6.5 Grendel Load Development

Elvis · Posted: Mon Mar 10, 2014 11:49 pm Post subject: Re: 6.5 Grendel Load Development

so what happens if you shoot group at 400 or/and 600yards and find drop from that then work backwards to find velocity???
then do same at 800....
if you are aiming to get out to 1000yrds you have nothing to loose. get big tall sheet of paper and go to it.

slimjim · Posted: Tue Mar 11, 2014 3:50 am Post subject: Re: 6.5 Grendel Load Development

wiersy111 wrote:

Are there any chrony's rated below 32*?

Nice catch. I've operated mine down to 35 and above 100 without issue. That operating limitation is there because of the LCD display. The LCD material is really a liquid. All LCDs have this temperature operating range limitation. If it gets too hot, there is no control of the material and the display just grays out. If it gets too cold it takes awhile for the display to switch to the next number. In military fighters, we have to use LCD with crystals made for very hot conditions then use heaters for cold weather operations (-20 to -40F). Probably more than you wanted to know. Behind the Chrony display, everything is still operating and captures all your data which can be reviewed. I know of no chrony that doesn't use an LCD display. In cold weather, you may just have to wait longer between shots for the display to update or change strings for every load and review data back in the warmth of your man-cave. The only issue I've had with mine is sunlight getting into the sensor slots and causing false/error readings (chronies work of sensing the bullet breaking the light pattern above it). I built a sunshade to block the sunlight coming in from the side during late morning and near sunset.

slimjim · Posted: Tue Mar 11, 2014 4:11 am Post subject: Re: 6.5 Grendel Load Development

Elvis wrote:

so what happens if you shoot group at 400 or/and 600yards and find drop from that then work backwards to find velocity?

Elvis, this is what I would do when I started as a way to derive velocity...and... why I say a chrony is truth. Most of my velocity estimates done this way were off by 200 fps with one being 400 fps.

PaulS · Posted: Tue Mar 11, 2014 5:37 pm Post subject: Re: 6.5 Grendel Load Development

There is also a margin of error for the electronics in chronographs too. As they cool down the clock runs slower and it runs a bit faster as the temps climb. This shows up as different velocities for the same loads in real cold weather than you get on a hot summer day. Powders will go the same way only not as much as the chronograph unless you are pushing max or near max loads. the level and direction of light over the sky-screens also can make a big difference in the velocity recorded.

The chronographs that the powder and bullet makers use are kept at a constant temperature and use artificial lights to keep everything constant.

wiersy111 · Posted: Tue Mar 11, 2014 6:47 pm Post subject: Re: 6.5 Grendel Load Development

So with that in mind how should I build the data necessary to be able to figure the dope necessary to be able to shoot in temperatures ranging from 0* to 80*?

slimjim · Posted: Tue Mar 11, 2014 7:38 pm Post subject: Re: 6.5 Grendel Load Development

You can still successfully use a chronograph. Those are limitations of the ones around $125. You can go up from there as they have new ones that use field generators that attach to the end of your barrel. Much easier to set-up. Regardless, I wouldn't be without one.

wiersy111 · Posted: Tue Mar 11, 2014 9:01 pm Post subject: Re: 6.5 Grendel Load Development

I am going to stay down in the $100 to $150 range for now.

Pumpkinslinger · Posted: Wed Mar 12, 2014 7:07 am Post subject: Re: 6.5 Grendel Load Development

I'm happy with my Shooting Chrony "Master". I bought the printer to go with mine too.

Both Shooting Chrony and PACT told me that the electronics of the chronograph are unaffected by the temperature but the battery is affected and may cause problems if really cold. They suggested keeping a spare in a pocket where it can stay warm. I haven't looked to see if anyone has an external power supply to address this (assuming you have power at your range). Maybe I need to look into this...

wiersy111 · Posted: Wed Mar 12, 2014 10:29 am Post subject: Re: 6.5 Grendel Load Development

Pumpkinslinger wrote:

I'm happy with my Shooting Chrony "Master". I bought the printer to go with mine too.

Both Shooting Chrony and PACT told me that the electronics of the chronograph are unaffected by the temperature but the battery is affected and may cause problems if really cold. They suggested keeping a spare in a pocket where it can stay warm. I haven't looked to see if anyone has an external power supply to address this (assuming you have power at your range). Maybe I need to look into this...

Cool it looks like the Chrony Master is tho only one I can get locally other than the RCBS. I will probably pick up a Chrony Master Friday.

PaulS · Posted: Wed Mar 12, 2014 4:47 pm Post subject: Re: 6.5 Grendel Load Development

Don't buy the RCBS - they have a consistent problem of burning up the capacitor. They won't admit or do anything to repair the problem. At least when you shoot a hole in your Chrony they will give a discount on a new or reman unit. If you can buy a reman they are as good as the new ones.

Ultimately you have to shoot your gun at the different ranges to gather "dope" for your rifle. Out of the eight different ballistics programs that I have none of them will give you the correct data beyond about three hundred yards - and even within that range none of them are in perfect agreement.

I have one program that is very close to "right on" with my 308 and 3006 out to 300 yards (within a half inch or so) but none are good for pistol trajectory even out to just 100 yards.