This has mostly likely already been asked before. Here is what happened today at the range while setting a 7mm hunting rifle in for hunting. I zeroed the rifle in at 100 yds with hornady 139gr. sst ammo. Had a box of federal 150gr. ballistic tips that was given to me years ago,wondered where these would group in relationship to the hornady 139gr. ammo. The fed. ammo printed a tight group at 3" high and 2" left of target/zero. Is the the federal 150gr. ammo traveling faster than the 139gr. ammo? Is that why it impacted a higher group than the hornady? Or is the hornady going faster and that is why it printed a lower group(shoots flatter therfore lower impact? Wonder about this before with other rifles and ammo,just have not gotten an answer. I do not have a chrony so here I am. Sorry if this has been asked before. thanks
Range Report Range/Bullet trajectory question
- Thread starter RTA
- Start date
Re: Range/Bullet trajectory question
In for answer...switched from 58gr to 100gr in my 243 this weekend and the heavier bullet went 2 or so inches higher and right
In for answer...switched from 58gr to 100gr in my 243 this weekend and the heavier bullet went 2 or so inches higher and right
Re: Range/Bullet trajectory question
POI change mainly due to different vibratory pattern, no doubt in this case.
POI change mainly due to different vibratory pattern, no doubt in this case.
Re: Range/Bullet trajectory question
So it would seem that it is harmonics and not velocity. I thought on it some more today and come to think it could be more powder/pressure from the 150gr. ammo doing the higher impact. If I took one of my pet loads and increased it from say 43.1 to 45.0 of powder. Everything else (brass,primers,bullet,etc.) remained the same,would the bullet impact higher or lower? I know this could be answered at the range,just wondering. Guess I need to spend some time reading the forums more. Thanks guys.
So it would seem that it is harmonics and not velocity. I thought on it some more today and come to think it could be more powder/pressure from the 150gr. ammo doing the higher impact. If I took one of my pet loads and increased it from say 43.1 to 45.0 of powder. Everything else (brass,primers,bullet,etc.) remained the same,would the bullet impact higher or lower? I know this could be answered at the range,just wondering. Guess I need to spend some time reading the forums more. Thanks guys.
Re: Range/Bullet trajectory question
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: RTA</div><div class="ubbcode-body">? Or is the hornady going faster and that is why it printed a lower group(shoots flatter therfore lower impact? </div></div>
you have this part exactly backwards - all other factors being the same, the projectile with shorter time of flight (you can think of this as "flatter" ) will always impact higher
at 100 yds there will not be enough time of flight difference between the 2 to account for that 3 inch drop difference, so like others have said it has to be harmonics
get out to 500-600 yds and you should see time of flight overcome harmonics (longer time of flight will hit lower regardless of where barrel harmonics initially sent the bullet) - but 3 moa initial divergence is a lot to overcome, since the drop from 100 to 600 yds is only typically 12-14 moa ( so it is possible the shorter time of flight could still impact lower)
this is probably better settled with the help of a chrony
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: RTA</div><div class="ubbcode-body"> If I took one of my pet loads and increased it from say 43.1 to 45.0 of powder. Everything else (brass,primers,bullet,etc.) remained the same,would the bullet impact higher or lower? </div></div>
higher, but again the big "if" of every thing else staying the same is harmonics
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: RTA</div><div class="ubbcode-body">? Or is the hornady going faster and that is why it printed a lower group(shoots flatter therfore lower impact? </div></div>
you have this part exactly backwards - all other factors being the same, the projectile with shorter time of flight (you can think of this as "flatter" ) will always impact higher
at 100 yds there will not be enough time of flight difference between the 2 to account for that 3 inch drop difference, so like others have said it has to be harmonics
get out to 500-600 yds and you should see time of flight overcome harmonics (longer time of flight will hit lower regardless of where barrel harmonics initially sent the bullet) - but 3 moa initial divergence is a lot to overcome, since the drop from 100 to 600 yds is only typically 12-14 moa ( so it is possible the shorter time of flight could still impact lower)
this is probably better settled with the help of a chrony
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: RTA</div><div class="ubbcode-body"> If I took one of my pet loads and increased it from say 43.1 to 45.0 of powder. Everything else (brass,primers,bullet,etc.) remained the same,would the bullet impact higher or lower? </div></div>
higher, but again the big "if" of every thing else staying the same is harmonics
Re: Range/Bullet trajectory question
The heavier bullet generates more barrel flip, resulting in a higher bore axis angle as the bullet emerges. This translates into a higher POI.
