JSB Exact King Heavy – 33.95 Grain – .25 cal – Diabolo Pellet Range Report

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Editor’s Note:  Our friend, Cliff, over at the VarmintAir Blog, got a chance to try the new .25 caliber pellets from JSB.  So, when he put up his post, on the JSB Exact King Heavy – 33.95 Grain – .25 cal – Diabolo Pellet Range Report, we asked if we could republish it over here on Varminter Magazine.  If you shoot airguns, you owe it to yourself to bookmark the VarmintAir Blog and visit it frequently.  Cliff has so much information on airguns in one place, that it is the one site that I refer people to, when asked about specific information on anything about airguns.  Click here to visit the VarmintAir Blog.
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Inspecting, Sorting, Sizing, Shooting:

A friend, recently sent me a tin of the new JSB Exact King Heavy, 33.95 grain, .25 cal pellets to test.  The only rifle in my collection, that could possibly start to do justice to these new heavy pellets, is my Kalibrgun Cricket.  At 33.95 grains, it is a substantial step up in weight from the 25.4 grain JSB Kings that I normally shoot in this gun.

The first thing that I wanted to do, was to give them all a quick visual inspection, and then get them sorted by head diameter and pellet weight.

Tools of the trade.  Left to right, PelletGage, Speedy Pellet Inspector, and my digital scale that weighs to .01 grain:

The first thing that I did with the 150 pellets, was to run them over my Speedy Pellet Inspector, to get a close look at the skirts and heads.  I could not find one pellet that I would reject for any reason.

Next up, using my PelletGage, was to get them sorted by head diameter. The 150 pellets sorted into three different head sizes shown below.

21 – 6.38mm
73 – 6.39mm
56 – 6.40mm

Next, was to get them weight sorted into groups separated by .1 grain. The spread was from 33.7 grains, on the light side, to 34.8 grains on the heavy side.  A little over a one grain difference.  The specified weight is 33.95 grains.   I held some back and didn’t weight sort those.

At this point, I decided to see if they would fit in my Cricket’s magazine. I had heard, on line, that the size of the skirts on these pellets were running a bit large.  What I found, was that they would not go completely into the Cricket magazine chambers.  The heads fit fine, but the skirts were definitely hanging up on the mouths of the pellet chambers.

I decided to use the magazine as a sizing die.  Using a brass punch, that fit the flat area at the bottom of the skirt, I pushed all of the pellets through the magazine chambers.  Measuring the skirt diameters, I found that they were .263 going into the chambers, and .260 coming out.  It took a fair amount of force to push them through, so I didn’t want to do it in the gun, while shooting, and risk damaging the pellet probe, or side lever action in some way.  As a reference, I measured some regular 25.4 JSB Kings, and the skirts on those measured .256.  Hopefully, I wasn’t screwing up the accuracy of the pellets by doing this.

Yesterday was showtime.  I got out into the forest, and had a chance to shoot these guys on paper for the first time.  Shooting off of a mechanical front rest, leather rear bag, and over wind flags, I shot the first group at 25 yards.  I always do this with a new, to me, pellet.  You might be surprised to see how many different pellets really stink at 25 yards.  If a pellet doesn’t shoot a bug hole at 25 yards, I don’t bother with it.  Most of my varmint shooting is in the 50 to 100 yard range.   Only accurate pellets need apply.  Accurate, as in half inch, or less, five shot groups, at 50 yards.

Very nice, that’s what I’m talkin’ bout.   Out to 50 yards we go.  I added some more wind flags to cover the additional yardage.

These pellets were all from the 6.39mm group.  Next, I wanted to shoot a group with some that I had selected by head size, but had not sorted by weight.  Below is that group.  The shot at 9 o’clock, was me not reacting fast enough to a wind shift.I shot one more group at 50 yards, with the 6.39mm pellets that had been sorted by head size, as well as by weight.  The weight on this group of pellets was 34.5 grains.

Needless to say, I’m thrilled with the accuracy of this new pellet.  Bug holes at 50 yards works for me.  But, just for the heck of it, I decided to stick a prairie dog target out at 80 yards, to see what this pellet would do at that range.  Digging through my stash of targets, I discovered that I was out of the life sized prairie dog targets.  What I did have though, was a life sized cottontail rabbit target, so I went with that instead.  I added a couple of more wind flags, so that I had one every ten yards, all of the way out to 80 yards.

Those five went into about 1.1 inch.  This new pellet is obviously a winner.  However, the one thing that I don’t know yet, is how fast this rifle is shooting them.  Based on the fact that it shoots the standard 25.4 grain Kings at around 940 fps, I’m guessing that these guys are going out in the low 800 fps range.  I’ll have a chance next week, to get the Chronograph set up, and then I’ll know for sure.  At that time I’ll add an addendum to the end of this post that has that information in it.

I think I’ll see if I can get the velocity, of this pellet, up to around the 900 fps range, or a bit more, out of this rifle.  That would make for one heck of a combination for use on prairie dogs.  The Cricket rifle can run on 4350 psi fills, and now that I have my own compressor, that is a non-issue. Before, relying on the local dive shop, I was lucky to end up with a 4200 psi fill.  A .25 cal rifle is an air hog, but running on a 4350 psi fill, the shot count would still be substantial.

