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Velocity Question...
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Member Posts: 168,427 ✭
Using published data and the ballistic tables provided in Nosler's Reloading Manual, I guesstimated a velocity for a particular load and dialed it in for a 300 yard zero. Here is my question: I dialed it in to be 3.5" high at 100 yards but when I shot it, I was actually 4.125" high at 100 yards. Does this indicate higher or slower velocities than I anticipated??? My initial thoughts were that I'm getting much higher velocities...but now I'm second guessing that line of thinking.
Is there a way to determine velocity based on ballistic tables, how much you dialed in, and how much higher you actually were.?.?...keep in mind that the 3.5" was based on a guesstimated velocity.
Thanks!
Is there a way to determine velocity based on ballistic tables, how much you dialed in, and how much higher you actually were.?.?...keep in mind that the 3.5" was based on a guesstimated velocity.
Thanks!
Comments
Using published data and the ballistic tables provided in Nosler's Reloading Manual, I guesstimated a velocity for a particular load and dialed it in for a 300 yard zero. Here is my question: I dialed it in to be 3.5" high at 100 yards but when I shot it, I was actually 4.125" high at 100 yards. Does this indicate higher or slower velocities than I anticipated??? My initial thoughts were that I'm getting much higher velocities...but now I'm second guessing that line of thinking.
Is there a way to determine velocity based on ballistic tables, how much you dialed in, and how much higher you actually were.?.?...keep in mind that the 3.5" was based on a guesstimated velocity.
Thanks!
It may indicate that. It may also indicate that your scope is higher than the one they used. The way to separate that is to document where you are hitting @ 100 and @ 300 then you can compare to the bullet makers ballistics (find their website). If you can't find what you want, compare it on JBM trajectory. Type that in to google and it'll bring up their site.
Edit:
I may have read your post wrong. If you were zeroed at 300 and got a 4.125" high @ 100 it would indicate your bullet was going slower and therefore needed more elevation to get out to 300. Again, scope height is a factor.
The Chrony, with the remote data box, minus printer has worked good for several years for me.
quote:Originally posted by ECC
Using published data and the ballistic tables provided in Nosler's Reloading Manual, I guesstimated a velocity for a particular load and dialed it in for a 300 yard zero. Here is my question: I dialed it in to be 3.5" high at 100 yards but when I shot it, I was actually 4.125" high at 100 yards. Does this indicate higher or slower velocities than I anticipated??? My initial thoughts were that I'm getting much higher velocities...but now I'm second guessing that line of thinking.
Is there a way to determine velocity based on ballistic tables, how much you dialed in, and how much higher you actually were.?.?...keep in mind that the 3.5" was based on a guesstimated velocity.
Thanks!
It may indicate that. It may also indicate that your scope is higher than the one they used. The way to separate that is to document where you are hitting @ 100 and @ 300 then you can compare to the bullet makers ballistics (find their website). If you can't find what you want, compare it on JBM trajectory. Type that in to google and it'll bring up their site.
Edit:
I may have read your post wrong. If you were zeroed at 300 and got a 4.125" high @ 100 it would indicate your bullet was going slower and therefore needed more elevation to get out to 300. Again, scope height is a factor.
That's what has me confused...one might think this is the case b/c one must dial in more elevation for the slower moving round as indicated by the ballistic tables, but you've to to remember...I dialed in for 3.5" and got 4.125". I was guesstimating around 3050 fps with a 180 grain Nosler BT. I think the bullet being higher would indicate higher pressures b/c I'm going to have to dial my scope back down to reach the guesstimated velocity...basically, I think it's shooting flatter than anticipated...which would mean higher velocities.[?][?][?] ...but it wouldn't be the first time I've been wrong.[^]
Eric, suck it up and GO BUY A CHRONOGRAPH [:D][:D]
The Chrony, with the remote data box, minus printer has worked good for several years for me.
Yeah...I got spoiled borrowing my buddy's Chrono back east...I'm going to have to spring for one but it's just not in the cards right now.[^]
Yes you can get a close estamate of velocity by using a ballistics chart, but your going to have to do a bit mor shooting.
