I have spent a good part of the initial range sessions of the year developing a couple of loads - a .270 Wby load based on 130 grs TSX and IMR 7828 and a .30-06 based on 180 grs AccuBonds and RL22. Things were coming together nicely, but my best accuracy seemed to come below charge weights deemed max in the various books. Still, not knowing what velocity was generated, it was possible to hope for decent speed, and accuracy was good.

Today I finally found time to set up the chronograph, and verify what speed I was really getting. Disappointment! Dare I say "as usual"?? I don't know how my Internet shooting buddies always seem to get velocites at or ABOVE book values, when I rarely even seem to approach them?? Yet, I use the same powders, but stay maybe a grain or so below book max.

I chronographed my velocities just about freezing temperatures - spring is late this year in Switzerland. I guess it was about 1-2 degrees Celcius (30-33 degrees Fahrenheit). Right now, the plan is to chronograph again when the temperatures have risen a bit - maybe to around 20 degrees Celcius (68 F). Maybe the numbers will look a bit better, but at the back of my mind is a nagging doubt... (Maybe I should take comfort in .270 Wby, 130 grs factory loads also measuring at 3190 fps??).

Are there any data (empiric or otherwise), which will allow you to guess on a quantified rise/fall in velocity with so many degrees air temperature?? Or have any of you got any experience with velocities measured in summer as opposed to winter??

I remember once chronographing a .300 Win Mag, 200 grs NP, RL 22 load in Montana in late October (probably around 20-30 F). It ran about 2750 fps, not exactly overwhelming and about 150 fps lower than what I had measured in warmer temperatures.

- mike

I subtract 2 fps/deg F when temps drop. This isn`t exact, but seems to be pretty close to what I find when cronoing the loads.

BTW. Don`t feel too bad. I also rarely get "book" velocities from my rifles. I have a couple with very tight chambers and good bores that give close numbers but the majority fall short.

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I don't know how my Internet shooting buddies always seem to get velocites at or ABOVE book values, when I rarely even seem to approach them?? Yet, I use the same powders, but stay maybe a grain or so below book max.

Mike, welcome to the world of BS and wishful thinking.

IMO there's two big reasons many of us will not duplicate the velocities reported by some.

1. There are folks running pressures far in excess of SAAMI and don't know it. They report no pressure signs and spectacular velocities.
2. It's the firearms industry.....we live in a world of more old wives tales, ancient myths, invalid assumptions, prejudice, half truths, and just pure bullshit than any other industry except for the political arena. One must take as suspect any information posted on the internet as being in that sea of contaminated data.

On the 30-06 however, the book velocities are normally confined to SAAMI pressures and one can normally improve on that by a few grains and 100'/sec or so.

I get 2,800'/sec with my 22" barrel and 180 grain interlocks. (no...pressures are not known)

On the 270 weatherby: IMO it's a good way to burn more powder than a 270 winchester and gain 100'/sec.

Sorry I don't drag out the chronograph when the temps go to freezing as the fun is lost rapidly and can offer no help on temps VS velocity.

If you're not getting the velocities listed by some it might just be that you're living in reality.

If you're getting 2700-2750 fps with your '06, that is normal. Shoot some Rem-Win factory loads out of it and you'll likely feel better as they'll probably go 2660 fps with 180's. The .30-06 should approach 2800 fps with a safe load and 180 grain bullets, some books are pretty conservative on the '06, or optimistic on velocity.

I usually expect to see a difference of about 3 fps per degree Celcius.

Thanks for the information and moral support guys. Sometimes I feel like I'm the only shooter in the World not capable of obtaining the velocities published in manuals, gun rags and on the Internet. It must be endemic to my reloading room...

Come to think of it, I did once get fabulous velocity out of a .300 Win Mag with a load of RL22 under a 168 grs TSX. Boy, did that thing ever GO!!! ...It also beat the cr*p out of me on the bench, and my cases became unusable after at most two loadings - primers could almost be seated without a priming tool... Ah well, I guess I ignored the most basic precaution of reloading, but lived to tell the tale - but that load sure moved...

I guess I'll resign myself to being the slow poke of the shooting world. At least I'm getting decent accuracy - although not quite the much advertized, consistent .5" groups. I must be the only one not getting those either. In fact, it sounds like all rifles not fulfilling this criteria have been sold, and must somehow have been annihilated... At least nobody seems to own them any more??

- mike

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At least I'm getting decent accuracy - although not quite the much advertized, consistent .5" groups. I must be the only one not getting those either. In fact, it sounds like all rifles not fulfilling this criteria have been sold, and must somehow have been annihilated... At least nobody seems to own them any more??

I sold all of my factory rifles and now hunt exclusively with customs using high grade barrels and quality workmanship.It usually does make a significant difference where accuracy is concerned,although one of my most accurate rifles was a .223 howa varmint that I bought for a very reasonable price.

Where I shoot, temps run from below freezing to about 95deg. I find vel. changes vary too much to say it's 1, 2 or whatever fps/deg. Diff. powders & diff. bore sizes yield diff. results. The best thing to do is chrono @ diff. temps then you know for sure. I have seen as much as 100fps diff. from loads shot at 90deg vs 40deg. So that falls into olwjoes guidelines.

Different recipes and rifles and temps can certainly give you some strange numbers comparing to book values and buddy values. I loaded some 270's for a freind and just focused on accuracy and not exceeding max and got some strange chrony numbers.
The Sierra 130 with 55 gr of H4350EXT and averaged 2936 fps and very accurate.
The odd thing is when I loaded the 130 TSX the best accuracy was at 54 gr of H4350EXT and averaged 3047 fps with less powder. I shot these on the same day also.
The Hodgdon Extreme powders are supposed to conrol speed swings with temp changes so you may want to read what they have to say on their web site. I know for a fact that the H4350EXT speeds are much more consistent than IMR4350.
Good Luck

Thanks again guys, interesting input. I like the velocity/temp correction chart Steve. Amazing the amount of information you have collected and made available to the World!

Just to make sure I read the chart correctly:

If one would measure 3100 fps at 70F (@ 4000 feet), then the correction factor for 30F would be 74 fps and for 100F 121fps?? I'm a bit surprised that the correction factors seem to increase with increased velocity. I guess I'll have to ponder that one... Good stuff, though.

- mike

quote:

Just to make sure I read the chart correctly:

If one would measure 3100 fps at 70F (@ 4000 feet), then the correction factor for 30F would be 74 fps and for 100F 121fps??

You have it correct...