Thread: .270 muzzle speed

I got nosler .270 130 gram ammo.
Bc 0.435
Muzzle velocity 3050 fps (nosler website)

From 100 meter to 300 meter it drops about 455 mm. (15x0.1mil clicks on my Bushnell elite tactical scope). Grooping was good

Going back to my computer no way this adds up. I have to get the speed back to below 2700 feet to make it work to the real world. Is this Normal?

Shooting with tikka

Its pretty close if you are zeroed at 100m.
I got 46.99 cm drop using your numbers

Shooting for drops and working back to calculate muzzle velocity isn't a very precise method. 100fps difference in speed only results in about .1mil different drop at 300m with your bullet, a .1mil variation is more or less to be expected in the system given the noise and imprecision of the measurements you have to work with. Zero error, parallax, shooter error, wind, angle, temperature, humidity, pressure, uncertainty around actual POI centre at 300m, on and on

a 10 metre ranging error has the same effect on your measured drop as 100fps difference in velocity. Either one gives you + or - .1mil at that range.

You can rent a chrono graph.
Get actual info from your gun.
Not sure how renting works, but rember seeing it and ages ago so looked it up.
https://www.gunworks.co.nz/shop/cate...ronograph-hire

Originally Posted by kruza

You can rent a chrono graph.
Get actual info from your gun.
Not sure how renting works, but rember seeing it and ages ago so looked it looked it up.
https://www.gunworks.co.nz/shop/cate...ronograph-hire

just be aware that renting an optical chrono is not always accurate and will give different velocities depending on light conditions so you will in theory still need to shoot for drop to verify your velocity, if you can borrow/hire/beg a magnetospeed or labrader that will give you exact velocity and you can adjust your BC to match your drop

Originally Posted by dannyb

you can adjust your BC to match your drop

this is just as fraught with issues as estimating velocity from drops.... have a play with a calculator and see what difference in drop a .1 difference in G1 BC makes - it pales in comparison to the uncertainty and noise in all your measurements.

Originally Posted by gimp

this is just as fraught with issues as estimating velocity from drops.... have a play with a calculator and see what difference in drop a .1 difference in G1 BC makes - it pales in comparison to the uncertainty and noise in all your measurements.

fair enough, to be honest I've never had enough discrepancies in calculated drop vs actual drop to worry about it out to 600yards

The calculators are good these days. Like any model they suffer from "shit in, shit out". Accurate BC measurements are available for a range of bullets via Bryan Litz' work but most published numbers seem to be accurate enough at realistic ranges.

Greetings @Taco,
What is your barrel length? The only way to know what your velocity is is to measure it but regardless I doubt if your velocity is anywhere near 3,050 fps, likely closer to 2,800 fps based on chronographing of factory ammo I have seen.
Grandpamac.

with the 3050 muzzle velocity?

@grandpamac I'll check tonight. @Seventy Six: with the bc 0.435 and velocity of 3050?

455=18" so yip your pretty good
now stop being silly unless you intend to use rangefinder and dail up..lift that zero up a bit
hold line caller and I will do the above again to show why...

@Micky Duck: scope hight higher. bushnell 3-12x50. would think it is closer to 2 inch. Won't make that much of difference though