Extreme Spread & Standard Deviation

[prosportfan]

When I read about SD & ES it's always associated with accuracy. But there were times that when I used a AA field Diabolo 18gr pellet that had a very low es & sd out of my rws 54 and accuracy was ok but I also used a jsb 18gr with a much higher es&sd and out performed the AA by a significant margin. So is that a rarity or is it that just cause a pellet produces a low sd & es out of your rifle is not necessarily the best pellet.

[dan_house]

Shoot the most accurate pellet

ES and Sd are INDICATORS of potential performance.  One thing that always get my attention is folks posting 20 shot strings then making perrormance assumptions about it.
50 or better 100 shot stirngs will be a better represnetation of what the gun is capable of doing. IMO 20 shots is way too few.

[prosportfan]

Good feedback Dan

[SILENT SQUIRREL]

Shoot the most accurate pellet

ES and Sd are INDICATORS of potential performance.  One thing that always get my attention is folks posting 20 shot strings then making perrormance assumptions about it.
50 or better 100 shot stirngs will be a better represnetation of what the gun is capable of doing. IMO 20 shots is way too few.

IMO the reliance on 10 or 20 shot strings could be the product of what we read, & the videos we watch.
You' rarely see a review or report about a gun that goes beyond 20 shots.
Even the careful, skilled, experienced reporters do this.
Thoughts??

[fwbsport]

AOA sent all that technical stuff on each rifle I bought from them.  After I looked and interpreted the results I went shooting and found the ES and SDs and velocities basically meaningless to the rifle(s).

Reason is they shot up what I wanted shooting up with the accuracy I can handle in off hand hold.  Never tried any of them seated or prone or benched and think it is a waste of time too.  Targets can be a complete waste of time.  Plinking is how you sight in and fine tune that with objects at various distances and size.  Just watch where the pellet hit if it misses!

Ever do a group on a benchrest with say 10 shots at one time?  Then go back the next weekend expecting all is fine?  HA HA ha!

These numbers may not even be "indicators" of anything until the actual rifle is shot with whatever and whoever when and where.

So one of my rifles has a wider extreme spread compared to another and shooting them I can't tell the difference.  Maybe we can invent a problem using statistics as you know!  You can prove or disprove anything in statistics!

[nced]

When I read about SD & ES it's always associated with accuracy. But there were times that when I used a AA field Diabolo 18gr pellet that had a very low es & sd out of my rws 54 and accuracy was ok but I also used a jsb 18gr with a much higher es&sd and out performed the AA by a significant margin. So is that a rarity or is it that just cause a pellet produces a low sd & es out of your rifle is not necessarily the best pellet.

I contend that another issue is the fit of the pellet in the leade of the barrel. If the pellets are large enough to be consistently "sized" when loading in the leade all pellets will have the exact same size starting down the bore. On the other hand inconsistently pellet head sizes where some fit the leade properly and others loosely in the leade" the accuracy may suffer because different head sizes starting down the bore. In my HW springers the consistently snug fitting pellets like the boxed 7.9 grain Crosman Premiers are accurate, however the 8.4 grain JSB Exacts were/are inconsistent and not very accurate in my .177 R9.

Anywhoo...while SD and ES are indicators of accuracy, there can be other factors that apply.

[prosportfan]

True that Ed

[Doug Wall]

ES and SD are statistical numbers, usually associated with velocity. Not necessarily related to accuracy.

[nced]

Shoot the most accurate pellet

ES and Sd are INDICATORS of potential performance.  One thing that always get my attention is folks posting 20 shot strings then making perrormance assumptions about it.
50 or better 100 shot stirngs will be a better represnetation of what the gun is capable of doing. IMO 20 shots is way too few.

IMO the reliance on 10 or 20 shot strings could be the product of what we read, & the videos we watch.
You' rarely see a review or report about a gun that goes beyond 20 shots.
Even the careful, skilled, experienced reporters do this.
Thoughts??

LOL...if I'm shooting 20 shot groups the measurement of accuracy is measuring "the shooter" rather than the pellet/gun! I will occasionally shoot a 10 shot group when I'm steady on the bucket, however I prefer to shoot several 5 shot groups oe even a bunch of 1 shot groups at multiple bulls.
A bunch of 5 shot groups at one setting (265 shots) from 10 yards to 50 yards.......