Recoil always takes place, ensuring that the POA is, in fact, always changing during the duration of the bullet's barrel transit. How much depends on each load's individual recoil characteristics/responses, which are not solely mechanical in nature, there's the human component, too. The barrel is essentially never pointing where we aimed it prior to recoil by the time the bullet is released to fly its trajectory. We are picking an arbitrary POA that, combined with recoil and ballistics, results in a particular POI.
The fact that recoil can be so dissimilar between shots, due to our own varying degree of relaxation, etc., is a key part of dispersion, and is also another key reason why I disregard the smaller issues associated with super-anal handloading compulsions. People get so hung up with the mechanical issues associated with accuracy, and pay far too little attention to the shooter's human aspects.
Whatever horizontal displacement occurs stems from similar causes, since recoil takes place along a three-dimensional path. This phenomenon is essential to why LL's advice to get straight behind the rifle is so effective. It is also at the core of why my elbow-on-sling-with-bipod technique works the way it does.
Both techniques modify recoil effect so it becomes more consistent. LL's deals with horizontal dispersion, mine deals with the vertical.
They can be used to complement each other and get recoil down to the point where the more arcane handloading techniques can actually become effective. It all contributes to the single system. We need to deal with each accuracy issue in the order of the magnitude each has on consistency. Until the bigger ones are resolved, resolving the smaller ones is not really effective.
In short, the different POI is a response to different recoil characteristics. While ballistics are also different for different loads, these differences are greatly overshadowed by the recoil effects.
Greg
The heavier bullet generates more barrel flip, resulting in a higher bore axis angle as the bullet emerges. This translates into a higher POI.
Recoil always takes place, ensuring that the POA is, in fact, always changing during the duration of the bullet's barrel transit. How much depends on each load's individual recoil characteristics/responses, which are not solely mechanical in nature, there's the human component, too. The barrel is essentially never pointing where we aimed it prior to recoil by the time the bullet is released to fly its trajectory. We are picking an arbitrary POA that, combined with recoil and ballistics, results in a particular POI.
The fact that recoil can be so dissimilar between shots, due to our own varying degree of relaxation, etc., is a key part of dispersion, and is also another key reason why I disregard the smaller issues associated with super-anal handloading compulsions. People get so hung up with the mechanical issues associated with accuracy, and pay far too little attention to the shooter's human aspects.
Whatever horizontal displacement occurs stems from similar causes, since recoil takes place along a three-dimensional path. This phenomenon is essential to why LL's advice to get straight behind the rifle is so effective. It is also at the core of why my elbow-on-sling-with-bipod technique works the way it does.
Both techniques modify recoil effect so it becomes more consistent. LL's deals with horizontal dispersion, mine deals with the vertical.
They can be used to complement each other and get recoil down to the point where the more arcane handloading techniques can actually become effective. It all contributes to the single system. We need to deal with each accuracy issue in the order of the magnitude each has on consistency. Until the bigger ones are resolved, resolving the smaller ones is not really effective.
In short, the different POI is a response to different recoil characteristics. While ballistics are also different for different loads, these differences are greatly overshadowed by the recoil effects.
Greg
Re: Range/Bullet trajectory question
Thanks for the info/advice,George&Greg. Your thoughts have given me more light on the subject.I work hard on the techs. and shooting form that has been given in the forums I've read here on the Hide. I try to slow down and go thru the steps before each shot to get the best out of it. There is just some shooting questions that I have not taken time to ask or research. This being one. Thanks guys...
Thanks for the info/advice,George&Greg. Your thoughts have given me more light on the subject.I work hard on the techs. and shooting form that has been given in the forums I've read here on the Hide. I try to slow down and go thru the steps before each shot to get the best out of it. There is just some shooting questions that I have not taken time to ask or research. This being one. Thanks guys...
Re: Range/Bullet trajectory question
I had a Swiss K31 that would print tight groups but put Prvi Partisan 2" higher and 2" to the right of Swiss surplus. It shot just as well in terms of accuracy. That rifle had a purposely stressed barrel.
I had a Swiss K31 that would print tight groups but put Prvi Partisan 2" higher and 2" to the right of Swiss surplus. It shot just as well in terms of accuracy. That rifle had a purposely stressed barrel.
Similar threads
