GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: skorec on March 28, 2018, 10:04:44 AM
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I have mentioned more times that up to 60-70 yard I do not need any another pellets than JSB Heavy .177 or .22. I was just finding good pellets/bullets which will be better for 70+ yd.
It seems that after long time I finally have found out right bullets for long distances.
The .177 Piledriver shots 1*MOA at 5 shots group and 2*MOA at 20 shots group.
Do you know ballistic coefficient for Piledrivers at 270 m/s = 885 FPS ?
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I have found out that Piledrivers have BC=0,82. But If I put value ( BC=0,082, sight high = 5,31, zero range = 70m, M velocity = 270m/s, ind Mag =24 ) into the chair gun real ballistic curve doesn’t agree with reality at all. Probably because ( 12x not 8x ) points at reticle at my Nicko Stirling 6-24x56 Neghtater are not one MilDot but two MilDot ???
https://zbrane.subrt.cz/puskohled-nikko-stirling-6-24x56-nighteater/
I have draw myself reticle.
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Nikko Stirling are 16x MD calibrated, not 12 or 8x...
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Skorec,
Have you changed the ballistic profile? The default GA is for diabolo waisted pellets. Maybe the RA4 profile will match the Piledriver shape better?
Taso
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Skorec,
Have you changed the ballistic profile? The default GA is for diabolo waisted pellets. Maybe the RA4 profile will match the Piledriver shape better?
Taso
No I haven`t . Where I can do it ?
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Here's a screen shot to where the drop down is:
Taso
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Thanks a lot. Anfortunately chairgan stiil show me 42m at up Mildot 4 but physical reality is at up Mildot 2.
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Direct measurement (getting velocity at two know distances) at short range (1yard and 30 yards) came up with .079. Typically, pellet BC changes with range, and is likely to be bit lower at short range.
Will mention, that in trying a whole lot of .177's (think last count was 14 rifles), only managed accuracy I could live with with one....and that one was not a power house PCP. But it managed about 1.4MOA.
If I might suggest a test....it's going to be "icky"....try catching pellets that exit a critter on a back stop that captures accurate pellet holes. I used a thawed whole chicken, cavity stuffed with some hot-dogs, and wrapped in a double layer or t-shirt as the target (about 25 yards) and a chunk of dry wall as the "exit catcher".
What I found, both by the exit holes in the dry wall and a dissection of the store-bought chicken, was that the long pellets tend to tumble shortly after meat impact.
This is a good news/bad news situation. Lighter weight pellets, like the 13.5gr. JSB's, tend to penetrate deeper (which would be good for larger critters), but the .21gr. PileDrivers tend to dump more energy/faster that you'd expect (like more gapping exit holes in little critters like squirrels).
This isn't too "freakish"....lots of military FMJ bullets tend to fly though air straight and stable, but go arse-over-teakettle once they meet firm resistance.
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Skorec,
Are you sure you have all your units in metric in Chairgun? Do you have an owners manual of your riflescope to share? Maybe we can find how the dots relate and at what power?
Taso
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It is low cost riflescope from e-bay. I have not user manual . Here are values.
Real POI for 42m is near point/dot 2 - see the picture.
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I honestly don't know how long the distances per dot in your reticle is but you could always get a meter stick, set it out at 50 or 100 meters and find at which magnification your dots match up.
Taso
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There is one reticle manual on the Nikko Stirling website but it's not for your scope. They're using 10 power for a 6-24x50 scope.
Taso
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I have found out the problem. cal Mag is 20 for my riflescope - seams to be 20.
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Taso thanks a lot.
Why the dot POI is not highest at 40m but at 25m ?
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Just I want to add info that I am shooting 4,46mm not 4,50mm Piledriver from my choked LW 15x605mm TR 1:17,7 barrel.
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Taso thanks a lot.
Why the dot POI is not highest at 40m but at 25m ?
Maybe because the scope line of sight is higher than the barrel? You can show the line of sight for the scope in the graph. There's an option to display it.
