velocity calculator

[Guest Scotland Rifles]

Hi Guys.

 

is there an easy use/setup calculator on the web,

 

i just wanted to work out the following.

 

1, a 40 gr bullet in .20 cal

 

2, being pushed down a 20" cooper 1/12 twist barrel with the following loads.

 

1. load 1 is with 23.5 gr of rl10x

 

2, load 2 is 24.5 gr of rl10x

 

3, load 3 is with 25.1 gr of rl10x.

 

i am not that interested with speed , but accuracy is the one I'm after, i would simply like to know the velocity i could be getting from the above data.

 

thank you

 

bob.

 

PS: if anything out runs it no matter what load im using, i will give up varmint shooting

[Vermincinerator]

Bob a velocity calculation is just that a calculation, there is no substitute for a good chrono reading and for any long shots where dialling in is required accurate velocity input is essential.

 

Ian.

[Guest Scotland Rifles]

Bob a velocity calculation is just that a calculation, there is no substitute for a good chrono reading and for any long shots where dialling in is required accurate velocity input is essential.

 

Ian.

 

 

Hi Ian

 

thank you. i think a chrono is the next thing to add to the list as well as a new 6ppc and a new scope.

 

bob.

[pat]

Bob,

 

If you don't have an interior ballistics simulator, try the following...

 

Since the powder that you are using is faster than optimal you should get slightly higher ballistic efficiency than "normal". I'de say about 23%-24% ballistic efficiency from the setup. RL10X yields 4000kJ/kg and you're using around 24gn of powder. There are about 15450 grains in 1 kg, so your powder should release about 6.212 kJ. At 24% efficiency that yields 1491 joules or 1099 lb/ft. You can now multiply by 450250 and divide by 40gn to get the square of the velocity.... taking the square root yields 3517fps. That would be quite respectable from a 20" barrel. The only problem you may encounter is that the powder may be too fast and you may get pressure problems.

 

Since you were looking at an upper weight of 25.1gn RL10X I'll run a QL sim with a 20 cal cartridge that will take that... 204 Ruger will at a fill ratio of 101%, so just about right for a full case! Unfortunately that predicts over 70,000 PSI which won't do the brass, barrel, action or your sanity any favours. Backed down to 23.5gn will give a 95% fill ratio and 57900 PSI, on the edge but sane-ish. Velocity prediction at that 3496 fps, so the above calc wasn't too far out! But slower powder might be sensible.

 

Top powders seem to be IMR 3031, Win 748, IMR 4895, RL-17 but they run around 106% fill ratio. Interestingly BL-C2 looks promising at 98.9% fill. The old faithful H322 is also there at 97.4% fill. If you like Viht powders the top option seems to be N530 but it's a fair way down in terms of speed ("only" 3500 whereas 3031 looks like 3580). N530 works well in a PPC sized case with 40gn bullets and longer barrels....

 

You may also like to consider dropping a grain worth of bullet weight and go for the 39gn Sierra. The 40gn Hornady is a barsteward to stabilise and you'de do well to get it to group out of a 1-12 twist 20" barrel. The 39gn Sierras work well, seem to stabilise better and seem to get positive press from everyone who has tried them, well if you ignore the "IF you can get any" bit, LOL

 

Hope this helps,

 

Pat.

[Guest Scotland Rifles]

Bob,

 

If you don't have an interior ballistics simulator, try the following...

 

Since the powder that you are using is faster than optimal you should get slightly higher ballistic efficiency than "normal". I'de say about 23%-24% ballistic efficiency from the setup. RL10X yields 4000kJ/kg and you're using around 24gn of powder. There are about 15450 grains in 1 kg, so your powder should release about 6.212 kJ. At 24% efficiency that yields 1491 joules or 1099 lb/ft. You can now multiply by 450250 and divide by 40gn to get the square of the velocity.... taking the square root yields 3517fps. That would be quite respectable from a 20" barrel. The only problem you may encounter is that the powder may be too fast and you may get pressure problems.

 

Since you were looking at an upper weight of 25.1gn RL10X I'll run a QL sim with a 20 cal cartridge that will take that... 204 Ruger will at a fill ratio of 101%, so just about right for a full case! Unfortunately that predicts over 70,000 PSI which won't do the brass, barrel, action or your sanity any favours. Backed down to 23.5gn will give a 95% fill ratio and 57900 PSI, on the edge but sane-ish. Velocity prediction at that 3496 fps, so the above calc wasn't too far out! But slower powder might be sensible.

 

Top powders seem to be IMR 3031, Win 748, IMR 4895, RL-17 but they run around 106% fill ratio. Interestingly BL-C2 looks promising at 98.9% fill. The old faithful H322 is also there at 97.4% fill. If you like Viht powders the top option seems to be N530 but it's a fair way down in terms of speed ("only" 3500 whereas 3031 looks like 3580). N530 works well in a PPC sized case with 40gn bullets and longer barrels....

 

You may also like to consider dropping a grain worth of bullet weight and go for the 39gn Sierra. The 40gn Hornady is a barsteward to stabilise and you'de do well to get it to group out of a 1-12 twist 20" barrel. The 39gn Sierras work well, seem to stabilise better and seem to get positive press from everyone who has tried them, well if you ignore the "IF you can get any" bit, LOL

 

Hope this helps,

 

Pat.

 

 

Pat,

 

thank you, you are a star mate, i have dropped the load a bit and i can 1 hole a 3 round group with the 40s, but i have just picked up the 32gr's and i will see how they go in it,

 

i will read and digest your calculations,tap my fingers a few more times and do a load test soon as i can tack 5thou of the bottom of my FL die, and get back to some shooting

 

kind regards

 

bob.

[Guest Scotland Rifles]

Pat,

 

thank you, you are a star mate, i have dropped the load a bit and i can 1 hole a 3 round group with the 40s, but i have just picked up the 32gr's and i will see how they go in it,

 

i will read and digest your calculations,tap my fingers a few more times and do a load test soon as i can tack 5thou of the bottom of my FL die, and get back to some shooting

 

kind regards

 

bob.

 

 

Pat.

 

I have an up date for you (no chrono yet but the 32 gr hornadys are stunning,) i had a chance of a late in the day shooting session yesterday so popped out to try the 10 i loaded up,

 

all i can say is i would not like to be down range with this wee beastie, running 25gr and the same brass/primers i thought i was seeing things, 3 shots to get on target then all 7 in a 10mm ragged hole at 100,

 

i have now set the shot zero for the 40's at 1.5" high at 100 yards and i managed to hit a can of lager out at 250 yards first time.

 

so just how good the 32's will be remains to be seen later this month. or sooner when i run out of 40's.

 

bob.

[Deserttech Europe]

what a waste of a can of lager, I hope it was empty ....

 

good shooting.

 

 

DTA

[Chris-NZ]

Hopefully it was only a can of Fosters.

 

That .20 sounds a good toy. Should have a good splat factor at that velocity, and certainly the accuracy is there.

 

Chris-NZ

[Guest Scotland Rifles]

what a waste of a can of lager, I hope it was empty ....

 

good shooting.

 

 

DTA

 

what a waste of a can of lager, I hope it was empty ....

 

good shooting.

 

 

DTA

 

 

well lads it was a blue can of fosters and it was full.

 

the bullet seems to work extremely well it open everything up like a time of tomatoes have exploded, stunning on fox destructful on bunnies and down right disgraceful on cans of beer,

 

bob.