Very light pellets at very high speed?
- Thread starter MrP
- Start date
I was going from data in an old bullet casting manual. If it's wrong, I apologize for the bad information.
Upvote 0
G
Guest
Guest
Well I wouldnt say its bad information. Pure lead hardness is about 5.0 on brinell scale where as pure tin is 2.3 but if you cast tin lead mix adds little hardness when compared to pure lead and also melts on lower temperature, flows better, dosent oxidize so fast as pure lead etc.
Upvote 0
GTO 25cal 16.54grains Muzzle velocity = 1400fps BC 0.022
Looks like velocity drops into transonic speeds before 15yards.
Won't be very accurate past 15yards?
Looks like velocity drops into transonic speeds before 15yards.
Won't be very accurate past 15yards?
Upvote 0
How about a round nose boat tail slug that has a BC of .15 in lead? It's 48 grain bc .15. I read on some blog about ballistics written by someone who knows a heck of a lot more than me that round nose boat tail type projectiles are not as affected by the trans sonic transition. The diablos with the skirt on the other hand... How else to explain people shooting 22 LR right around the speed of sound with plenty of stability over long ranges? Bullet shape I believe
Can you estimate bc for a tin slug of the same size with a weight of 31 grains? I will cast these and shoot them as fast as I can. Should be interesting. My modified airforce will shoot 50 grain in the 1000-1100 FPS range.
what will happen if I shoot a 31 grain tin slug in this gun!!?
Can you estimate bc for a tin slug of the same size with a weight of 31 grains? I will cast these and shoot them as fast as I can. Should be interesting. My modified airforce will shoot 50 grain in the 1000-1100 FPS range.
what will happen if I shoot a 31 grain tin slug in this gun!!?
Upvote 0
G
Guest
Guest
Around 0.096BC but where did you find 48gr 25cal slug with 0.15BC
? Seems fairly high seeing some 257cal slugs with significantly more weight barely reach that. If I remember correct most slugs that I shot out from 25cal sumatra from 48-55gr had 0.07-0.095BC.Upvote 0
I am sure that probably is wrong. But an altaros slug in the same design is advertised as 0.15 they say. And don't smaller slugs have higher BC maybe since smaller diameter? At same weight and Basic form anyway. I have no specific knowledge of this and can only parrot what I saw for similar projectiles. Definitely looking to learn!
Upvote 0
For the same weight, the BC will increase as the caliber decreases. This is because BC increases as sectional density, SD, (weight/caliber) increases and SD increase as caliber decreases at a constant weight.
Upvote 0
Ok well it seems like .15 is a high number based on a vendor's claim for a product. I would love to know the actual BC of the slugs in the previous post of mine. Based on a BC database maintained by Robert Sterne (I think?) it looks like bc's above 0.1 In .25 slugs is verified and the slugs with that BC were flat nosed rebated boat tail with prominent drive bands and less aerodynamic so maybe those in the pic above would be unusually high like .12 or .13. I don't have two working chronographs and my airgun is unregulated so I don't think I can test it.
Upvote 0
G
Guest
Guest
Noe 50gr FN BT seems to be 0.1282bc and 60gr 0.1480. Nose of the bullet dosent have much to do with ballistics on subsonic speeds FN, spitzer or RN dosent matter much. Main problem with BT bullets and airgun barrel twistrates tho is the fact BT requires faster twist and atleast my 25cal 1:18twist barrel didnt balance any of the BT bullets I tested from oldschool .254 bore sumatra. Best bullet I found for that gun was https://noebulletmolds.com/site/shop/251/tl255-50-rf-cb2/tl255-50-rf-cb2-2-cavity-pb/ that BC is wrong on that it surely isnt 0.176 but more of like 0.0760 if I remember right. If you have 1:18twist 25cal barrel I highly recomend that bullet as long as you size them to right bore size.
Upvote 0
Thanks. The slug i posted a pic of was designed/tested etc. to shoot out of LW choked .25 barrels in older huben k1, and stable at a range of velocities out of that gun. Worth taking a look at and I never see folks posting about these slugs.
