Is there an explanation?

[ElmerThud]

Yesterday With a good friend we chrono’d his ammunition - 6.5x55SE.
His loads are very accurate, around 3/4” @ 100yds, so consistently pretty fair.

Set chrono up & shoot five rounds with avg. MV established at 2788fps.
Then another five rounds shot, and average fps similar resulting in the above avg fps figure.
But the extreme spread was large at 146fps.

I know this is a ‘field test’ not under lab conditions, but plainly ES and accuracy seem loosely linked.
Low ES may indicate good ammunition ‘consistency’, but doesn’t necessarily appear to determine accuracy consistency.
Can this be right? :roll:

 

[Anonymous]

With an ES of 146fps, there'd be a large vertical dispersion at considerably longer ranges.

I've watched a friend do a ladder test at 100 yards and the group was no larger than 1MOA and the range of MV was at least that large, maybe more. So, it's possible to have a large ES and an accurate load, at least at fairly close ranges. That's one of the reasons LR shooters go for low ES numbers...it controls the vertical spread out past Ft. Mudge.

FWIW- chromo some factory ammo...you find fairly high ES numbers pretty routinely, including in loads that shoot extremely well at 100yds.

 

[mjcmichigan]

+1,
I shot a ladder this weekend. 2” at 100 yards, spread was 400fps between min and max.


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[truck driver]

Elmer I don't mean to steal your thread but do you know anything about Burtren Brass out of Australia? My spell may be off on the name but close enough I think. LOL

 

[Gunner46]

ES May be an indicator for Potential accuracy, however it is Not a guarantee. If you're not within a Node for your rifle you're chasing a ghost and wasting powder.

ES is simply telling you that statically each load is consistent. Has nothing to with the vibration pattern of the barrel.

 

[ShadeTree]

ES May be an indicator for Potential accuracy, however it is Not a guarantee. If you're not within a Node for your rifle you're chasing a ghost and wasting powder.

ES is simply telling you that statically each load is consistent. Has nothing to with the vibration pattern of the barrel.

Correct on both points in my opinion. Low ES really comes into play on the long range stuff. It's way down the list of what I work at to get or maintain a good shooting load within the ranges I typically shoot. If I have a good shooting combination that chrono's out at a real low ES, great. If not I still have a good shooting load for me.

 

[Nimrod84]

"Can this be right?"

The above responses are correct and at short range, big ES doesn't necessarily mean bad accuracy; especially from the usual hunting or military rifles. On the other hand, benchrest shooters with barrel tuners can and do see significant changes in impact from changes in ES at short range...

However, I have seen jumps in velocity like that when clouds or tree branches cast a shadow over my optical chronograph. Usually, shade shifts the numbers lower somewhere in the 50-75 fps range, but has been in the 100+ fps range and accuracy has stayed very good despite the chronograph reading. Personally, if you were using an optical chronograph I would suspect an environmental issue like odd lighting from clouds, tree branches or a low battery. Even the Magentospeed can shift around under recoil and give weird readings at times.

Shooting at longer 300-500 yards usually shows me if the ES is real, or if the chronograph was having old timer moments...

 

[ozarkpugs]

"Can this be right?"

The above responses are correct and at short range, big ES doesn't necessarily mean bad accuracy; especially from the usual hunting or military rifles. On the other hand, benchrest shooters with barrel tuners can and do see significant changes in impact from changes in ES at short range...

However, I have seen jumps in velocity like that when clouds or tree branches cast a shadow over my optical chronograph. Usually, shade shifts the numbers lower somewhere in the 50-75 fps range, but has been in the 100+ fps range and accuracy has stayed very good despite the chronograph reading. Personally, if you were using an optical chronograph I would suspect an environmental issue like odd lighting from clouds, tree branches or a low battery. Even the Magentospeed can shift around under recoil and give weird readings at times.

Shooting at longer 300-500 yards usually shows me if the ES is real, or if the chronograph was having old timer moments...

Very good point about light and true for sure a lot of people say its not as accurate but on days when clouds are on / off I shade my chrono and put the light bars on .

