scopes tracking.

I didn't get atmospherics either time, only temperature and humidity. Haven't tested the scope since I got it but it was super solid and has been solid every time (SB PMII). I know scope brand doesn't necessarily mean a damn thing but I think the poor shooting is me and likely not the cartridge or equipment. When I trued the dope it was spot on. I got crushed by the wind at 1K. thank you

 

[Gregor.Samsa]

This is normal.

You will almost always have to 'true' your ballistics software to match what happens on the range. We do this by adjusting muzzle velocity and BC. There's a great thread on it here.

Don't chase your tail with load development. Take your actual dope, adjust your calculator, and go shoot.

you think I should bump powder up a tad to reach 2700 like I had during load development so as to have a summer load and a fall winter load? Thanks

 

[TheOfficeT-Rex]

you think I should bump powder up a tad to reach 2700 like I had during load development so as to have a summer load and a fall winter load? Thanks

Did you measure a velocity loss, or are you just going by what the calculator thinks your MV is?

I've never seen big swings with H4350, and while I've seen temp sensitivity with other powder, it did not manifest with a degradation of precision. In my experience, the drop change is not enough to drop you off a steel target if your baseline DOPE or trued software is good.

 

[Gregor.Samsa]

Did you measure a velocity loss, or are you just going by what the calculator thinks your MV is?

I've never seen big swings with H4350, and while I've seen temp sensitivity with other powder, it did not manifest with a degradation of precision. In my experience, the drop change is not enough to drop you off a steel target if your baseline DOPE or trued software is good.

Good point. I did not have a chrono while shooting yesterday. Just my observations that my dope was off by more than a couple tenths of a mil. I will re chrono to verify this load. Appreciate the feedback.

 

[Dthomas3523]

This is normal.

You will almost always have to 'true' your ballistics software to match what happens on the range. We do this by adjusting muzzle velocity and BC. There's a great thread on it here.

Don't chase your tail with load development. Take your actual dope, adjust your calculator, and go shoot.

It is not normal to need a lot of adjustment at 400.

He didn’t say how much it was. But if it’s more than .2-.3 at 400, there’s likely an error in the software inputs.

I can take most any rifle and guess what the dope is for 3 and 400 based on what it is (.308, 6.5, 6, etc etc) and be within a couple tenths.

 

[Dthomas3523]

Also, get a magnetospeed sporter if you can’t afford the v3 or a labradar. Very little reason not to know your velocity nowadays with the sporter being available. If you can afford ammo, you can afford the sporter.

 

[Gregor.Samsa]

Also, get a magnetospeed sporter if you can’t afford the v3 or a labradar. Very little reason not to know your velocity nowadays with the sporter being available. If you can afford ammo, you can afford the sporter.

Yeah. I have the sporter and used it during load development to determine my 2715 velocity for the ballistic calculators. That’s why I was flummoxed by the dope being pretty far off. I knew it wouldn’t be spot on but I was off .3 to .5 mils at further distances.

 

[Dthomas3523]

Yeah. I have the sporter and used it during load development to determine my 2715 velocity for the ballistic calculators. That’s why I was flummoxed by the dope being pretty far off. I knew it wouldn’t be spot on but I was off .3 to .5 mils at further distances.

Well, .3 - .5 at distance can be a lot of things.

What was it off at 400?

 

[TheOfficeT-Rex]

It is not normal to need a lot of adjustment at 400.

He didn’t say how much it was. But if it’s more than .2-.3 at 400, there’s likely an error in the software inputs.

I'm not contending it's normal to be off a half mil at 400, I'm saying it is normal to not have actual MV match calculator MV when truing. My 4DOF thinks my 223 load is 100 fps slower than it chronos, but the drops line up.

Either way, it's a software issue, not hardware (the load). No need to alter the load or process if that is still performing.

 

[clcustom1911]

Zero at 100.

Shoot at 300 without changing your scope elevation. Measure your drop from POA to POI in mils, inches, whatever unit...put this measurement into ballistic calculator. This will true your velocity for that given powder temperature and other atmospherics.

