7 mag reloading conundrum?

[tazzman]

Good afternoon pyro,

I've learned from experience that lighting changes affect chrono readings. I use incandescent lighting over the diffuser no matter what lighting I shoot under(indoor or out). I found out that my erratic chrono readings all but disappeared.

Cheers,

Phil aka tazzman

 

[Tikkamike]

I guess I should have read it closer, sorry, I just got on a tangent in my head and went with it.

 

[pyroducksx3]

I guess I should have read it closer, sorry, I just got on a tangent in my head and went with it.

I know you were just trying to give me ideas and I appreciate your help. Thanks for giving me possibilities of what could be going on, I really do appreciate the time you took to offer me some help. I was just saying I had expirenced this issue, sorry if my reply came off harsh.

Re: 7 mag reloading conundrum?
Good afternoon pyro,

I've learned from experience that lighting changes affect chrono readings. I use incandescent lighting over the diffuser no matter what lighting I shoot under(indoor or out). I found out that my erratic chrono readings all but disappeared.

Cheers,

Phil aka tazzmancould you explain how to set up my chrono to do this? I am very interested in making my process more reliable. Thank you

 

[tazzman]

OK, this is how I do it.
My Chrony has two measuring gates. They both accomodate a diffuser(which is provided at purchase, of course).
I have installed 1 each incandescent bulb(aka bulbs used for painting(s) display) over each diffuser(c/w socket and switch). Chronys are susceptible to changing lighting conditions and to lighting that is frequency-sensitive, aka fluorescent lighting. Incandescent lighting is not frequency sensitive and produces even lighting(it cancels out frequency-derived lighting influences). This even lighting, according to my results, also cancels out the variables found during daylight measurement sessions. The drawback, of course, is that you require an AC source to provide this even lighting.

If you have power nearby, try this method. If it works(I found this to solve my irregularity problems) then Bob's your uncle. If it does not work, then look at your Chrony. I hope this solution(aka known as simple-to-complicated method) works for you.

Cheers,

Phil aka tazzman

 

[pyroducksx3]

Thanks for your reply, I'm sure I could create some kind of mounting system for thaws lights but if there already a good way please let me know. Like off the rods that hold the diffusers or of the chrono body? Thanks

 

[pyroducksx3]

Well I got shooting today and re-shot those two groups, measured the chrony out to 20 ft sky was overcast. It was a chrono lighting issue it appears. I got 3065, 3030, and 3030 with the first group and with 72 gr of H1000 I got 3037, 3044, 3044. Primers are starting to look a little flat so this is top end. Thanks to everyone who helped

 

[AZShooter]

Thanks for getting back to us. Glad you solved your problem.

Don't forget to add more velocity to your velocity for a chrono at 20 ft depending on the ballistics progam. I crunched the JBM program for a 140 hunting VLD G7 BC of .261 and it added 9 fps. (there is an input for chrono distance which it automatically compensates in finalized calucations)

Hope you get to use this rifle on a hunt this fall.

 

[pyroducksx3]

Actually I was originally going to use swift scirocco bullets but they sorted poorly, like 50% failure. But I had to go the range to test these two berger loads so I decided to do a test on the swifts and I found a load that had an ES spread of 6 and shot a .66" group, so I'm going to run this load this year so I can get off the range and in the field practicing. Final load is 68.5 gr of H1000 150gr swift scirocco II max lenth go ogive of 2.644 and .010 off the lands, velocity is 2956-2962. What me my muzzle velocity be if the chrono was a measured 20 ft while testing?

 

[Jammer]

Do what Mr. Burger says put the bullet on the lands. Don't give it a jump to the lands. Start back at your start loads and work up with the bullet on the lands. makes the power build presser faster.

Jammer

 

[Pistol packer]

looks like you are getting really good advice and glad you picked up on the lighting issue. i have several chronographs but use the chrony some because of the ease. found muzzle blast and lighting the two tempermental issues. the lighting thing you seemed to got ahold of. another way to handle the muzzle blast : i put my chrony down somewhat and let the concrete bench protect it. often the blast hitting the unit is what screws it up and as long as the unit is protected it will register just fine.
even if it knocks off the screens.
the bearing surface would not produce such a drastic change. as long as the bullet is in the barrel the powder will be buring with that slow burning powder, so length of time in the barrel is critical to the total amount of powder burned. the bearing surface (shorter one) would decrease the overall length of time, but very small amount and actually often produces faster velocities because of the lack of friction, although it is very small usually (sort of like moly coated bullets). sounds like you are getting great groups, but you should probably use a faster powder. i agree with the previous comment that IMR 4350 would be the best or at least better as i usually get 2950 with 175 grainers with just mild pressure signs and no jump to lands. even the 300 WM usually performs better with that powder and that is substantially more powder. the really slow powders are for large bullets in really overbore cartridges such as the edge, or RUM's.
keep experimenting and keep talking. always keen to hear from someone's experiences.

 

[Pistol packer]

oh, yeah,
with the 150 sirrocco at 30 feet you would loose about 20 fps.

 

[Pistol packer]

13 fps at 21 feet