Do you have any pictures of the groups you refer to? When working up to the best load you want to look at vertical more than horizontal. If your groups are tall the charge is wrong but flat and wide your seating is off a little. A 3 inch wide group at 300 yards that is only 1/2 inch tall is a great group that needs the bullet seating adjusted. I hope i have made this at least as clear as mud now.Originally Posted by limige
"And you shall know the truth, and the truth shall make you free.” John 8:32 (New King James Version)
Interesting I havent heard that before. No I havent taken pics of those groups. Ill be going home tonight and can do so but they were not really tall or wide more triangular from what I remember.
Im going to see if the scope change makes any difference before going back to load work.
Ok scope didn't change anything so I continued load work up. Ran a seating test at 100 yrds using 37 gr
-50-90 looked decent so I loaded some up at -70. 37 gr and 38
I see that not everyone (anyone) agreed or found what I found. So I offer the following. First I used the JBM ballistics program using the following parameters to check my previous answer; bullet, 55gr Hornady VMax; environment 85 degrees, 30" barometric pressure, 15% humidity (dry here), 4900' elevation, pressure was corrected (this is the little check box in the environment section). Scope height 1.5" above bore. For speeds I used the min and max speeds from the Hogdon website for H380 powder which were 3507 and 3713 fps. The table below shows how the bullet heights will spread with different sightin distances. The difference shown on the right is conservative as ballistics tables don't let you sight in for one velocity (say the slow one) and then shoot a faster bullet, ie, sighted in at 200 is the same for both velocities. We all know that the faster bullet would hit somewhat higher than the slower bullet if you first sighted in with the slow bullet then fired the faster bullet. Therefore the differences shown are conservative and off by some distance that I can't measure easily. I have done the calculations for 4 different sight in differences; 300, 200, 100 and -1.5 inches at 50 (essentially a 0 degree horizontal barrel). The use of 50 yards won't help the OP as a zero at 50 is the same as a zero at 200, and the spread generality was too large for such a short distance, my mistake. Using longer distances, like the 650 I eventually used, can increase the ladder height to over 11". There is a difference, but at 325 yds it is probably not over 3.5 to 4". That is why I quit using straight ladder tests and use an OCW like test as shown at the link below to find nodes on targets at closer ranges.
http://forum.accurateshooter.com/ind...opic=3814361.0
Bullet drop at these velocities at 325 yds
Zero @ 3507 fps 3713 fps difference
300 -1.7 -1.5 .2
200 -7.3 -6.4 .9
100 -10.5 -9.0 1.5
-1.5"@50 -17.9 -16.1 1.8
Last edited by Bigguy; 07-07-2014 at 09:59 PM. Reason: the table was crushed when posting
Bullet drop at these velocities @ 325 3507 3713 difference Zero @ 300 -1.7 -1.5 0.2 200 -7.3 -6.4 0.9 100 -10.5 -9 1.5 -1.5 @ 50 yd -17.9 -16.1 1.8
I think i see what you are doing Bigguy. If i am reading what you say correctly you are rezeroing for each load. All you want to do is get on paper at 300 and then shoot all loads without making any adjustments to you scope for a ladder test.
"And you shall know the truth, and the truth shall make you free.” John 8:32 (New King James Version)
Hes way overthinking and confused himself.
A proper ladder test will show the same thing as ocw in less rounds and less questions any day of the week. Unfortunately its hard to find 500 yrds to shoot one.
Theres not enough velocity spread at 300 to determine much.
Im pretty close to the end but unfortunately im also just about out of bullets. I may shoot another ladder now that I have a window and seating narrowed down.
It was just really odd how the one ladder test worked out. Something strange happened there
Exactly why I went to the other method.
Earl
I'm not rezeroing, you either zero with the high velocity round or the low velocity round and then shoot your ladder, the nodes will show up if you have enough yardage for the bullets to spread vertically. The table shows how much vertical difference you can expect with the different velocities and the yardage you zero at.
Here's what a ladder shot at 500 yrds can look like. Very easy to see where your nodes are and 1/3 the ammo spent doing it. Any reject can spot the nodes
And I may resort to ocw in the future since 300 doesnt seem far enough for a good ladder.
100 yrds is too confusing to ocw for me. Its going to be 200 or 300.
My issue is the group size at 100 yrds. If you have two kissing with one flyer I have a hard time with where the center of that group should be
Your table is rezeroing itself for -1.5 @ 50yards. You are working way to hard to make it not work and that is your choice. A ladder is not a way to find the perfect load it is just one more tool to get close and not waste so much time and ammo getting to where you want to be and it allows you more time to fine tune with group shooting and less wasted powder and lead.
"And you shall know the truth, and the truth shall make you free.” John 8:32 (New King James Version)
Bigguy. Im still pondering the data you put up. Drop is fixed but when dealing with line of sight of the scope and the trajectory of the barrel the bullet makes a curve and the scope line of sight is straight. Im beginning to wonder if there may be merit to your comment and you have me curious.
First thought is velocity drop is a fixed constant and it doesnt matter how many clicks up you dial the spread will be the same. But you think of the line of sight intersecting the ballistic curve and you may have brought up something ive heard nothing about so far.
I looked at the ladder test and have a question about the results. I don't understand the horizontal spread. It looks like it could be over 10 inches. is this from wind or just powder charge?
Wind. The one posted above was shot in about 15-20 mph crosswind.
you look strictly at vertical dispersion.
Those three shots only had 3/4" vertical over 1.5 gr of powder change. What your seeing is the point at which the barrel is changing direction on the whip of the harmonics. Trying to do that at 100 yrds is extremely difficult but a veteran shooter can do it with enough practice. Telling newbies to do this at 100 yrds causes a lot of questions and spent ammo.
This was the first time ive attempted a ladder at 300 yrds and was disappointed at the results. Couldn't really tell where the barrel was stabilizing. So im going to try an ocw at either 200 or 300 yrds. This should help get some vertical
Shot an ocw today at 200 yrds. -.070 off the rifling
Then loaded 4 at -.060 and shot 36.5 gr at 200. Looks just over an inch. Going to do a more in depth seating test after I resize and reprime my brass.
I'm with you on that. At first seems out of whack but when you consider a bullet shot perfectly level will drop at a rate of 9.8m/s/s but if it is fired in an arc it actually rises, requiring it to decelerate to zero vertical velocity before accelerating downward at the same rate. My physics is a little rusty so I won't try it on paper, gonna have to use a long range and a taaaaaaall target haha.
I like the looks of your two groups at 100yds at -70 with 37 and 38grains. If it were me I would probably start back at 36.5 and work up again in .5 increments at -70 at 100yds in 3 shot groups. Pick a day when the mirage and wind are very low so that you can be fairly certain the groups you are getting have as little external influence as possible. From there if you are not pleased with the best group you get, I would start over with another powder or bullet combo. Hopefully you wont have to do that! but I have had to before and have had completely different and much better results by just trying a different powder or bullet or both.
I had not heard of it either. I was just playing with the tables when it hit me in the face. Something to look at.
Posting Permissions
Reply With Quote
Bookmarks