Zero (by firing) your rifle at one distance (say 300yd)
Now WITHOUT touching the scope and maintaining the same aiming point, fire groups at several other known ranges (say 100, 200, 400 and 500yd). The more distances, and the further apart they are, the mor accurate your estamate will be.
Deterimine the center of each group and measure the up/down from the aiming point for each. Now you can go to a ballistics table and adjust the MV to get the best fit for the drops. You will find that this fit is not exact, and that the largest errors will most likely be at the shorter ranges.
Also remember that the advertised BC may not be exact, and that it's a safe bet that your bullet dosn't match the form factor used for the BC (advertised BC is for a G1 form, your bullet is mor than likely a G7 or one of the other more "aerodynamic" forms).
Of course having done the shooting, you could just create a personal drop chart and forget all the MV worries.
Edit
Your midrange 300WM load, being fired in a AI chamber will (as a rule) give lower velocities.
BTW, breakin has nothing to do with accuracy, it has to do with ease of cleaning/reduced fouling.
Your shooting after cleaning is counterproductive, as you haven't "fouled" the barrel. IOW your spinning your wheels right now, so put 5 rounds down range (don't give a carp where they go) than shoot your group/do your load testing. When your done for the day, than go home and clean. Before shooting another group, fire 5 fouling rounds than go for the groups.
ECC
Yes you can get a close estamate of velocity by using a ballistics chart, but your going to have to do a bit mor shooting.
Zero (by firing) your rifle at one distance (say 300yd)
Now WITHOUT touching the scope and maintaining the same aiming point, fire groups at several other known ranges (say 100, 200, 400 and 500yd). The more distances, and the further apart they are, the mor accurate your estamate will be.
Deterimine the center of each group and measure the up/down from the aiming point for each. Now you can go to a ballistics table and adjust the MV to get the best fit for the drops. You will find that this fit is not exact, and that the largest errors will most likely be at the shorter ranges.
Also remember that the advertised BC may not be exact, and that it's a safe bet that your bullet dosn't match the form factor used for the BC (advertised BC is for a G1 form, your bullet is mor than likely a G7 or one of the other more "aerodynamic" forms).
Of course having done the shooting, you could just create a personal drop chart and forget all the MV worries.
Yeah...thanks. I'm aware of all that. I just do not have a long range set up here without going to a LOT of work (in clear cuts, etc). I'm still breaking the barrel in on this rifle, but in doing so, I'm also sighting it in, working up loads, etc. Trying to combine steps here...the Snow is right around the corner.
Do you have an opinion on this specific question: "Here is my question: I dialed it in to be 3.5" high at 100 yards (based on an estimated velocity) but when I shot it, I was actually 4.125" high at 100 yards. Does this indicate higher or slower velocities than I anticipated???"
Thanks again!
If so, it is most likely a scope variance, not MV.
...
Do you have an opinion on this specific question: "Here is my question: I dialed it in to be 3.5" high at 100 yards (based on an estimated velocity) but when I shot it, I was actually 4.125" high at 100 yards. Does this indicate higher or slower velocities than I anticipated???"
Thanks again!
If everything matched. The temp, humidity, barrel length, harmonics of the barrel, height of scope, focal dynamics of the scope, etc... Then yes it would mean a higher velocity. But 5/8th's of an inch is a lot of velocity gained on an already high velocity round. Now if you're talking about a low velocity round, then not much velocity to increase that 5/8th's inch. High velocity would be like 2800 to 3000 vs. low velocity of say 1800 to 2000.
If you are at the top of the load chart, see what going back to minimum is like. Likewise if you are at the midrange, keep working up and see if groups climb. Maybe see what another bullet of the same weight does.
I'm of the opinion it's a dynamic of your set-up that is giving you the extra height. Not extra velocity. The only way to know for sure is to a.) chronograph it or b.) measure drop over given distances.
When you Dialed it in, are you saying you counted clicks to raise the impact Distance XXX and found you actually had distance YYY in elevation increase????
If so, it is most likely a scope variance, not MV.
