need help

[Bart B]

There's some misconceptions going around in this thread. I'll try to explain some realities behind them that are typically overlooked.

First, the muzzle velocity one gets from a published load may well be as much as 200 fps different than what was stated. Different lots of powder, ways of holding the barrel, bore and groove diameters, bullet release force from the case and the pressure measuring method will easily do this.

Second, if shot impact starts to wander as the barrel heats up, there's one or two causes. Poor stress relief of the finished barrel will sure make that happen. The finest stress relieved barrel on earth torqued up to a receiver whose face ain't square with the barrel tenon shoulder bears hard at one point. As the barrel and receiver heats up, pressure at that point forces the barrel to bend/vibrate more in that direction. When even an average barrel is fit to a squared up receiver face, it'll go many dozens of rounds fired once every 20 to 30 seconds and not change point of impact. There's several instances where folks shoot from 10 to several dozen shots every 2 to 30 seconds and 100-yard groups would be 1/3 MOA or smaller.

Third, there's easily a 100 fps difference between a given load and rifle when fired by two people holding the rifle atop a bench tight to loose against their shoulder.

 

[rscott5028]

[...]Third, there's easily a 100 fps difference between a given load and rifle when fired by two people holding the rifle atop a bench tight to loose against their shoulder.

That's news to me. I'll have to remember to hold tighter in cold weather to maintain velocity.

I have observed many times where 2 different shooters may shoot tight groups using the same rifle. But, with different POI. Parallax aside, then it really does come down to technique.

-- richard

 

[Bart B]

I have observed many times where 2 different shooters may shoot tight groups using the same rifle. But, with different POI. Parallax aside, then it really does come down to technique.

That's true.

I've coached a more than a few long range rifle teams "hot-gunning" the same rifle using the same ammo. There's sometimes a 1 to 1.5 MOA change in zeros across 4 people shooting the same ammo. Yes, their technique varies based on how they hold the same rifle and the specific position of arms, legs and body is on the ground. But accuracy doesn't suffer, just the zero. And when using aperture sights, there is no parallax. Plus, once a scope's focused for the target range, it's the same for everyone and doesn't need adjusted; parallax is zero for everyone. Parallax exists only in the scope, not our eyes which only see the effects of it.

 

[rimfiresniper]

Nosler data is way to conservative, speer or barnes are better manuals, as for online go to Hogdons load data page. 58.5grns H4831 with a oal of 3.165" is max. I use 57grns Imr4350 at that length both will put you close to 3500fps from a 26" pipe. Your probably only getting 3000-3100.

25-06 Remington - 85 Grain Load Data

Iam using H4831SC I should be getting a little better than 3257. When it comes to max loads I dont play around with H4831 is the same as H4831SC. They may pressure up different and a bolt through the face isnt what I call a fun day at the range.

85 GR. NOS BT Hodgdon H4831 .257" 3.230" 54.0 3302 46,000 CUP 58.0 3473 51,700 CUP

 

[backwoods83]

2 grains of any 4831 isn't gonna put the bolt through your face unless you somehow got a plastic one. Oh and when a cartridge is SAAMI certified it has to be able to withstand 125% of its pressure rating, so max book, still isn't max but that's neither here nor their. Also H4831SC is just the "Short Cut" version of H4831, just easier to meter and work with, burn rates are the same, and I doubt you will find much change from lot to lot with that powder either.