Chronograph question.

[Classyusa]

Hello,

Casual lurker/ first time poster.

I purchased a Caldwell chrono recently to get a more accurate fps value on my ammunition. I plan to change my custom elevation dial to use Federal Premium 168gr Berger Hybrids.

The manufacturer has the velocity listed as 2870 fps.

I shot 7 rounds out of my Ruger M77 MKII 7mm REM Mag through the chrono today. The velocity was disturbingly inconsistent. ...

Shot
1. 2768
2. 2828
3. 2756
4. 2772
5. 2852
6. 2824
7. 2842

I get that there will be inconsistencies with shelf ammo but this seems pretty severe. Any ideas ? Is Federal Premuim garbage? Are Caldwell chronos not accurate? Was there another variable that I overlooked?

Barrel was slightly dirty. 20- 40 rounds since last cleaning, the same barrel condition that I hunt with. I used rounds out of 5 different boxes of ammo to see how consistent this ammos is from box to box. Something to note, rounds from shots 1,2 & 3 came from different boxes. Shots 4 & 5 were from the same box ( had an 80 fps variation). Shots 6&7 were from the same box. Barrel was cool for all shots except shot 7.

* I did have the chrono sitting on a white table. Could there be possible reflection issues?

* Chrono was only 6-7' in front of my muzzle, not the reccomended 10-15' away.

* Overcast. 50 degrees F. 300' elevation. No wind.

Any constructive input is appreciated.

 

[hereinaz]

My only advice is return or sell it and buy a Magnetospeed Sporter.

Don't have any experience with lots of ES of boxed ammo, but 100 fps isn't out of the question.

 

[Bater]

I bet that’s correct. My magnetospeed showed 250fps variation in a buddys Rem corelokt factory ammo. There is a reason we reload.

 

[Classyusa]

Copy. I knew factory ammo was inconsistent. I didn't realize it was that severe. This is a good lesson learned. I suppose my best bet is to hold of on getting a new dial built until after the primer shortage ends and I can get a load developed for this rig.

I will look into the magnetospeed as well. Thanks for the replies.

 

[archp625]

How far do you plan on shooting out to? I bet your chrono is fine. No need to sell. Factory ammo can be that off in ES.

 

[Classyusa]

With how this rifle is setup now, I have killed animals with the current turret/elevation dial made for the another factory load( not the Federals) out to 500~ yards.

I thought I was comfortable on an elk out to 600 with that setup. I then started talking to friends in long range shooting clubs and reading online forums last year. The information that I gathered was that I was foolish for the confidence that I had in the factory ammo set up I had been using.

I am a pipeliner. So life on the road rarely affords me time at home to shoot as much as I would like, let alone trying to develop hand loads.

I did purchase reloading equipment last fall but that is a long term project. In the short term, I had heard from a few people who I respect that the Federal's with the Berger was a good load for factory.

Hearing what I have so far from dedicated shooters and forums , it sounds like I was lucky to kill anything past 300 yards with the factory ammo that I was shooting (I have shot and hunted for decades but have just started trying to learn the INS and outs of what all goes into being good at shooting, recently after wounding a big bull at 400~ yards and not recovering it. First unrecovered bull of my career ).

With what I had heard about the Federals/Bergers I thought it would be a reliable set up out to 500-600 yards. After seeing the speed variation though, I am leery about proceeding with this load.

That said I am learning and listening. I dont want to wound and not recover another animal. What I had been doing had been working for me for years until it failed me. I have since been trying to learn as much as I can to improve. Technique, equipment, eliminating variables, etc.

I appreciate all input.

 

[dieselchessy]

Your ES/SD is crap.
Could of been muzzle blast being only 6 or 7 feet from the chrono.
Also could be the rifle doesn’t like the ammo.
Or the ammo is just that inconsistent.
Most often I find factory ammo is 50 to 100 FPS slower than advertised, and ES/SD is poor 50-80fps range.
Out to 500 yards that 100fps ES could cause about 4” of vertical stringing with that load.
Most folks worry about the LOT numbers on the boxes more than the individual boxes the ammo comes out of.
If you have a dial made, it won’t work for elevation changes. And may not work for different ammo lot numbers. Them pre-marked for yardage dials are a crutch for folks just starting out. You’ll outgrow that pretty quick if you start shooting.

Your on the path. Chrono is a good move. Leupold with CDS dial (guessing) maybe not so much, but some folks like them.
A Kestrel would be a good move. The 2700 ($180) would do you well.
Sounds like you have an LRF.

