Chronograph speeds

[Guest nosajpo]

Very puzzled and new to reloading/chronographs. I bought an f-1 chrony at cabelas and took it out yesterday. I was shooting a sendero 7mm mag 168 gn berger vld. I used 70 gn retumbo and winchester brass. Remington magnum primers. Shot avg was 3070 fps. Not bad and good groupings. What i am puzzled with was i was shooting my 30-06 with factory nosler ballistic tips 165 gn and the speed from almost every bullet was 3140 fps. Never heard of 30-06 at those speeds especially with factory ammo. Am i crazy or has anyone seen those speeds from a 30-06. Gun was a rem 700 with 23 inch barrel. Or is something wrong.

[.270]

bore diameter. 7mm is a considerably smaller bore than 30 cal. the 30 cal bullet has a lot less bullet in the lands. the 165 gr 30 cal bullet is a lot shorter than a 168 gr 7mm bullet. the long 7mm bullet will make a lot more pressure than a 30 cal bullet so you have to trim the loads to keep from getting excessive pressure. there is a lot less bullet "in the lands" with the 30 cal and it has the potential to shoot faster. i don't know what kind of load the '06 has and that velocity seems to be pretty quick but it isn't really surprising. if you want high velocity out of a 7mm you need to shoot 140's or maybe 154's. the long skinny bullets have a better bc but they ain't made for speed. a good example of what i'm trying to explain is the .270 and '06. both have the exact same case but with identical weight bullets the '06 is capable of a couple hundred fps more than the .270 because there is less bullet in the lands and you can load it hotter before it reaches overload pressures. jump up to a 180 in the '06 and it starts to turn into a slug, but up to 165, it's a pretty swift round. and the animals don't have a clue how fast the bullet is going. Lark.

[.270]

don't get caught up too much in velocity. i used to shoot everything as fast as i could possibly make it go. i was always trying to flatten out the arc and make things as flat shooting as possible in order hit things better at all ranges. burned up a few barrels doing it too. after 500 yards, everything drops like a rock. most rifles really do it around 400. when you start shooting 600 to 700 you have to be 10 or 20 feet high. accuracy and knowing what your rifle does at different ranges is the trick. with a range finder and some simple balistic knowledge, with an accurate rifle, you can hit anything at about any range. i shoot stuff at ranges i never thought possible 10 years ago with a range finder and knowing where my rifle hits. shot a goat at almost 500 a few weeks ago. drove over a thousand miles round trip, shot once and came home. either rifle will work. depends on which one is more accurate and how well you shoot it. my dad has shot more coues with a 30/30, .348 and a .270 than anybody on this sight with any rifle. that deer doesn't know how fast the bullet is going or what caliber it is. Lark.

[oz31p]

There is normayl a wide variant of speeds depending on where the Bulets pass thru. I can get my 300wm from 2800 to 3200. Just a matter of where you aim thru the bows

[billrquimby]

Something is wrong here.

 

Nosler's 165-grain Ballistic Tip loading data show maximums of 2700-2800 fps in a .30-06 with a 24-inch barrel. Factory loads that push them 400-500 fps faster than this simply do not make sense to this old geezer's muddled brain cells. It has been my experience that factories purposely "load down" because their ammo will be used in many different types of firearms, including some that border upon being unsafe.

 

Granted, there is much to Lark's observation of longer bullets traveling slower than shorter bullets of the same weight because there is "more bullet in the lands," and this requires loads for the smaller-diameter bullet to be reduced to avoid dangerous pressures.

 

However, this would apply only if the short and long bullets were fired from cases with identical powder capacity. In fact, although I've never measured them, a .30-06 case's capacity appears to be considerably less than a 7mm Rem. Mag's.

 

I have never owned or used a chronograph, but I suspect OZ31P is correct in saying that results can vary widely, depending upon the operator.

 

Bill Quimby

[DesertBull]

You need to have the chrono at least 15 feet away from the muzzle or you will get false readings from the muzzle blast.

[Red Rabbit]

Another problem with some chronographs is the variations in speed one gets in different lighting conditions. I can sometimes get excessively fast readings on clear sunny days, even with the diffuser panels, wiht my old chrony F1. Try shooting on a cloudy day, or some say to put a piece of matte Scotch tape over the window of the sensors. I have thought of making a big diffuser from a 2 1/2 gallon water jug to block direct sunlight from the sides and angles.

[feenz]

Thst would make sense red rabbit. By the time i was shooting the 06 the sun was directly overhead.

I always chrono in the shade with my chrony or I get bogus readings.