Interesting Tuner Results

[ricco1949]

Thank you Mike.

 

[seymour fish]

That's external ballistics. Powder burning is a chemical reaction and as such, is temperature dependent. So, as temps increase so do velocities. That results in less in bore time of the bullet. It's fairly calculable, say you're running 3000fps at a given temp but the temp increases and you get a 20fps increase. That's .6%. The in bore time is reduced approximately the same... .6%. Say 1.5 milliseconds minus .6% = 1.491 milliseconds. So what we need is to increase frequency, again, about .6%...Small adjustments of the tuner will do that. We're timing bullet exit to occur at the best possible position of the muzzle for best accuracy.

Not that da doesn't affect velocity but that I believe that it's affects on internal ballistics are miniscule as compared to just temp's affect on effective powder burn rate and energy. Another small consideration is the affect temps have on natural frequency...Again, a factor in being able to precisely calculate tuner setting, but a small one. Anything that affects powder burn, affects tune so absolute peak tune is a moving target. Us BR shooters have done the same thing with powder charge for years that moving a tuner accomplishes...optimizing bullet exit to occur when the barrel is at its best place for small groups. Tuners are just way easier to learn and it can be done on the fly. Although, I don't recommend doing it during a record group. There is at least one person that I know of that does.

So, go “in” a hair with increased temp . Correct ?

 

[gunsandgunsmithing]

So, go “in” a hair with increased temp . Correct ?

You got dis!

 

[ratbuster]

Finally after all these years people are starting to see that density altitude is what is changing the velocity. I have been saying this for 20 years and no one ever believed me. The bullet is a wing... It flies. Same as any other wing. In thin air it goes faster and thick air is goes slower. It is not "temperature sensitivity".

There are density measures altitude measures for tuning engines.

But DA won't affect muzzle velocity

 

[seymour fish]

But DA won't affect muzzle velocity

Rat, if the DA is derived from a radical change in barometric pressure or derivation from extreme altitude change, while holding temp constant, you have a supportable notion. This is not the usual case.

 

[ratbuster]

Rat, if the DA is derived from a radical change in barometric pressure or derivation from extreme altitude change, while holding temp constant, you have a supportable notion. This is not the usual case.

DA affects affects velocity (and wind drift) down range; the farther the bullet travels the more it is affected by air density. The effect air density has at the muzzle is too small to be concerned with.

 

[seymour fish]

DA affects affects velocity (and wind drift) down range; the farther the bullet travels the more it is affected by air density. The effect air density has at the muzzle is too small to be concerned with.

Point is, temp effects chemical reaction, MV, Barrel Time, Tune. Better question to address is what shape group at 100 puts you tight at 600-1000.

 

[ratbuster]

Seymour,

When it comes to temperature I agree with what you said. Realize I have not been discussing temperature but rather Density Altitude.

 

[Tim Singleton]

Point is, temp effects chemical reaction, MV, Barrel Time, Tune. Better question to address is what shape group at 100 puts you tight at 600-1000.

Little bitty!
I’m thinking

 

[urbanrifleman]

But DA won't affect muzzle velocity

Of course it does.

 

[ratbuster]

Of course it does.

Would you mind explaining how Density Altitude affects muzzle velocity?

 

[ratbuster]

I did a quick web search....Bryan Litz agrees with me on that one:

https://www.longrangehunting.com/threads/muzzle-velocity-at-different-altitudes.42140/

 

[CharlieNC]

DA is a function of barometric pressure and temperature. A temperature change affects MV, while changes in BP do not. DA is just one convenient way to express the combination of BP and temp, but the associated density of the air which the bullet is traveling through is the true governing factor.

 

[ratbuster]

Charlie,

I look at DA the same as Air Density which in and of itself does not affect muzzle velocity. I guess what some are thinking is a change in temp will change DA which is of course true. But you can also change DA without changing temp....by changing altitude, barometric pressure or dew point.

 

[Ccrider]

You got dis!

Just curious. Any corresponding general rule for bullet seating as temp goes up.

I assume that generally, as temp goes up, charge weight can be adjusted down to stay in tune.

 

[gunsandgunsmithing]

Just curious. Any corresponding general rule for bullet seating as temp goes up.

I assume that generally, as temp goes up, charge weight can be adjusted down to stay in tune.

I can't help ya there. That's probably why I prefer to use a tuner.
I suspect there are too many variables to predict a general rule for seating but it may be feasible to figure it out for a specif rifle, with enough testing. Then the barrel is toast and you'd start over. Lol!

 

[gunsandgunsmithing]

I should add to my post above...I haven't chased the lands at all..since going to a tuner.