Some 10 shot 18 yard groups before and after a bore clean.........


Here are 110 one shot groups after practicing my "bucket and sticks" shooting form at 18 yards..........


Now here are a couple 5 shot "bucket and sticks" groups at 18 yards, one from my HW95 and one from a HW98 after I did some work on it.......

These targets compared to the "10 shot target" and the "100 bull target" indicates to me that the accuracy (or lack there of) was due to the shooter, not the equipment!
Here is a 50 yard group shot with the HW95.........

[Bayman]

The trick is matching good numbers with accuracy. The numbers only really tell you the health of rifle. Crossman boxed CPLs chronograph terribly in all my guns but for accuracy rival everything else in most of them. Only testing reveals the best for the rifle. Chronographs have a purpose but cannot answer all our questions.

[prosportfan]

Great feedback from everyone. Thank you

[Luis Leon]

Targets can be a complete waste of time.  Plinking is how you sight in and fine tune that with objects at various distances and size.  Just watch where the pellet hit if it misses!

While I do shoot targets for initial sight in... and shoot groups to reconfirm zero on occasions. Plinking at small, very small objects, acorns, black walnut husks, small pieces of chalk, etc. out to 64 yards almost everyday. Has netted me a much higher kill ratio when pesting in the field. I do run some chrono strings, but let what the pellets are doing on target determine whether I use them or no.

[nced]

The trick is matching good numbers with accuracy. The numbers only really tell you the health of rifle. Crossman boxed CPLs chronograph terribly in all my guns but for accuracy rival everything else in most of them. Only testing reveals the best for the rifle. Chronographs have a purpose but cannot answer all our questions.

"Crossman boxed CPLs chronograph terribly in all my guns"
A couple days ago I took a few shots over the chrony with my .177 Beeman R9 and .177 HW95 (different home tune levels). The CPLs had a higher velocity over the AA domes from both guns however there was little difference in fpe with either pellet or gun.......
.177 Beeman R9
CPL 7.9 grain-----------------849,844,849,850 (12.7ish fpe)
AA Domes 8.4 grain-------839,833,836,833 (13.0ish fpe)

HW95
CPL 7.9 grain-----------------881,881,884,887 (13.7ish fpe)
AA Domes 8.4 grain-------856,859,860,862 (13.8ish fpe)

Humm.....interesting that the softer tuned R9 gave the heavier AA dome had a 0.3ish fpe advantage over the faster CPL, however, with the faster shooting HW95 both the AA dome and CPL had a similar fpe with only a 0.1fpe advantage going to the AA dome.

[Bayman]

The trick is matching good numbers with accuracy. The numbers only really tell you the health of rifle. Crossman boxed CPLs chronograph terribly in all my guns but for accuracy rival everything else in most of them. Only testing reveals the best for the rifle. Chronographs have a purpose but cannot answer all our questions.

"Crossman boxed CPLs chronograph terribly in all my guns"
A couple days ago I took a few shots over the chrony with my .177 Beeman R9 and .177 HW95 (different home tune levels). The CPLs had a higher velocity over the AA domes from both guns however there was little difference in fpe with either pellet or gun.......
.177 Beeman R9
CPL 7.9 grain-----------------849,844,849,850 (12.7ish fpe)
AA Domes 8.4 grain-------839,833,836,833 (13.0ish fpe)

HW95
CPL 7.9 grain-----------------881,881,884,887 (13.7ish fpe)
AA Domes 8.4 grain-------856,859,860,862 (13.8ish fpe)

Humm.....interesting that the softer tuned R9 gave the heavier AA dome had a 0.3ish fpe advantage over the faster CPL, however, with the faster shooting HW95 both the AA dome and CPL had a similar fpe with only a 0.1fpe advantage going to the AA dome.

Yeah Ed, it seems that the CPLs require more starting pressure than heavier JSB /AA pellets. Probably because they are a harder alloy and usually fit tighter in the leade. Only my stronger guns (14lb+) shoot the CPLs faster than heavier JSB /AA pellets. My lower power guns shoot the heavier JSB /AA pellets the same or faster than the CPLs. Seems the CPLs need a good kick in the pants to get moving. Your results does not surprise me. The CPLs are a conundrum for me. Very accurate but don't produce as much energy downrange as other options.

