What Makes Ammo Accurate?

[whitfang]

Just got my first Encore centerfire rifle barrel, in 308 Winchester.  Looking at 150gr ammo for it, you can spend under $5.00 for 20 rounds of Wolf Russian-made, all the way up to $31 for 20 rounds of Federal Premium.

The five factors that I see in ammo accuracy are bullet, case, primer, powder and assembly.  Are ALL of these made cheaper in discount ammo, and do they all affect accuracy?  

If this Encore shoots 100yd groups of 6 inches with the Wolf ammo, will it shoot 2 inch groups with the Federal?  

Also, it's easy to see how the bullet needs to be the proper size and weight to be accurate.  But how do the case, primer and powder enter into the accuracy equation, besides the fact that everyting needs to be consistent from shot to shot?

[rocky_taco]

[quote="besides the fact that everyting needs to be consistent from shot to shot?[/quote]

You pretty much sum it up with one word consistent.  Assuming that you do your part and the gun does its part, the following list is some (a very small part) of what the ammo needs to do to be consistent.

Case size
Neck length
Head space
Distance bullet to lands
Primer pocket hole size
Primer pocket hole burr
Primer square to hole
Primer pocket depth
Primer seating depth
Consistency of primer
Amount of powder
OAL  and the distance bullet to lands
CL bullet to CL bore
How tight the bullet is in the neck
Etc. etc. etc. etc. etc.

The tighter the tolerances the tighter the groups.  Usually, tolerance costs money.  How tight of group do you want to spend?

[Lone Star]

While many of the minute case manipulations listed above don't hurt, the reality is that they do almost nothingto improve accuracy in the average rifle.  Even top long range shooters don't mess with primer pockets, etc. and most find that powder charges don't need to be weighed to the 0.1 grain to get top accuracy either.  We've been sold a bill of goods over the years by the slick writers who want to help sell products for advertisers.

No matter how "good" the ammo is, its accuracy potential is limited by the rifle.  Most factory rifles have a multitude of problems which eliminate them from extreme accuracy:  
* Poor bores (oversized, not a consistant diameter, rough finish, bad rifling design)
* Poor chambers (not concentric with bore, oversized)
* Poor action (not square, slow jarring lock time, poor trigger, uneven lugs)
* Poor bedding (not tight in stock, stressed, twisted)

The above are a few of the issues with factory rifles.  Some will shoot very well due to "luck" in assembly, some never will.  I have to laugh at all the posters who state that they have a 1/2 moa rifle, when what they mean is that their rifle will sometimes shoot a 1/2 moa group.  Somehow whenever many of them are asked to consistently reproduce that level of accuracy they can't.... :roll:

I do perform all the anal case preparation for cases in my firearms which actually do shoot aggregates of 0.5 moa or less, but none of them are factory-stock rifles.  For the others I carefully size the brass, keep it trimmed, and shoot it.  In my own testing over the years, the anal prep work doesn't make enough difference to measure with these arms.

[whitfang]

Thanks rocky-taco and lone-star for your input.

I shot 60 rounds of cheap Wolf ($5) thru the Encore today, then 20 rounds of Winchester Super-X ($14).  You get what you pay for (to some extent), no doubt about it!

The Wolf shot about 6-8inch groups while the Win shot 2-3 inch groups, all off a rest at 100 yards.  Had to shoot the last 20 left handed because my right shoulder was getting sore.

(1) If I spend $21 for ammo, should it tighten the groups?  Will $28?
(2) Do you have to let the barrel cool between shots?
(3) Does shooting left-handed (for a normally right-handed shooter) do anything to accuracy?
(4) How accurate should a stock Encore 308 be?

I see what you are saying, lone-star, that you can't get a barrel to perform over it's potential with expensive ammo.  But it does look like you can detract from it by going too cheap with ammo.  Do you have to get a custom barrel to eliminate all those problems?

[Lone Star]

Do you have to get a custom barrel to eliminate all those problems?

No, but it helps.  I have a number of custom Contender barrels, and the best ones shoot extremely well.  The best is my .25 Bullberry, which with the best loads will agg in the low 0.5s with ocasional groups in the high 0.3s  

Custom barrels use far better barrel stock than T/C does and are very carefully chambered - both the mechanics of cutting and in reamer selection.  T/C (I'm just using them as an example, most factories do the same for production guns) uses cheaper barrel blanks with wider tolerences, chamber their barrels on a drill press (!) and try to get all the mileage they can out of each reamer.  This means they order it on the large side of the SAAMI tolerences, then over time as it wears they sharpen it, reducing it's dimensions.  

If you get a good barrel with minimum dimensions, a chamber cut with the reamer when it had been sharpened down to minimum dimensions - and which happened to be concentric to the bore, then it has the potential to shoot very very well.  But it still needs good ammo and a good shooter.  A lot of the accuracy potential is in the shooter and how he handles his rifle on the bench.  Being able to compensate for range conditions (wind, mirrage, that ported .416 at the next bench) can mean the difference between 0.5" groups and 1.5" groups.

[skb2706]

The "nut at the butt" is what makes most of mine accurate assuming I load it accordingly.

[swampthing]

If I was not a reloader I would buy a box of each of the factory available ammo and shoot them to see what was most accurate and use them.  Rem Core lokts and Federal's seemed to be the most accurate out of my T/C. I also liked that Syms recoil pad on my smokepole.

[ihookem]

Lots of things effect accuracy. First, since you asked about ammo we'll start there.Probably the most important is  you must have a real good bullet. This is why, a cheap bullet is not consentric. In other words shooting a bad bullet is like a tire off balance. As the bullet spins, it gets further and further away from the bullseye because it's like it's off balance. That is why sometimes you see bullets all over the target and hitting the bullseye is luck. Some hit the target high then the next one low then right and left. This is why some say it doesn't pay to measure the powder. Most of the time it's true if the powder shoots consistantly. But powder is all different because one powder might make one barrel vibrate more than another when the bullet goes down the tube, and that effects accuracy. Thats why one powder works for one barrel and not the other even of the same caliber. My guess is the second most important is that people don't clean the barrels well enough. If you have a dirty barrel you can forget all about tight groups. And don't let anyone fool you about their super accurate gun that never gets cleaned. For real accurate loads about every 15 rounds. But for hunting loads about every fifty or so is all you need.

[whitfang]

You guys have convinced me about the ammo - that Wolf 308 I shot was all over the place.  I've got some Remington, Winchester and Federal ammo to test, but now winter weather is 'back home again in Indiana',  so it might be awhile before I can test again.

Do you need to let your barrel cool between shots, or can you crank 5 rounds thru an Encore with good accuracy on all shots?