Using chairgun for rimfire ammo?

[Colster]

Been tinkering with Chairgun to work out how much flat range (aim straight at it) I can acheive by trying different pellets in my AA S400 FAC and it suggests changing the range I zero at to maximise this so I decided to do the same for my .22LR

 

Trouble is I'm struggling to get the right data for the rimfire ammo. Does anyone have any accurate figures for velocity and ballistic coefficient for Winchester Super X Subs?

 

Currently using 1080fps and 0.1246 for BC with a weight of 40 grain which then gives me an optimum zeroing range of 53 ish yards. Sounds about right I think which then means given a 1" killzone I can aim on at between 10.6 - 60.4 yards.

[drut]

Been tinkering with Chairgun to work out how much flat range (aim straight at it) I can acheive by trying different pellets in my AA S400 FAC and it suggests changing the range I zero at to maximise this so I decided to do the same for my .22LR

 

Trouble is I'm struggling to get the right data for the rimfire ammo. Does anyone have any accurate figures for velocity and ballistic coefficient for Winchester Super X Subs?

 

Currently using 1080fps and 0.1246 for BC with a weight of 40 grain which then gives me an optimum zeroing range of 53 ish yards. Sounds about right I think which then means given a 1" killzone I can aim on at between 10.6 - 60.4 yards.

 

Chairgun : 0.137 works fine for me,1080fps is about avg through F! chrony at 2m from my 16" 452 although I zero @ 60yd(1.9"scope height).Seems to give close enough predictions.

[wymberley]

Hi,

It's so long ago that I did this that I can't actually remember. I know that I got the velocity from a Winchester publication, but I have it in my programme as 1065 unlike yourself. From the limited velocity/energy figures provided, I calculated the BC as 0.138. At the 53 zero this gives about 9 to exactly 66.

[drut]

""but I have it in my programme as 1065 unlike yourself"

 

Funny that was about the figure I expected! I only tested one batch in fairness but was surprised by both the speed & the consistency: within 11 fps over 20 rds.

[Colster]

Thanks for that guys, so it looks like 55yards is a better bet (ok so chairgun says 54.7 is the optimum). Found I hit the target fine on longer ranges (60-80yards) but can often struggle a bit when they're 20-30yards, this way I should be able to avoid having to hold under based on the following:

 

 

One other question though, I assume the 1065fps is based on without a moderator and that a moderator would slow the bullet down a bit but by how much as I use a SAK on my LR?

Edited April 2, 2010 by Colster

[wymberley]

Hi,

My figures were for a 2" sight height, just noticed yours looks like 1.8. Yep, agree, at 55 it's about 7.5 to 67. The moderator may make a slight difference, but the thing to remember is that all this ballistic theory is all well and good and is a great help but there's usually a discrepency in the field. It's there that you need to finally check on what's going on.

Cheers

[drut]

One other question though, I assume the 1065fps is based on without a moderator and that a moderator would slow the bullet down a bit but by how much as I use a SAK on my LR?

 

In my experience on .22lr SAK moderator makes no appreciable difference to velocity:hope this helps.

 

Regards:D.R.

[Colster]

Have to say it worked a treat, had my best bag ever last night. Anything between 12 to 60 yards was a straight at it, down it goes nail-a-thon!