.20 Baracuda Match (sized down from .22)

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Franklink

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Sep 3, 2017
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(Again, credit for this idea to Motorhead)

This is the next step of this heavy .20 from .22 experiment....

Prior testing and general process described here....

https://www.airgunnation.com/topic/20-jsb-exact-jumbo-heavies/?referrer=1

https://www.airgunnation.com/topic/noe-22-19-6-grain-mold-sized-down-to-20/?referrer=1

So, these....

bm tin.1636856598.jpg


Become these.....

21.2grain baracuda match.1636856612.jpg


I'm getting 0.201 for head size, 0.205 for the skirt, and 0.335 for oal. Weighed the post-sizing and they're coming out at 21.1-21.3grains.

The fastest I can get them without bumping to a heavier hammer spring is 745, for 26fpe. (Test gun is .20 Veteran Short). 

Accuracy results to follow....

A couple of asides here:

  • It's been very interesting to see the "flow" properties of JSB lead vs cast lead vs H&N lead. They simply don't behave the same. The cast was 95%+ JSB and it didn't size as easy as the JSB 18.13s. One airgun friend suspects the casting process gives it more of a granular structure. 
  • I've been measuring ratios of overall length to the caliber size and finding some interesting ratios of the "best" (wind resistance/BC/long range accuracy/etc) performing pellets. I'll likely create a post on my thoughts and notes on that seemingly magic ratio in a separate post at some point in the future. 
  • The two large "driving bands" on the head and skirt are robbing me of some energy. JSB knows what they're doing in having minimal contact area on the head and skirt. The same hammer tension that throws a 15.89gr JSB factory .20 @ 910 will only push my 21.2grn H&N .20s at 630fps. I've got to max out the hammer tension for the 745fps cited above. The roughly 5grain difference definitely accounts for some of the loss in speed, but it seems to me there shouldn't be as large of a disparity in speeds. I'm chalking it up to friction from the large driving bands that result from the sizing process. 








 
Hey Fuss,

Yeah, we had similar first impressions of them seeming quite slug-like. It intrigued me enough to go this far with it. So far, nothing spectacular though. Nothing has shot better than just .20 factory JSBs yet. I would like to note that the best .22 sized down to .20 so far has been the 18.13s. And really interesting to see that they had a better BC as a .20 than they do as a .22. 

The tin of 18.13s was horrendous as .22s, that's why they got sacrificed to the experiment. Perhaps I'll revisit the 18.13s, but start with a good tin and see where that gets me. 

Fun stuff.
 
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Nice, does the resizing shave a grain or two of weight off the pellet?

.25 cal to .22 cal possible?

Click to expand...

I've not preweighed a pellet, and then compared that to the post sizing weight so I can't answer that question. 

When I get around to revisiting the accuracy of the 18.13 sized down, I will do exactly that and see if the weight changes. I don't suspect it will though. To me it seems I'd be finding some lead somewhere of the weight was changing, either smeared/stuck to the inside of the die or little flakes on my workbench. I'm not seeing either but I'll pre and post weigh to find out for sure. 

I mainly want to revisit it to shoot from a bench (instead of prone) and do it on a day when I haven't been awake for 24hrs+ like I was last time. That converting back to the land of the living from night shift makes me pretty jittery, and that was the state I was in the last time I shot the 18.13s as .20s. 

As to your other question about .25 down to .22....I don't know for sure, but shared my thoughts in the other related topic https://www.airgunnation.com/topic/20-jsb-exact-jumbo-heavies/
 
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The other day when we spoke of taking the JSB .22 cal 25.4 MONSTERS down to .20 cal ..... tried that with a few.

The older straight waist turned into SLUG of straight side profile indistinguishable it was ever a diablo waist pellet. The taper skirt "Redesigned" did not fair much better.

BOTH were excessively LONG and while able to shoot them from the Airwolf / Heliboard at MAX POWER at @ 38 fpe, they lacked enough speed to get spinning fast enough and flew unstable. * figuring the same issue present with the H&N 21 grain ... Too long and barrel twist rate not fast enough.



Scott S
 
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