[nced]

The trick is matching good numbers with accuracy. The numbers only really tell you the health of rifle. Crossman boxed CPLs chronograph terribly in all my guns but for accuracy rival everything else in most of them. Only testing reveals the best for the rifle. Chronographs have a purpose but cannot answer all our questions.

"Crossman boxed CPLs chronograph terribly in all my guns"
A couple days ago I took a few shots over the chrony with my .177 Beeman R9 and .177 HW95 (different home tune levels). The CPLs had a higher velocity over the AA domes from both guns however there was little difference in fpe with either pellet or gun.......
.177 Beeman R9
CPL 7.9 grain-----------------849,844,849,850 (12.7ish fpe)
AA Domes 8.4 grain-------839,833,836,833 (13.0ish fpe)

HW95
CPL 7.9 grain-----------------881,881,884,887 (13.7ish fpe)
AA Domes 8.4 grain-------856,859,860,862 (13.8ish fpe)

Humm.....interesting that the softer tuned R9 gave the heavier AA dome had a 0.3ish fpe advantage over the faster CPL, however, with the faster shooting HW95 both the AA dome and CPL had a similar fpe with only a 0.1fpe advantage going to the AA dome.

Yeah Ed, it seems that the CPLs require more starting pressure than heavier JSB /AA pellets. Probably because they are a harder alloy and usually fit tighter in the leade. Only my stronger guns (14lb+) shoot the CPLs faster than heavier JSB /AA pellets. My lower power guns shoot the heavier JSB /AA pellets the same or faster than the CPLs. Seems the CPLs need a good kick in the pants to get moving. Your results does not surprise me. The CPLs are a conundrum for me. Very accurate but don't produce as much energy downrange as other options.

The boxed 7.9 grain .177 Crosman Premier lights have larger heads than most pellets..........
Here are a few 8.4 grain .177 Air Arm domes measured at random...........


Here are a few 7.9 grain .177 Crosman Premier lights measured at random.........

[dan_house]

IMO the reliance on 10 or 20 shot strings could be the product of what we read, & the videos we watch.
You' rarely see a review or report about a gun that goes beyond 20 shots.
Even the careful, skilled, experienced reporters do this.
Thoughts??

Agree with your assesment there. If the “big guys” reviewers and forum experts are using 20 shot strings, then it has set a precedent.

I’d add though, if your a reviewer and have 5 guns to review, then doing 50 -100 shot strings over the chrony is time consuming, and really not necessary for the review process. A reviewer is simply giving opinions an reviews of the gun as it comes out of the box, not trying to wring out maximum potentional from that platform.

Also mostly agree with whoever said the mubers have nothing to do with accuracy, erratic numbers can cause goofy results at the target. Ive had a couple of guns with good chrony numbers yet wouldnt group well even across the shop. 

You need good chrony data to plug into your ballsitics program, to use as baselines before and after mods. That data is one component of a bigger performance picture, not an end unto itself.

not a lot a right or wrong here, do what works for you. Im just saying the more data you have to work with, the more you can get out of yer gun

[rsterne]

ES and SD are indeed only measures of the consistency of the velocity.... With PCPs, it is generally accepted that for 50 yards and under, an ES of 4% is good enough that the average shooter will not be able to see the difference in group size or POI caused by the velocity variation.... If your gun is shooting 800 fps, that is a range of 32 fps between the fastest and slowest shot.... At 100 yards, you should strive for an ES of 2%.... and at 20 yards, it is doubtful you will be able to tell any difference if the ES is 10% or significantly less than that....

An exceptional shooter, shooting from a bench, with a very accurate combination of pellet, barrel and velocity.... MAY be able to see the difference between the ES levels quoted above and a narrower one.... on a windless day, when he is shooting well....

I can't.... 

Incidently, the very best .22LR target ammo has an ES of over 2% (typically 25 fps or more) over a box of 50 shells.... 

Bob

[prosportfan]

Awesome replies from everyone. I thank you