High standard deviation??

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GcG166

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Took my rifle out shooting today with handloads I recently did development for and came up with a load that grouped under a half moa at 200 yards. Today I took out the chronograph to get a velocity on these and the velocities were all over the place:

2680
2751
2864
2853
2918
2891

Along with 3 error messages

I shot at 340 yards today and got a vertical spread on a 7 round group of about 2.5 inches (1.3" vertical 6 shot group excluding 1 round) . I didn't feel I was shooting to my fullest potential so I thought the grpupi g wa pretty good for the day. The group shot and measured speeds were ifferent rounds of my load. Could my chronograph be off? There was a chassis switch between development and today but from what I read it should have only affected poi. Should I leave it alone? Measure again? Maybe look into action scre torque?

Some relivent info:
Savage 10 .223 in mdt lss chassis
69gr smk over 25.1gr cfe223
2.305 oal
 
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I read posts like this and think "What would I do?"

First i would re-shoot over the chrony and back off at least 20 feet. i have found muzzle blast to scramble the numbers.

Second, I would switch to a 80 gr Sierra MK. I was involved with the Savage introduction/switch to a 1:9 and that barrel would stabilise the 80, so long as the velocity was kept up.

The 69 can be stupid accurate, but is far more wind sensitive than the 80

The 69 gr velocities look low. Is it a short barrel?

In testing, you play with one variable at a time. Changing the stock is a major change. Should be tested with a proven load.
 
It's a 20" barrel.

I plan to re test to see if I get the same result. The load has worked great for me, took it out yesterday which was the first shooting after the new chassis and didn't shoot to well but just took it to be my shooting, took it home and cleaned since it wasn't cleaned in a while, shout about 50 rounds today with the group and measured rounds being the last.

The group's werent bad at all just the numbers which is making me think it might be the chronograph off
 
What are you using for a chronograph? If the light conditions over the sensors aren't the same shot-to-shot you'll see more variation than is actually occurring.
Second, color the bullets with a Sharpie, the chronograph may be having a tough time seeing them (errors).
My chrono (CE Digital) recommends 12-16 feet from the muzzle for rifle. The blast does affect results if you're too close. More distance won't hurt unless you stray from the "window". If that happens the new chronograph is unlikely to have the same issue, ruling it out as a cause.
 
Bullets were shot seconds apart outdoors so I do t think the light conditions were a factor, I may have been a little to close now that I'm thinking about it so I'm going to check the manual for a suggested distance and re shoot.

I'm suspecting that it's the chronograph giving bad readings since the group shot did not represent a 250+ fps difference
 
With a velocity number spread like that I would be taking a serious look at the chronograph. If you are consistently loading at 25.1gr CFE223 with a 69grSMK, you should be seeing very consistent velocities, even with a 20" barrel, somewhere in the 2950-3050fps range. I am not a big fan of CFE223 or H335 in my bolt gun. While it measured nice, I found it gave me more velocity spread than I liked (but nothing like what you are seeing) and accuracy was not what I preferred. I now run H4895 at 24.7gr with the same bullet and barrel length and get right around 3025-3055 with an average of 3042fps over the last 250 rounds. On the other hand, since it is a stick powder, every charge must be carefully weighed. I don't mind. The rifle with this ammo is easily capable of sub 0.25MOA in the hands of my son, but I am personally only capable of around 0.3MOA on my few and far between absolute best of days shooting at 300-500m. I really enjoy shooting it.

Bottom line: A) Try setting the chrony up further from the muzzle or B) See if you can borrow a different chrony.
 
That's my plan for next weekends shooting! Crazy spread to still be accurate with so I believe it's the chronograph.

I'm starting to load for a 6.5 creed very soon so I plan to switch my .233 over to 4895 or varget and use the same powder in both and just buy it in 8lb jugs to keep it simple and save on powder cost a little
 
H4350 for the 6.5CM. Best powder I have used for it although I have heard that RL17 and Varget are supposed to be pretty good as well. I tried H4350 in the .223. Works so-so at best but H4895 works best. Same thing for Varget in the .223. Way better than H4350 but not nearly as good as H4895, at least for me. Others like it so you are right, give Varget a try in both the .223 and 6.5CM. One thing about feeding the Creedmoor, it uses about twice the amount of powder that the .223 does so an 8lb jug of whatever doesn't last that long. I keep a reasonable supply on hand. Nothing like Ganderite or a few others on here, but enough that I can feed my various rifles for a year with a years reserve. I keep costs down by buying 4 x 8lbs at a time, topping up the supply of the powders I have settled on: H4895, H4350, Varget, H4831SC, H110 or W296 as it gets used. Powder seems to be the easy part. Finding the bullets I want, in quantity, at a reasonable price is difficult. Note the 'I want'. There are all sorts of bullets available, but getting the ones I want in quantity is difficult. Best source of large quantities I have found on a semi-regular basis is Mystic Precision. I generally buy 2 boxes of 100 locally if possible of all sorts of makes and weights when I am working up a load, but once I have settled on a bullet, buying them 100 at a time usually gets expensive fast. Sometimes Prophet River or X-Reload have bulk amounts available, but the standard amount seems to be a box of 100.
 
"I read posts like this and think "What would I do?"

First I would re-shoot over the chrony and back off at least 20 feet. I have found muzzle blast to scramble the numbers."

20 feet for a rifle. 15 for a pistol. It also helps if you are aiming at something, so the bullet takes the same path across the screens each time.
 
Re shot over the chronograph. Shot a 5 round group.
2789
2836
2815
2835
2799

These rounds shot a sub half moa group at 100

I backed the chronograph out to 20 feet and that seemed to be my problem.
 
Putting a light crimp on the 223 will lower the ES, as well as exact powder measure case to case.

Overall I found the 223 a pain in the butt to reload and get bench quality ammo, to that end sold it off and built a 6 dasher.
 
Might try crimping when I run out of the cfe223 and switch powders in the next month or 2. But for this load I'm happy with consistent sub half moa, dont wanna mess with it and ruin a good thing
 
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