Range Report Real life vs. JBM Ballistics questions

[79M1a-texas]

Gentlemen – I need your help. This morning, I shot in a local event 3 relays of 20 rounds for score + 2 sighters @ 600 yards. Temperature was at 60 degree and 40% humidity. Wind was almost zero.
Relay #1 – Nosler CC 168g, Win Brass, RL15 @ 42.5g. My best guess velocity was at 2900 f/s with a 600-yard come-up of 13.0moa based on JBM Ballistics. Real life come-up was 17.75moa
Relay #2 – Nosler CC 175g, Win Brass, RL15 @ 43.0g. My best guess velocity was at 2630 f/s with a 600-yard come-up of 15.5moa based on JBM Ballistics. Real life come-up was 17.50moa
Relay #3 – Berger’s 185g BT, Win Brass, RL15 @ 42.0g. My best guess velocity was at 2590 f/s with a 600-yard come-up of 15.75moa based on JBM Ballistics. Real life come-up was 17.50moa.
Do any of those numbers appear out of whack? I am happy with Relay #3 which produced a score of 199-9X. However these numbers are bothering me. I zeroed with scope yesterday at a 100-yard zero. Scope is a NF NXS 12x42.

 

[Rob01]

Re: Real life vs. JBM Ballistics questions

If you are guessing at velocity then you won't get good info from a ballistics program. Garbage in, garbage out. I have used JBM for years and the most I have been off is about .2 mils at 1000 yards which is about 7". Chrono and rerun the numbers and I bet they are close to your real world.

 

[ewoaf]

Re: Real life vs. JBM Ballistics questions

so you guessed your velocity wrong?

I do this as I dont have a chrony either. What I do is take my best guess and shoot out over 1000yd. I then go home and take my real life dope and play with the velocity until JBM feeds me the real life come-ups. This gives me my real world velocity that I can use later on with different enviro, etc.
Make sure you select the bullet from the library with the (Litz) behind it as this will use a very accurate G7 BC. If you give this program good input, it will give you awesome output.. It's some good friggin dope.

 

[doc76251]

Re: Real life vs. JBM Ballistics questions

If nothing makes sense on a ballistic program calibrate your turrets and things usually work out.

Cheers,

Doc

 

[BobinNC]

Re: Real life vs. JBM Ballistics questions

My best guess, is you guessed wrong on velocity, and maybe you guessed wrong and used G1 BC's, instead of G7 BC's, and is the scope height your using correct, ditto temp, humidity, and altitude, can all have a bearing.

Not saying you did wrong, but garbage in equals garbage out. And some of the most important inputs, are your true velocity, G7 BC's and altitude. Get those wrong, and you got gonzo. Get those right and JBM is pretty close.

Also are you sure your turrets are MOA, and not IPHY, or the other way?

Bob

 

[79M1a-texas]

Re: Real life vs. JBM Ballistics questions

I guessed my velocity based on the many others you have listed their dope in the Reloading Section. Does my powder weight that I listed along with velocity appear to be heavy? Also, Nightforce's turrets are MOA.

 

[jrpilot]

Re: Real life vs. JBM Ballistics questions

My 168 Nosler CC load is 44.5 RL-15 26in barrel. Im getting 2726fps @ 70degF. I wouldnt think you would be getting 2900fps with 42.5gr.

 

[jwoolf]

Re: Real life vs. JBM Ballistics questions

This is interesting. I've been working on a load for my 300wm.

I went to the range and printed groups until I found the right node and all the bullets were flying through one hole.... cronod them.... crono said 2720fps average .... well, I think the crono is WRONG.

I plugged all the data into JBM and it gave me my come ups out to 1000yds.... they were WAY WAY off but, I fault the crono in this case.

This is not the first time this has happened.

JBM is saying that my load is going about 2860fps and, to me, that is way more believable. I was at 27.0 moa up from my 100yd zero and this load was shooting VERY well and consistent.

All the come ups I ended up with match this velocity.

FWIW: my load was 220gr SMK over 75.7gr H1000 at about .010 off the lands in a 26" 1:10 barrel.

 

[MALLARD]

Re: Real life vs. JBM Ballistics questions

jbm works well but you have to put in the correct info. Im sure you can find someone at the range with a chrony that will let try it, but you could measure your drop and plug in to.