Size Does Matter (in relation to speed)

[jking]

I've been sorting by weight and now resizing some 33.95 Heavies to shoot out of my FX500. This morning I shot four pellets that were in the 34.8-34.9 lot, four that were out of the same lot sorted by weight and resized from a max OD of .263" to .250" and then four that were out of the 34.2-34.3gr lot and sized to .250. Here are the results. Thought is was interesting and also something else to complicate this "hobby" aka "possession". Also found that very few were actually in the weight range as advertised. The range was from 33.6-35.0 though not many in the outer limits.

Weight sorted to 34.8-34.9 but not sized
858
859
849
855

Weight and sized 34.8-34.9 and .250"
868
874
871
871

Weight sorted to 34.2-34.3 and sized to .250"
881
885
884
884

 

[fe7565]

@jking...I am working on something similar. Happens to be the same King heavy 33.95 MKI pellet. So far my observation is that: Weight Does Matter (in relation to distance). More on that below...but first...

Did you shoot the pellets at a target to see how much the POI changes due to the velocity difference? I've been shooting at 100 yards with the MKI's lately as I was trying various rifle holds/rests. I think I am onto something as I am able to reduce considerably the group sizes based on various holds, but there isn't a magic one-track solution. I will post a new thread on that soon once I nail it down....for me it's very eye opening. 

As far as the .25 King Heavy 33.95 pellets one thing that surprised me also how much the weight varied pellet to pellet. But also surprised me how consistent the head size is. I took randomly 40 pellets from one tin and 20 from a separate tin and measured them with my "pelletgage" http://pelletgage.com/. The head sizes all fit in the 6.37mm opening, albeit about 20% needed a little wiggle to drop in, but none were forced. That's a near 100% uniformity based on 60 pellets selected from 600. So I gave up head measuring.

But I also set down to measure weight because I had a couple of fliers at 100 yards, and some vertical strings (indoor range). I also found that the weight range based on a sample of approx. 50 pellets from the 300 pellets in the tin varied between 33.32gr to 35.32gr.

The breakdown:
5ea at 33.32-33.45gr
14ea at 33.60-33.80gr
17ea at around 33.90-34.05gr
7ea at 34.15-34.25gr
6ea at 34.45-34,57gr
1ea 34.80gr
1ea 35.32gr

The difference in velocity (caused by weight variance) at 100 yards WILL MAKE a difference...at least based on Chairgun. I know that some people argued that somehow the POI as calculated by Chairgun is in discrepancy with reality...but I am not convinced until I got test it myself using the sorted pellets.

If I plug into Chairgun the following data at 100 yards and set a baseline of 33.95gr; 900fps, I get a POI of -11.313.

When I change the pellet weight (reset to baseline between tests):

JSB 33.32gr: reset to 900fps; 49.8yard zero; BC 0.042 (Yrrah's ST test); => I get this : POI -11.041 inches at 908.5 fps
JSB 35.32gr: reset to 900fps; 49.8yard zero; BC 0.042 (Yrrah's ST test); => I get this : POI -11.903 inches at 882.4 fps

So at 100 yards if you pick 33.95gr Heavey King pellets randomly from the tin, you can get a 2gr variance in pellet weight which will lead to a 0.86 inches POI shift vertically. Now realistically, it's unlikely that you pick the lightest and heaviest pellet from the tin during the same string, but even if the weight difference is smaller you may get a half inch variance from shot to shot at 100 yards if you do not weigh them. At 50 yards that difference is not noticeable.

 

[bill_dd97]

I notice a difference at 50 yards with 25.4gr JSBs out of my Marauder. I measured a tin once and found similar results. Percentage of weight change makes a difference also, as in 2 grains is a greater difference in the 25.4gr pellets. Precision shooting requires this kind of attention to detail.

Your post may have just inspired to me to make a video about this in the nearish future. I currently have 2 unopened tins for 25.4gr AA pellets. Perhaps I'll size them with my pelletgauge and weigh them. Sort them to size and weight groups before shooting them for groups at 50 and 100 yards.

 

[fe7565]

I just did a quick weighing and head size check on the 33.95gr MKII King Heavy pellets. Took out around 70ea and found that head size fits into 6.36mm vs the 6.37mm of the MKI (in the past I got better groups with my MKI using my FX Impact but the jury is still out). The weigh was in a narrower range between 33.50gr-34.80gr. Two largest weight groups were 33.90-34.00gr and 34.15-35gr.

 

[jking]

I was figuring a half inch at 100yds could be the result of different weight/speed. But it could be half inch high from center line horizontal and half inch below center line giving you a one inch spread there. I shot some of my weight sorted and sized to .251 this afternoon at 97yds. One of the best if not the best rounds of almost 100yd shooting I've done.
Fe, your break down was similar as far as overall spread but I had more that were up in the 34+ range. Maybe a difference in scales. I sorted two consecutive tins when I did mine as well. Thanks for sharing what your finding.
Jimmy

 

[fe7565]

Jimmy, curious how those 97 yards groups turned out. How much measurable difference was compared to unsorted pellets? Is the difference due to weighing or head sizing?

 

[jking]

Well, I don't have a firm answer for you. I can tell you it wasn't nothing like it is now. Actually my groups with the MKII's and MKI's weren't all that great but I have also polished the barrel on the gun, went with the larger valve and picked the speed up from 790-800 to 880. I've done too much at one time to really break it down and pin point where the biggest improvement came from. fe7565, you've mentioned head sizing but I'm sizing the whole pellet to .251". I was finishing up my last few pellets of when shot this group. I think there was somewhere between 8-10 or 11 pellets left so I just shot them all..
Jimmy

 

[NMshooter]

Nice job Jimmy, I would be VERY happy with thoughs groups!

 

[fe7565]

Jimmy...excellent group! Any group that you can cover with a quarter near 100 yards is a winner!

I'v'e been shooting only 10 shot groups lately (all indoors) a 100 yards. tried various holds, bi-pod, sand bag, Caldwell the Rock BR and combinations of them. I can affect groups size from 2-2.5 inches down to 1.5-1.75 inches. A more firm hold on the front did make a difference. Had some 1" groups too, but cannot yet determine what was the "perfect" combination (or a single thing) that made it happen, thus I cannot repeat it when I want it. I need to do better record keeping on the various holds/rests I am trying. One thing I did not try yet is the vary my velocity. So far shooting MKI's at 900fps only. Will try 820fps and 960fps next.

Looking at Ted's FX Impact video, he uses a bi-pod and a rear sand bag. He does not seem to touch anything but the trigger and the rifle butt (for aiming).

 

[jking]

Thanks Doc and fe7565 I've tried different techniques too, Seems like the harder I try the worse the groups.sometimes. I think consistency is the key. My 500 seems to like to be butted up and somewhat held. I'm shooting 880 and haven't tried backing if off some.
jimmy