.308 winchester

[xhodzax]

ok i have a problem
i load 47g varget with 155 bergers 24" barrel 1:10 twist
my chrono shows 2840 +- 15fps
1/4" groups @ 100 yard
i sighted in my gun @ 200 and shot it @ 500 and 600 yards
@ 500 yards i need 6.75 moa elevation and @600 yards i need 8.75 moa elevation.
i run these numbers through berger balistic calculator and i get that my bullet travels 3100 fps to get these results.
is my chrono broke or what
.308 win shooting 3100 fps possibe???
any input please

 

[scout1]

I will say that its not impossable but more so improbable with a 24" barrel. Are you seeing pressure signs?(Primers falling out) Are you using a custom action with a bushed firing pin hole? Is it a custom chamber? or did you place some lighter bullets back in the wrong box ;D

I have had what I'll call anomolies with the 155 out of a 26" barrel but nothing consistantly that fast or even close. Mid 2900's is where I keep them

 

[spclark]

Too many variables to say with any assurance, but my guess is your chrono's probably close enough. What may be the problem is the values you plug into your program. If you're using optics for sighting, your MOA numbers may not be quite "right" if your 'scope clicks aren't calibrated to actual POI results with your rifle.
Just dialing in MOA corrections isn't enough if you don't know what those changes will affect ON PAPER at 100 or 200 or 600 yards. Same applies to open sights with an added complication of the sight radius.

2 MOA change between 500 and 600 yards is possible for Berger's 155 bullets... you using the VLD or the BT? The former may fare better with your faster-than-normal twist for the 155's.

Just as a comparison I get 2950 fps with 46.5 grains of Varget in Win cases in a 30" Broughton 5R 1:11 with the Berger 155 BT and Sierra's new 2156 Palma 155. I don't have come-ups for anything short of 800 yards & beyond as I only shoot this combo for Palma, where ~ 5 MOA is the change from 800 to 900 & another 6 or 7 from 900 to 1K. In a 24" 1:10 I'd be using 175 grain at minimum, maybe 185 or even 210 out to 500 & beyond.

 

[1000yardstare]

XX,
I shoot 155 Sierra MKings (Palmas) out of a 26 inch 10 twist Savage .308 VLP. Chronos at 2850 with RL15.

Zeroed at 300 yds, I need 6.5 moa up from 300 to 500 and 10.5 moa up from 300 to 600.

So zeroed 100 yards further out I need almost 2 moa more in elevation at 600 than your Bergers zeroed at 200.

Sierra Palmas have a BC of .450, Berger 155s, depending on type, have a BC of between .438 and .464 which is "around" the Palma BC.

So assuming all your calculations are correct, it would appear on the surface that your muzzle velocity is higher than 2840.

But there may be other conditional factors at your range that I don`t know about (strong tail wind, mirage?). Also commercial ballistic packages and their equations are sometimes conservative and sometimes overly optimistic depending on manufacturer. How`s that for a weasel clause?

 

[bheadboy]

mirrage at longer distance, fake the need for fewer moa

Bob

 

[scout1]

I ran your load and speed through Q.L. and it puts you right at 92,000 psi. @ 3100 fps w/ a 24" barrel. WoW

 

[Beau]

What happens when you plug that into JBM Ballistics on the web?

ETA: Hmm.. Same thing. I'll bet it is your scope.

 

[xtightg]

Hi I am using the 30 cal Dyer HBC-BJD 155grain Palma projectiles, Lapua brass. I tried the felt pen seating depth set up in my Sako TRG 22 1:11 twist to just missing the lands, resulting grouping all touching almost one hole at 100 yards. Got me a Hornady seating depth gauge set up I have 0,063" jump !!! I thought I was just missing. Tried closer as per all the advice still shoots best with the big jump !!!. My powder is 47.5 grains ADI AR2208 I think this is Varget you best check this out , Federal 210 primers. Velocity 26" barrel high 2898 fps low 2861 fps average 2885 fps, ES 37, ED 10. No pressure signs or bolt lift or brass issues. 300 yards 60 x60 500 yards 60x 60 900 yards 59x60 first try seams to work for me. Standard Sako TRG 22, Schmidt and Bender PMII 5-25x56, Sinclair F/Class bipod with their rail adaptor and rear bag.
Be careful work loads up safely per the manuals this works ok for me in New Zealand maybe not you. Have fun zero at 100 yards 300 4.00 moa 500 8.50 moa 600 13.5 moa 800 20.5 moa 900 25 moa 1000 30 moa. These are actual range tested data.

 

[1000yardstare]

NZtight. You have just verified a sighting-in logarithm that I have never tried. Urban legend has it that if you have only a 100 yard range, sight 30 inches high at 100 and you will be on the paper at 1000. Legend verified.

 

[xtightg]

Thank you sir glad to be of assistance ;D

 

[whiskey08]

I wonder if the ballistic coeficient is right, a higher coeficient would get you less drop with less velocity. Play with that number and you see a change. Sierra has the 155 palma at a bc of .504 as long as your above 2700 fps.