The bottom line is, this is a great new .25 cal pellet from the folks at JSB. Now to go on line and get a bunch more coming.

Shot String – .25 JSB King Heavy Pellets:

 

 

 

 

 

 

 

 

This was fun.  Yesterday I had a chance, for the first time, to shoot this gun on a full 300 BAR, 4350 psi fill.  Until I bought my own compressor, I would never have enough air, from dive shop fills, to get me up to that pressure.

I ran a couple of mags over the chrono, to see what the Cricket rifle was doing at the factory settings. It turns out that these pellets were being launched at an average velocity of 848 fps.  That’s a bit higher than I expected.  I wanted to see if I could maybe get the velocity up to around 890 fps, so I pulled the barreled action out of the stock, and increased the hammer spring tension.

It turns out, that the spring tension was already just about maxed out.  I could only increase it by one half of a turn.  With that limited amount of adjustment, left on the tension screw, I wasn’t expecting much of an increase in velocity, and I didn’t get much.  The velocity went up by 12 fps, to an average of 860 fps.  To get to 890 fps, I’d have to get into the gun, and start changing out components, and for now, I’m not interested in doing that, so I’ll just shoot her at the 860 fps level, and see how we do.

I filled the gun to 300 BAR, 4350 psi, and started shooting the string.  I am very pleased with the results.  I shot her from 4350 psi, down to 1595 psi, where she fell off of the regulator.  At that point I had 65 full power shots.  Here are the numbers.

Hi   –  868 fps
Lo   –  854 fps
Avg –  860 fps
ES   –  14 fps
FPE – 56

Since I can’t easily get the velocity up to the 890 fps range, I’ve decided to move my sight-in zero out from 65 yards, to 75 yards.  Then, I’m going to shoot a trajectory plot/curve, in ten yard increments, from 55 yards out to 95 yards, to get my hold under and overs for each of those distances.  The reticule in the AEON scope, that I have on this rifle, makes precisely holding over or under very easy.

Final Day of Range Work – Dialing in for Prairie Dog Season:

As I mentioned in a previous blog post, prairie dog season starts next week, so I took my .25 Cricket rifle out to get my hold under and overs plotted.  I decided to set my zero at 75 yards, and then shoot the rifle, in ten yard increments, from 45 yards all of the way out to 105 yards, making note of how much I would need to hold over, or under, to put a pellet where I want, depending upon the range.

Once I had all of that data logged, and to verify the collected data, I put a Visicolor prairie dog target out at 45 yards, and using the hold under data for that distance, put two pellets on the head.  Moving the target on out to 55 yards, I did the same. I continued to do this, in ten yard increments, all of the way out to 105 yards.  Winds were running from 3 to 8 mph, and swirling.

At 75 yards I held dead on, and at 85, 95, and 105, I held over a prescribed amount, based on my trajectory plot data.  One shot was a close miss, much like what happens on a real hunt, but the rest went into 1.5 inches between the widest shots.  The windage was right where I wanted it, but I did add two clicks of elevation to bring the average POI up just a bit.  The trajectory data tracked accurately, and I think we’re good to go.

Fortunately, I’ve been able to lay in a five tin, 300 count per tin, supply of these new heavy .25 cal, JSB pellets.  Now, I’m going to get busy and sort at least one tin by head size and weight, and then set those aside for upcoming prairie dog hunts.

 

 

 

 

 

 

 

 

 

 

 

 

All of the pellets were sorted by weight, as well as by head size.  This batch all weighed 34.1 grains, and had a head size of 6.38mm.  Next, I switched to a batch that weighed 34.3 grains, and have a head diameter of 6.39mm.  I put five of those on a fresh diamond shaped sight-in target at 105 yards.  Three of them went into a half inch near the center, and two drifted slightly low left, to open the group up to one inch.  Not bad for an airgun at 105 yards.  Since the kill zone on an adult prairie dog’s skull is two inches wide, that’s half minute of prairie dog skull all day long.

I am very impressed with these new 33.95 grain JSB .25 cal heavy pellets.  Super accurate, especially when sorted by head size and weight, and they buck the wind really well.  My .25 cal Cricket rifle is going to be my primary prairie dog rig this year.  I only had a chance to hunt her a couple of times last season, but I hope to remedy that this season.

On my way back to the Hacienda, I swung by one of the local dog towns to check for fresh inventory.  I’ve been doing this at least once a week, for the past month and a half or so, and much to my delight, this time, a new shipment of prairie dog pups had finally arrived.

I’m keeping an eye on the weather for next week.  Right now, the forecast, for the area I want to hunt in, is calling for 30 mile per hour winds.  I’m hoping they die down, for at least one day, so I can get this rig into the field and get the, “2015/16 Prairie Dog Games” under way.

To read about the first Prairie Dog hunt, head over and read the latest post on the VarmintAir Blog with Cliff’s hunt results using the JSB King Heavy 33.95 grain – .25 caliber pellets:  The 2015/16 Prairie Dog Season – Is Underway

Cliff just added another hunt to his blog today (06/30/2015), where he took numerous prairie dogs with the new 33.95 grain JSB pellets:  Kalibrgun .25 Cal Rifle Continues to Impress

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