Hunting Washington Forum

Equipment & Gear => Guns and Ammo => Topic started by: Hornseeker on November 16, 2010, 10:35:25 AM

Title: Chrono'd Velocities compared to Published Velocities??
Post by: Hornseeker on November 16, 2010, 10:35:25 AM: I have a chrono and will be messing around with some loads of the winter, but I'm curious if you'all have chrono'd some loads and compared them to the published velocities in the reloading manuals? Usually pretty close? Way off?

Thanks!
Title: Re: Chrono'd Velocities compared to Published Velocities??
Post by: Bofire on November 16, 2010, 10:58:41 AM: :)some pretty close some a mile off. In general the manuals seem to be a bit optimistic. The factory ammo I tried varies from cartridge to cartridge also but seems to be quite optimistic.
from memory :P 308/270/30-06 seemed pretty close, many "magnums" were way off! my 7mm mag reload was supposed to be 3100fps never could get a higher readout than 2850-2900.
It is fun tho!!
Carl
ps: don't shoot your chrono!!
Title: Re: Chrono'd Velocities compared to Published Velocities??
Post by: wildmanoutdoors on November 16, 2010, 11:02:48 AM: I think your barrel length also plays a factor. Probably twist too. Ballistic tables in the books usually say what length barrel they were from don't they?
Title: Re: Chrono'd Velocities compared to Published Velocities??
Post by: Hornseeker on November 16, 2010, 11:34:26 AM: Cool... preciate the info!
Title: Re: Chrono'd Velocities compared to Published Velocities??
Post by: high country on November 18, 2010, 08:11:51 AM: the gun makes a big diff too. I had a buddy who had a 257roy in a vanguard, mine a wby ulw.....we both shot the same loads from the same lot of brass, his was faster through the lights then mine by 100fps, but I had 2" more barrel.
Title: Re: Chrono'd Velocities compared to Published Velocities??
Post by: thinkingman on November 18, 2010, 12:39:00 PM: My first experience reloading metallics was 300WSM and I was kind of chicken re powder charges but still never got within 200fps of the book. I have been told those loads in the book are 'lawyered down' and you can approach max without fear....well, not me, and I wouldn't recommend it to anyone.
Good luck.
Better safe and slow than sorry.
Title: Re: Chrono'd Velocities compared to Published Velocities??
Post by: high country on November 18, 2010, 01:57:23 PM: I stuck the bolt on a 300wby using the lee loader with the scoop back in the 80's.....they needed to be "lawyered down"
Title: Re: Chrono'd Velocities compared to Published Velocities??
Post by: Big10gauge on November 18, 2010, 02:16:18 PM: So many variables that can cause velocity differences from the published loads
throat, OAL(bullet against the lands), primer, lot of powder used, barrel length, neck tension temp, humidity etc. etc. Usually you can count on the powder having the published highest velocity to have the highest velocities in your gun ( but not always).
Title: Re: Chrono'd Velocities compared to Published Velocities??
Post by: Jamieb on November 18, 2010, 08:04:10 PM: With custom barrels you'll normally be pretty close to book velocities at book powder charges thats because of tighter more uniform tolerances and custom cut chambers.
With the sloppy factory barrels I haven't been close to book speeds at the published powder charges. Reloading manuals are guides, written for all rifles.
Velocity comes from pressure, if the velocity is low so is the pressure.
Heres a example .
The Hornady book under 7mm Rem Mag shows a Max charge of Rl-22 of 62gr under a 162gr bullet. I was loading 162gr A-max's.
The first thing is Hornady makes three bullets in 7mm/162gr and only list data for the gr weight not each style of bullet, the A-max is the longest, pointy, sleek bullet Hornady makes, it has a long tapper with a short bearing surface, giving it less resistance in the barrel. My rifle in a Rem 700 BDL with a long throat. Hornady shows 3000FPS at 62gr but in my rifle to get the pressure up enough to get 3000fps I worked up to 68gr of RL-22.
I weight a case empty and then full of water to get the water volume, using case water volume and COL I ran the numbers through Quick load.
QL shows this my load at 53000PSI and going 3000FPS.
Safe for the 7 mag.
Title: Re: Chrono'd Velocities compared to Published Velocities??
Post by: Wanttohuntmore on November 19, 2010, 07:32:22 PM: I've found most of my rifles to be about 100 fps slower then the manual. Again, probably due to chamber dimensions and barrel lengths. My encore and contenders are spot on though, almost exactly. Actually, my 15" encore 7-08 is about 75 fps faster! That thing is a cannon! What is even more strange, that's with a slow powder, IMR 4350, I'm getting a flame, and velocity, something I thought was not possible. I tried toning it down, with a faster burning powder, and velocity and my accuracy suffered, so I'm back shooting 4350. So if you see a guy with a helluva flash, it's me shooting my encore.