GTA
All Springer/NP/PCP Air Gun Discussion General => Projectiles => Boolit and Pellet Casting => Topic started by: rkr on September 03, 2019, 06:10:47 AM
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What do you think, would a Lyman 225438 bullet work in a 16" twist rimfire barrel if sized down?
I have a mold and Brownells has those reasonably priced .22lr liners, could make a fun project to make an airgun that more or less matches a subsonic .22lr.
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Rkr, I’m shooting the NOE version of that bullet from the Brownells liner in my Impact. Getting about 1” groups at 50yards . I think it needs more speed but that remains to be tested . I did send Knife some of those to test but I think he was having problems with them .hopefully he’ll chime in .
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Rkr, I’m shooting the NOE version of that bullet from the Brownells liner in my Impact. Getting about 1” groups at 50yards . I think it needs more speed but that remains to be tested . I did send Knife some of those to test but I think he was having problems with them .hopefully he’ll chime in .
What speed do you get? I was able to reach 980 fps with 47 grain bullets and 24" .224 barrel in a gun designed for 12 fpe, so 44 grains and 25" barrel should easily pass 900 fps even in less able airgun.
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I was getting them up to 750 “ish” FPS . I’m going to be able to get them up much faster in the WIndy City using the same barrel .
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I was getting them up to 750 “ish” FPS . I’m going to be able to get them up much faster in the WIndy City using the same barrel .
That should give you proper speed and sidelever makes cocking easy. I wouldn't be surprised if you went over 1000 fps with 44 grainers. One question though, how do you plan to attach that liner to the thimble you made? I mean it's so thin walled that you can't really have set screws to touch that liner, not much anyway.
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The thimble is held in the breech using the existing setscrews . The liner is slip fit into the thimble , once the shroud is on , the end cap presses the liner into the thimble in compression . I have it set at about .050” right now .
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It will be interesting to see what kind of accuracy you get. Tom has got excellent results with his tensioned barrels and this is just the opposite approach.
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The way it is set up right now , it’s going to be near identical to how the FX Impact X barrel system works . The difference being the shroud compresses the barrel rather than the smaller barrel tube . This set up sure is light in comparison to say a 15mm solid barrel. Heck even compared to 13mm there is some weight saving .
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those liners are made about 100 mile north of me... they are only 5/16 O.D. a bit thin...
tho the 225438 was made for the .22 hornet I do think it should do well in a 1:16 twist... but I think there are different 225438 molds and some will drop large...
also I think there is an older version that is closer to 40g... and have read length is .51"
so I looked at a generic 44g .225 and well I still think it will stabilize at 700-900-1000fps... I do think depending on the lube grooves effect on the center of pressure it should be ok... even if it does not stabilized decking a bit of the gas check would get it stable imo...
using linotype density of 10.4
http://www.geoffrey-kolbe.com/cgi-bin/drag_working.cgi?unit_length=inches&weight_unit=grains&bullet_name=Custom+bullet&re_calculate=yes&boundary_layer=L%2FT&diameter=.225&length=.51&nose=.22&meplat=.03&drive_band=.225&base_diameter=.225&angle=0&boat_tail=0&secant_radius=&weight=48.3&density=10.4 (http://www.geoffrey-kolbe.com/cgi-bin/drag_working.cgi?unit_length=inches&weight_unit=grains&bullet_name=Custom+bullet&re_calculate=yes&boundary_layer=L%2FT&diameter=.225&length=.51&nose=.22&meplat=.03&drive_band=.225&base_diameter=.225&angle=0&boat_tail=0&secant_radius=&weight=48.3&density=10.4)
http://www.geoffrey-kolbe.com/cgi-bin/barrel_twist.cgi?diameter=.225&length=.51&nose=.22&meplat=.03&base_diameter=.225&angle=&boat_tail=&b_twist=16&secant_radius=&unit_length=inches&temperature=59&humidity=0&local_pressure=29.92&pressure=29.92&altitude=0&density=10.4&custom_density= (http://www.geoffrey-kolbe.com/cgi-bin/barrel_twist.cgi?diameter=.225&length=.51&nose=.22&meplat=.03&base_diameter=.225&angle=&boat_tail=&b_twist=16&secant_radius=&unit_length=inches&temperature=59&humidity=0&local_pressure=29.92&pressure=29.92&altitude=0&density=10.4&custom_density=)
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Denis, do I understand that you have a 5/16" OD liner in COMPRESSION ??? .... If it is not a close slide fit inside a much stiffer tube to support it, I would expect it to wobble around like a piece of spaghetti with a brick on top of it.... It might even kink on firing.... Well, maybe that is an over-exaggeration… but I hope you get my point....
Bob
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Thanks K.O.! My mold is indeed 0.51" or maybe even 0.514" long, hard to say what the bullets will actually drop at. It looks like if I sized these bullets for rimfire barrel and shot them at 950ish fps they would remain stable up until 200-250 yard range, perhaps even 300 yards if muzzle velocity was closer to 1000 fps.
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Yes Bob , the thin liner is in compression . I sure sounds like a bad idea when thinking about it . But , this is exactly how the FX “X “ liner system works in both the Impact and Crown in all calibers including the .30 . And as you know they tend to be some of the most accurate guns out there. FX use Orings on their liners to keep them centered in their outer barrel . I’m going to fab up some Delrin spacers . Here’s a video from Ernest Rowe. https://youtu.be/OxP2VSjgrD8
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As long as the outer barrel keeps it in column, that is a different story.... You would be surprised how much compression occurs with 0.050" of end load.... I always use a "buckling load" calculator for my outer shrouds when tensioning the barrel, because I use about 1000 lbs. of tension, which ends up as compression in the shroud....
Bob