JSB Mk1s beat the Mk2s again - 25cal

[Spartan]

Re the JSB 33.95gn 25 cal pellets. Unsorted.

When I had my Cricket in 25 the Mk1s outperformed the Mk2s. It was subtle but noticeable. About 10-15% better in group size. I figured it was a fluke. The Mk2s must be better because they're the redesigns, right?? Almost everyone seems to shoot the redesigns and there must be a reason for that, right? Figured I just had an oddball setup. So I shot the Mk1s and figured I was just the odd man out with this gun.

Now a few years later and putting my M3 through the trials (.25, 600mm standard liner, tuned to ~890fps). Been getting decent groups with the Mk2s, hovering right around 1.1 MOA quite consistently, so I'm happy with that at this point with my still mostly stock setup. But I remembered those Mk1s and got a couple tins delivered yesterday just to see. Sure enough, I put down three groups of five shots each at 70yds and they very consistently averaged 0.9 MOA. Tested the Mk2's under the same conditions right after and the same 1.1 MOA. And the gun was still technically tuned for the Mk2s

When I read the forums and watch the videos, 9 out of 10 people shooting JSB Heavies in 25 are shooting the Mk2s. It's almost a standard.

So what gives? Do I just have a couple oddballs here, or are people just automatically bypassing the Mk1s since there is a newer, sexier flavor in town, and potentially missing out on some better performance??

 

[Trucker3573]

I have no experience with them as I just shoot 25.39. However, from the vids I’ve seen maybe try running the mkii a little faster like 925-930 fps ?

 

[Spartan]

I have no experience with them as I just shoot 25.39. However, from the vids I’ve seen maybe try running the mkii a little faster like 925-930 fps ?

I did. Tried them everywhere from about 800 to 950. 880-900 was a sweet spot for the tune in this setup. Groups didn't change much, but air usage starts becoming very uneconomical above 900 with those pellets in the 600mm barrel. At least for me.

 

[JakeRico]

Mk1 always shot better for me as well

 

[scubajeeper]

Re the JSB 33.95gn 25 cal pellets. Unsorted.

When I had my Cricket in 25 the Mk1s outperformed the Mk2s. It was subtle but noticeable. About 10-15% better in group size. I figured it was a fluke. The Mk2s must be better because they're the redesigns, right?? Almost everyone seems to shoot the redesigns and there must be a reason for that, right? Figured I just had an oddball setup. So I shot the Mk1s and figured I was just the odd man out with this gun.

Now a few years later and putting my M3 through the trials (.25, 600mm standard liner, tuned to ~890fps). Been getting decent groups with the Mk2s, hovering right around 1.1 MOA quite consistently, so I'm happy with that at this point with my still mostly stock setup. But I remembered those Mk1s and got a couple tins delivered yesterday just to see. Sure enough, I put down three groups of five shots each at 70yds and they very consistently averaged 0.9 MOA. Tested the Mk2's under the same conditions right after and the same 1.1 MOA. And the gun was still technically tuned for the Mk2s

When I read the forums and watch the videos, 9 out of 10 people shooting JSB Heavies in 25 are shooting the Mk2s. It's almost a standard.

So what gives? Do I just have a couple oddballs here, or are people just automatically bypassing the Mk1s since there is a newer, sexier flavor in town, and potentially missing out on some better performance??

My Cricket is exactly like yours, except it shoots the mk1’s way better than the redesigns.

 

[PumaCarl]

What is the actual deal with the Mark 1 pellets anyway? When I got into shooting.25, some years ago, they were nowhere to be found and people were saying that they were discontinued when the Mark 2 came out. There were also some people that reported buying Mark 1 pellets that had Mark 2 pellets in them. Either way, many have often said that the original Mark 1 shot better. I never bought any because I didn't want to become invested in a dead end. Does anyone know if JSB is going to stop making the Mark 1, or are committed to it? I would definitely try some if I had some faith that they weren't going away. What problem with the Mark 1 got JSB to decide that they needed a Mark 2 to correct it? I probably read it somewhere, at some point, but I honestly forgot and maybe by now someone has the story straight.

