Pellet selection Criteria, group size or ES and Std Dev?

[JimD]

I had an interesting experience today.  I've been messing with my P35-177.  I shortened the hammer spring because I could not decrease spring force to the point where velocity went down.  I hoped that would make the extreme spread and standard deviation better but I didn't shoot a shot string to find out until today. 

I've sometimes used whatever pellets I did not mind using up to do things like find out where the reg falls off (the P35 has no gauge for the regulated pressure).  I thought it didn't make much difference in the extreme spread until today.  My first string was 10 H&N Baracuda Match and then 40 Baracuda Power.  The Match were a little higher velocity so I calculated the ES and Std Dev separately for the two types of pellets.  To my surprise the Match ES was under 10 while the Power ES was almost 40!  That's 40 shots for the Power, however, and only 10 for the Match.  So I shot 30 more Match.  The temperature had risen about 6 degrees F since the first string.  But the ES of all 40 Match pellets was 15.74 with a std dev of 3.41!  If I do only the last 30 the ES drops to 14.76 but the std dev goes up to 3.58.

I've shot quite a few groups with both the Match and Power pellets but only out to 34 yards, the limit of my yard.  My shooting is not as consistent as I would like it to be and I thought they shot similarly.  But during this shooting I started concentrating more with the Match and shot a 3/16 5 shot group at 30 yards and a 5/16 5 shot group at the same distance.  Most of the groups were larger but because of one shot outside the ragged hole. 

But ES and standard deviation are not dependent on my concentration.  It seems like possibly the most accurate pellet for my guns is also the one that gives me the best ES and std deviation.  Here is a bit more data (including the above):

P35-177 Baracuda Match 40 shots 15.74 ES, 3.41 std dev
P35-177 Baracuda Power 40 shots 38.38 ES, 8.66 std dev
P35-177 Crosman 10.5 20 shots  26.57 ES, 8.02 std dev
P35-22 Baracuda Match 30 shots 16.07 ES, 3.38 std dev
P35-25 H&N FTT 28 shots 12.8 ES, 2.94 std dev
Avenger 25 FX 25.4 12 shots 9.84 ES, 3.24 std dev

I only put in the worse shooting pellets for the 177 but it seems like all my guns have their lowest ES with the pellets they shoot the most accurately.  So maybe I better looks at that more closely in the future instead of my more inconsistent group sizes. 

Have you had similar experiences?

[rsterne]

ES and SD contribute to accuracy, so the bottom line is accuracy is everything....

Bob

[dan_house]

Group size
DO NOT get hung up on any numbers.... it'll drive ya nuts chasing them

If its not accurate at the ranges you'd be shooting, the best ES and SD dont matter a whit......

[sactargetshooter]

ES and SD contribute to accuracy, so the bottom line is accuracy is everything....

Bob

Bob is right. On some rifles, accuracy also correlates with muzzle velocity. The Brocock Ranger XR, for example, does great when the muzzle velocity is about 700 FPS, regardless of caliber!

[Fred J]

I am seeing the same thing. The most accurate pellets have a tight es (7-10 fps) in TX200 (AA 10.3gr and AA 7.9gr pellets). AA and JSB 8.4gr pellets shoot poorly and have a large es (27 fps).

However, THe AA 8.4 gr pellets shoot well in my S500 when I have the power set a 12 fpe.

[JimD]

I'm not sure that velocity variation, within reason, does a lot to group size at 30 yards and under.  I think it would make more difference at longer range.  But I think that the lower ES and std dev I measure may just indicate the gun is more balanced and working better than with the higher ES and std dev pellets.  I thought my regulator didn't work as well in the P35-177 but now I see that it works pretty well - but only with the pellets the gun really likes.  That is at least how I am looking at things right now. 

Looking at an older target today I found a really good group (3/16 center to center at 30 yards) with the Baracuda Power I measured a much higher ES for.  But I am still convinced the Match are what I want to use in this gun longer term based upon the ES.  I think it will help more for longer shots, the velocity is slightly higher, and to me the low ES indicates the gun is just "happier" with those pellets.   

[Hoosier Daddy]

Group size
DO NOT get hung up on any numbers.... it'll drive ya nuts chasing them

If its not accurate at the ranges you'd be shooting, the best ES and SD dont matter a whit......

If I am getting good groups repeatedly with a certain pellet, then I might break out the chrony to check ... but usually I just keep shootin 'em 

[Goose]

Group size
DO NOT get hung up on any numbers.... it'll drive ya nuts chasing them

If its not accurate at the ranges you'd be shooting, the best ES and SD dont matter a whit......

If I am getting good groups repeatedly with a certain pellet, then I might break out the chrony to check ... but usually I just keep shootin 'em 

That's pretty much how it works for me.  Once a pellet that performs well is tested, I might check the velocity for long range hold-over data.

J~

[JimD]

I often shoot groups and measure velocity at the same time.  I bought a tripod mount Chinese chrony so I didn't have to attach the clamp on to the gun.  I put it on the handrail of the side porch my bench is on and then shoot through it to test pellets.  I have to remember to record the velocity before studying where the pellet went but as long as I do things in the right order it works pretty well.  I know group size before I calculate ES and certainly before I know std deviation.  I do that in a spreadsheet later. 

But I'm thinking the velocity statistics are at least a good check on what I think I know about how a pellet groups.  If I thought it was grouping so-so but the statistics look good, it may need a retest for grouping.  Conversely, if it groups OK sometimes but not consistently and the statistics are no so good, it may be time to move on.  So far for my 4 regulated guns I see no instances in which I measure a low ES but have consistently big groups.   

[Hoosier Daddy]

For example....
My R10 shoots very nice groups with the JSB .20 13.73g tin after tin.
I wanted to see just what it was doing out of curiosity so I broke out the Caldwell Chronograph.
Low and behold the "proof was in the pudding" when I compared the others that did not group as well.