HOW TO USE A TUNER, Part 4

Well said, Gene

Another way to "visualize" this is to use an empty garden hose. Turn on the water and you hear and wait for the water to go out the end. BUT, if that hose has a spray nozzle on the end, you get a burst of high pressure air before the water comes out...........it's being pushed out by water, like the bullet in a barrel.
Everyone knows we are pushing 60-70K psi BEHIND the bullet, but it would be interesting to know what kind of pressure builds IN FRONT of the bullet while still in the barrel! Remember the pics you have seen of a barrel plugged with mud and then fired?
Food for thought......
Bryan
 
I read somewhere...

...that the burn rate of smokeless powder is affected by the pressure. If the bullet met various resistance, wouldn't the burn rate offset the variance?

To that you might say something like - "not entirely".

And I might say - "you don't know that for sure".

"do too"
"do not"
"do too"
"do not"
 
Gene,
I have to admit, I haven't read the previous installments of your tuner threads, something just made me click on this one and read it thru.

I don't want to appear to be criticizing your work (which is very commendable and seems to be the most successful and repeatable to date). However, I've got some thoughts about the relationship of density altitude to the correct position of the tuner.

First of all, I'm not challenging any of your observations. I believe your experiments are repeatable, exactly as you describe. I'm only questioning the reasoning you offer for it working the way it does.

You say that the density altitude affects the average velocity of the bullets. Higher DA means thinner air, more speed, got it. I'm questioning the magnitude of the change due to the air density inside and outside the barrel. Over 100 yards, a DA change of 500 feet probably only causes a difference of a few fps. I doubt that bullet speed in the barrel is effected much at all by changes in DA, at least not compared to the round to round variation of velocity. So how would I explain your observations...?

DA is affected most strongly by air temperature. The next most influential factor is air pressure, followed by humidity. So when the air temp goes up just a few degrees, DA is noticeably affected. I suspect that a change in ambient temperature will cause the powder to burn a little faster and raise the average muzzle velocity (decrease barrel time) more than the reduced 'drag' on the bullet while it's in the barrel. The fact that DA is higher may just be a side affect of the increasing temperature, and not the sole reason for the higher velocities.

To summurize my position, I suspect it's more likely that the increased temperature that accompanies a higher DA is the reason for decreased barrel time, and not the lower drag of the bullet thru less dense air. I think the effects of temperature on the powder burn rate is a more likely culprit.

In the end, it doesn't matter. As long as you can repeatably tune your barrel as a function of DA, the real reason behind it doesn't matter. I'm only speculating here, and as always, stand to be corrected.

Great work by the way, you are a real pioneer!

-Bryan
 
HI BRYAN! Welcome aboard !!

bsl135 said:
Gene,
I have to admit, I haven't read the previous installments of your tuner threads, something just made me click on this one and read it thru.

I don't want to appear to be criticizing your work (which is very commendable and seems to be the most successful and repeatable to date). However, I've got some thoughts about the relationship of density altitude to the correct position of the tuner.

First of all, I'm not challenging any of your observations. I believe your experiments are repeatable, exactly as you describe. I'm only questioning the reasoning you offer for it working the way it does.

You say that the density altitude affects the average velocity of the bullets. Higher DA means thinner air, more speed, got it. I'm questioning the magnitude of the change due to the air density inside and outside the barrel. Over 100 yards, a DA change of 500 feet probably only causes a difference of a few fps. I doubt that bullet speed in the barrel is effected much at all by changes in DA, at least not compared to the round to round variation of velocity. So how would I explain your observations...?

DA is affected most strongly by air temperature. The next most influential factor is air pressure, followed by humidity. So when the air temp goes up just a few degrees, DA is noticeably affected. I suspect that a change in ambient temperature will cause the powder to burn a little faster and raise the average muzzle velocity (decrease barrel time) more than the reduced 'drag' on the bullet while it's in the barrel. The fact that DA is higher may just be a side affect of the increasing temperature, and not the sole reason for the higher velocities.

To summurize my position, I suspect it's more likely that the increased temperature that accompanies a higher DA is the reason for decreased barrel time, and not the lower drag of the bullet thru less dense air. I think the effects of temperature on the powder burn rate is a more likely culprit.

In the end, it doesn't matter. As long as you can repeatably tune your barrel as a function of DA, the real reason behind it doesn't matter. I'm only speculating here, and as always, stand to be corrected.

Great work by the way, you are a real pioneer!

-Bryan
Click to expand...

Bryan, it's great to know you're still out there my friend; thanks for joining in the discussion.

For those of you who do not know him, this young man, Bryan Litz, otherwise known as BSl135, is the aerospace engineer that I sometimes refer to as "The Rocket Scientist" and he is that in spades! When he speaks,, LISTEN,,, CAREFULLY, he is the 'real deal.'


Bryan, you bring up a good point and at one time, I would have agreed with you, but I have since come to believe that it is atmospheric resistance not temperature and its effect on the burning rate of the powder that is responsible for the greater in-bore time at lower density altitudes, i.e., heavier air. I don't know how it could be proven one way or the other and you make a good point when you say that it really doesn't matter, the result is the same.

I hope you will review the other posts in this discussion, I greatly appreciate your views and input in such matters.

Best regards,

Gene Beggs
 
Gene Beggs said:
Bryan, you bring up a good point and at one time, I would have agreed with you, but I have since come to believe that it is atmospheric resistance not temperature and its effect on the burning rate of the powder that is responsible for the greater in-bore time at lower density altitudes, i.e., heavier air. I don't know how it could be proven one way or the other and you make a good point when you say that it really doesn't matter, the result is the same.

I hope you will review the other posts in this discussion, I greatly appreciate your views and input in such matters.

Best regards,

Gene Beggs
Click to expand...

Gene,

I think temperature affects on powder burn rates, in competition settings, has been thoroughly disproven by countless competitors that have pre-loaded for matches and kept loaded rounds in temperature controlled containers, all for not.

You are definitely on the right track in looking at in-bore atmospheric variations.........................Don
 
To Wilbur...

I read somewhere...
...that the burn rate of smokeless powder is affected by the pressure. If the bullet met various resistance, wouldn't the burn rate offset the variance?

To that you might say something like - "not entirely".

And I might say - "you don't know that for sure".

"do too"
"do not"
"do too"
"do not

This has to be the best post I've seen!!!
 
You must log in or register to reply here.
Back
Top