What affects accuracy?

[no_problem]

Take a look at the M4 Barrel, it's pencil thin under the handguards, then it bulges out until the M203 grove where it is profiled down for about an inch. Then it increases in diameter again. The original M16 is a pencil thin profile all the way, while the commando if a full bull barrel for 11.5"

These barrel profiles vary greatly. I think what affects accuracy more than barrel length is the crown of the barrel. Also, the bullet weight and rifling contribute to accuracy. Maybe the long barrel contributes marginally to accuracy.

Now, I know there are lots of super long bull barrels. Maybe the longer barrel contributes more to velocity, and marginally at that? It may not contribute to accuracy that much.

what do you think?

 

[Wes Janson]

Thicker barrel=less vibration, bigger heat sink. Longer barrel=more velocity. When you're discussing a military-issue M4, you're not really talking about precision match accuracy anyways.

 

[Art Eatman]

If the crown isn't dinged or marred, the shape won't affect accuracy. If shape was a factor, all rifles would be the same.

Barrel length, by and large, isn't much of a factor. For ultra-small groups, read about the conclusion for 21.75" as the ultimate, at http://www.angelfire.com/ma3/max357/houston.html

Bedding is very important, as is the consistency of any pressure on the barrel from the way a rifle is held or how the forearm fits against the barrel. Barrel bands on Mannlicher stocks, for instance, can create problems.

Skinny barrels heat up more quickly, and the changing stress can cause minute changes in the alignment of the bore with the sights. That's the main problem with the Mini-14, as near as anybody can tell.

 

[JHansenAK47]

Twist affects bullet stability. 1in7 for 77gr bullets is preferable to prevent tumbling.
Length affects velocity. 11.5" barrels don't perform as well at 500 yds.
Chromed barrels are not as uniform as unchromed barrels. Negates the use of match ammo if your barrel isn't uniform.

 

[WNTFW]

Loose nut behind trigger is usually biggest problem.

Bull barrels are nice as long as you are not carrying them any amount.

What are you trying to do with the rifle? I like to shoot from different positions with iron sights so barrel is not my biggest problem. A sling can do a lot at a relatively low price. Trigger may give more bang for the buck. I narrowed, trued round & squared the top of my front sight post and that made a small jump in my ability to hit accurately. Sight radius helps also.
I look at everything as 1 part of a system.

 

[Bitswap]

In the pureist sence, the main determining factors for accuracy are going to be the twist rate and crown. The twist rate to stabalize the bullet (weight) your firing and the crown to control the pressure on exit.

Length is not important.

The chambering can be important. The lands must taper to the throat and not be square. This is usually considered a mistake but does happen.

Chamber neck sizes, (match or tight) are usually important if you reload. They will improve accuracy as well but not as significient as other factors.

Barrel thickness determines how many shots you can fire before the barrel is considered 'hot'. Bull barrels can fire more shots. The thickness also affects the harmonics and may or may not be more accurate because of this.

It really boils down to what your going to use it for. For a hunting rifle where you'll only fire a few shots at the highest velocity you can get, then a thin 24" barrel is fine. For match or varmints where you'll be fireing alot of rounds, you'll want a heavy barrel. For a camp self defense rifle, 20" is fine.

 

[rangerruck]

the less whip, and the less harmonics a bbl goes through, and the less contraction/expansion , etc., in other words, the more things don't move at all, and stay exactly the same, the more accurate. So a big fat huge bbl, that doesn't heat up at all, and doesn't have any whip, all other things being equal,
should be more accurate.