velocity estimating

[cen.cal.hunter]

i just found a good load and doesnt have chrono to run it through. the load is a 308 winchester using federal brass, federal match primer, 150 sierra gameking, 45.8 grain of rl15 seated at 2.73. with a 22 inch barrel. the nosler manual reads somewhere around 2940 for 46 grain of rl15 with there 24 inch barrel so im guessing its around 2900 for my 22. btw im only shooting 500 yard max. what do u guys think

[Shoney]

Combinations of factors can cause great variances in velocity. Here are a few factors:

Primer: strength, brisance - is a measure of the rapidity with which an explosive develops its maximum pressure
Barrel: length; tightness of bore; height of the lands; distance of bullet to lands; temperature of barrel;
Bullet: bearing surface of bullet, alloy of bullet; shape of bullet;
Brass: new/used elasticity; manufacturer, volume;
Powder: new, aged, old, batch powder was from;
Weather: ambient air temp., barometric pressure, humidity
Elevation: above sea level
Other: I am sure I have not listed all

Now, mix and match them. You have listed only a few of the variables, and with that number of possible combinations, unless you are good at Voodoo, you will need a chronograph.

[Scorch]

Other factors to consider:
Your firearm's barrel length- the Lyman manual shows 150 gr bullet, 24" barrel, 46.2 gr of Rx15, yielding 2,847 fps as the max load. The velocity gain/grain of Rx15 powder is about 60 fps, and you are .4 gr below the listed load, with a 2" shorter barrel. Hornady shows a 150 gr bullet over 45.4 gr yielding 2,700 fps out of a 22" barrel. My guess would put your velocity around 2,730 fps.

[Unclenick]

QuickLOAD calculates 2764 fps. That assumes a tight chamber and brass with 56 grains of water capacity, which is less capacity than Winchester brass.

[kraigwy]

I have a chronograph. The one thing I learned in using it, is I have never seen a sugested load in a reloading manuel that matches my guns actual velosity. Even two exact same guns, shooting the same load is differant.

The question is, it the load shoots good, and no sign of excessive pressure, Who cares. Consistency is more important then velosity, you determine consistency on the target, not 25 ft from the barrel.

I have loads that have lousy SDs on the chronograph but shoot great at 600 yards. I have loads with good SDs on the chronograph but can't group for poop.

Chronographs are fun to play with, but I'm more interested on how a given gun/bullet preforms on what ever target I'm shooting.

[freakshow10mm]

Divide the actual powder charge into the maximum powder charge and multiply that by the maximum velocity. That's ballpark what you'll get. Shorter barrel can be anywhere from 20-150fps difference depending on components and environmental, but should give you a working idea.

Example: (just opened my manual to a page)

338 Win Mag 225gr bullet using IMR4350

Start is 66gr, max is 71gr for 2795fps.

Say we are loading 69.4gr. 69.4/71=.977464788 times 2795= about 2732fps.

[fourdogs]

Another way would be to look at the ballistic tables in your loading manual. I know my old Speer's book has it. Look for your bullet caliber, weight, and BC. Zero for 50 or 100 yards, or whatever the tables say.

Then shoot at 500 and compare the bullet drop against the ballistic data. With a few slight adjustments in the numbers because your bullet drop probably will not exactly match the tables, you can get very close to your true velocity at the muzzle, and throughout the flight path in 100 yard increments. Make sure you adjust for temperature and altitude. I think most ballistic tables are set up for sea level at 60 F.

[cen.cal.hunter]

thanks for all your responses. ill probable get up to my hunting area tonight for a friday morning pig hunt and then maybe in the afternoon, ill give 500 yard a shot to see its drop at 5000 ft evelation. then compare it to the drop tables like mention.

[WESHOOT2]

Guessing velocity is as easy as guessing the future.

I guess.


"Test, then know".

(If you intend for the bullet to do 'work' terminally, more than paper-punching, velocity can matter. For placing holes close on paper then accuracy is your guide.)

[ringworm]

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