Working out ballistics!

[toxo]

I'm slightly cocerned that this may be a really stupid question but...

My 17 Hornet is zeroed at 150yds at around 3550fps.

I'm aiming to find a load that's a bit under HMR for quiet night time bunnies.

The question is this. Using a lower charge giving say 1550fps and shooting from say 100yds because that's roughly where I want to be, is it possible to work out the bullet drop in advance?

I ask because I was surprised (and frustrated) at the time it took to find the quite large target. I know I could have started off a lot closer to the target and worked back but my logical if somewhat mathematically challenged mind says there should be a way to work it out but I can't do it.

 

[User00033]

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

 

[Eric the Red]

Assuming you have an accurate load - you can scenario run in most applications - Strelok, Ballistics ARC, etc. to look at drops.

 

[Cottis]

In a word, yes.

Use an online ballistics calculator to figure out the trajectory of your round based on the bullets ballistic coeffecient (you will this online if you hunt around. It is 0.125 for .17HMR but not sure on Hornet) the MV, height of scope from barrel and some other basic parameters. This will give you the info you need at whatever measured intervals you want.

If you want real time (to the yard) holdovers for elevation or windage, donwload Strelok App on your phone. It is bang on as long as you put the right info in. It amazes me what my HMR can do in benign conditions with the right info input. It will tell you bullet drops/holds and what to allow for windage as long as you give it the correct info for the current conditions.

 

[toxo]

Sorry guys, you'll have to walk me through it. I have Strelok and a couple of others. I'm zeroed at 150yds with 3550. I then fire a low load from 100yds that the Chrony says is 1550 but it's not on the target at all. Without changing my zero, how far below my 3550 zero will the bullet hit?

 

[toxo]

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

Thanks for the reminder Dodgy. I used this to establish that the little 17 grain bullet would still be stable at subsonic speeds in a 1:9 twist.

 

[NigelM]

Done some rough sums with a few assumptions.

20 grain bullet with BC of 0.200 zero'd at 150 yds at 3550fps will be 0.4" high at 100 yds

Same bullet at 1550 fps needs to 4" higher at 100 yds (dial up 4 MOA) to hit the same 150 yd zero

Leave the zero the same at 0.4" high at 100 yds and you POI is going to be 6" low at 150 yds.

 

[Whitebeard]

Toxo my go to rifle is a 17 Fireball, 20 grn bullet at 3950fps, with my 17 dedicated Wildcat Evolution mod it is as quiet as my mates 17HMR

Ian.

 

[NigelM]

Just as a matter of interest, what have you done to load down to 1550 fps. Reducing case fill is a notoriously dodgy practice and can result in a bigger bang than expected due to the volume of air left in the case. The only safe way to do it is change to a very slow burning powder. I don't know much about the subject other than people have got hurt trying. Wouldn't want you to get blown up.

 

[Tis1979]

I can understand what your trying for but really the speed your talking about it's not worth it, your not getting rid of the sonic crack unless you drop below 1125 fps so just use sub-sonics. Sorry if I've missed the point here.

.regards Tristram

 

[takbok]

Toxo, I think you're asking how to work out where a slower load will shoot compared to the faster load. A ballistic calculator won't be able to help you with this. You're going to have to remember the different scope settings for both loads.

Ballistic calculators help to determine the trajectory of a bullet with a known velocity and ballistic coefficient, they cant predict where 2 different loads are going to print on the target relative to each other.

Are you using pistol powder for the 1500 fps load?

 

[kenbro]

Just as a matter of interest, what have you done to load down to 1550 fps. Reducing case fill is a notoriously dodgy practice and can result in a bigger bang than expected due to the volume of air left in the case. The only safe way to do it is change to a very slow burning powder. I don't know much about the subject other than people have got hurt trying. Wouldn't want you to get blown up.

Trailboss is safe in a 17 Hornet and even if you don't get subsonic, it's still very much quieter than full loads.
Try heavier bullets too.
Blue Dot can be temperamental!
Ken.

 

[NigelM]

Toxo, I think you're asking how to work out where a slower load will shoot compared to the faster load. A ballistic calculator won't be able to help you with this. You're going to have to remember the different scope settings for both loads.

Ballistic calculators help to determine the trajectory of a bullet with a known velocity and ballistic coefficient, they cant predict where 2 different loads are going to print on the target relative to each other.

Are you using pistol powder for the 1500 fps load?

Try the Norma Ballistic Calculator on their site. It's in the form of a graph, really easy to fiddle with and the graphic output is very east to understand. I don't use it for accuracy as it isn't particularly, but for a big picture fast view of this sort of question it's really easy to understand. Easy to compare what the OP is asking.

Ballistics Program - Norma

 

[Edinburgh Rifles]

Toxo, I think you're asking how to work out where a slower load will shoot compared to the faster load. A ballistic calculator won't be able to help you with this.
You're going to have to remember the different scope settings for both loads.

Ballistic calculators help to determine the trajectory of a bullet with a known velocity and ballistic coefficient, they cant predict where 2 different loads are going to print on the target relative to each other.

Are you using pistol powder for the 1500 fps load?

