How do you go about finding best load for your Gun (.308)


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Martyk
January 5, 2009, 08:13 AM
When it comes to precision shooting and tight groups, the common school of thought is that every rifle has a particular load, both in bullet weight, and powder charge, which will attain the highest degree of accuracy.

http://www.accuratearmsva.com/html/accurizing.html

Exactly how does one go about developing the best load for a particular rifle? Is there a scientific process that is commonly followed? Or is it more like Poke-N-Hope?

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Friendly, Don't Fire!
January 5, 2009, 08:39 AM
the common bullet weights for that gun. I go by various loading manuals and see which powders are also the most common for the gun and weight bullet.

I buy some bullets, usually several different ones. I buy (or have on hand) various powders.

I try five loads, usually loaded with minimum powder charges, or just above minimum.

I take my rifle to the range. If, when I get to the range, it is windy at all, I stop and go home. I will only work up loads and test them on perfectly calm days.

The rifle is completely clean. I fire off one or two rounds of factory ammo (or make up several light loads) just to get any oil out of the barrel.

I carefully shoot one string of the five rounds I loaded at 100 yards.

I take time between shots to let the barrel cool down. After the fifth shot, I retrieve the target, set up another target and mark the target with everything, bullet, weight of powder charge, any slight crosswinds that may have started, etc. Since you are waiting for the barrel to cool, you might want to consider taking another gun with you to shoot while the gun you are working up the load for is cooling.

I clean the barrel. I fire off one or two rounds to foul the barrel and continue to do the same thing as mentioned above.

When I see which bullet pulls the tightest group, I then go back and experiment with different powder loads and possibly different powders. I typically step up by .5 grain increments on the powder loads. You only want to change one thing at a time, so you can see what difference the change has made. Typically, the less powder a cartridge holds, the smaller increments to try with the varying powder weights. If your cartridge has 98 grains of powder, you would be safe working up in 1 grain increments as opposed to 1/2 grain. For a 308, you could try 1 grain increments and then narrow it down to .5 grain increments if you see tight groups. If you have discovered a particular bullet and powder combination that pulls the tightest five-shot groups, then experiment with powder weights, again usually in 1/2 grain increments. I have already found a load that works extremely well between two different weights of powder (i.e., 23.0 grains and 23.5 grains). If that happens, you might want to try the powder load in between the two the gun likes (like 23.3 grains). If that powder weight shoots the same (extremely well), then you can "go" with that particular load, knowing that any little variance between different lots of powder and any imperfection of your scale probably won't matter at all in your finished loads. Sometimes a gun will shoot a real tight group and then you change the powder weight by only 1/2 grain and the group opens right up! In cases like that, you want to be sure you are on the "side" of the powder weight that the gun likes before opening up. For instance, you might want to calm down the powder load just a tad to see if you are still pulling a tight group with a bit less powder than before the group opened up.

I find that typically middle of the road loads are the most accurate (not minimum, and not maximum), however I have one rifle that loves the maximum load the best, hands down.

Assuming all your equipment (gun, any scope, etc) is in good working order and everything is tight, you should see differences in different loads.

When I buy bullets (the 'pills') for the first time, I always make sure I get something that is identical to what they sell today. Don't buy some old boxes of bullets that may not even be made anymore, as if you find your gun likes those particular bullets, you will have a problem when you run out!

Also, instead of buying bullets, you could maybe get five or so of each bullet from a friend who might reload the same caliber. That way you don't end up with nearly-full boxes if your gun doesn't "like" them.

I do find that for the most part, any reloads are typically tighter shooting than factory ammo. This isn't always the case, however I have found it to be true about 90% of the time.

Make sure you record EVERYTHING. Case length, whether crimped, and if so, a light crimp or tight crimp, OAL of the case and bullet (if not set into a cannelure), etc. That way, between your notes on each cartridge and targets, you can go back home and study everything. Keep your empty cases in order and identified so you can go back when you get home and study them, looking for signs of excessive pressure (flattened primers, cratered primers, etc).

I typically don't use the chronograph to measure the bullet's speed until I have settled on a load that is tack-driving accurate at 100 yards. Then I will calculate ballistics based on muzzle velocity. If I were testing defense loads, then I might want the chronograph for every load, however I would not use reloads in a defensive situation, so the only time I might chronograph is for my factory loads to see what the ballistics are for them.

1858rem
January 5, 2009, 09:12 AM
typically what range do you shoot at for developing loads? ....i just started reloading for .308 that i recently got thinking i could tighten up groups, which after i put my first couple groups down i was too surprised! factory federal 150g soft points were cutting ragged holes at 100 yards, only shot 3 groups at 100 so far though...rem 788 .308 22" bbl 4-16X40mm... now i really dont know if i can improve on that!! generally i do get a "flier" with more than 3 shots:neener: and maybe i can eliminate those? i tried 50 yards for working up loads for a .204 ruger since i could not see the target well and ended up getting 1/4 inch groups and typically 2/5 extend it to .5" at 50, but then i get 1.5" at 100, leaving me fairly confused, maybe cause the wind was kinda heavy too lol:rolleyes:. would SMK 168g or Remington corelokt 165g be better with max range of 3-400 yards and typically 5-10mph wind?

Friendly, Don't Fire!
January 5, 2009, 09:26 AM
Typically, the further out you can shoot, the more you will know about how accurate each load is. I always used 100 yards for centerfire rifle and 25 yards for pistol -- off a STURDY BENCH with sandbags or lead shot-filled bags. Once my pistol loads are worked up, I have been known to then go to 50 yards, then 100 yards and sight in the pistol at 100 yards (like 44 Magnum, 500 Magnum).

