What affects a barrel/action's accuracy more than anything else?

So I got out to test my son's 700 build and found the results to be much less than I even thought they would be. Nasty group and each shot seemed to be different than the last. Moved over to my rifle and put 3 holes through the shoot-n-see target that looked like one hole (100yds).

Since both guns are .308, both are in pretty decent alum. bedded stocks (mine is in an HS Varmint, son's is in a B&C Medalist Tactical), both have Timney Triggers set to ~2Lbs...

This gives me a chance to really see the difference in a factory barrel (granted, my action has been blue-printed, but I don't know why that alone would make a drastic difference in accuracy).

I've got to get some more range-time in with it and I've got to try some different ammo just to make sure it wasn't a fluke (I was in a hurry to get it out to the range today). I'll probably go over all the torque in the bolts that hold the stock/action, base/action, base/rings, rings/scope too just to make sure, but I seriously expected a decent performance increase by going to a bedded stock (son's rifle is a factory 700 ADL skinny barrel).

I remember being somewhat disappointed at the accuracy gain when I got my HS precision and put my SPS Varmint in it, but it was still noticeable. This ADL in the B&C stock seems pretty sporadic.

So here's the question:

What affects the accuracy of a barrel/action most if you eliminate the stock as a factor?

I don't honestly think that the tolerances and exact-cut of the rifling could be so out-of-spec that it makes for a crappy shooter, but I could be wrong.

Again, I don't see how the changes made to the action would be so drastic that it would greatly improve accuracy (that would mean that Big Green is pretty sloppy with their tolerances and I've heard this is true, but that's kind of ridiculous at that point).

I would bet that the chamber is the biggest contributor to the issue (once I test it out with more ammo, I'll know for sure if it is as bad as I think it is), but I don't know that I'm willing to risk paying to have my SPS Varmint barrel cut and mounted just to find out. I've read a bunch of stuff that says that OAL is the biggest thing to worry about in reloading and I assume it works the other way around as well - OAL of the chamber (if off or sloppy enough) could make a substantial difference.

I'm debating now whether or not to spend the money on having this SPS varmint barrel cut and installed on my son's project rifle. Steve's going to have to re-cut the chamber, cut and add more threads for a larger recoil lug (assuming that I can even do that with the meat on the factory barrel), and chop it down -I don't think I'll spend the money to have it fluted yet, and since the damn QDs for my can are super-hard to find, I'll probably not have him thread it until I can find one (or just wait until I can get another barrel - son needs to learn how to shoot without any cushion anyways right ).

So, the rifle's barrel as of now is the factory skinny barrel? If that's the case, then I would say the bad groups are probably most likely from barrel vibration and flex coupled with the factory chamber.

Plus one on harmonics.

Yep, factory skinny. Sorry I forgot to post the other thread (and I forget which threads I've put the most info in so far):

http://okshooters.com/forums/showthread.php?p=796143&posted=1#post796143

Larry Morgan said:

So, the rifle's barrel as of now is the factory skinny barrel? If that's the case, then I would say the bad groups are probably most likely from barrel vibration and flex coupled with the factory chamber.

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Forgot to mention that I had a couple of flyers (up tp 3" off) and my groups were wildly inconsistent (up to 2" apart) at 100yds.

You think harmonics could be that much of a factor? Guess I never really thought of the skinny as being that much worse off than even my SPS varmint contoured barrel. Is that normal for a factory skinny barrel?

First (and cheapest) thing I'd check after the screws is the crown. Even undamaged factory crowns have been known to cause poor accuracy if they're out of whack.

#1 crown.

Glocktogo said:

First (and cheapest) thing I'd check after the screws is the crown. Even undamaged factory crowns have been known to cause poor accuracy if they're out of whack.

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Ohhhhh, yeah. Totally forgot about that one too. Crown can definitely screw accuracy.

Harmonics can possibly cause inconsistent groups. Case in point, early mini-14 barrels are too darn skinny and suffer from barrel whip. They generally have not so hot groups at 100 yards. I've heard one person joke that they've seen some 1911's group better.

In general, accuracy is proportional to the barrel's stiffness. This means that increased diameter HELPS stiffness and increased length HURTS stiffness, and therefore, accuracy. Getting the accuracy you want is a balance between the two. Right now, you've got a skinny diameter and good amount of length, which is kind of backwards when looking for stiffness.

Another argument is that since it's skinnier, it heats up faster and can add to the inaccuracies. I don't know if this has any merit, especially since I don't know how quick you were shooting, or if that would even cause it.

I don't buy into the harmonics hype. I'd say it's a combo of a really crappy chamber and the factory rifling and crown. That our your bottom metal wasn't torqued evenly.

I've always heard the crown was the most important part.