BC vs. SD

[AnimalHitman]

Attached please find a full-bottle regulated shot string for my Daystate Pulsar HP .25 (Hi Pwr) shooting JSB King 25.39 gr. I hope they group better than they Chrony. I know a good BC can compensate for a bad SD. I sure hope so here. Anybody else have shot strings for the Pulsar HP .25 set on high power shooting the JSB King 25.39 gr?

Also attached is a shot string for the same gun using H&N Baracuda Hunter Extreme 28.24 gr. They Chrony much better, but I'm getting 4" groups at 100 yds using a DeadShot.

Both strings were taken with a Chrony Beta Master.

View attachment 1538198374_10223293815baf0b6698a336.93243425_Shot string_Pulsar HP .25_JSB 25.39 gr.xlsx

View attachment 1538198534_21332263755baf0c066e49a4.30283607_Shot string_Pulsar HP .25_11SEP18.xlsx



Mod edit: moved to Pellets Projectiles section 

 

[jwrabbit123]

HI Animal . I dont have a pulsar but I have many regulated pcp guns which are regulated , your string is fine , I believe speed will open your groups up and depending on how you get to higher FPS changes harmonics which affects grouping dramatically , Like say you tune a gun for accuracy start , with lower powers for grouping and increase setting and see how groupings improve here is an example . I have a 25 cal which can shoot from 25fpe to 80fpe .

If I shoot heavy slugs I use hi power for this lets concentrate on say just JSB pellets 25 grains ,

First thing make sure ammo is constant like skirts , weights, sizing , next start mid reg setting and hst low and groups and increase till you fine best grouping .

I have guns which shoot best at 830fps with mk2 , I have others which can shoot a 25 grain best at 950 fpe so it all depends on the harmonics and settings , small amounts show up at 100 yards and beyond I have had guns group fine at 50 and fall apart at 100 and I have guns lazer spot on past 300 yards so harmonics and twist rates and ammo for gun matters most .

Can you post your groups at say 50 and 100 yards for us to see ? and are your pellets the jsb out of tin or sorted? Deviations can be also related to weights skirts and ammo .

 

[AnimalHitman]

rabbit, thanks for your comprehensive and detailed response . I am going out today to zero and group my Pulsar with the JSB 25.39s. I will post my zero and groups at 50 and 100 yds (five-shot groups, no mulligans; using a DeadShot.) Since I am a hunter, I shoot my Pulsar exclusively on high power per the shot string. I want 50+ ft#. I shoot out-of-the-tin; I do not sort except to the extent of inspecting them as I load.

Here are my zero, 50 yd & 100 yd groups with my Pulsar for the H&N Baracuda Hunter Extreme 28.24 gr (DeadShot). Keep in mind that I used my Chairgun holdovers for these groups.to also test for accuracy (bull's eye) as well as precision (grouping). When I group today, I will use no-holdoffs for the groups so that I can use the center cross-hairs to get a more reliable result for precision. I will test for accuracy separately.

Zero (42.9 yd per Chairgun optimal zero):

50:

100:

 

[AnimalHitman]

jw:

Helluva day at sea, Skipper! I just got back from the range where I zeroed, grouped (precision), and Chairgunned (accuracy) my Pulsar HP .25 with the JSB 25.39 gr. All targets are five-shot series. The results are substantially better than with the H&N Baracuda Hunter Extreme 28.24 gr! The JSBs shaved off an MOA @ 100 yds. The following were shot off a Caldwell Magnum DeadShot FieldPod (mild intermittent winds):

Zero Group (44.9 yds - Chairgun Optimal Zero Range):

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Complete Zero:

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50 yd Group (No Chairgun holdover because 50 yds is effectively within my Chairgun 1/2' kill zone):

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100 yd group:

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100 yd Chairgun holdover (What is interesting is that this has a tighter spread than the group shot; I guess it was the wind):

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This last shot was from my Primos Trigger Stick tripod with the two-point rest, which is what I use while hunting. It is a 47.9 yd shot, which is within my Chairgun 1/2" kill zone. The crosshairs were set dead-center on the bull's eye. I literally had one shot left before I got a low-pressure warning!:

 

[AnimalHitman]

I think I may know why my 100 yd Chairgun holdover returns a tighter group (and red-dot accuracy) than a straight group. I believe that it is because I correctly derived the scope height Chairgun input metric. This measurement is not a simple parallel measure from center bore line to scope tube center. It is the measurement of the distance between the bore line at the muzzle and the scope line of sight, which by definition must be less than the simple parallel measure from center bore line to scope tube center due to the scope line of sight crossing the bore line. The scope height metric is a major significant input to Chairgun. It is right up there with fps. If the scope height is not right, POI is materially affected.