Author Topic: 55 gr. BBT HP  (Read 255 times)

rsterne

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55 gr. BBT HP
« on: March 07, 2019, 03:02:23 PM »
I have a hot .25 cal Disco that is a genuine 100+ FPE gun, so I pulled it off the wall today to try some velocity experiments with different size bullets.... I have some 50.4 gr. FN BBTs (NOE 250-51), and also some 58.3 gr. FN (NOE 250-60), plus the HP versions as well.... I tried them as cast (0.250" nose / 0.252" drive band), and they were hard to chamber in my TJ's .25 ACP barrel.... so I sized some of each down to 0.251", 0.250" and 0.249".... I tethered the gun at 2950 psi (it is modified for 3K plus) and both bullets picked up a lot of velocity between as cast and 0.251", gained more at 0.250", and then lost about 10 fps at 0.249", presumably from a small amount of blowby….

The 58.3 gr. FN were well over 900 fps, so I thought I would tune the gun for the 55.0 gr. HP version of that bullet, sized to 0.250".... Mean looking little devil....



I maxed out the preload and hit 993 fps (120 FPE), and then backed it off a turn and got 965 fps.... At that setting, off the tether, I got 2 equal shots and then a 3rd at about 940 fps, so I backed the preload out a bit more and ended up with 3 shots off tether of 956, 963 and 945 fps (111 FPE average) within a 2% ES.... Tethered, of course, it shoots 956, within a few fps.... which will give me a good platform to test these HP bullets.... The gun is loud, and not very efficient.... but at 110 FPE it should really lay a smackdown on a Marmot....  8)



This is a penetration test of the 55 gr. BBT HP in soap at 110 FPE.... The nose came apart.... penetration of the base was 95 mm (3.75")….

Bob


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rsterne

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Re: 55 gr. BBT HP
« Reply #1 on: May 01, 2019, 03:59:14 PM »
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....  8) …. These were sized to 0.250", and shot at 950 fps, like the ones in the posts above.... I shot a Ground Squirrel with one and the results were NASTY.... I'll be posting a pic in the Hunting section....

Bob
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oneshot61

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Re: 55 gr. BBT HP
« Reply #2 on: May 02, 2019, 05:03:36 PM »
 Very nice group! And that is some serious power out of that platform. I love the bbt 51 and 48 hp. That hp is wicked in full lead.

steveoh

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Re: 55 gr. BBT HP
« Reply #3 on: May 02, 2019, 06:01:23 PM »
I bet my Sumatra would like these... hmmm Rats? Not so much. Overkill? You bet!
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rsterne

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Re: 55 gr. BBT HP
« Reply #4 on: May 02, 2019, 06:26:34 PM »
The BBT HPs all work well, providing the velocity is high enough for the alloy used.... I have also used the .217 cal 27 gr. HP on GS's and it does a lot of damage too....

Bob
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