Beat me to it
what you can do is try to tune a load to a point of impact if that is more important

You may want to try a calibre matched moderator

I spent 5 years cleaning up urban foxes with a 22WMR until I ran out of stupid ones that would come inside 150yds
After that I needed a lights out cartridge capable of an easy 200yds, relatively quiet and easy to load
Didn't want a .17 cf

I went with a .222 with a moderate load using 50-60gr and a oversized T12 scout
Turns out it was no more noisy and sometimes appeared less noisy than the 22WMR

 

[Orion]

The only safe way to do it is change to a very slow burning powder. I don't know much about the subject other than people have got hurt trying. Wouldn't want you to get blown up.

Not necessarily. Hodgdon Trail Boss is a relatively fast burning but high bulk powder that is ideal for experimentation in low velocity or subsonic loads. As an example, Hodgdon advise filling the case to the calculated base position of the bullet as a starting point, and then reducing the charge weight until the bullet dips below the subsonic threshold!

 

[Laurie]

Just as a matter of interest, what have you done to load down to 1550 fps. Reducing case fill is a notoriously dodgy practice and can result in a bigger bang than expected due to the volume of air left in the case. The only safe way to do it is change to a very slow burning powder. I don't know much about the subject other than people have got hurt trying. Wouldn't want you to get blown up.

You have this totally a*se about face I'm afraid. To go to a light, low velocity load in any cartridge, one always goes to light loads of faster burning powders. A bit faster burning grade compensates for the low fill-ratio and consequent airspace. So H4895 is used in Hodgdon's 'Youth Loads' in a whole bunch of cartridges that would oftentimes use slower powders. Likewise in the days when 200 yard competition was very common in the USA and the 308 was still young, light loads of Hodgdon H322 were used with relatively heavy match bullets of up to 190gn - with very good results too according to the late Ken Bird in Handloader magazine.

What you are getting confused over is true (very over bore capacity) magnum cartridges such as the Weatherby Magnums which employ exceptionally slow burning powders in any event. It was found under certain very rare circumstances that reducing loads too much in these very roomy cases of the standard super-slow burners, result in rifle wrecking detonations believed to be due to pressure wave build-ups in the case. Actually, one can download these large cases very successfully, but again by going to very much faster burning powders than used in the full-house loadings.

Even where a detonation event is unlikely, reduced loads of slow powders in these big cases can see wildly inconsistent pressures, velocities, and performance. So if you look at the data-sets for the real big b*gg*rs in loading manuals, starting loads are often not that much below maximum in percentage terms and there will be a footnote saying they must not be reduced further.

 

[toxo]

I shoot mainly at night for bunnies with an Archer behind a 24x scope. I won't take the shot unless it's a clear no miss head shot. My 22lr will only give me this to around 65yds at night. My CZ 527 in 17 Hornet is scary accurate but very loud and blows up bunnies even using the little 17 grain vmax (which I'm trying hard to use because Henry Krank sells em for £5.50 per hundred) My normal load is 9 grains of Lilgun because that's all I had. Then I managed to get to the RFD and got hold of some Trail Boss. Reading that a load of TB is about the same as HMR that's where I started and last Saturday was the first test.
I loaded 3 rounds each of 2 gr/ 1.8 gr/ 1.6 gr/ 1.4 gr.
My buddy took the pics and we got mixed up. This first pic was either the 2gr or the 1.8gr. Didn't bother shooting the 1.4gr.




The noise level was great. I'm using a Gen V Hardy but don't like it. It's not cal specific and they quote between 17 and 30 cal. When I can afford it I'll also get a Wildcat specific. Don't know if it'll be the Evo - I believe they've just come out with a new one, Panther maybe?
I'm well chuffed at getting somewhere I want to be.
I've worked out that 1800fps will give me somewhere near less than a half inch low at 50yds and an inch high at 100yds with an 80yd zero. May not end there but it's a starting point to aim at.
My farmer asked me to sort out the field next to the house first. Huge warrens about 90 yds away from cover and being so close to the house meant I couldn't use the Hornet. I'm hoping the new loads will sort that.

Ha Ha! I only read the last few posts after I wrote this. Thanks for the input guys.

 

[NigelM]

You have this totally a*se about face I'm afraid. To go to a light, low velocity load in any cartridge, one always goes to light loads of faster burning powders. A bit faster burning grade compensates for the low fill-ratio and consequent airspace. So H4895 is used in Hodgdon's 'Youth Loads' in a whole bunch of cartridges that would oftentimes use slower powders. Likewise in the days when 200 yard competition was very common in the USA and the 308 was still young, light loads of Hodgdon H322 were used with relatively heavy match bullets of up to 190gn - with very good results too according to the late Ken Bird in Handloader magazine.

What you are getting confused over is true (very over bore capacity) magnum cartridges such as the Weatherby Magnums which employ exceptionally slow burning powders in any event. It was found under certain very rare circumstances that reducing loads too much in these very roomy cases of the standard super-slow burners, result in rifle wrecking detonations believed to be due to pressure wave build-ups in the case. Actually, one can download these large cases very successfully, but again by going to very much faster burning powders than used in the full-house loadings.

Even where a detonation event is unlikely, reduced loads of slow powders in these big cases can see wildly inconsistent pressures, velocities, and performance. So if you look at the data-sets for the real big b*gg*rs in loading manuals, starting loads are often not that much below maximum in percentage terms and there will be a footnote saying they must not be reduced further.

I did mention that I didn't know much about the subject Laurie. I was just worried that the OP had got to the low velocity buy merely reducing charge weight which I understand can be dangerous under some circumstances. Just worried about the OP.

Thanks for the education.

 

[Sauer90]

Yet to come across real evidence of SEE.