I find they are only inaccurate below 650 FPS I think but otherwise as good as any I can buy out of my airforce barrels at my level of shooting skill which is "advanced plinker" at best.
https://www.mp-molds.com/product/635-mm-air-rifle-pellet-8-cav-mold/
I find they are only inaccurate below 650 FPS I think but otherwise as good as any I can buy out of my airforce barrels at my level of shooting skill which is "advanced plinker" at best.
https://www.mp-molds.com/product/635-mm-air-rifle-pellet-8-cav-mold/
Upvote 0
G
Guest
Guest
Orginally that bullet was designed for 22cal huben to fit and stay in mag and barrel was unchocked also.. 25cal is just enlargened version of that not really designed or tested for huben 25cal and havent heard much about that 25cal. Maybe it just dosent work.
I personally have ditched all regular airgun calibers like years ago due I only shoot from bench and I have no problem to use external regulator so I only currently own my custom 224cal M10 and texan 257. You simply can get much better ballistics and if you have no problem to shoot with external reg there is no downsides.
Upvote 0
Thank you - learn something every day. And I feel terrible having given out misinformation on that mold. Somehow I had it in my head they were tested in choked .25 lw barrels. Guess that will be my job. They seem accurate enough but I haven't tested at any kind of long range.
Upvote 0
Those 16gr would probably be about 1200fps, and it will get progressively more difficult to go higher. I adjusted my .25 caliber HP airgun to shoot 70gr lead slugs at about 960fps. It shoots identically shaped 8gr PLA slugs at about 1660fps. The BC is so poor that it would be subsonic before it reached 15yards.
The hollow 3gr PLA pellets had a muzzle velocity of 1750fpsand would be subsonic before 5yds.
Velocity increases with the square root of energy supplied. It takes a certain mass of air to provide a certain amount of energy. High pressure air is heavy. Once you get up near sonic velocity, the mass of the air quickly exceeds the mass of the projectile, so less and less percentage of the energy ends up in the projectile. 2x the speed of sound with decent BC would be nice, but totally impractical (near impossible) when using air at room temperature. It would take a near infinitely long barrel and near infinite amount of air to reach 2x the speed of sound.
Upvote 0
The standard velocity 22lr is just subsonic (about 1060fps). The high velocity 22lr is about 1250fps. The high velocity 22lr seems to do well enough out to about 50yds, but is subsonic before 100yds. If I want to shoot accurately at long range (over 50yds) with a 22lr, I use standard velocity.
Upvote 0
scotchmo - Makes sense, thank you.
- interesting post on projectiles - nice work on that... Of course the idea that the air itself becomes a large part of the equation at those kind of velocities I hadn't thought of and it makes sense that there would be a rapidly diminishing return.
What is the source of the mold that casts those slugs?
- interesting post on projectiles - nice work on that... Of course the idea that the air itself becomes a large part of the equation at those kind of velocities I hadn't thought of and it makes sense that there would be a rapidly diminishing return.
What is the source of the mold that casts those slugs?
Upvote 0
G
Guest
Guest
If you want to shoot with really high speeds and high BC value your only change is to shoot sabots out from big bore and preferably use helium.
https://youtu.be/86lKPZqxFDo
That is 20mm worlds most powerful pcp EVER shooting 50cal 450gr bullets at 1600+fps with helium using 75grain sabo. Not really practical but can be done.
https://youtu.be/86lKPZqxFDo
That is 20mm worlds most powerful pcp EVER shooting 50cal 450gr bullets at 1600+fps with helium using 75grain sabo. Not really practical but can be done.
Upvote 0
Source of mold for lead slugs:
http://arsenalmolds.com/products/257-Bullet-boattail
The Arsenal mold is of good quality.
The PLA projectiles were printed.
Upvote 0
Air would not be able to do that. Helium weighs <20% of what air weighs. So much easier to get the high velocities. But then you have a "helium-gun", not an "air-gun".
Upvote 0