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[Europe]

Elmer I don't mean to steal your thread but do you know anything about Burtren Brass out of Australia? My spell may be off on the name but close enough I think. LOL

Rodger, Bertram Brass is in Australia and Elmer is from Jolly Old England but he may know more than I do about them.

They have been around a while and they make good but expensive brass, but only for odd and obsolete caliber's.
The only first hand experience I remember with them in our family was for the 455 Webley and 500/450 N.E.

 

[truck driver]

Elmer I don't mean to steal your thread but do you know anything about Burtren Brass out of Australia? My spell may be off on the name but close enough I think. LOL

Rodger, Bertram Brass is in Australia and Elmer is from Jolly Old England but he may know more than I do about them.

They have been around a while and they make good but expensive brass, but only for odd and obsolete caliber's.
The only first hand experience I remember with them in our family was for the 455 Webley and 500/450 N.E.

Thanks April, I saw where they made 308 Norma brass and was interested since it was cheaper then Norma.

 

[1Shot]

I agree with the light/shade/low battery statement. With optical eye chrno I have found that even with blue bird sky just the time of day and position of the sun can effect your readings. Low battery can really play havoc. I had just put a new battery in my chrno one morning when setting up. I began to shoot with three different rifles testing. Shot maybe 1hr then one of the Sherriff's deputies shows up to practice. I shoot on their range but they have president so I had to wait until he finishes. I forgot to turn off my chrno. It was very frustrating sitting there for 2 hrs and 45 min waiting for the slower than molasses in winter time deputy to do his shooting, he was on the clock getting paid so he was taking his time. This was the only day I would have for a while to shoot and I had already set up everything so I just sat and waited. When I went back to shooting my velocity was all over the place. I wasted a lot of time and some ammo because I suspected that the battery was getting weak and did not have another. Next range trip I shot a few over the chrno with that same battery and got same all over the place readings. I changed to a new battery and everything went back to functioning perfectly. Lesson learned, put new battery in before every session and keep new battery's on hand.

 

[RiverRider]

There is a youtube video where a guy shoots several shots over a Oehler and a Shooting Chrony set up in series. The averages between the two instruments were very similar, but there were discrepancies of 50 fps and more between the two chronos on individual shots. That got me to thinking, and I got rid of my Shooting Chrony and bought Oehler 35P.

I trust the stats the Oehler turns in, but I don't think I'd take any stats to the bank with any other optical chronograph.

 

[AzDak42]

Folks are spot on.

I become a much better reloader when I had a lab radar or magnetospeed chrono.

My ES/SD's fell consciderably with no change in reloading practices. Optical chronos will get you in the ballpark, but you need a LOT of data averaged to really trust the readings.

 

[ElmerThud]

Optical chronos will get you in the ballpark, but you need a LOT of data averaged to really trust the readings.

Now this, I think really has merit.

After all, a Chrony while inexpensive and only used in general field testing will never provide lab. quality data, so it follows an average over a considerable number of shots would get you closer to your own barrel/ammunition performance, but still leaving a lower +/- % tolerance.

 

[Wyo7200]

If you have the shot values, you can determine where the ES occurred. Was the lowest FPS the first shot/ first recording? Clean barrel / fouling shot maybe? Or was one FPS value abnormally high?


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[wildgene]

...well, E.S. is a measure of 'statistical consistency'. not accuracy, but 'accuracy' depends on consistency, the more 'consistent' everything, be it 'trigger control', cheek weld, neck tension, or ES, the higher the probability of 'accuracy'...

 

[Nimrod84]

Elmer,

I'm not trying to keep a dead conversation alive, but on Saturday I had a round register over 140 fps faster than the others at the same charge weight. The increase came from shifting targets - guestimating a 2 degree difference - and the round went over the sky screens (Oehler 35p) at a different angle. The front screen showed my normal data but the check / proof screen on the back registered the 140+ fps increase. I realized what happened, adjusted the chronograph and all was right at the range. Just throwing that experience out there as something consider.