 

[hereinaz]

I looked at two loads for 100 fps difference. At 500 yards it is 4 inches elevation change. At 600 yards, its 7 inches. That was for a slower 178gr .308 load. Your 7 would be a little better.

If it shoots 1 inch groups at 100, then at 600 you could shoot 3 inches high or low of aim, the group is about 6 moa around. Because of velocity, it might shoot additional 3.5 high or low of aim. So, if it all combined to be worst high or low, then it would be 6.5 inches from center up or down, a random group would be 13" tall because of the velocity variation, but 6 inches wide because it is an MOA group. Most would fall into the middle, because you won't always get the error stacking in the same direction.

For elk, it could technically on its vitals. Is it preferable? Nope.

Order custom ammo if you can't reload.

 

[hereinaz]

IME modern day match or premium factory ammo will have a SD in the mid-to upper teens. The Federal loaded Berger had one of the worst approximate SDs. For Lot #D164P04, the following is eleven shots through a Caldwell G2 (not an ideal piece of equipment)

1-2849
2-2831
3-2865
4-2872
5-2887
6-2856
7-2829
8-2827
9-2838
10-2841
11-2872

Although this data set is too small to evaluate statistically, the following are some rough descriptions

Mean = 2851.5 fps
Median = 2849 fps
SD = 20.3 fps
ES = 60 fps

I know there is a fad to only look at ES, but that is a poor choice for the majority of situations. Looking at +/- 2 SD from the Median will be roughly where 95% of the shots will go.

View attachment 266901

Where I live/hunt, that factory ammo would do fine out to about 700 - 800 yards on big game provided the shooter has the abilities.

View attachment 266902

There is a small set of skilled reloaders with good equipment that can obtain consistent single digit SDs. And an even smaller set that shoot enough to see the benefits of that ammo. However, contrary to what the internet says, most dudes with a $200 rock chucker in their garage aren't reaching single digit SDs, and may not even be in the teens.

Excellent advice. Absolutely, use the same lot. That was my limited experience with match ammo. I shot 6.5 cm match ammo before I reloaded and it was under 20 for SD.

Statistically, most shots are gonna be on target, its the "fliers" though. But, poor shooting form and skill is the biggest factor for misses at long range. Of course, wind...

I agree most reloaders are not making good ammo. It is a shame, because quality reloading is in good components and a few simple steps. The average guy in the basement doesn't buy the right stuff or follow the right process.

 

[wind gypsy]

IME modern day match or premium factory ammo will have a SD in the mid-to upper teens. The Federal loaded Berger had one of the worst approximate SDs. For Lot #D164P04, the following is eleven shots through a Caldwell G2 (not an ideal piece of equipment)

1-2849
2-2831
3-2865
4-2872
5-2887
6-2856
7-2829
8-2827
9-2838
10-2841
11-2872

Although this data set is too small to evaluate statistically, the following are some rough descriptions

Mean = 2851.5 fps
Median = 2849 fps
SD = 20.3 fps
ES = 60 fps

I know there is a fad to only look at ES, but that is a poor choice for the majority of situations. Looking at +/- 2 SD from the Median will be roughly where 95% of the shots will go.

View attachment 266901

Where I live/hunt, that factory ammo would do fine out to about 700 - 800 yards on big game provided the shooter has the abilities.

View attachment 266902

There is a small set of skilled reloaders with good equipment that can obtain consistent single digit SDs. And an even smaller set that shoot enough to see the benefits of that ammo. However, contrary to what the internet says, most dudes with a $200 rock chucker in their garage aren't reaching single digit SDs, and may not even be in the teens.

^This. Every time i see someone on the internet claim they found single digit ES easy with their load my internal BS meter starts screaming. Getting single digit ES on a single 3 or 5 shot group doesn't make it a single digit ES load but that doesn't stop the internet claims. Single digit SD's is relatively uncommon too.

In the OP's case, at 500 yards i'm guessing a roughly 4" difference in elevation between the fastest and slowest speed clocked. If average is roughly in the middle you're talking 2" high or low from POA (less than a half MOA). That's a hit as long as other factors dont pull the bullet significantly further off course. I would be more worried about the Leupold CDS functioning correctly or the solution being accurate for the shot than I would that velocity spread inside 500 yards.

 

[rayporter]

if you can prove that there is something wrong with your chrony i will be surprised.

 

[dieselchessy]

I too am skeptical of folks claiming really low ES/SD with non-bechrest type rounds.
But I find extreme spreads less than 50fps with 7mm rem mag hand loads made with my Rock chucker pretty easy. But I don’t load in a basement. That’s half of that factory ammo.

