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Thread: which bullet weight?

  1. #1

    which bullet weight?

    just wondering if any of the reloading boffins out there could give me a little info or point me in the right direction. im having a little trouble finding a nice flat shooting load for my .223. it has a 1 in 8 twist which does not like the normal 55gr heads (4" grouping @ 100yrds) so i went up to a 60gr head which gave me the acuracy but not the trajectory. so i had a little chat with my local gun shop and he said use a heavier bullet and that will fly flatter?. so i decided to give it a go and bought a box privi 69gr target ammo and at 230yrds i had a drop of 5.5 inch but terible grouping and my 60gr home loads i was getting a 7.5inch drop. so to be honest i would like to get it even flater which i'm sure i can do and i now dont know if i should be trying to push the 60gr head faster (i'm using 25gr of varget which acording to my data i should be pushing around 2950fps but i dont own a crono) or switching to another weight of bullet and any help would be apreciated as ive just become a dad and time spent with the rifle pressious at the minute and i dont want to waste it playing about to much with loads

  2. #2
    Heavier bullets will never shoot flatter than lighter ones.. it just defies the laws of physics, if all other things are equal... Heres a link to find out the optimum weight of bullet to give you stability with a given barrel.

    http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi

    If your looking for flat shooting, what range are you looking to shoot out to maximum. Light bullets are faster and flatter but bleed energy faster so when they start to drop, they drop!

    I shoot 40gn BTs out of my .223 with H335, getting velocities around 3200fps. If your not 'dialling in' elevation adjustments, then you want to think about MAX Point Blank Range. If its a foxing rifle, then a kill zone on a fox is 3-4 inches diameter. The idea is that you zero it so that your rifle will shoot MAX 1.5 inches high to 1.5 inches low. where it gets to this amount of drop is where your MAX range is.

    I would think more about this than getting an ultra flat shooting round..

    Just my opinion.. whats the rifle used for and what is your max range you want to shoot at...?

    ATB, FF

  3. #3
    Quote Originally Posted by sir-lamp-alot View Post
    just wondering if any of the reloading boffins out there could give me a little info or point me in the right direction. im having a little trouble finding a nice flat shooting load for my .223. it has a 1 in 8 twist which does not like the normal 55gr heads (4" grouping @ 100yrds) so i went up to a 60gr head which gave me the acuracy but not the trajectory. so i had a little chat with my local gun shop and he said use a heavier bullet and that will fly flatter?. so i decided to give it a go and bought a box privi 69gr target ammo and at 230yrds i had a drop of 5.5 inch but terible grouping and my 60gr home loads i was getting a 7.5inch drop. so to be honest i would like to get it even flater which i'm sure i can do and i now dont know if i should be trying to push the 60gr head faster (i'm using 25gr of varget which acording to my data i should be pushing around 2950fps but i dont own a crono) or switching to another weight of bullet and any help would be apreciated as ive just become a dad and time spent with the rifle pressious at the minute and i dont want to waste it playing about to much with loads
    Hi Daniel
    Do you specifically want to go with a heavy bullet you might try going lighter i have some v-max 40 gn and 50gn you can have a go with if you want give me a shout and i will drop them over
    Geordie

  4. #4
    Quote Originally Posted by flyingfisherman View Post
    Heavier bullets will never shoot flatter than lighter ones.. it just defies the laws of physics
    this is the exact agument i had in the shop the chap then went on to try and explain how it works and i wouldnt call my self stupid but i lost him after 5mins but said i would give it a go and it worked dont know how but it did the 69gr bullet flew flatter i have it on paper and yes it is a foxing rifle and i must admit i did slip up a little getting the 1 in 8 twist barrell but i have it and now its time to work with it and make somthing of it. i also see your point about the max point blank range but what i dont want to do is have to think about hold under on that fox which is 50yrds away led dead flat in the grass thinking i cant see him and my general max range would be around about 200 yrds with the odd fox maybe pushing 250 at the very most

  5. #5
    many thanks geordieh ive sent you a pm

  6. #6
    Quote Originally Posted by sir-lamp-alot View Post
    many thanks geordieh ive sent you a pm
    Hi Mate
    i will give you a ring tomorrow are you still on same mobile no
    Geordie

  7. #7
    i will pm you my mobile number

  8. #8
    The faster the bullet, the flatter the trajectory, that part is correct.

    The lighter the bullet the faster it goes, initially, but the further you shoot a lighter bullet will lose velocity a lot more rapidly due to a lack of momentum. This means that a long thin heavy bullet (called high cross-sectional density) will travel further, hold its velocity better and penetrate better at any distance.

    You just have to find the crossover point. Rule of thumb is that if you are shooting further than 200yds you will probably be better off using a 69gr bullet or whatever the heaviest is you can find. Your 1 in 8 twist should accept any heavy weights you can find. I had a 1 in 9 twist 223 and I could not get good results with 55gr either but great up to 600yds with 69gr on targets where hold over don't matter.

    Remember gravity sucks .

  9. #9
    Gravity, as has been said, sucks and the truth is that it sucks the same for everything. If it were not for air resistance then a feather would hit the ground at the same time as a brick if dropped from the same height. In fact I think this was one of the experiments they did on the moon, where there is no air and so no air resistance, though I think they used a hammer rather than a brick. However, on the moon the feather and the hammer hit the ground at the same time.

    In the vertical plane, and speaking in practical terms, a 40 grain and a 70 grain bullet will drop to the ground in the same time. Gravity effects them both in the same way and at the speed at which they are dropping their air resistance is as near the same as to make no difference.

    How "flat shooting" they are then becomes a matter of time of flight in that the bullet which takes longest to reach the target will drop further than one that reaches it more rapidly.

    If we go back to our feather and brick again you can move your arm really quickly to throw a feather while you can throw a heavy brick a lot less quickly to start off. However, the feather very quickly sheds the speed advantage and it isn't long before the brick passes it. At distances beyond an inch or two a brick is flatter shooting than a feather. This is, of course, a very extreme example, but it demonstrates clearly a concept that is also seen with bullets.

    A bullet that starts off travelling really quickly and which will, therefore, be a very light bullet will reach (for example) 100 yards much faster than a slow and heavy bullet and so it will be flatter shooting at these close ranges. However, because it will be shorter for its mass (as the size of the bore of your rifle is a constant and bullet construction is usually similar the only dimension you can increase to increase mass is the length) it will have a lower ballistic coefficient and so it will lose speed more rapidly than the longer, heavier bullet.

    At some point down range the light bullet will have shed a lot of speed and so will be moving more slowly than the heavier one, which will be retaining its speed better, and at this point the heavy bullet starts to become "flatter shooting." From this point onwards there will be an increasing difference in the speed of the light and heavy bullet and it will always be to the advantage of the heavy bullet.

    So, if you are looking to be flat shooting then you need to consider the distance at which you will be shooting. The 223 is a pretty small bullet so it is possible that you are seeing this effect at 240 yards but I would imagine it becomes more important at much longer ranges, certainly with the likes of my 308.

    Not only does gravity suck but at the sorts of velocities we are talking about air resistance is like hitting a brick wall and if you can reduce it even slightly then at longer ranges you reduce your time of flight which, in turn, reduces the amount of sucking gravity is able to do.
    Last edited by caorach; 05-07-2011 at 16:18. Reason: typed "longer" where I should have said "shorter"

  10. #10
    hi try 23.5 of reloader 7 with 40 grain vmax it will do 3614 fps very flat my 1in 9 gets sub 1 inch at 110 yard.good shootin ian

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