Gamo Urban with 30gr BBTs

[EdinGa]

Here's a shot string from this afternoon. This is 22 shots from 2900 psi to 1400.

622
622
632
644
641
633
629
630
637
Err
641
639
640
639
629
634
636
632
641
621
620
608

[K.O.]

Well Ed the reason I want another Urban is to put a 23" Remmy 514 barrel I have on it.. they are the same O.D. ...

Oh remember the charts I made in the other thread comparing the BBT 30g to the JSB 18g... if I get motivated I may go back and redo them... I went conservative and used the NOE estimated B.C. of ~ .06 tho I thought the B.C. was better than that...

well  Bob did a data base and has it at about .08 which is about what I got using trajectory and Chairgun... pretty sure that is closer to reality...

So point is performance is better than those charts show by a bit... sorta figured that and it was shown in that thread when your
drop at 80 yards was less than predicted...

So I think I should go back and make note of that and/or redo those charts...

My habit has been starting at 2900 psi and sending a mag then refilling...

[K.O.]

Man I wish Money grew on trees... PA sale has the Urban back down at $239 for a day or two...need a couple more..

You're wanting another Urban, and I'm yearning for more power. 😉

My bullets are definitely harder than they were after I cast them. I can't dent them with a thumbnail now. I did manage a small scratch, but that's it.

I shot one through my "ballistic play doh" today. It passed all they way through and bounced off the water bottle backstop. I'm attaching a picture of the setup and the recovered round.

From what I have been told and read...non heat treated alloys with antimony will harden for about a week or so before the reach max hardness as the grain size and such sorts out... they also tend to grow a touch... I think it is called precipitation hardening...

[K.O.]

Did a quick seach to check... have not read results yet...

https://www.google.com/search?rlz=1C1AFAB_enUS481US481&ei=FQDeXIz9AobctQX4yJzoCA&q=precipitation+hardening+with+boolits&oq=precipitation+hardening+with+boolits&gs_l=psy-ab.3...18688.29158..29896...0.0..0.194.2280.0j13....2..0....1..gws-wiz.......0i71j0j0i67j0i22i30j0i333j33i160.pO6Sbpt2LF4

[EdinGa]

From what I have been told and read...non heat treated alloys with antimony will harden for about a week or so before the reach max hardness as the grain size and such sorts out... they also tend to grow a touch... I think it is called precipitation hardening...

I'd say it's definitely true. I had no trouble denting them with my thumbnail after they were cast. They've aged a few months now, and there is no doubt they are harder. I really don't see any difference in velocity or accuracy though.

These Urbans are phenomenal little rifles in my opinion. I don't blame you at all for wanting more. If money did grow on trees, I'd have several myself. I've actually been toying with the idea of selling a couple of my powder burners and investing in another pcp or two..

[EdinGa]

My habit has been starting at 2900 psi and sending a mag then refilling...

Based on what I saw today, I think I'm going to start filling to 2700 psi and topping off again after a mag.

[EdinGa]

I failed to mention that I haven't been sorting either. I did measure a few tonight and they were all  .2185 to .2195.

[K.O.]

Wow that is a large variation... surprised you are getting any accuracy with that... I suppose that if you are measuring across the seam on some and not on others it would account for some of it but still... but also if you are using digital verier calipers... they tend to round to the nearest .0005... Heck I use a Fowler mic and am not sure how far to trust my measurements...

But My .25 Mrod does the same poi and spread with the 40g .25 BBT sized to either .2495 and .250... is ~.2495 groove at the choke and .250 groove at the chamber...My other .25 Mrod is .249 groove at the choke and .250 groove at the chamber...

[EdinGa]

Another group at 60 yards with my "hard cast" BBTs. The cross was the point of aim with a 3 dot holdover. The bottom group is with the NSA 19gr 217 hollow-point. It's a little over an inch. It was shot with a center hold on the reticle.

[EdinGa]

One more.

[K.O.]

that be a grouse dinner accurate to me... If can do very close to that near on to every time I would say you have a "bonafied" 60 yard Grouse Rifle...

But Bob would be a better judge of that than I... but  have taken Chukar with less fpe  decades ago...

https://www.gatewaytoairguns.org/GTA/index.php?topic=36105.0

https://www.gatewaytoairguns.org/GTA/index.php?topic=19635.0

https://www.gatewaytoairguns.org/GTA/index.php?topic=17819.0

[K.O.]

Did a fingernail test with one of my 4% tin mix would say maybe 9-10 for hardness...I seems I will eventualy have to go harder... I doubt the SASS_y Girls And the CASS guys are using much more than 18 bhn for their subsonic stuff... could be some harder cast used some tho... but yep you are probably 14-18 BHN... are you sending unsized..? if so .219 might be just a tad more consistent/tight... but then the barrel might like doing the sizing with the harder cast...

figuring out the exact %sn and % sb well would be hard...

so yeah I think you are doing a touch better with your hard cast cause you hit the point where both size and hardness support the nose better than my 4% and 1.5% mixes... is the alox working better than the mink oil based case lube...

Thank your sharing is helping me learn... and it is like when I was molding and pouring aluminum... a lot to learn... Like play dough is pretty good for helpin catch a round to look at...

[Wayne52]

I haven't had a chance to shoot these yet but it won't be long.  I'll definitely be using my Airmax Dominator for the testing though.

[Bob Pratl]

I haven't had a chance to shoot these yet but it won't be long.  I'll definitely be using my Airmax Dominator for the testing though.

Looking GOOD! I'm kicking myself for not picking up one of these molds when NOE showed one left. 
I'm anxious to how they perform in the Liberty.

[Wayne52]

Bob the bore in the Liberty is smaller than my Crosmans and SPA's and they would need to be resized to work in the Liberty or Freedom.  My Airmax Dominator chambers and shoots them really good.  I can shoot them out of the SPA co2's and Crosman co2's, Prod and Disco as well.  I have never tried them in my DAR22 yet though but if they chamber and shoot from that gun my guess would be they'd shoot really good because that gun is unchoked like my Airmax Dominator.

[Hobbyman2007]

With a bit of leade work , the 220 version is a tack driver from the PP700SA. Just about the perfect pesting combo . Good out to 30 yards

[EdinGa]

I turned up the power on my Urban yesterday. I'm at 16 turns on the hammer spring which is max from what I understand. From a 2800 psi fill, I'm getting a 10 shot average of 645.6. My standard deviation is 4.2 with an extreme spread of 12. My low was 639 and the high 651. This is 10 shots at 60 yards.

[Insanity]

I ordered 25 each of 26 and 28gn hollow points from mr hollopoint. Cant wait to test them.

[EdinGa]

I finally got my hands on some pure lead, and had a chance to cast some this afternoon. Initial results look very promising. 60 yards again.

[Hobbyman2007]

I finally got my hands on some pure lead, and had a chance to cast some this afternoon. Initial results look very promising. 60 yards again.

Great shooting . Bob really hit the nail on the head with this bullet . I’d really like to know why I just can’t get the .25 cal 52 grain to group like the .22 cal . Hope Al gets the RG style HP pins worked out .