chrony MV!!

[PELOW300WM]

hello reloaders!! need some help! I have a Remington 700 sps tactical aac-sd 20" barrel.
I have loaded up some hand loads, (168gr nosler ballistic sliver tips, hornady brass, cci primers and 39gr of H4895) my 3 shot groups are just under an inch at 100 yards. my problem is the load data states a MV of 2400fps I know I know I have a shorter barrel so it would be less. my issue is I took out my cadwell chronograph to get my actual MV so I could input it to my ballistic calculator and I'm shooting through the middle of the window and all I'm getting is 1263fps! am I missing something and that's the true MV or is my chrony screwed up? thanks.gun)lightbulb

 

[gohring3006]

Chrony is screwed up. I would use drop data to verify.

 

[PELOW300WM]

thanks for the quick reply! I will have to load some more and do that.

 

[gohring3006]

The biggest problem with the drop data test is using a true BC.
I would look for some data from someone like Bryan Litz for BC data. I wouldn't use Noslers BC data...

 

[PELOW300WM]

ok I will look into it!

 

[Dr. Vette]

On occasion my Chrony will do that. Be sure that 1) the 9V battery is new, 2) you don't have direct sunlight on the unit, and 3) you try turning it off and then back on if this happens. One of these 3 usually fixes the problem.

 

[Wachsmann]

Today must have been a bad day for chrono's...I took out some new loads that I had made up and was hoping for some consistant results. They were a reproduction of some I had on another day that yielded fair results. 57.6 grains of retumbo pushing a 140 berger in the 6.5x284. Last time I shot them they gave a .7 to .75 inch group and was running in the 2960ish range. Well today I went out after cleaning brass, doing all the prep work, making sure all loads were same charged weight etc..etc..etc.. I shot my first load cold bore was 2949...Second load was 2965...Ok this is not real bad then the third 3016...fourth 3012...5th 2989, 6th 2989...So now the ES and SD was shot to hell which I was hoping for some good numbers. Was shooting at 200 yards and they printed about 1.5 to 1.7 inch group...I measure out side of bullet holes...So I thought well there printing about what I would expect from when I done this at 100 yards a few weeks ago. Nothing great but the velocity variations really chapped me. So next I have a set of rock I shoot at on a side hill that are depending on where I park and shoot its about 1000 yards to 1030 yards. Now I took the average of the shots and put in on my shooter app and dialed for the largest rock that I like to shoot at. I also thought it was about 1050 yards from where I was at. Range finder only get me to about 950 on a good day..Well I shoot and I'm shooting over the rocks...So I drop it down to the 1030 and dial I think was 23.2 so I just do 23.25...I hit the rock. Then I went 3 for 3 on the next 3 shots. Rock is about a 3MOA long and 2MOA tall. Next I know there is another small rock that about 1 to less than 1MOA that is 15 yards below where the bigger one is. This I have marked off and ranged when I was spray painting them. Well I dialed for it and hit it as well 2 time. So came back home and long story short I figured my chrono is about 30fps off or can vary about 30+fps. I worked through the Gseven page adjusting velocity to check my drops and finding that my bullets are running at 2945ish for the dope that I used and what I measured out on goggle earth. Probablly need to get exact cordnates on a gps and just put them in and get a range that way as well. Also measure this on google earth from where I parked at today and the rock I was shooting its 1030 to the top rock..... 2 thing I need, a beter chrono and a better range finder because it leaves me guessing. Its always good to proof out you data so you know what is happening. I think I'll be saving up for a magneto speed next and one of the sig kilo's. Also read on the chrono box that accuracy on the chrono is 1%. So there is my 30 plus FPS I'm probably seeing.

 

[dsculley]

When using a chronograph you have to remember that at best they provide a good estimate of MV. No matter what my chronograph says, I always trust my target. If I am shooting what to me are acceptable groups then it really doesn't matter what the chronograph says.

I do use a chrony for working up loads, primarily to help watch for over pressure loads. After I identify my load, then I can use my target to determine the standard deviation for the load, but that SD tells me what I can expect my group size to be at other ranges not the SD of the MV. Since it is target engagement that really matters, I feel this is a good method.

I am not concerned with the ES of a particular string of shots because that has no real bearing on the expectation of ES in future strings.

FWIW,

 

[rcoody]

nothing worse than a bad croney when you are doing load development. It will screw up your head. Better no croney than a bad one.

get a magnetospeed.

 

[Rich Coyle]

hello reloaders!! need some help! I have a Remington 700 sps tactical aac-sd 20" barrel.
I have loaded up some hand loads, (168gr nosler ballistic sliver tips, hornady brass, cci primers and 39gr of H4895) my 3 shot groups are just under an inch at 100 yards. my problem is the load data states a MV of 2400fps I know I know I have a shorter barrel so it would be less. my issue is I took out my cadwell chronograph to get my actual MV so I could input it to my ballistic calculator and I'm shooting through the middle of the window and all I'm getting is 1263fps! am I missing something and that's the true MV or is my chrony screwed up? thanks.gun)lightbulb

Your chrono may be too close to the rifle.

 

[Wachsmann]

Well my bad day of shooting on the chrono turned out to be my on mistake. My little girl came down while I was reloading and wanted to point out, touch, and look at everything I was doing. So in my haste I seated the bullets only slightly down in the case so she would not dump them over. She is 3 and always wants to know what I'm doing. I left almost all the bullets at .006 off the lands. Usually I think I'm about .100 of jump. I came home and had some more bullets out that I had seated before and noticed how much longer these were. So hopefully my load will settle back down with velocity and ES. Some of those loads showed some pressure also. The ones that were running over 3000fps.