Which way to Get back in tune?

[NC/Br Shooter]

I just got done shooting a round of practice. I took my load with me of 30g. I shot 22 rounds at score targets 100 yards. Only hit 4 Xs. All shots in the 10 ring of course. But not really killing it. According to my last few practice sessions. My X count after My barrel is warmed up is , well let's just say it's a lot higher. I was expecting this to happen here at some point. ( My load to change). I'm at 100 rounds down the barrel.

So, my question is , which way to go? I understand I can just go back and load up a small ladder and shot groups. But I know there's a science to it. And it's all got to do with the conditions. My load that I got was shot from 29 to 30.5 grains, and I had teens, and dern near zeros 29.8 and 30 grain charge. The weather those good days was high humidity, 65 degrees.
Today, the weather is 50 degrees, humidity is under. 25% , and borameter is at 30 according to accu weather.
Only thing, I didn't bring my chronograph out today.
The good load was shooting good at 3275
In the wet, warmer condition.
So, if I had a good load in the wetter, warmer condition,
And, today's condition was dryer and cooler,
What does that mean for the bullet going through air? Does it make slower or faster?
I'm just trying learn what I can , to adjust this thing back in tune.
So what's your guess? Thanks

 

[RGRobinett]

Warmer & higher humidity both make air thinner, thus, less air resistance . . . RG

 

[NC/Br Shooter]

I believe you, but I really thought it was the other way around. So if the air is more dense, That means I'll need to add charge .
Regardless, I'll test both ways, but I'm trying to learn this so I'll develop confidence.
Thanks for the reply

 

[fkimble@charter.net]

At 100 rounds down the barrel, it may still be speeding up as round count increases. Too bad you didn't crono them, that might ave provided a clue or even an answer. I'd drop the charge a couple .1's and put another 50ish rounds downrange. And crono them!

Frank

 

[Dimner]

I believe you, but I really thought it was the other way around. So if the air is more dense, That means I'll need to add charge .
Regardless, I'll test both ways, but I'm trying to learn this so I'll develop confidence.
Thanks for the reply

Air is denser in cold weather. The way I remember is as a making a gas into a liquid, you have to cool it. and gas to liquid is more dense.

Conversely, you boil liquid (water) to get water vapor and the vapor is much less dense than water.


In my opinion if 15 degrees and less humidity can cause your load to be out of tune, you might have too small of a tune window. I'd look for a different window. And to fkimble's point with only 100 down the barrel, doing a new test for a window might not be a bad idea. You could end up with different results. Maybe you are at one side or the other of a node.

 

[NC/Br Shooter]

Very true. Both replies. I will rerest. 29.5 to 30.5
And take the chronograph with me.
Iv been doing. .2 grain increments

 

[ShtrRdy]

Air is denser in cold weather. The way I remember is as a making a gas into a liquid, you have to cool it. and gas to liquid is more dense.

Conversely, you boil liquid (water) to get water vapor and the vapor is much less dense than water.


In my opinion if 15 degrees and less humidity can cause your load to be out of tune, you might have too small of a tune window. I'd look for a different window. And to fkimble's point with only 100 down the barrel, doing a new test for a window might not be a bad idea. You could end up with different results. Maybe you are at one side or the other of a node.

When it comes to humidity, it's not the air density that's a problem, its the moisture content of the powder.

 

[Murray Brook]

I believe I would just chronograph the load. If it is below 3275 then I would go up on powder or down if the velocity is higher. JMO

 

[NC/Br Shooter]

I believe I would just chronograph the load. If it is below 3275 then I would go up on powder or down if the velocity is higher. JMO

I thought about that. So no matter what the conditions, I should load powder to get 3275 ,however up or down in charges?
3275 was good, dang good!

 

[Sleepyhollow]

What caliber you shooting ? Ppc ?

 

[Murray Brook]

I thought about that. So no matter what the conditions, I should load powder to get 3275 ,however up or down in charges?
3275 was good, dang good!

That is what I would do. As for charge it would depend on the velocity you get now.
To Add: I had something of the same thing happen to me with my 6br a couple of years ago.. I was shooting the 64 Berger over 31.5 grs of AR-Comp. Vel was 3475 and accuracy was great. Changed lots of powder and lost my tune. Checked my velocity and it was off. Can't remember just how much but it had speeded up. Reduced till I got the vel back to where it was , which now was 31 grs and got my accuracy back. JME

 

[Wellington]

At 100 rounds first thing I would try is going about 2 thou longer. Might be wear on your lands, especially if the barrel is practically new.

 

[NC/Br Shooter]

I rechecked my jam distance as soon as I got home. It's in the same spot. I'm touch in on marked ojive, but not hard jam.
But will keep tabs on it. I got a good lot of pills,
I'm interested to see how many rounds it takes to see it change.[/QUOTE]

 

[Murray Brook]

In my 6br after after 514 rds it had eroded .011 and after 1000 rds it moved .031.

 

[Longranger81]

I thought about that. So no matter what the conditions, I should load powder to get 3275 ,however up or down in charges?
3275 was good, dang good!

What cartridge you shooting and bullet to get that velocity?

 

[NC/Br Shooter]

What cartridge you shooting and bullet to get that velocity?

It's 6br , 13.5 twist, 68 hottsteins

 

[AlNyhus]

I'm not sure what your understanding of a 'ladder' is. If you're doing it in the traditional way, that's a sure fire way to get lost in short range accuracy tuning. Until you can interpret what the barrel is telling you what it wants for a tune change, just go back and test by shooting groups in .3's increments (obviously over flags). Do it over a chrono so you can see if the velocity is a driver on tune up. Or not.

The good thing is...you've found out just how important a sharp tune up is to shooting 'X's on a Score target. Some look at the math and say: "You only need to shoot (whatever size) groups to shoot X's.". The reality of competitive Score shooting is much, much different. The ability of a combination to stay in tune (by whatever means) is absolutely critical. Lacking this, it makes holding off worse than a guessing game.

Good shootin' -Al

 

[JEFFPPC]

I agree with Al and have another thought. How often is loss of tune actually a loss of being in or out of tune mentally with the conditions. I think more often than many want to consider.

 

[Ccrider]

I'm not sure what your understanding of a 'ladder' is. If you're doing it in the traditional way, that's a sure fire way to get lost in short range accuracy tuning. Until you can interpret what the barrel is telling you what it wants for a tune change, just go back and test by shooting groups in .3's increments (obviously over flags). Do it over a chrono so you can see if the velocity is a driver on tune up. Or not.

The good thing is...you've found out just how important a sharp tune up is to shooting 'X's on a Score target. Some look at the math and say: "You only need to shoot (whatever size) groups to shoot X's.". The reality of competitive Score shooting is much, much different. The ability of a combination to stay in tune (by whatever means) is absolutely critical. Lacking this, it makes holding off worse than a guessing game.

Good shootin' -Al

Man you just said a mouthful!

 

[NC/Br Shooter]

I'll get some shooting done tomorrow. When the thing was in tune. As in, I shot a dang good 5 shot round ground in the teens and then I went to shooting the most xs I had ever done. Shot over ten that day. And thought, " There's nothing to this"
I thought that but I knew full well that wasn't the case. The gun shot really good 29.8 , 30, and 30.1
That day. That day was like I had described. Wet, warm. It did it the next day aswell, same conditions. Sounds like I'll need to step it down. Shoot a few more groups over chronograph.

I understand you want to be in the middle of charge window. Since I was at 30g, and if my gun sped up, And I was in lighter air conditions, I can see where it could throw it out .
I'll hope to find it again tomorrow