Anyone ever see this; big differences between JBM and FFS?

[TheGerman]

Was trying to make a print out range card for different temps/altitudes for my 22LR to keep in the data book.

I put in the exact data in setting up a rifle/bullet/turret profile in FFS as I do in JBM. Exact same environmental, zero, exact same bullet velocity, BC, etc and then run a simple range card.

By 200 yards, JBM is already .6mil different in elevation (.6 less than FFS) even though everything is 100% identical. I know from shooting it literally everyday, that the FFS data is undisputed.

It isn't until I basically just keep reducing the BC in JBM manually from .172 to .118 that they then match up 99% of the way. Mind you, this isn't 'truing' published BC vs shooting BC, but rather, just calculator input vs calculator input straight across the board.

Usually any straight input data I've put into other calculators are always .1 or so different, but this is a huge swing that started at basically 50 yards from a 25 yard zero. Is JBM just not that great, or whats the deal?

 

[pyrotechnic]

My understanding is that FFS isn't a straight up point mass solver and uses some different methods that I haven't read up on. JBM is a point mass solver, so it just references a G1 (or whichever you select) drag curve and scales it by your BC.

From Mach 0.7-1.3 these drag curves change drastically. Since .22LR projectiles are in this velocity range, it's going to be super sensitive to any changes in inputs. This is also why the point mass predictions don't do so well at ELR ranges when the projectile's start hitting that Mach 1.3 range. I don't know what voodoo FFS has going on, but it doesn't surprise me that you're getting different results.

This probably wasn't much help.

 

[Rocketvapor]

I use "http://www.shooterscalculator.com/ballistic-trajectory-chart.php"
since I can see several bullets/loads at the same time.

But, it is BROKE now.

 

[Deleted member 113831]

Was trying to make a print out range card for different temps/altitudes for my 22LR to keep in the data book.

I put in the exact data in setting up a rifle/bullet/turret profile in FFS as I do in JBM. Exact same environmental, zero, exact same bullet velocity, BC, etc and then run a simple range card.

By 200 yards, JBM is already .6mil different in elevation (.6 less than FFS) even though everything is 100% identical. I know from shooting it literally everyday, that the FFS data is undisputed.

It isn't until I basically just keep reducing the BC in JBM manually from .172 to .118 that they then match up 99% of the way. Mind you, this isn't 'truing' published BC vs shooting BC, but rather, just calculator input vs calculator input straight across the board.

Usually any straight input data I've put into other calculators are always .1 or so different, but this is a huge swing that started at basically 50 yards from a 25 yard zero. Is JBM just not that great, or whats the deal?

In JBM for 22LR you use the RA4 drag model, not G1.

 

[ZiaHunter]

I believe both FFS and Coldbore use the Pejsa ballistic engine. I run both and have done head to head tests at Gunsite out to 2200 and solutions were virtually identical. Over the years tried a number of phone based apps as well as a Kestrel 4500AB and never use them anymore and exclusively use FFS now. CB and FFS only use G1 and still provide the most accurate solutions at ELR ranges. FFS's functionality especially when tethered to a LRF has no peers.

 

[Lowlight]

3DOF vs 4DOF
Point Mass be MPM

I would agree with using the other 22 value in JBM it’s a good clean program with no author based flourishing to add in missing pieces trying to make it work.

it’s a solid program, the others are better FFS CB1 TRASOL the programs that use the Pejsa changes are better than the McCoy stuff

 

[LastShot300]

I believe both FFS and Coldbore use the Pejsa ballistic engine. I run both and have done head to head tests at Gunsite out to 2200 and solutions were virtually identical. Over the years tried a number of phone based apps as well as a Kestrel 4500AB and never use them anymore and exclusively use FFS now. CB and FFS only use G1 and still provide the most accurate solutions at ELR ranges. FFS's functionality especially when tethered to a LRF has no peers.

CB uses G1 and G7 and it's not a Pejsa solution (the full detail is on Patagonia website) FFS only uses G1

 

[LastShot300]

3DOF vs 4DOF
Point Mass be MPM

I would agree with using the other 22 value in JBM it’s a good clean program with no author based flourishing to add in missing pieces trying to make it work.

it’s a solid program, the others are better FFS CB1 TRASOL the programs that use the Pejsa changes are better than the McCoy stuff

Hopefully we can put our hands on Genesis pretty soon, or at least when Gus and Theis are done with its development.

 

[Lowlight]

Genesis is nice I am using it,

It's so close to CB1 it's feels familiar

it is Pejsa based, it not like FFS because it's MPM, but it has elements which is why it does some thing better, he just wants all the credit

Gus is being Gus, LOL

 

[Lowlight]

Just Gus...

note the AI Hat in Argentina, Malvinas, I don't know that girl.

 

[LastShot300]

View attachment 7527913

Just Gus...

note the AI Hat in Argentina, Malvinas, I don't know that girl.

Is the girl ignoring you? AI in Malvinas country LOL how come they didn't kill you? what about Gus hat? ain't it cool?