With your now trued velocity, and the G1/G7 BC the bullet it supposed to have shoot at 700-800. Measure the difference.

Example: Calculator with the supposed BC said it was 3.8mils up at 700, but you needed 3.6. Put this into Strelok, JBM, or AB, and you have your BC for that lot of Bullets.

 

[Gregor.Samsa]

Well, .3 - .5 at distance can be a lot of things.

What was it off at 400?

It was .3 mill off at 400

 

[Gregor.Samsa]

Zero at 100.

Shoot at 300 without changing your scope elevation. Measure your drop from POA to POI in mils, inches, whatever unit...put this measurement into ballistic calculator. This will true your velocity for that given powder temperature and other atmospherics.

View attachment 7466653

With your now trued velocity, and the G1/G7 BC the bullet it supposed to have shoot at 700-800. Measure the difference.

Example: Calculator with the supposed BC said it was 3.8mils up at 700, but you needed 3.6. Put this into Strelok, JBM, or AB, and you have your BC for that lot of Bullets.

View attachment 7466654

I will try this. Makes sense. Thank you

 

[Dthomas3523]

It was .3 mill off at 400

.3 is quite a bit at 400 if the bullet is a popular bullet and you know your velocity.

Make sure all your inputs and settings are correct in the software.

 

[Greg Langelius *]

I can't tell, but I'm assuming the shooting was all done at the same altitude.

If not, altitude can present air density issues that alter time of flight. This directly affects drop, wind drift, and velocity on target; including the distance at which a load goes transsonic.

I moved from 1200ft ASL in NY to 4350ft ASL here in AZ, and the difference in drop can be quite surprising.

Greg

 

[Gregor.Samsa]

.3 is quite a bit at 400 if the bullet is a popular bullet and you know your velocity.

Make sure all your inputs and settings are correct in the software.

Yes, I'll double check my inputs. the bullets are 140 ELDMs so I think I can rule them out as an anomaly. thank you

 

[Gregor.Samsa]

I can't tell, but I'm assuming the shooting was all done at the same altitude.

If not, altitude can present air density issues that alter time of flight. This directly affects drop, wind drift, and velocity on target; including the distance at which a load goes transsonic.

I moved from 1200ft ASL in NY to 4350ft ASL here in AZ, and the difference in drop can be quite surprising.

Greg

Pretty much the same elevation, but different temperatures and humidity levels. I have not delved into Density Altitude yet, I made the assumption that the ballistic software made that calculation based upon my entries. thanks

 

[clcustom1911]

Pretty much the same elevation, but different temperatures and humidity levels. I have not delved into Density Altitude yet, I made the assumption that the ballistic software made that calculation based upon my entries. thanks

Of all the variables, temperature will have the greatest impact because that directly effects your powder temperature, therefore velocity.
H4350 is pretty good about not doing big velocity swings, but it still does like 0.5-1.5fps per degree depending on the lot.... I think. It depends on where you read the info. It's all over the interwebs.

The only way to know the sensitivity on your lot of powder is the do the velocity test thingy (100y the. 300y drop test) on a 50, 75, and 100 degree day, then track your results.

For instance, in my Kestrel 4500 AB, I put in my velocities with one load in 3 different temperatures so when it does the atmospherics, it takes into account the powder temp into the shooting solution.

 

[TheOfficeT-Rex]

For instance, in my Kestrel 4500 AB, I put in my velocities with one load in 3 different temperatures so when it does the atmospherics, it takes into account the powder temp into the shooting solution.

Hornady 4DOF will also do this, either by specifying your own coefficient or picking a powder from their drop down menu.

 

[DMP]

My Hornady experience has shown their BC to be overstated. IE the G7 for the 147 was listed at .351. I used .335. Once I plugged that in I was always right on (adjusting atmospheric only.)

 

[clcustom1911]

My Hornady experience has shown their BC to be overstated. IE the G7 for the 147 was listed at .351. I used .335. Once I plugged that in I was always right on (adjusting atmospheric only.)

100% I ended up using .330 when I was shooting the 147's