 

[Spartan]

What is the actual deal with the Mark 1 pellets anyway? When I got into shooting.25, some years ago, they were nowhere to be found and people were saying that they were discontinued when the Mark 2 came out. There were also some people that reported buying Mark 1 pellets that had Mark 2 pellets in them. Either way, many have often said that the original Mark 1 shot better. I never bought any because I didn't want to become invested in a dead end. Does anyone know if JSB is going to stop making the Mark 1, or are committed to it? I would definitely try some if I had some faith that they weren't going away. What problem with the Mark 1 got JSB to decide that they needed a Mark 2 to correct it? I probably read it somewhere, at some point, but I honestly forgot and maybe by now someone has the story straight.

All questions that I have as well!! I remember being concerned a few years ago that the Mk1s were going to be discontinued. Doesn't look like that has happened, but they do sometimes cost more than the Mk2s these days. I just stocked up again with a dozen tins taking advantage of a Pyramyd sale, so shouldn't have to worry about it again for a while.

 

[gendoc]

i guess it depends on your gun's build characteristics.
my maverick 700mm sniper in .25 with heavy slug liner,
slug probe & heavy hammer.
it really likes the MKII at 920fps. when im not using slugs while hunting crows,
i use the MKII's for critters within 50yrds grouping around 3/8"
and they pack a punch yes !!

the MK1's are not even close in accuracy.

 

[Ezana4CE]

What is the actual deal with the Mark 1 pellets anyway? When I got into shooting.25, some years ago, they were nowhere to be found and people were saying that they were discontinued when the Mark 2 came out. There were also some people that reported buying Mark 1 pellets that had Mark 2 pellets in them. Either way, many have often said that the original Mark 1 shot better. I never bought any because I didn't want to become invested in a dead end. Does anyone know if JSB is going to stop making the Mark 1, or are committed to it? I would definitely try some if I had some faith that they weren't going away. What problem with the Mark 1 got JSB to decide that they needed a Mark 2 to correct it? I probably read it somewhere, at some point, but I honestly forgot and maybe by now someone has the story straight.

@PumaCarl This was discussed a while back. Here’s one thread I found discussing the difference.

JSB .25 King Heavy 34 grain

Has anyone recently received .25 JSB King Heavy that were actually King Heavy and not the Mk2? It seems for the past year + that JSB has been putting Mk2 in King Heavy tins. Then they dreamed up the big lie that said yes they were different in that the King Heavy skirt was 6.68mm diameter...

www.airgunnation.com

I think there were other threads where this was discussed as well.

 

[Ezana4CE]

@Spartan Apparently some gun barrels shoot the MKIIs more accurately and with consistency. I have both iterations and I have a gun that shoots MKIIs noticeably better from what I can remember. I really don’t know why, I just went with what has worked for me. When I got out to 100 yards and saw how the MKIIs performed I was content. I have yet to take the original King Heavy pellets out that far.

 

[PumaCarl]

@PumaCarl This was discussed a while back. Here’s one thread I found discussing the difference.

JSB .25 King Heavy 34 grain

Has anyone recently received .25 JSB King Heavy that were actually King Heavy and not the Mk2? It seems for the past year + that JSB has been putting Mk2 in King Heavy tins. Then they dreamed up the big lie that said yes they were different in that the King Heavy skirt was 6.68mm diameter...

www.airgunnation.com

I think there were other threads where this was discussed as well.

Thank you for the effort Ezana4CE, but as that link demonstrates there was never an answer to the question put forward to JSB. I never remember seeing an official answer and I read this site just about everyday. Plenty of speculation, never a hard answer. Maybe I missed it, so I asked.

 

[Ezana4CE]

@PumaCarl I don’t know if JSB ever addressed the discrepancies. However, there was at least one thread that I recall where a member was measuring skirt depth and width (thickness), and comparing them. I just didn’t look that hard for it. I think @Centercut may know. I recall him being engaged in a couple of those conversations. I think @Motorhead may have been as well. I can’t recall the details. It’s been a while since I saw those posts.

 

[PumaCarl]

@PumaCarl I don’t know if JSB ever addressed the discrepancies. However, there was at least one thread that I recall where a member was measuring skirt depth and width (thickness), and comparing them. I just didn’t look that hard for it. I think @Centercut may know. I recall him being engaged in a couple of those conversations. I think @Motorhead may have been as well. I can’t recall the details. It’s been a while since I saw those posts.

