.117 BB Ballistics

[Willtallica]

I'm extremely curious of what the ballistics are of small 177.cal BBs at ranges of 30ft+ when fired at high velocities.

Has anyone ever use a BB for such a distance, and is there a lot of drop off?

[bloomautomatic]

Originally Posted by Willtallica

I'm extremely curious of what the ballistics are of small 177.cal BBs at ranges of 30ft+ when fired at high velocities.

Has anyone ever use a BB for such a distance, and is there a lot of drop off?

what do you consider to be high velocity and what do you consider to be a lot of drop of? at 30ft, it shouldn't be too bad. the higher the velocity, the less drop it will have.

since a BB gun barrel is smooth bore, depending on how much spin and in what direction it spins, the BB can curve this way or that. if it curves up or down, that throws off your trajectory calculations.

vince

[Lycanthrope]

My BB guns were rifled......and threw at about 900fps. A rifled barrel will stabilize round ball.....just ask the muzzleloader crowd. You just have to get the twist right.

Weigh a BB in grains and I can plug it into the ballistics calc (I don't have one on hand). We'll need the ballistic coefficient as well.

[bloomautomatic]

what kind of BB gun did you have that had a rifled barrel? seems that a steel BB wouldn't engrave on the rifling like a lead pellet would.

Vince

[Willtallica]

Well I hear rifling does little for round rounds, however rounds that can mold to the rifling is proven to be another story.

I just have a daisy btw, and I can pump it way up to over 2000 FPS, but lets just say at 30 ft 750 FPS. What kind of drop off would there be then?

[Lycanthrope]

Originally Posted by bloomautomatic

what kind of BB gun did you have that had a rifled barrel? seems that a steel BB wouldn't engrave on the rifling like a lead pellet would.

Vince

The first one was a simple Daisy 880. The ball only has to flow along the track of the riflings, not mold to it. The riflings did cut into the pellets, though. You need very little twist to stabilize a round ball. 1 turn in 70 inches in some muzzleloaders with heavy ball.

OK, I'm intrigued with this..... I'll play.

Check this out:

http://www.airgunexpo.com/airgundb/pelletbc.cfm

The Daisy BB has a BC of .009. (wow, that sucks).

The Copperhead BB weighs in about 5.1 grains.

At a Starting velocity of 700fps....

At 5 yards: 652.9fps -.09 drop
10 yards: 609.3fps -.39 drop
15 yards:568.6fps -.92 drop
20 yards: 530.3fps -1.72 drop
25 yards: 494.3 fps -2.83 drop
30 yards 460.4 fps -4.3 drop

[bloomautomatic]

Originally Posted by Willtallica

I just have a daisy btw, and I can pump it way up to over 2000 FPS, but lets just say at 30 ft 750 FPS. What kind of drop off would there be then?

2000fps out of an air gun? that seems awful fast for a pneumatic. what kind is it and have you ever chrono'd it at that velocity? you should be getting a sonic crack at that speed.

Vince

[Lycanthrope]

Originally Posted by bloomautomatic

2000fps out of an air gun? that seems awful fast for a pneumatic. what kind is it and have you ever chrono'd it at that velocity? you should be getting a sonic crack at that speed.

Vince

Yeah, I was overcharging mine to get 900.....

On the other hand, several guns can be had for about $200 that will break 1100fps. Plenty fast enough for small game and worthy of scoping.

[bloomautomatic]

Originally Posted by Lycanthrope

On the other hand, several guns can be had for about $200 that will break 1100fps.

Most of the really powerful ones are spring piston guns, not pump-up pneumatics. also some precharged guns, like the airforce guns will exceed 1000fps.

i fired a winchester spring piston pellet rifle and it went supersonic. i volunteered on the indoor range at the NRA convention in pittsburgh. during setup, we had to sight the guns in, etc. took it out of the box and CRACK went the sound barrier. they put it away. little too loud for indoor use. since it was new it could have had some oil left in it and dieseled.

seems like most of the newer pump guns will only let you get so much pressure before the bleed off. like more than 10 pumps and you can feel it's not really pumping any more.

vince

[Willtallica]

75 PSI a pump, and 30 pumps later mathematically = 2250 fps Mr friend told me he tried it for 100 one time. I'll never even think about it.

So I'm looking at about 4inch drop. That's good to know just for starters. I'm buying a cheap scope, and after I get it put on I'll be doing some target practice at 30 ft.