Taso
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OK and is it possible to show ballistic curve reach at line of sight/laser line ?
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OK and is it possible to show ballistic curve reach at line of sight/laser line ?
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How well do you do benchrested with the piledrivers at 50 yards? I remember doing about 2-3 inches at that distance. Not very well. There was quite a bit of variation between the pellets, some with Xtra material on the skirt, some with flattened heads:
(https://lh3.googleusercontent.com/gNbr0q8uL0uBSiQTB8ueuLsmy3LgF_9oaSpM8_suQFVDqXrA_XNKy7htkooJvZZ25Op_Xdg0KSz4DTB1KhaxcpBp-H_cbuUjAEIRpeuv-qFL9mkuEf67K89GgSxV5Qdg6yY7srxngytKKJwUkha4Szg5VMwQwXaTRvI0-JGXcRT-qHupJW_YOOlHGckG3JsjNjfABKuTn9-YU2TLuY15V0M9jEe5IpYfeZcbgXQChPv9hIvfw-dUmKh3CufU6UQEntdjOcJ-bfJfkQuD2gRImWrbXE71U8vYUmE5HcDMcA30Yl3-oLSRV_hFWA9FE7-f_sT5P_V7o0KnmFscl1R4LA6AZSU2MglyGRGbiIHBSybkwdQ5Rft6Zy8Ac9r6-X-sHox92_jT_eg0FIeux_h6rugKY0o06C1-AaJYRdXwOqq2eOXqhksl22NB9iHng1X_dzPl647ufQN6odD276z2UEQc8dsdARIbBCU3WcsXTmxk5XkQ0zMPlhTkZWqBaAcB-u-Zcg8KLBzU7Bq8HBGmXMwKPaHwltcT8bFNQhKpMdb9czD2OpenfstVmny1CYuZbuUpaKCS78CU8BHyyITCQxnv2_ibCCtEXDePcelydPzlRjfM9b6DFNsEnj6QsgWCBJIOywXB9GEtK6YmKYv27WaTllGWMZ_1IKbt=w186-h193-no)
...Same thing with the 15.x grain snipers, and they grouped even worse:
(https://lh3.googleusercontent.com/W85Uz91BXDm_iOqoxW6nXMe0Zn6U-QymQ-ZdOcXY7Ndx4tVaUx8Cbphar-mrf9GaxU-2EvkeLVVup_xOWmJUi9EyVxgCPwZIOcjjTLa6Om2IopEN_8DTcgyw5oIFIv2Hsv62rkKNI_yoLOKzCpyg_Zak7YPZNh2wJw8ZJZGOUWfn7x_1jUePGXZdVG3tGciZT0QnJ2kl1H3YuaE9B_TlyX3XnZDyD7jBoGH_YJ71ev8ZaLQ62XdHWbRduLwAc3B0nFc4rnjNowCJ80FJNXoQiYSwg_3G9DaEh3e4SHsbEG7f0vtjsGjl01uNm6q0v7H2TLuwXde4vwehZoMR20yTCcXgi_M2eEZ-syAQ7oHbRnDGzekBGHin-B6woFz8QY_tbsjsN0jQGa0W7OpmM_u1kW9Ua8E8mprzjV3Z6nFVvocAPmG0Y6s-GKxD5KiHXKJeEtD6f6t9cQ6YnstOBYg66Rjg_WRnrQS7sy1hvbUzod2wewbwnh5Q1Wn-JeglAeopJMC5vXiy67ZFcFBP0u2EwG0HGfTq02w5N7e3V3hkGe9-VQIcjcs0d8M40XUV7Uk4GfN6MSXiRW6lrC3WBYZMyYFgWaegWXkln1X2rzaGbltdP1aheHz2esQIUM58QdPqv4eoZ1wMrB2MfqSRaYaW8nTt1uzCO7V0U96z=w437-h401-no)
I have been shooting the JSB Beast (16.2gr) ever since. They group nice and tight for me...