Yes, and the posts showed the MKII pellets in the MKI cans, and never a peep from JSB themselves, that I could find, about all the discrepencies at the time, or since, and never a word about the future of the MKI, so it's still an open question to me. Just mostly curious at this point.

 

[Ezana4CE]

@PumaCarl Got me on that one.

@Spartan My Brocock likes the MKIIs. I currently shoot them around 790 fps. Seems to do well within 50. Beyond that I need more practice. I’d taken the gun out to 100 last year or maybe 2021 and they did ok from what I recall. I don’t know much about FX barrels. I’m not sure what some other folks are buying, but it does seem that within that past 6 - 12 months there’s been a shift from MRDs towards King Heavy MKIIs in some bench rest circles.

 

[PumaCarl]

I don't mean to "get" anybody but I would like, at some point, to get an answer. For the record, my favorite pellet (even though I shoot more .22 18gr) is the MKII. This might be changing though, I'm really liking the new Zan .30 56gr. Time will tell.

 

[Ezana4CE]

@PumaCarl No No. I just meant that I wish I knew. I never figured that one out myself.

@Spartan @PumaCarl What type of shooting are you guys doing?

For those with guns shooting MKIs well, have you ever faced issues with availability?

 

[PumaCarl]

Mostly, just fun, but that ends quickly when I see a woodchuck. Lately I have been getting opportunities to shoot coyotes but I have not shot one yet and was hesitant to use my .25, so I got a .30. Once I get comfortable plugging them with the .30, then I will try the .25 on them.

 

[bigHUN]

I cannot get the MK1's in Canada suppliers for decent money so whenever ordering slugs from ZAN I include at least five tins of MK1.

First I noticed the MK1 skirt size is slightly larger and want to rub agains the wall in the OEM 28 mag. This may be a reason for a change also this may be a reason aftermarket mags surfaced.
I have slugged my liners with each pellet type and I am noticing the land-grove ratio makes deeper grooves in MK1 head size, and the MK1 is automatically slower for about 20 fps @ 930.
In the past one month, I compared the MK2 vs MK1 with four liners.
I shoot 5 groups x6 @ 100 meters, with Impact MK2, Power Block and 720c plenum, tried diferent combination of HW and HS and now back to OEM.
.25x700 STX-A
.25x700 Superior Heavy
.25x600 STX-A
.25x600 Superior Heavy is currently mounted for tomorrow gun range time.

So, I spent a 1-2 days for each liner shooting 100 meters BR over a 300 shots each , and I can confirm with all these liners the MK1 groups are consistently tighter. I cannot confirm the MK1 tooling number or batch number, I got mine from ZAN, and the MK2's from my local store AGS in Canada.

For tomorrow testing I have prepared two group of pellets (MK2 and MK1), washed + lubed + weight sorted the same, and
a small batch that I resized both to same OD.
Also I resized a smaller batch for each straight from the tin = non-weight-sorted (but still washed and lubed).
I am planning this exercise for some longer time, I want to proof to myself that the head sizing is more important then weight sorting.
I will see tomorrow how my plan goes. If my prediction proves positive next week I will repeat the same with .22 MRD's.

 

[okieairgunner]

I just recently switched my Red Wolf HP .22 too .25. I have also been doing alot of testing. I have some old tins of MK1 2021 and newer tins 2022 of MK1 and you can definitely see the difference in skirt thickness and depth. The 2022 MK1 and MK2 2021 have almost the exact same skirt depth and thickness with the MK12022 having just an ever so slightly thinner skirt but really not by much. I think that to me the slightly bigger difference in the two is that it seams the 2022 MK1 are again ever so slightly longer. My ART barrel in my RW hp shoots the mk1 2022 again like posted above slightly better than the mk2

 

[bigHUN]

I measured last night with a digital caliper.
The MK1 what I got in 2022 from ZAN has a larger OD skirt for 0.1mm and the skirt "cavity" is deeper by eye and that pin that forms it has 3 steps/angles.
Heading now to my club for group testing.

Edit: and I made a big mistake before heading out not checking what liner I have in my Impact ... turns out after cleaning/polishing I put back the STX-A. So tomorrow afternoon I will be back to my range to finish my testing the Superior Heavy with pellets (random and resized).