Calculating bullet speed

[roymunson]

How are you guys figuring bullet speed?

I have a muley hunt coming up that I have a Tikka T3 in 7RM that's shooting great.
Norma brass
H4831- 65 grains
150 grain Barnes TTSX

Feeling good about it, but then I see threads about the speed needed to make sure my copper bullet fully opens. How can i figure my speed roughly without an chrono?

I wanna kill the animal efficiently, I'm not all that worried about the details. But I'd like to know how fast that bullet will be running when its at different yardages.

Do I need to buy a ballistic calculator? Help would be appreciated.

 

[Pickettpuncher]

A chronograph. If you don’t have one you shoot at 100 yards and again at say 300 and do calculations that way using how much drop you had

 

[roymunson]

Is a chrono the only way to get it accurately? Like I said, I don't care if I'm off a little bit, I just don't know enough about it to know if I'm traveling at a fast enough speed to ensure expansion. I think I am, but would like to be sure and would like to know where that reliable expansion ends.

 

[roymunson]

Or anyone with experience, just tell me that that copper bullet is moving fast enough at 400 yards to do what I want it to do.

 

[Northpark]

It’s probably doing just fine at 400 yards. If you want a close guess though go shoot. Set up a paper target at 100 yards and zero. Then run your best guess on velocity through a ballistic computer (Hornady 4dof is pretty good) and see what the drop is a 400 yards per the computer. Shoot paper at 400 yards and see if it matches what the computer says. If your actual drop doesn’t match adjust your velocity in the computer until it matches what happened on paper. That’ll get you close on real velocity.

 

[roymunson]

I know my MOA at 300, 400, and 500 and plugging in an ELD-X as the closest comp puts me around 3180 @ 300, 3025 @ 400. 2900 @ 500

May not be exact, but I don't think I'm even crowding the line of expansion at 500 yards. I won't shoot farther than that.

That'll be plenty. Thats all I wanted to make sure of that I wasn't real low and wouldn't get expansion.

Thanks for the help with the Hornady app.

Appreciate it.

 

[Pickettpuncher]

I would think you’re fine to 500 based on your concern for expansion. North park explained it much better than I did.

 

[z987k]

I know my MOA at 300, 400, and 500 and plugging in an ELD-X as the closest comp puts me around 3180 @ 300, 3025 @ 400. 2900 @ 500

May not be exact, but I don't think I'm even crowding the line of expansion at 500 yards. I won't shoot farther than that.

That'll be plenty. Thats all I wanted to make sure of that I wasn't real low and wouldn't get expansion.

Thanks for the help with the Hornady app.

Appreciate it.

There is no way a 7RM is pushing a 150 fast enough to still be doing 3180fps at 300yd.

Your 150gr 284 ttsx has a published bc of .45

To get 3180 at 300 you'd need to be doing roughly 3900 at the muzzle. Barnes publishes their Vor-TX line with the 150 ttsx in the 7rm at 3060fps.

That said a 150gr ttsx out of a 7rm should still be at or slightly above 2000fps to 500y. How you'd accurately shoot that far without a muzzle velocity, I don't know.

 

[AZ_Hunter_2000]

Buy a chronograph as it can be less expensive in time and ammo over the long haul.

 

[EdP]

You don't need to buy a ballistic calculator, they are available for free online. I use Hornady's but there are plenty of others. Look up the BC for the bullet. Shoot at 100 and 300 and measure the drop. Plug in the BC and your zero then enter MV's until you find a match for the drop.

Even better, do like others said and buy a chrono. The free standing models only cost about $120 and it is well worth having. In some cases you may find the chrono is more accurate than the mfgs listed BC, especially since BC is somewhat dependent on velocity.

 

[roymunson]

There is no way a 7RM is pushing a 150 fast enough to still be doing 3180fps at 300yd.

Your 150gr 284 ttsx has a published bc of .45

To get 3180 at 300 you'd need to be doing roughly 3900 at the muzzle. Barnes publishes their Vor-TX line with the 150 ttsx in the 7rm at 3060fps.

That said a 150gr ttsx out of a 7rm should still be at or slightly above 2000fps to 500y. How you'd accurately shoot that far without a muzzle velocity, I don't know.

That makes sense to me... I'm a novice here. I just wanna know what distance is too far to not trust trust the speed and bullet opening.

I don't see a way I'm shooting farther than 500. We'll keep it below that and I'm happy

 

[eric1115]

Are you zeroed at 100 yards? What is your vertical correction to get a good center hit at 500 yards?

 

[roymunson]

i'm centered at 200. I'm at 7.5 MOA @ 500 so, 37.5" give or take my human margin for error

 

[eric1115]

That puts you in the 2850-2900fps range for muzzle velocity, still around 2000 fps at 500. I think I'd call that the minimum I would want to expand that ttsx.

Side note, that's well under what you can probably run that bullet in a 7mm RM. I would not be surprised if there's room for another 4-5 grains of powder and 200+ fps before you reach pressure.

Another side note, and it gets brought up a lot (for good reason), make sure you are being realistic and honest with yourself about your shooting ability. How are you doing wind corrections? A 3mph error in wind call takes you from center to edge of deer vitals at 500. That means if you have a 1moa cone, half your shots are misses with if you guess 5mph and it's actually 8mph.

 

[roymunson]

I don’t anticipate a shot that far. I want to be aware of what my gun and I can and can’t do at that range. I’ve shot some cross wind and gave a sense of it. But I’d rather be 300 and in.

Good advice. And I’m practicing farther than I intend to hunt at.

 

[Wrench]

Grab some milk jugs and go pop them at range. If they dont explode....you know you're below the upset velocity.

I can field validate using drops measured in the field and come inside the es on my chronograph....and so can anyone, it takes a lot of shooting though.....AND your scope has to have known values proven on the tall target test.

 

[Jfjfrye]

You can probably look up the ballistic chart for your exact ammo and it will give you a rough idea of bullet speed.

 

[Jfjfrye]

https://www.barnesbullets.com/wp-content/uploads/2021/03/Barnes-CFR-Specs-and-Ballistics.pdf

 

[roymunson]

You can probably look up the ballistic chart for your exact ammo and it will give you a rough idea of bullet speed.

Reloads are my issue.

I think I'm ok with where I'm at. Its shooting well. I guess I could whip up some nosler partitions that I have laying around, but i don't like to start tinkering with it a month before i go just because I can't leave well enough alone.

 

[Jfjfrye]

I think of you’re reloading that investing in the magnitospeed sporter chronograph is a great idea. It’s a one time investment that will help tremendously. Just my .02