Sighting in your rifle with 2 different bullets.
I have 2 loads made up for my 243, one is for deer 95 grain BT MV 2820fps sighted in dead on at 215 yards. I also have 65 grain vmax for coyotes MV about 3600fps. I haven't shot the coyote loads yet with my gun sighted for deer at 215 yards which puts me a 2.5" high at 100 yards with my deer load.
My question is what can I expect to be the difference in the point of impact for the coyote load at 215yards, should it higher or lower?
My question is what can I expect to be the difference in the point of impact for the coyote load at 215yards, should it higher or lower?
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This is a question---or at least parallel to one---that I myself have been dying to ask. I've been told that if you sight in a rifle for a fixed distance with a given weight of bullet, all other things being equal, a HEAVIER bullet will strike slightly HIGHER. Why? Dunno. I have yet to hear a cogent, physically reasonable explanation for it. But I'd wager that with the lighter coyote bullets, you'll hit maybe a fraction of an inch lower at the same distance. I'd be amazed if it turned out to be MORE than an inch.
Gunbroker experts: Help us both out here! Can anyone point me to a source where this heavier-higher/lighter/lower issue is discussed? Or is this a myth to begin with? Or does it only apply to rifles shot free-hand (i.e., not from a bench-rest?)0 -
Without knowing exactly what your loads are it is hard to say. What I come up with is this.
95GR-200 yd zero 100 yd +1.75"
65GR 200 yd zero 100 yd +.87
Would need to know what powder and how much
Trstone-- Your heavier bullet is going to hit higher at 100 yds because you are having to arch it to get it out as far as a lighter bullet.
Guncontrol-The ability to hit what your aiming at.0 -
scsims, I can generate a chart that will give trajectories for both bullets at those velocities. Will take me a little while and will post back later. HOWEVER!!!! The safest way to test them is to shoot them in your rifle and see what the results are. I generate the charts but will always try to test the data before just flinging bullets at varmints! It is surprising how close the charts are but they are not absolutely the last word in what the bullets will do! GHD 0 -
The heavier bullet will hit higher because it is going slower, therefore it is in the barrel longer during the recoil process. Hence, higher strikes on the target.
AlleninAlaska
Delta Firearms & Supplies
http://canadianfirearmsexchange.com
aglore@gci.net0 -
quote:Originally posted by trstone
This is a question---or at least parallel to one---that I myself have been dying to ask. I've been told that if you sight in a rifle for a fixed distance with a given weight of bullet, all other things being equal, a HEAVIER bullet will strike slightly HIGHER. Why? Dunno. I have yet to hear a cogent, physically reasonable explanation for it. But I'd wager that with the lighter coyote bullets, you'll hit maybe a fraction of an inch lower at the same distance. I'd be amazed if it turned out to be MORE than an inch.
Gunbroker experts: Help us both out here! Can anyone point me to a source where this heavier-higher/lighter/lower issue is discussed? Or is this a myth to begin with? Or does it only apply to rifles shot free-hand (i.e., not from a bench-rest?)
Fellows...
That is a pure physics question., and please excuse me if I get a bit verbose with this answer (we Engineers are noted for being a little long-winded sometimes[:)])
First, one must mentally picture the ballistic arc that a bullet takes in order to reach the target at any given distance.
The heavier bullet is traveling considerably slower (which is the most important factor), so in order for it to be dead-on at 215 yards, it must rise higher above the horizontal plane than a faster moving bullet (notice I did not say lighter bullet). To back up a little, we must first establish a few known facts. (1) gravity affects bullets of different size and weight equally and is the first constant. (2) time of travel is also a very important factor (it takes less time for a faster moving bullet to reach it's target, hence gravity has less time to act upon it). (3) bullet coefficient is a contributing variable in that the higher the coefficient, the slower a given bullet will lose velocity, thereby affecting the time to target.
OK... if two bullets are fired down range at the exact same time, with different initial velocities, and along an identical sight plane, which hits the ground first? The correct answer is that BOTH bullets hit the ground at the EXACT same time... with the only difference being that the bullet with the higher initial velocity traveled a greater distance before hitting.
So, what this means to the shooter, is that the sight plane must be compensated more (higher angle) for the slower moving bullet. This however does not change the ballistic arc, just the initial angle of it. Keeping that in mind, if a your load is dead on (zeroed) at a specific range with the slower moving bullet, and then you shoot the faster moving bullet with the exact same sight plane, it will take less of an arc getting to that preset "zero" distance. This causes the faster moving bullet's flight path to be higher above the horizontal plane during the entire flight, and to be high at the preset terminal end of the flight. This is a direct result of the "time to target" (velocity) and the "distance" to the target (time).
There are software ballistic programs available that will provide you with the precise bullet arc if you plug in all the appropriate information (velocity, distance, bullet coefficient, elevation, and wind speed... both cross & head or tail wind speed).
Bert H.
Real Men use a SINGLE-SHOT!0 -
Bert, I think you lost me. You are saying, all other things being equal the lighter bullet would hit higher??
My heros have always killed cowboys.0 -
If there was absolutely positively no muzzle rise, yes the lighter bullet will strike higher.
AlleninAlaska
Delta Firearms & Supplies
http://canadianfirearmsexchange.com
aglore@gci.net0 -
quote:Originally posted by He Dog
Bert, I think you lost me. You are saying, all other things being equal the lighter bullet would hit higher??
My heros have always killed cowboys.
Yes... provided the exact same sight settings and conditions (of importance is the exact same exit angle of the bullet) are used for both loads. I kind of figured that I might lose a few people with my long winded explanation [:)]. It is too bad that I can not provide an illustration of this in this forum, as I am sure that there are (or will be) some doubters to what I have stated, but it simply is a mathmatical equation based on the laws of physics.
What fools some people, is that they plug their information into a ballistics program, and it shows that for any given load with an identical "zero" distance, that the faster moving bullet has a lower trajectory along its entire flight path... leading them to falsely believe that it will hit lower than a slower moving bullet at any given distance. What those people are not taking into account, is that the program has "adjusted" the sights (exit angle) for you, to enable the "zero" point to be exactly the same.
Bert H.
Real Men use a SINGLE-SHOT!0 -
That make sense to me, but us engineers are usaully on the same wave length.
What I did was, I had my rifle zeroed at 100 yards fist and I tried both of the foremention loads. At that range my 95 gr bullet hit dead and the 65 gr bullet was 1.5" high. In Kentucky deer season is this weekend so I sight in my deer load at 215 yards. I had to sight my rifle in about 2.5 inches high at 100 for the bullet to be zeroed at 215. It made me wonder where the 65 gr bullet would be at 215 yards.
With Berts explaination, it looks like since it was 1.5" high before adjusting my scope up 12 clicks wich pretty much centered me at 215. ( If you all are wondering why I picked 215 yards it's just how my land lays and that's about the closest I could get to 200 yards).
So, I can assume now that my 65 gr bullet will be about 4.5" at 100 yards now and that would put it at about 5.77" high at 215 yards.0 -
No I wouldn't assume anything. Go shoot it out to your max range on a target and find out for sure where it is hitting.
AlleninAlaska
Delta Firearms & Supplies
http://canadianfirearmsexchange.com
aglore@gci.net0 -
I'm with aglore, forget about all them their Dangles and Angles, Go Shoot them.[:D][:D][:D] 0
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