JSB Exact Jumbo Heavy vs Monster Redesigned .22 results

[PCPhack]

I did some plinking  today and compared the JSB 18.13 to the JSB 25.39 redesigned .22 pellets.

Same Marauder .22 rifle, no settings changed between groups. All pellets lubricated with FP10.

18.13 shooting approximately 950 fps. .43 inches CTC
25.39 shooting approximately 850 fps .55 inches CTC

Huma regulated at 2050 psi
.6 barrel port, .1875 TP and valve
JSAR valve, air tube, and MDS hammer with striker set flush.
Marmot Militia barrel
Hill shroud rail (non floating barrel)

50 yards. 5 shots per group. 5-10mph crosswind from my right.

I know that I pulled that last shot on the 25.39gr pellet, which is the one that I then needed to measure against. So long story short, it would appear the 18.13 are much better, but if I did it over again and didn't pull that shot, then the 25.39 might be just as good.

What are the conclusions others have reached with the 25.39 redesigned?

[PCPhack]

Here are the 18.13

[PCPhack]

Here are the 25.39.

[PCPhack]

As you can see, I have the scope now mostly zeroed (a little shot high here) for the heavier pellets. I want to try them for a while. I want to also redo the test, as this was late in my session, and I was getting shakier due to needing to eat lunch. It was already 2pm.

[Hobbyman2007]

Both my BT65 and K550 love these pellets . I’ve found them to be more accurate from 800 to 860 FPS. Just remembered I need to stock up as I’m down to my last 1k .

[triggertreat]

Here are the 25.39.

WOW! Nice group at fifty and encouraging.  I haven't even opened my tin of those 25.39s yet, but it's coming up after the LW tube install and tune.

[bowdoc64]

Nice group

[Tonykarter]

Nice group! 

[K.O.]

I would test in almost no wind and a bit more wind next... cause those could be interped to mean the 25g are better bucking the wind..

[PCPhack]

Both my BT65 and K550 love these pellets . I’ve found them to be more accurate from 800 to 860 FPS. Just remembered I need to stock up as I’m down to my last 1k .

You found them more accurate in that range as opposed to what, slower? I was actually  thinking about upping my regulator pressure a little and see if they are any more accurate up near 900 or a little over, rather than the 850.

[Hobbyman2007]

They seem to open up when shot faster than 900. I didn’t try them any slower , I started above 900 and slowed them down .

[KnifeMaker]

Once past the 860 to 890 range, it is extremely rare for a pellet to to become more accurate with more speed. In fact at longer ranges, it is almost guaranteed to become less so.


Knife

[K.O.]

Pellets being being high drag lose velocity pretty quickly but not the rpm of their spin... at distance that can create dynamic instability and they will tend to corkscrew...

[PCPhack]

Yeah, after sleeping on it, I think I will just leave it as is. Both pellets are grouping nicely, and I have done just about all the upgrades there are for the gun. I might tweak the hammer tune a little to see if there is an even more accurate tune for the pellet, but at this point I need more practice and to shoot out to 100 yards. I might put my camera rig on it and shoot to 100 just to also see in slow motion what the pellet does.

[mackeral5]

Pellets being being high drag lose velocity pretty quickly but not the rpm of their spin... at distance that can create dynamic instability and they will tend to corkscrew...

I'm trying to better comprehend this..  Are you saying that at higher velocities pellets not only travel at a higher FPS, but also spin at a higher RPM.  At longer ranges, a pellet's loss of spin is NOT linear to its loss of speed?  This creates an excess spin to speed ratio, and can induce corkscrewing? 

[nervoustrigger]

Right, if you do the math, a typical 1:16 twist rate produces the following spin rates:
 
At 900fps muzzle velocity:  40,500 RPMs
At 600fps muzzle velocity:  27,000 RPMs
 
As Kirby said, the pellet loses velocity quickly but the spin rate doesn’t decay nearly as fast.  So if you look at it what it’s doing out at a distance, it’s much slower but still spinning really fast and that may cause it to wobble.

[mackeral5]

Jason/Kirby- thank you for this explanation.

[Wayne52]

They're both very accurate in my 22's.  I used the Monsters today for a couple of red squirrels

[mackeral5]

They're both very accurate in my 22's.  I used the Monsters today for a couple of red squirrels

Can you please share your MV and rate of twist?

[Harpoon1]

Right, if you do the math, a typical 1:16 twist rate produces the following spin rates:
 
At 900fps muzzle velocity:  40,500 RPMs
At 600fps muzzle velocity:  27,000 RPMs
 
As Kirby said, the pellet loses velocity quickly but the spin rate doesn’t decay nearly as fast.  So if you look at it what it’s doing out at a distance, it’s much slower but still spinning really fast and that may cause it to wobble.

Jason

So then, all things being equal, do you believe “most” corkscrewing issues are caused by excessive speed/spin rates?