I'm really getting myself confused now...I doubt that it's a problem with the scope. It's a new Leupold VX-III 8.5-25X50mm with the Varmint Hunters Reticle. I bought the scope probably 4 years ago, but I've only just started using it to break this barrel in. I seriously do not believe it's the scope...but you would think if you dial it an inch, it should move an inch...??? My head is beginning to hurt here...
quote:Originally posted by ECC
...
Do you have an opinion on this specific question: "Here is my question: I dialed it in to be 3.5" high at 100 yards (based on an estimated velocity) but when I shot it, I was actually 4.125" high at 100 yards. Does this indicate higher or slower velocities than I anticipated???"
Thanks again!
If everything matched. The temp, humidity, barrel length, harmonics of the barrel, height of scope, focal dynamics of the scope, etc... Then yes it would mean a higher velocity. But 5/8th's of an inch is a lot of velocity gained on an already high velocity round. Now if you're talking about a low velocity round, then not much velocity to increase that 5/8th's inch. High velocity would be like 2800 to 3000 vs. low velocity of say 1800 to 2000.
If you are at the top of the load chart, see what going back to minimum is like. Likewise if you are at the midrange, keep working up and see if groups climb. Maybe see what another bullet of the same weight does.
I'm of the opinion it's a dynamic of your set-up that is giving you the extra height. Not extra velocity. The only way to know for sure is to a.) chronograph it or b.) measure drop over given distances.
I just dialed the scope back to my 100 yard zero. I'm going to go back out and shoot it and it should be back dead center of the bull. If if is, I think I can safely determine that it's the velocity. My barrel is longer than the test barrel and I'm firing a .300 Win Mag Case in a .300 Win Mag A.I. chamber...fire forming my cases. This AI chamber could be giving me significant velocity gains.?.? I'm just using a mid range loading (73 grains of RL 22), with the bullet seated at the lands.
3.5" of adjustment moved me 4.125" in elevation though and that just ain't right. I know one thing...she either doesn't like being seated at the lands or she doesn't like 73 grains of RL-22.
JustC...please lock this topic and let it go into oblivion before I drive myself mad.[B)] I'm not thinking about it anymore![^][:I]
quote:Originally posted by sandwarrior
quote:Originally posted by ECC
...
Do you have an opinion on this specific question: "Here is my question: I dialed it in to be 3.5" high at 100 yards (based on an estimated velocity) but when I shot it, I was actually 4.125" high at 100 yards. Does this indicate higher or slower velocities than I anticipated???"
Thanks again!
If everything matched. The temp, humidity, barrel length, harmonics of the barrel, height of scope, focal dynamics of the scope, etc... Then yes it would mean a higher velocity. But 5/8th's of an inch is a lot of velocity gained on an already high velocity round. Now if you're talking about a low velocity round, then not much velocity to increase that 5/8th's inch. High velocity would be like 2800 to 3000 vs. low velocity of say 1800 to 2000.
If you are at the top of the load chart, see what going back to minimum is like. Likewise if you are at the midrange, keep working up and see if groups climb. Maybe see what another bullet of the same weight does.
I'm of the opinion it's a dynamic of your set-up that is giving you the extra height. Not extra velocity. The only way to know for sure is to a.) chronograph it or b.) measure drop over given distances.
I just dialed the scope back to my 100 yard zero. I'm going to go back out and shoot it and it should be back dead center of the bull. If if is, I think I can safely determine that it's the velocity. My barrel is longer than the test barrel and I'm firing a .300 Win Mag Case in a .300 Win Mag A.I. chamber...fire forming my cases. This AI chamber could be giving me significant velocity gains.?.? I'm just using a mid range loading (73 grains of RL 22), with the bullet seated at the lands.
When you are fire forming, you will use a certain amount of pressure to form the case to the new chamber and your velocity will be decreased.
If you sighted in at 300 yds and your POI(point of impact) was higher then expected at 100 yds. Your velocity is slower, you will have a lower POI past 300yds. Think of it as not as flat shooting or slower.
An example with a different bullet.
154gr(.525bc) at 3000fps/300yd sight in
100yds +3.6 300yds 0.0 500yds -26.3
Same as above but 2600fps
100yds +5.1 300-0 500yds -36.3
Same as above but 3400fps
100yds +2.5 300-0 500yds -19.9
Hope that helps, keep it simple.