Range Report Predicted Vs. Actual range results.

[I'm in]

How does your actual shot compare to your predicted
bullet drop with changes in ambient temperature at the range?

I was taught many years ago that 15f degrees change in temp = a 1moa change. I'm not seeing this and wondered what everyone else is getting? What is a more accurate predictor for temp and or density altitude changes?

 

[Lowlight]

Re: Predicted Vs. Actual range results.

You have to test it, and actually the old rule of thumb was 1 MOA per every 20 degree change in temp, the problem is, they never said, "where" that change took place. (Generally it was at 1000 yards)

Since 1978 when this rule of thumb was established, we have improved powders, barrels and bullets, so old rules no longer apply. Our powders are much less temperature sensitive then the powder used 40 years ago.

Only way to know it to check, test your system and see what your results. Rules written long ago, are now obsolete.

 

[I'm in]

Re: Predicted Vs. Actual range results.

I appreciate the reply but is there a software program
that is considered more reliable? Further more, is there so much varience between powders and environmental factors that none are reliable?
I hear what you are saying about actual shooting but I'd like to be close before launching dollars downrange. Thanks again.

 

[I'm in]

Re: Predicted Vs. Actual range results.

Funny about 15 degrees vs 20. That's obviously a big difference. My memory from school in 1986 obviously needs refreshing. I shoulda pulled out the manuel instead of going by my memory. The only thing leaving faster is my hair. Lol.

 

[Lowlight]

Re: Predicted Vs. Actual range results.

Lots of software works, but you still have to put forth effort to calibrate the system and true your software, there are no free rides.

 

[turbo54]

Re: Predicted Vs. Actual range results.

If you're rocking a 308, honestly know your velocity and have proven your scope truly tracks FULL RANGE, any of the software calculators will serve you well.

 

[kraigWY]

Re: Predicted Vs. Actual range results.

Temp up and down will affect the velocity of the bullet. But it may not have the same effect on the zero the same way each time.

On the average I've found a 20* change up or down will have a 1 MOA change to 300, 15* gives a 1 MOA change at 600 and a 10* change will give a 1 MOA change at 1000.

We know the hotter the ammo gets the faster the velocity. We can take a themometer in our pocket to give us the out side temp but what about the chamber of the rifle??

I was playing with my Model 70 Featherweight (Pencil Barrel). last week. I took a Mechanics Laser Temp gage and checked the rifle right in front of the chamber of the barrel. It measured 88 degrees before I fired it. About the same as the outside temp.

I then fired 10 rounds as I could. Them measured the temp just ahead of the chamber. It measured 146*.

I think it matters how long the round stays in a hot chamber before you shoot.

Another observation. I took two rounds, layed on in the sun and one in the shade of my shooting stool. In the shade the temp was 79, in the sun it got to about 105.

There is more to think about then the outside tempeture.

 

[muleman]

Re: Predicted Vs. Actual range results.

Correct Me if I'm Wrong, but shouldn't the program your useing
make the corection for temp on the given day your shooting just like Baro. & Altitude?

 

[kraigWY]

Re: Predicted Vs. Actual range results.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"> shouldn't the program your useing
make the corection for temp on the given day your shooting just like Baro. & Altitude?</div></div>

It's a guide, you still need to shoot the gun and see what happens.

Trust but varify.

Plus the computer BC programs don't know if you left your ammo in the shade or son, nor can it tell how long you let the round set in a hot chamber before you let the hammer fall.

You can notice this when at a long range rifle HP match. Watch as the shooters try to wait our a boil or slow pit service. Some will let the round set in the chamber, some will pull the round, wait, and load another the instant they are ready to shoot. Now look at the targets after the shot is scored and spotted. You'll the the elevation changes.

 

[Graham]

Re: Predicted Vs. Actual range results.

If you can't be bothered calibrating your software and measuring your actual bullet drop every 100 yards, shoot a .308 with 175SMKs, chrono the load, then take your data to 1000 from Exbal using the multiple BC feature.

No one who has ever tried this has told me that they found any difference between computer dope and actual DOPE to 1000 yards.

 

[I'm in]

Re: Predicted Vs. Actual range results.

I'ts not that I can't be bothered, I don't want to come across that way. I was just looking to save a little time and money because my range time is limited due to a full time job and a business on the side that was supposed to be part time but isn't. It's given me the opportunity to get some nice toys and no time to play. I really appreciate the advice here and the people that take the time to impart a little wisdom.