Velocity Calculation

[Cinco Peso]

Is there a way to calculate velocity for a particular load. My loading manual shows a minimum and maximum loads and provides the velocity and pressure. I start with the min, but as I increase from there how can I calculate velocity?

[Litl Red]

Sure, you can interpolate the expected MV for a powder charge between the min and max.  It will be reliable as the MVs shown for those min and max charges.    http://www.eng.fsu.edu/~dommelen/courses/eml3100/aids/intpol/

Only problem is that your powder, in your mix of cases, fired by your primers, in your gun, at your altitude, at the temperature and pressure when you shoot, etc etc etc, with your crimp, and.......  we ain't halfway there....  etc 

The best way to get your info is a $100 chronograph.  It is awesome how much real info can tell you.  Chronographs can save you from wasting a bunch of time and money, especially if you like to tune or experiment.

BTW, it is entirely safe to try powder charges that are interpolated.   But that doesn't mean that extrapolation is safe at all.  In fact it's obviously unsafe to try charges greater than the maximum recommended, but going less than minimum is often unsafe.  https://www.google.com/search?q=extrapolate&sourceid=ie7&rls=com.microsoft:en-US:IE-Address&ie=&oe=&gws_rd=ssl     

Interpolation works out results between your min and max charges.   Extrapolation works out results below min and above max.   And with powder working the way it does, it's not safe to load above or below the recommended charges for the listed components.   

[Cinco Peso]

I appreciate your response and will calculate using the formula.
As per the chronograph can you recommend one?

[Litl Red]

I appreciate your response and will calculate using the formula.
As per the chronograph can you recommend one?

I've got personal experience with Chrony and Pact.  They were both priced less back when chronographs were affordable for the first time.   A buddy shot my Chrony and that wipes 'em out.  I was about to buy another (with my buddy's money) one when I noticed the Pact used wires to keep the machine out of the line of fire.   It turns out the Pact has another feature that is even more significant.  It's sensors are the farthest apart and that makes it a touch more accurate and a bit easier to align for accurate readings.   

I've used the least expensive Pact for over 20 years now.   I had a chance to compare it with a "professional" brand once and it read the same.   That professional set happens to be the only other chronograph I've ever seen at the range(s) in 20 years, btw. 

A lot of the higher priced ones, and deluxe versions have printers and do heavy duty computations.   They also offer data bases and such.   Truth is, average velocity, max variation, standard and average deviation is about 100% of the really useful info and every one of them tell that without delay.   Having a printout would be nice, but a couple that have printers look like their printout formats don't include all 4 of the above.   

It's amazing how valuable they are to working out loads.  I recently bought a 223 that shoots every powder I've tried in it at least 100fps faster than the factory recipes predict.  Some are even more.   I've never run into any gun like that before.  Thanks to the chronograph info, I know it's faster, and no other before was faster.   So thanks to the chronograph info, I load one powder 2 grains below factory max and know I'm getting about 50fps higher velocity.   If I threw in that 2 grains, the velocities would be borderline 22-250.   And possibly over max pressures.   

Without the chronograph, I wouldn't have been able to "wildcat" a 1000yard target 22-250.   VLDs had just started showing up and it dawned on me that a quick twist barrel on a 22-250 might work for the long range matches that were just then seeing the serious magnums.   Chronograph info is way more valuable than most people imagine.  At least for honestly serious results. 

[JeffinTD]

I've used a buddy's older chronograph which was equipped with a printer. Nice to not have to write down velocities when you are shooting a bunch of 5 shot strings with different loads. Also nice to have velocity displayed on the bench.

I recently bought the Caldwell delux kit, but haven't used it yet. I chose it because it links to a smart phone with a included wire so you can see the velocities at the bench and can text or e-mail the string. I thought that would be as handy as the ones with a printer, but without the hassle of having a printer at the range (which needs batteries, spare paper, and so on).

Also the kit comes with a tripod, normal screens, and LED screens for use indoors. Also comes with a nylon bag that everything fits in. Should be a lot handier than having the chrono in a box, a printer in another box, plus a seperate tripod to pack to the range.

Hope to get to try it out on my next set of days off.

[Litl Red]

Would someone with a printing chronograph PLEASE post a photo of the printout.  please

Every search through the sales info on them shows nothing.  It's like they don't want anyone to see what they're buying.

There was a Utube of one in action some time back that flashed the printout, but didn't show it.  However, the blur that swept by looked like a bunch of ballistic computations that didn't show AV, SD or AD.  Really...    

I really can't see buying something to find out what it does.   Like ObummerCare....  

A printout would be very useful, unless it doesn't include AV, SD or AD.

edit:  10:42am  ......   found a still of the printout that flashes by.  They obviously don't have just this format.  Anybody know how to find out what the more useful one looks like?   There is a more useful one, right.

 

[Trailrider]

The chrongraph I've used for years, which has two channels and a printer is the Oehler 35P. For awhile they had discontinued production, but I recently saw an ad in one of the gun magazines (I think it was Handloader), saying they were back in production. I don't know how much they cost, and it may be too much and overkill for you, but combined with their Skyscreen detectors, they will give two readings which can be compared to determine if the reading is correct or not. (Sometimes, glare or glint off a jacketed bullet or if the sun angle is bad can give you false readings with a single circuit. The second circuit should compare with the first one within +or- 10 ft/sec or so.) The others may give you good service for casual use, but if you are going to do a lot of testing, I'd recommend the 35P.