Pellet head size and velocity differences

[sharroff]

I took an unsorted tin of Crossman Premier's out for some FT shooting and had groups way more open than normal (a rough hole at 50 yards is normal). I had some side to side variation which I'll call as wind but lots of vertical difference. Came back inside and did the weight check. They were almost all 7.9 and 8.0 with a few 7.8's. Nothing extraordinary there. Checked the head sizes and there were all over the place from .450 to .453 which make a big velocity difference in my FT gun.

For 10 shot groups of these Crossman Premiers over my chrony:
.453 were around 970 fps
.452 were around 990 fps
.451 were around 955 fps

So 45 fps spread when those are mixed together vs my normal 5-10 fps spread. At 50 yards, that's a big difference.

 

[ajshoots]

Your results further prove that sizing to a very specific size is key. There is way to much evidence that sizing head and skirt to the same bore appropriate size is a proven success. Still unsure why more people who demand accuracy don't do it??

 

[Guest]

Question: does the .25 pellets have different head sizes? On the back of all my jsb tins all say 6.35.

 

[ajshoots]

No, .25's aren't available in varied head sizes. Only .177 and .22, even though buying by head size is almost worthless since most tins are probably less than 50% the marked head size.

 

[Guest]

Thanks aj.

 

[sharroff]

Just picked out 50 of the Crossman Premier (they need to change that name for sure) and sized them hoping to get a decent number of .451 and .452 pellets. No such luck - I have 14 pellets usable out of 50.

These things ran from .446 to .453. And some are smaller than .446 (the smallest hole on the Pelletgage) but I was too lazy to get my digital caliper and see how small they got. No wonder these things group poorly when not sorted!

I'm going to send each size by itself out to 50 yards and see where they land.

 

[Strever]

which is why i am buying all the time looking for a new die/batch # to get good ones for competition
and is how one winds up with over 200 tins

AJshoots ......
buying by head size is almost worthless since most tins are probably less than 50% the marked head size.

 

[ajshoots]

Really sucks how much variation is in tins!! Thanks for this thread as it should serve as a good learning experience for new airgunners and a great reminder for all. Next time you get a flier with unsorted pellets, remember this thread!! +1

 

[sharroff]

And here are the downrange results at 50 yds. They were all shot from an AZ modified Steyr LG100 w/ Nikko Diamond Sterling 10-50x60 at 50. The gun was in a Lead Sled DFT bench rest, and all I touched was the trigger so the variation is in the pellet. All the Crossmans were shot aiming for the center of the target. I had a 5-7mph left to right cross wind. 

I started with the .446s on #1, .447s on #2 and so on.

The hole in the #11 is a flyer from the ,446 group as is the flyer in the upper left hand corner of the page. Imagine trying to get a good group or hit a squirrel/bird in the head at 50 yards with these from an unsorted tin!

My Styer likes .451s but for some reason the .450 Crossmans (11 pellets into one rough hole) shot better than the Crossman .451s. My Steyr doesn't usualy like .453s but all three of them went into the same hole.

The last group is 5 .451 H&N Barracuda Matches (all 10.7g) with me holding 2 squares to the left to correct for wind. One rough hole as usual, and I must have had the vertical turret set one 1/8 click low.

 

[clgraham82]

"sharroff"I took an unsorted tin of Crossman Premier's out for some FT shooting and had groups way more open than normal (a rough hole at 50 yards is normal). I had some side to side variation which I'll call as wind but lots of vertical difference. Came back inside and did the weight check. They were almost all 7.9 and 8.0 with a few 7.8's. Nothing extraordinary there. Checked the head sizes and there were all over the place from .450 to .453 which make a big velocity difference in my FT gun.

For 10 shot groups of these Crossman Premiers over my chrony:
.453 were around 970 fps
.452 were around 990 fps
.451 were around 955 fps

So 45 fps spread when those are mixed together vs my normal 5-10 fps spread. At 50 yards, that's a big difference.

Good info! I'm having the same wide fps spread with my .22 Wildcat using both 15.9 & 18.1 JSBs. I'm going to try some sorting and see if the strings tighten up.