If you ever measure the run out on factory loads you can quickly see why hand loading can help. Or maybe get a setup for measuring run out and correcting it. Pretty easy to get run out to .003 or less with good bullets.

 

[N2TRKYS]

^This. Every time i see someone on the internet claim they found single digit ES easy with their load my internal BS meter starts screaming. Getting single digit ES on a single 3 or 5 shot group doesn't make it a single digit ES load but that doesn't stop the internet claims. Single digit SD's is relatively uncommon too.

In the OP's case, at 500 yards i'm guessing a roughly 4" difference in elevation between the fastest and slowest speed clocked. If average is roughly in the middle you're talking 2" high or low from POA (less than a half MOA). That's a hit as long as other factors dont pull the bullet significantly further off course. I would be more worried about the Leupold CDS functioning correctly or the solution being accurate for the shot than I would that velocity spread inside 500 yards.

How many shots does it take from your reloads before you to believe the data?

 

[N2TRKYS]

I too am skeptical of folks claiming really low ES/SD with non-bechrest type rounds.
But I find extreme spreads less than 50fps with 7mm rem mag hand loads made with my Rock chucker pretty easy. But I don’t load in a basement. That’s half of that factory ammo.

If you ever measure the run out on factory loads you can quickly see why hand loading can help. Or maybe get a setup for measuring run out and correcting it. Pretty easy to get run out to .003 or less with good bullets.

How much runout are you measuring in factory loads? Have you organized the amounts of runout together and shot groups comparing the different runout groups and poi?

 

[wind gypsy]

How many shots does it take from your reloads before you to believe the data?

If I have a group show consistent velocities over 5 shots while developing a load and come back another time and shoot 15 more shots of the same load and see the same results, I'll trust it.

I've had a lot of loads show single digit ES over 3 or 5 rounds during load development only to end up with 20-25 FPS ES and 7-12 FPS SDs once a bigger sample size is observed. That is typically sufficient for my uses but I'm not shooting at critters at 800+ yards.

 

[N2TRKYS]

If I have a group show consistent velocities over 5 shots while developing a load and come back another time and shoot 15 more shots of the same load and see the same results, I'll trust it.

I've had a lot of loads show single digit ES over 3 or 5 rounds during load development only to end up with 20-25 FPS ES and 7-12 FPS SDs once a bigger sample size is observed. That is typically sufficient for my uses but I'm not shooting at critters at 800+ yards.

Do you think it has more to do with the load or the consistency of the process?

 

[wind gypsy]

Do you think it has more to do with the load or the consistency of the process?

I think the majority of it is randomness. Not uncommon to shoot 3 shots that happen to have an ES of 5 that over 20 might show an ES of 30 and in the same day shoot 3 shots of a load showing ES of 14 that might only have an ES of 18 over 20 shots.

3 shots just isn't statistically valid in most cases.

 

[N2TRKYS]

I think the majority of it is randomness. Not uncommon to shoot 3 shots that happen to have an ES of 5 that over 20 might show an ES of 30 and in the same day shoot 3 shots of a load showing ES of 14 that might only have an ES of 18 over 20 shots.

3 shots just isn't statistically valid in most cases.

I think it has more validity than folks realize. For example, when shooting a load work up do you choose to work with the worst performer or the best for further testing?

If the initial 3 shot groups were the best of a 20 shot group that expanded 10 fold, the same could be said in reverse for the worst 3 shot group. But, we don’t use that worst group.

 

[dieselchessy]

How much runout are you measuring in factory loads? Have you organized the amounts of runout together and shot groups comparing the different runout groups and poi?

Easy to measure .006 and find the occasional .008 or more in factory ammo.
I used to sort everything above and below .003. Good ones for hunting and long range work, bad ones for short range stuff. Now days I just fix them all to .003 or below.
Up to .005 I didn’t see much difference, but more than that you can see the flyers.
It seems to depend on bullet, load, rifle, ect... as to how things react.

 

[N2TRKYS]

Easy to measure .006 and find the occasional .008 or more in factory ammo.
I used to sort everything above and below .003. Good ones for hunting and long range work, bad ones for short range stuff. Now days I just fix them all to .003 or below.
Up to .005 I didn’t see much difference, but more than that you can see the flyers.
It seems to depend on bullet, load, rifle, ect... as to how things react.

Back when you sorted them, how was the accuracy compared to the acceptable ones?