Home Forums Hunting & Shooting Ask The Gunwriters What causes accuracy?

I have been pondering lately, what makes one load more accurate then another?

Say for example, the sweet spot the 270wsm I had was 63.4 grains of H4831sc, 140 NAB, F215GMM primer....

What is the reason/scientific or not behind the reason that say 63 or 64 grains, or a non GMM primer wouldn't shoot the same?

Why do most guns/barrels like or not like some certain powders? Example: My .257 wby shoots well with R25 but not R22 with the 100 grain bullets, and shoots better with H1000 then R25 on the 115 grain bullets.

Can anybody explain this to me?

Witchcraft

KC

It's democrat barrel maker schemes using different metal formulas to ensure they won't all like the same components. This ensures them that rich republicans will have to buy more and more gun barrels to shoot elite loads.

you can take 2 exact same factory models & sometimes one will get 3/4s in. at 100 & the other will only get 1&3/4s in.that is the reason one handloads--TO TAILOR THE LOAD TO EACH RIFLE THAT MAKES IT SHOOT THE BEST.---cranky72

There are various theories on causes of inaccuracy. Accuracy is found by eliminating the causes of inaccuracy.

Here is a link to some info (with some references linked there) you could look over for info on some of the theories:
Finding an accuracy node

Its magic.

The internet and key board jockeys.

+1

I am sure seating depth has an effect to some degree, but I have never seen a more dramatic effect than by changing powders or changing charge weight. The plot thickens...tell me why some guns of mine will shoot any load I try in them, and some of them only shoot one.

t hope you are not trying to apply logic to this quandry.---cranky72

I shoot benchrest, and have put 5 rounds into a 0.05" group at 100 yards. My friend Rick put 5 rounds through a 0.02" group with my old rifle that I gave him. Where accuracy comes from.

I would have to start with the right barrel because without a good one, there is nothing you can do. I have Bartlein, Shilen, Douglas, and Hart barrels on my guns. Premium barrels.

I would then pick a caliber that is inherently accurate and that you can get good bullets for. .22 cal, 6mm, 6.5mm, and .30 cal have been competition calibers and have excellent bullets available for them. I buy hand made bullets from Brady Knight, Bart Sauter, and Don Lahrs. J4 jackets and good quality control.

So, you have a premium barrel chambered for an inherently accurate cartridge. My 0,05" group was with a 6 ppc and a Bartlein barrel.

Next, the platform you are shooting from needs to be solid. Your barrel has to be bedded into a sturdy stock, and you've got to shoot off a heavy rest and a solid table. I can see my rifles rock left to right with my heart beat off a wood table, while a cement table will keep it steady.

Now, past the gun, you need to know what the wind is doing. I put out 3 Smiley Hensley wind flags for 100 yard shooting. I watch the flags and shoot when they are doing the same thing. You can squeeze off a round after the wind has shifted and mess up a real tight group.

If you have a good rifle in an accurate caliber with good bullets, you will close your group by shooting off a solid rest and watching the wind. I've seen lots of people shocked their guns shoot so well when I put reloads in it and let them shoot off my Farley rest.

I have a Rem 40X in .22L.R. that I shot with my buddy last Sunday at 100 yards. We get together and shoot the spinners. The wind was blowing 20 to 30 miles per hour and we were shooting .22s at 6" gopher targets at 100 yards. We're watching the wind flags and calling out 3" hold left. 4" hold left... We're hitting the things left and right. My rifle will shoot RBS .22 ammo under 1/4" at 100 yds and it is a blast to shoot with a 36 power scope at 100 yds. Accurate gun, good ammo, steady rest, and playing the wind.

Consistency, in all it's various forms.

RobP's post is a good one, but if you're really interested you might want to buy a copy of RIFLE ACCURACY FACTS, by Harold R. Vaughn. He's a scientist who analyzes accuracy as well as anyt source I've seen, though there are also some good books on benchrest rifles, loading and shooting. And they all apply to hunting rifles as well as target rifles.

However, some rifles I've owned have apparently been possessed by demons.

The saying is accuracy comes from the 4Bs; barrel, bullets, bedding and brass ...

From there, one heck of a lot of skill. The skill normally comes from practice and experience.

Blessings,

Steve

Yes, it is; and the magic that works one day will not necessarily (in fact, probably won't) work on another day.

You beat me to it.

A good friend that I shot the single shots with for years did an article for one of the Sierra load books that was titled: The Name of the Game is the Same. Meaning try to eliminate or get a handle on All variables and there are a bunch of them.

And in load development, work with a single variable at a time.

Blessings,

Steve

Steve once again speaks the truth! I know the biggest variable in the search for accuracy is me. When I am able to shoot a lot, groups shrink. When it has been a while, like it will be when I return from the sandbox and get to shoot again, I know my groups won't be so great.

I tried to be brief. If you've got the time... I spent a good 20 years reloading with a Rock Chucker and RCBS dies before I bought a benchrest gun. Lessons learned will benefit anyone.

I bought Lapua brass, a Sinclair case neck turner, Wilson tap dies, an arbor press, and some other stuff.
The rifle chamber is cut to a .262 neck diameter. The .220 Russian brass to be formed is turned down to .095" which will give you .010 neck clearance. This helps accuracy. Having a Minimum SAMMI spec neck and touching up hand loads with a neck turning tool will make your loads more accurate.

I had a .300 WSM built when the caliber first came out that was loose enough that you could take the firing pin and spring out of the gun, load a cartridge and shake the gun and hear the cartridge rattle. It had .05" clearance, which, although SAMMI spec, hurt the accuracy of the gun quite a bit. It shot 3" groups at 100 yds. I had to experiment with neck dies and sizing bushings and a concentricity gauge to get it down to about an inch.

Back to the bench gun. I fire form my .220 Russian brass to fit the 6 ppc. After that, I use the Wilson tap dies. I have 3 different diameter neck bushings to get the best fit on my bullets. I neck size until the rounds get stiff in the gun. I use a Redding bump (shoulder) die to set back the shoulder a thousandth measured by a RCBS headspace gauge. I also roll my finished rounds on a Sinclair concentricity gauge. I found a Wilson die out of whack and sent it back to them. Their customer service, to put it mildly, sucked eggs and it was 3 or 4 months of phone calls before I got a new die from them. I had to buy another one from Sinclair in the mean time.

It's important to accept the fact that dies aren't always good. What I found with a run out gauge is fairly common. Mike Rattigan a World champion bench rest shooter gave the advice to use a "float test" on questionable dies. Basically, you throw the die in the nearest body of water. If it floats, you keep on using it. Check your reloads.

Where do you seat your bullets. The benchrest standard starting point is 8 thousandths into the lands. You can fiddle with this and it may help. It's just like varying the amount of powder in the rounds. Another variable.

Nice bullets. The standard are bullets made with the venerable J4 jackets. It is actually preferred if you find a bullet that shoots to go and buy as many as you can from the same lot. Apparently there is variation from lot to lot in match grade jackets! Imagine what goes on with hunting bullets. Weigh a hundred and sort them. You might find them to be a grain over or under. You'll never know about the jackets unless you're getting solids. If I had the opportunity to get all my rounds from the same lots... I buy benchrest bullets by the thousand. That seems to be a good thing.

I could go on and on and on. You have to realize that all this and more is to win competitions decided by under a thousandth of an inch at a hundred yards. It seems far reaching but I remind myself that the military has always gone to competitive shooters for innovations and techniques to advance their own marksmanship.