ladder test question

N

Nishon

Guest
gentlemen i have a question which may sound a bit silly to most of you guys but i need some input from the well experienced.If you do a ladder test and find the accuracy node with a particular combination of components which include a 100gn softpoint bullet and you wanna keep that combination yet setup another load with the same case,powder and primer with another 100gn bullet of stronger construction,will the accuracy node remain more or less the same if you set up the new load using the same velocity of the first load that you did the ladder test with.I have set up with 100gn hornady interlock BTSP in 243 and now want to do it with 100gn nosler partitions.
 
I'd bet the node would be real similar, but I wouldn't depend on that. I would do another test with the other bullet.
 
You need another ladder test. The results depend on the relationships among bullet exit time, barrel vibration and external ballistics. While you haven't changed the barrel vibration (not much, at least) by switching bullets, you most likely changed the other two.
 
Dont Understand

mks said:
You need another ladder test. The results depend on the relationships among bullet exit time, barrel vibration and external ballistics. While you haven't changed the barrel vibration (not much, at least) by switching bullets, you most likely changed the other two.
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MKS
If the bullets weigh the same and have the same velocity (These were given in description) why do they exit at different times????
I'm not trying to argue--just don't understand!!!!

If they weigh the same and exit at the same time (for discussion lets say they exit at the same time) should the barrel vibration then not be the same with the only variable then being the external ballistics?????

I agree he needs to do a separate ladder test.
This needs to be done under the same conditions (Temp., Humidity, Altitude, gun/ clean barrel) as the first ladder test--or as close as possible.

Will be interesting to see the comparison ladder tests.
Keep us posted.

CLP
 
I don't know anything about the ladder test but different bullets will have different drag. Even using the same bullet from lot to lot they'll have a little different friction from the jacket and lead composition.

I'd just shoot a few shots and see what happens.
 
Sir Francis of Michigan used to be the authority on ladder tests. There have even been articles written about it. Supposedly the group that hits just under the peak location on the target of the test groups is supposed to be best. Personally, I never could get it to workout ad advertised.

I'm with CCBW on thid, put them on paper. That is where the measurement counts.
 
C.L. Peterson said:
MKS
If the bullets weigh the same and have the same velocity (These were given in description) why do they exit at different times????
I'm not trying to argue--just don't understand!!!!

If they weigh the same and exit at the same time (for discussion lets say they exit at the same time) should the barrel vibration then not be the same with the only variable then being the external ballistics?????

I agree he needs to do a separate ladder test.
This needs to be done under the same conditions (Temp., Humidity, Altitude, gun/ clean barrel) as the first ladder test--or as close as possible.

Will be interesting to see the comparison ladder tests.
Keep us posted.

CLP
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Wilbur is wise. Two bullets can have the same muzzle velocity, but different exit times because of different acceleration profiles as they travel from breach to muzzle. Different drag between bullet and bore affects the pressure behind the bullet, which affects the burn rate of the powder. All of it affects bullet exit time. You get different drag from variations in materials, diameter and bearing surface area. It's reasonable to expect that exit time would be in the same ball park for the same weight and velocity, but it would be pure coincidence if it turned out to be exactly the same.

The different acceleration profile affects the force input that drives rifle/barrel vibration. So even if the rifle/barrel responded exactly the same each time to the same input, the difference in the input could make the vibration different. But I am guessing that this is a smaller effect.

This is off on a tangent, but vibration mode testing typically uses a hammer to impart an impact to the object being tested. The steady-state response is measured well after the impact. In a rifle, the "impact" is the powder burning, which occurs throughout the time of interest for accuracy purposes (the time that the bullet is in the barrel). As shooters, we want to know the response of the rifle during the "impact." It is the transient, rather than steady-state response that we need. VarmintAl recognized this years ago. Really have to give him credit for his insight.
 
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I'll have to see if I can scan and send the pages regarding the sine wave and the ladder test. I need the refresher course myself anyway.
 
Jeez....

I have that book somewhere and I think somebody gave it to me.....The earth will end before I could find it.
 
FBecigneul said:
You have to buy one; Being stupid can be expensive.
No, wait a minute, that sounds more like being smart can cost you.
I tried, not too hard, to get the book to open enough to be placed on the copier but I didn't want to wreck the book.
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;) Francis, so many have told me, "that book has nothing to do with bench rest shooting . . ." , my reply, "ok" ! :p ;) Oh, I was brain-dead (couldn't read or, write) for most of two years, where did Charles E. go?? RG
 
I just got the following from Roger Haney who frequents the range mostly used by Charles.

""Jerry, I don't know, he had Cancer a few years ago, but was treated with a new treatment and was pronounced clean, but i have not heard or seen him in 3 years, hope and pray he is ok""
 
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