Can any one give me an idea of the muzzle velocity of this .308 Win load. I have shot it through two chronographs and have about a 100 fps difference.The barrel is from Shilen heavy barrel and has a 10 twist and 25 inches long. The chamber was cut with a tight neck.

This load will shot .5" all day long

Norma cases
Federal 210 Match Primers
46.5 gr Varget.
150 gr SBT GK
2.220"OGL
Pressure is 46900 psi

Plus or minus quite a bit between different barrels, but my 26" Rem VSSF does 2910 with a 155 and that much Varget lit up by F210's. I am getting better velocity and slightly less pressure with VV 140. Smaller charge weight as well.

Same load with 155 SMK we are seeing slightly under 3000 FPS with 30" 1 in 13 barrels.

quote:

Norma cases
Federal 210 Match Primers
46.5 gr Varget.
150 gr SBT GK
2.220"OGL
Pressure is 46900 psi

How are you measuring the pressure.....how do you know the pressure is 46900 psi?

I think the guy called it a strain gauge or something like that. We went as high as 47.0 gr and a pressure of 55125 psi but our groups had almost tripled in size

quote:

Originally posted by NESIKA308:
I think the guy called it a strain gauge ...

The correct technical term is Haphazard Strain Gauge System Fiasco.

There are a good number of Pressure Indicators listed in the Poll as well as the thread - if you are interested in such stuff.

Average the two Chronograph readings and it will be close enough. Or you can "guesstimate" it close enough from your Load Manual.

Knowing the actual Velocity is not of any significant use to you anyhow. It is only good to use for "estimating" the Drop Rate to get you onto the paper. But, the actual Drop Rate you use, should be determined from where your specific Rifle and specific Load place the Bullets on the Target.

Best of luck to you.

Hodgdon's website shows a charge of 47 grains of varget at 2937 fps and a pressure close to 58,000 psi

Here's the rub.....if you measured 46,900 with 46.5 grains and then got 55,125 with 47 grains of varget.....you have something other than velocity to be concerned about. 1/2 grain should not make that much difference.....are you using mixed brass?

Velocity variation of 100 fps isn't at all uncommon.....accept it or change powders....it may or may not improve.

Ignore Hot Core, he has an axe to grind but mostly just grinds his nose to spite his face

Actually I use an Oehler M43 PBL. If installed correctly a strain gauge measurement is as accurate as any of the factory used methods. All pressure measurements (even the factory measurements), as Dr. Oehler notes, are approximations as nonee of the methods are taken inside the case. Hot Core goes off all the time about "reference ammunition" that he claims is used to "calibrate" to "calibrate" pressure machines. Reference ammunition is not used to calibrate but is used as a "reference", hence its name. Reference ammuntion is also horribly expensive (Winchester provides it). I tracked it down and it's beyond what I want spend. I did however contact Federal and they gave me the pressure of the 3 different lots of .308W Federal factory ammunition I had. I fired a 10 shot test string of each lot through 2 different .308W rifles. One with a 10" twist and the other with a 12" twist. Of the 3 lots tested in the 10" twist barrel 2 lots measured pressure (M43) slightly higher than the Federal psi. With the 12" twist it was just the opposite; 2 of the lots tested were below the Federal psi. All of the test strings were within +/- 2,000 psi of the Federal psi. I ran the tests with a temperature of 75 degrees. Both rifles have tight match chambers. The 10" twist barrel has less than 800 rounds through it and the 12" twist barrel has almost 3,000 rounds through it.

The psi's measured were, of course, average peak preassures as were the Federal factory psi's. One can hardly expect the figures to match exactly but it was quite interesting to see just how close the two different systems were. Perhaps not quite so "haphazard" after all, eh!

15 years ago I tried the 155 Plma bullets over Varget. It took 48.5 gr to push the Palma bullet to 2910 fps out of a 26" barrel with 12" twist. I bought a case of Varget back then and still have most of one jug left. Maybe the newer lots of Varget are faster. Perhaps I should get a new pound and run some pressure/velocity tests. If anyone is interested I can post here?

Larry Gibson

All were new norma or lapua and I decided on norma. Have yet to fire any once fired brass.

quote:

15 years ago I tried the 155 Plma bullets over Varget. It took 48.5 gr to push the Palma bullet to 2910 fps out of a 26" barrel with 12" twist. I bought a case of Varget back then and still have most of one jug left. Maybe the newer lots of Varget are faster. Perhaps I should get a new pound and run some pressure/velocity tests. If anyone is interested I can post here?

Larry Gibson

About 10 years ago I was using 4064 with 155 grain SMK for Palma matches. Velocity was slightly under 3000. At that time I tried Varget with dissapointing results. I quit shooting competively in 2001 and just recently started again. I tried the Varget again and can reach 3000 FPS with 47 grains in even a 28" barrel. Maybe they made some changes???

After firing a follow up load development this morning I must strongly recomend the use of VV 140 and the 155 Lapua Scenar bullets. 9 rounds into 1/4 MOA at 300 yards. oad development is finished.

quote:

Originally posted by larry:
... If installed correctly a strain gauge measurement is as accurate as any of the factory used methods. ...

Feel free to quote me on -

If you've shot the identical load thru two chronographs, then you pretty much know the vel. Your spreads could be temp. &/or chronograph related. Were both strings hot under sim. weather conditions, were the distances to the screens identical w/ each chronograph? I'll grant you that 100fps is a big swing but I'm betting user error has something to do with it.

quote:

Originally posted by vapodog:
Hodgdon's website shows a charge of 47 grains of varget at 2937 fps and a pressure close to 58,000 psi

Here's the rub.....if you measured 46,900 with 46.5 grains and then got 55,125 with 47 grains of varget.....you have something other than velocity to be concerned about. 1/2 grain should not make that much difference.....are you using mixed brass?

Velocity variation of 100 fps isn't at all uncommon.....accept it or change powders....it may or may not improve.

Vapodog,

My mess up i checked and the 55125psi was a 165 gr bullet in the notes