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Ten shoots of Piledrivers 4,46mm from 272m/s( 3000 PSI ) to 266m/s( 2600 PSI ) at 77 yd. I am just thinking to ad Huma regulator adjusted to 180bar/2600PSI. Also I will need to solve some better/clamp gun rest. I believe I stay at 1MOA very similar as with JSB heawy at 295m/s. With the JSB Monster REDESIGNED I am 1,5-2,5 MOA
I had 10 MOA grouping with old style JSB Beast and JSB Monster. When they produce REDESIGNED Beast I will test them for sure.
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And you are not seeing the wide variations in the pellets themselves, with the extended skirts and flattened heads? Perhaps I will try a tin again. I was able to group similar (though still not as good) when I hand picked the good pellets from the tin. I don't own a scale, so it was just quick eyeball inspection...
Keep in mind that if you put a regulator in that gun it will slow things down, and I am thinking piledrivers will not like that very much. You will need to keep your plenum size large which will reduce usable shot count. Myself, I have a regulator at the end of a bottle feeding a disco tube so the plenum size is large.
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They are my first Piledriver and therefore I never see some with extended skirts and flattened heads. I am amazed that they are shooting well from only 1: 17,7” TR. In according the theory twist rate 1:10” should be better . If it willl be able to buy some faster and a litle bit tighter barrel at EU I will do it for sure.
I have notice but I am not sure for now that best accuracy is betvween 268-272 m/s or between 284-288 m/s. Btween 275-283m/s they are more flyers.
Unfortunately I can not reach velocity abou 290 m/s
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Hi,
Today I noticed that some bullets hit the paper target side ways and not accurately at all. Therefore I had try to lube Piledrivers with PTFE spray and I was confused that speed decreased not increased and accuracy was worse and therefore I return to not lubed bullets .
Next I had soot 30-50 of them and I not noticed any other side ways hitting however 5cm flyers was more often than at another not very strong wind days.
I am still happy with .177/38FPE piledrivers but I am thinking that they will need to use gun with 4500 PSI air reservoir and adjustable up to 3000 PSI regulator and home 4500 air pressure compressor. Very long and very fast twist rate barrel can help too.
I hope that after 2-3 years some producer will do it. We have to wait.
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Also at dead calm weather some flyers exist.
On another side also with JSB exact Heavy similar percentage ( 10%-25% ) of flyer there is however not so big.
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Ricky noticed that “ Piledrivers do not shoot well in barrels with an aggressive/abrupt choke, or with a very tight choke”
https://www.gatewaytoairguns.org/GTA/index.php?topic=128074.msg1438374#msg1438374 (https://www.gatewaytoairguns.org/GTA/index.php?topic=128074.msg1438374#msg1438374)
Unfortunately I do not know if he was meaning 4,46mm or 4,50mm Piledrivers.
I also have red more times that slugs/bullets do not like choke.
Weinhrauch barrels have a litle bit faster twist TR=1:16,3 and therefore will be good to taste next barrel with CFS.
http://silco.co.uk/products/-BARREL-BLANK-.177-X-12MM-DIA-X-635MMLONG-%252dAIRGUN-WEIHRAUCH-CHOKED.html (http://silco.co.uk/products/-BARREL-BLANK-.177-X-12MM-DIA-X-635MMLONG-%252dAIRGUN-WEIHRAUCH-CHOKED.html)
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I have found out interesting info. Dirty barrel bore produce less Piledriver flyers. ::)
Probably because they are only 4,46mm.
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After adding Loctite 638 between CF tube and barrel the Piledrivers start to shoot 2,5*MOA above and grouping at 77 yard seems to be OK.
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After I have used up approximately thousand of 21gr Piledrivers I am persuaded for now that a little bit shorter but exact Piledriver shaping 16-19gr bullets enable to shoot them at ideal 950-980 FPS and also therefore probably would avoid 20% flyers.
Do you have any experiences with the .22/30gr Piledrivers at 950FPS/70+ yd ?