However, you must shoot on perfectly calm days (at least I must because I cannot read the wind like a sniper would), or the wind may be causing opened-up groups and you are then wasting your precious time spent at the loading bench working up these loads.

1858rem
January 5, 2009, 09:34 AM
yah! wow rifle loads take way longer than my 45 colt loads, i think im doin about 20 or maybe a few more in a hour lol. is a bipod good enough for developing loads? 9-13" normally only on the 9" setting, could this make me shoot zero at 100yds and .5 higher at 200 yds if my targets center is only 8" higher than i am shooting from? ex.. my bbl is 10" off the ground and the bulls eye is 18" up?

Friendly, Don't Fire!
January 5, 2009, 09:46 AM
is a bipod good enough for developing loads? 9-13" normally only on the 9" setting

A bipod with you prone (lying down, legs spread apart a bit) should be good. Do you only have open sights or are you using a scoped rifle?

Crimp
January 5, 2009, 10:14 AM
Here's how I do it:

Optimal Charge Weight (http://optimalchargeweight.embarqspace.com/#)

1858rem
January 5, 2009, 01:19 PM
i have a Center Point 4-16X40mm on the .308 and a Nikon prostaff 3-9X40mm on the .204...9x is a little less than i might like for shooting at a 100 yd target that's supposed to be replicating 200 yds(1/4" bull)! the 16x really helps there lol

Ridgerunner665
January 5, 2009, 01:30 PM
I always enjoyed the "poke-n-hope" method...and I learned a lot that way.

I enjoy shooting...so why would I read up on what works for everybody else...that would just knock me out of the experience of learning it for myself.

Yes...I know...I'm a bit "backwards" sometimes, but I am one of those guys that believes none of what he hears and only 1/2 of what he sees.

I load 10 of each round...fire 5 of them over the chrono and onto a target @ 100 yards. Then fire 5 of them over the chrono at 300 yards and onto a target right behind the chrono.

That way I get velocity, accuracy, and the "real" ballistic coefficient out of 10 rounds.

1858rem
January 5, 2009, 01:33 PM
what sort of accuracy have you gotten on avg at 300 yds?... while trying not to hit the chrono also lol

Ridgerunner665
January 5, 2009, 01:50 PM
Out of my SPS Tactical...several groups of slightly less than 1 inch.

The best being 5 shots that measured .623" center to center.

That rifle consistently shoots .3 MOA @ 300 yards with my loads (sometimes a tad better).

Not hitting the chrono at 300 yards is easy...I have been known to hit a couple of them when doing that at 1000 yards though :D

I learned my lesson though....now I put the "important" part of the chrono behind a piece of railroad rail.

1858
January 5, 2009, 11:32 PM
Crimp, I use the OCW method too with all of my bullets seated 0.020" off the lands. The next step is to use a chronograph to get the average muzzle velocity of the "best" load and use that to calculate bullet drop and wind drift for various distances.

The OCW method is good since the best load at 100 yards will be the best load at any distance ... well, that's my understanding anyway.

:)

NuJudge
January 6, 2009, 06:30 AM
If you want to shoot out to 500 or more yards, use something heavier than 150 gr bullets.

I've always had good results with IMR 3031, 4895 and 4064, so I've stuck with them. I started using them because M1A and M1 rifles need that burning rate.

CDD

redneck2
January 6, 2009, 06:54 AM
I would strongly suggest you get the newest edition of Handloader Magazine. They have a very, very extensive article on accuracy loads for the .308 specifically. Covers cases, bullets, powder, primers, etc

All work was done in an extremely methodical and well documented manner.

Martyk
January 6, 2009, 08:07 AM
Thank you guy's. My dies came in yesterday and I started getting them set up. Lot's of good info and a solid starting point here. Appreciate your sharing the info.

Hey Ridge...no worries.. it sounds like as scientific an approach you try to take, it's a good amount of poke-n-hope anyway. It's the process that makes it fun!

Afy
January 6, 2009, 02:59 PM
I try and use a combination of Poke 'n' Hope... but my poking is done using Optimal Barrel Time.
So far I am not really disappointed, but am not yet into the bench rest accuracy space.

1858rem
January 21, 2009, 11:10 PM
whats optimal barrel time, how accurate is it? i think ill settle for consistent 3/4 MOA lol

1858
January 21, 2009, 11:22 PM
whats optimal barrel time, how accurate is it?

Take a look at this website ...

http://www.clik.to/optimalchargeweight

and this website ...

http://www.the-long-family.com/

Here's an excerpt from Dan's page ...

"Engineer Chris Long's model of barrel
behavior suggests (simply put, and in part)
that the initial shock wave, generated by the powder
charge's ignition, travels at the speed of sound in
steel (about 18.000 fps) from the chamber to the muzzle,
then back, in a repeated pattern. When this wave is present at the muzzle,
there is naturally much turbulence and obturation of the
"roundness" of the bore at the muzzle. However, when
this main shock wave has reverberated back to the
chamber end, the muzzle is relatively stable. This
window of opportunity, according to Chris, is the best
time for the bullet to exit the muzzle. The barrel is
basically straight, and relatively calm.

(Read later about the "scatter node" which is the point
at which the bullets are being released from the bore
when the shock wave is at the muzzle. I call this area
the "scatter node" because it will produce a scattered group,
throwing flyers at random. This is the most
inopportune point of all for bullet release, the scatter node area
can be easily seen during an OCW test, and generally 1 to 2
powder graduations above the scatter node charge will have
you right in the OCW zone. The existence of the scatter node
is the main reason the conventional ladder (Audette) test often fails
to yield useful results)."


There are believers and non-believers ... so it's really down to the individual to find the system that works best for them.

:)

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