55 gr. BBT HP

[rsterne]

Michael, it's a given that a bullet that heavy in .257 would require Helium, that was stated in the first post about a 160 gr. by Kirby.... I was trying to point out that a bullet that heavy would either have to be so long that the twist rate would be in the 5" range.... OR would have to be 4-4.5 calibers long and basically cylindrical (with a bit of tapering on the ends, maybe)…. and so would not have as low a Form Factor as, for example, my 113 gr. BBT.... Since you would be driving either at the same velocity (113 gr. on air, 160 gr. on Helium), if they slowed down even at the same rate (same BC) then ballistically they would have the same trajectory, the only advantage to the 160 gr. would be FPE....

There is always the challenge of building the biggest, baddest .257 around, I get that.... My .308 Whiteout 200 gr. bullet (using Helium) was the same idea, and all it did was ruffle a bunch of feathers at the EBR.... Too bad the fact that we duplicated the ballistics of the .300 AAC Blackout was overlooked.... Different calibers have different advantages and disadvantages.... Here is a bullet that is 6 calibers long....



The SD is fairly high, at 0.241, but using 4500 psi of air you could push that into the high 900s.... The problem is that the twist rate required would be less than 4"....  …. The get a similar shape to work in .257 (it would weigh 166 gr.) you would need Helium....

Bob

[KnifeMaker]

I completely missed the mention of Helium to push it. My bad!


Considering the dwindling supplies of Helium, I don't think I would want to use it.


Mike

[rsterne]

They just discovered a huge source of Helium in Africa.... When they stop selling it for use in party balloons, I would think about not using it in airguns…. JMO....

Bob

[rsterne]

I had a chance to shoot these at 100 yards today from my .25 cal Disco with the 14" twist TJ's barrel.... Here is a 3-shot group I got while sighting in the gun.... It is actually the smallest group I have ever shot with an airgun.... and rivals the best group I got decades ago with my .222 Rem handloads.... It was shot from bags, front and rear....



It gets lost under the dime....  …. These were sized to 0.250", and shot at 950 fps, like the ones in the first post above.... I shot a Ground Squirrel with one and the results were NASTY.... I'll be posting a pic in the Hunting section....

Bob

[K.O.]

That has to be rewarding after all the effort you have gone to since what about 2013 developing the BBT concept... Thanks for the work   
I like down at stock ish fpe and love the 30g .22... this 55g .25 looks to be a very good round also if you have the fpe for it... has to fly very well for that kind of accuracy...

I do think the design is about the best that can be done for an exceptional general purpose/hunting round...

[rsterne]

Well I can tell you, it hits like a .22LR HP.... WOW !!!!

Bob

[KnifeMaker]

They just discovered a huge source of Helium in Africa.... When they stop selling it for use in party balloons, I would think about not using it in airguns…. JMO....

Bob

Yeah, No kidding GRRRR!

[KnifeMaker]

Congrats on the Group Mr. Bob!

[Wayne52]

Awesome group you got there at 100 yards Bob !!!

[Hobbyman2007]

Great shooting Bob . Good to see you’re getting some time behind the trigger shooting at range . Looking at the bullet design , I’m wondering why I can’t get the 51grain to group well . I’m going to have to revisit them once I get the .22 bullets sorted out .

[rsterne]

The 55 gr. in .25 cal is 2 calibers long.... I am beginning to think that and longer is where boattails really begin to shine.... Just a gut feel, no hard data yet.... other than that stellar 3-shot tease above....

Bob

[K.O.]

What is amazing to me is your best group in decades was out of a 7/16 barrel.. and a modded Disco.

[rsterne]

I guess the bullet and barrel are a good match !

Bob

[K.O.]

Well I can tell you, it hits like a .22LR HP.... WOW !!!!

Bob

well with its , B.C., and M.E. it should match well enough you could call it a Pnu 25lr..