Shorter Action vs. Long Action

[WSSM]

We hear it all the time. Short actions are inherantly more accurate than a long action rifle. Which is generally true. BUT.............. it seems that the vast majority of the opinions on this is that the bolt being shorter and the receiver being shorter make them more stiff and this is conducive to better accuracy.

Now before I get started explaining my thoughts about this let me say that I do know why short actions of the same caliber are generally more accurate. I has everything to do with the shorter powder columns and the more moderate velocities generated.

When you look at a bolt action rifle the bolts lugs are on the front of the bolt. The lug seats are inside the front of the receiver. The recoil lug is in front of both of the other two. So being that the recoil is transfered to the stock before it ever gets past the recoil lug seats what differance could it possibly make how stiff and rigid the rear of the bolt and receiver are? They don't do anything but just sit there looking pretty until you cycle the action.

So why do the majority of folks always say that short actions are more accurate because they are more stiff?

Anyone else have an opinion on this?

[Omaha-BeenGlockin]

Its stiffer by the very shortness of the action itself------kind of like trying to bend bars that are equal in every way except for length-


Say one is 12 inches and the other is 24 inches----the 24in bar will be easier to deform.

Since the shorter action is stiffer it will provide a better support for the barrel that's screwed into it and the barrel will flex less.

[jvs]

Its stiffer by the very shortness of the action itself------kind of like trying to bend bars that are equal in every way except for length-

Say one is 12 inches and the other is 24 inches----the 24in bar will be easier to deform.

Since the shorter action is stiffer it will provide a better support for the barrel that's screwed into it and the barrel will flex less.

That would be true if the walls of the receiver were the same thickness, but what happens if the receiver is milled with thicker walls for a long action?   I would hope that the walls would be a little thicker for modern long action and magnum calibers.  A little extra weight in the receiver is not your enemy when it comes to long actions and magnums.   Not when it comes to flex or harmonics anyway.

[Ramrod]

WSSM, there must be something to the stiffness thing. Most benchrest guns have sleeves installed over their short actions, to make them even stiffer.

[mountainview]

Its stiffer by the very shortness of the action itself------kind of like trying to bend bars that are equal in every way except for length-


Say one is 12 inches and the other is 24 inches----the 24in bar will be easier to deform.

Since the shorter action is stiffer it will provide a better support for the barrel that's screwed into it and the barrel will flex less.

I agree that the action is stiffer when it is shorter, with all other factors being equal under certain loading conditions such as pure bending moments. But given that a barrel is a cantilevered mount (i.e. only attached at one end and essentially free elsewhere), how would a shorter receiver provide better support than a longer one with respect to the barrel? For a given length barrel, the free length will be the same in both receivers.

[bajabill]

WSSM

I agree with your assessment of the stiffness (or lack of) differences in the recoil reaction.  I have been thinking of bringing this very subject up.  And, I am a stress analyst of machined parts by trade.  THe bolt never comes into the stiffness equation and the larger cutout in the reciever is not in the direct load path to the recoil lug.  As a matter of fact, many sources will tell you that the torque on the rear action attach bolt is not critical.

[Vern Humphrey]

Think of the barrel as a lever, and the forward action screw as the fulcrum.  As the barrel is moved up and down, the tang should move in the opposite direction -- but it's anchored by the tang screw.  So the action flexes slightly.  The longer the action (all other things being equal), the greater the flex.

The effect on accuracy is not in the flex of the action, per se, but in the movement of the muzzle.  Longer actions allow more muzzle motion, and hence less accuracy.

[bajabill]

has any sporter rifle design attempted to place the recoil reaction up, more in line with the barrel.  This would eliminate the eccentricity due to the common recoil lug being lower and there would be little or no muzzle jump within the metalic portion of the system.  The eccentricity would/could be introduced in the stock however.  I think various military  autos have tried to allign all of the important players vertically to keep the later rounds from climbing up the ladder.

But, if there is more than one separate load path (ie, one to the left and one to the right, both at the same level of the bore), the bedding stiffness would need to be really controlled.

[Ramrod]

Vern Humphrey has done the best job of explaining this phenomena, and that is probably why alot of benchrest guns are not only sleeved, but  glued into the stock!

[Lawdog]

That would be true if the walls of the receiver were the same thickness, but what happens if the receiver is milled with thicker walls for a long action?   I would hope that the walls would be a little thicker for modern long action and magnum calibers.  A little extra weight in the receiver is not your enemy when it comes to long actions and magnums.   Not when it comes to flex or harmonics anyway.

The walls are not thicker on a long action.  Short action or log they are made the same thickness so the shorter action is stiffer thus adding to the added accuracy of the shorter action.  Lawdog
 

[Yukon Jack]

From a purely theoretical point of view, yes the short action provide a more accurate base from which to build.  However, on mass produced rifles, especially hunting rifles, manufacturing tolerances are much greater than any minimal flexing or stiffening benefit that is recognized from a short action.  From a tolerance here or there across the wide range of accepted specifications for the action, barrels, bolts locking up lopsided, bedding in the stocks, even powder scales, brass, or bullets, primers, etc... pretty much would negate any small advantage of one type of system over the other.  I doubt most competition shooters, even with the most precision made "sporter weight" firearms shoot well enough realize the difference.  The theory is there, no question.  Question is, are our manufacturing processes and shooting abilities exacting enough to take advantage of the theory?

[Vern Humphrey]

From a purely theoretical point of view, yes the short action provide a more accurate base from which to build.  However, on mass produced rifles, especially hunting rifles, manufacturing tolerances are much greater than any minimal flexing or stiffening benefit that is recognized from a short action.  From a tolerance here or there across the wide range of accepted specifications for the action, barrels, bolts locking up lopsided, bedding in the stocks, even powder scales, brass, or bullets, primers, etc... pretty much would negate any small advantage of one type of system over the other.  I doubt most competition shooters, even with the most precision made "sporter weight" firearms shoot well enough realize the difference.  The theory is there, no question.  Question is, are our manufacturing processes and shooting abilities exacting enough to take advantage of the theory?

You're exactly right -- Jeff Cooper would call this "PII,"  Preoccupation with Inconsequential Increments.

On the other side of the coin, though, the last few decades have seen real advances in firearms.  New rifles tend to be more accurate and reliable out of the box than in the "good old days."  They are actually cheaper, too, when you allow for inflation.

Factory ammunition is more accurate, bullets more effective, and so on.

And we got where we are not by a "Hail Mary Pass," where everything suddenly got a lot better, but by tiny improvements, sparked by people who were preoccupied with inconsequential increments.

[Don Fischer]

Perhaps this stiffness bit is going to be history someday. Darrel Holland uses a mounting system that seem's to be like a ,,,,,machine rest. It look's like something wrapped around the barrel and the action just hang's off the back giving no support whatever. I believe Steve Timm of "Varmit Hunter" magazine has at least one of them and he has nothing but good to say about Darrel Holland's work.

The biggest reason I usually hear for short action's is weight reduction. Really now, why not just use a long action for cartridge's that need it, ie. 6mm Rem, and leave your cigerette lighter at home!

[FURocious]

From a purely theoretical point of view, yes the short action provide a more accurate base from which to build.  However, on mass produced rifles, especially hunting rifles, manufacturing tolerances are much greater than any minimal flexing or stiffening benefit that is recognized from a short action.  From a tolerance here or there across the wide range of accepted specifications for the action, barrels, bolts locking up lopsided, bedding in the stocks, even powder scales, brass, or bullets, primers, etc... pretty much would negate any small advantage of one type of system over the other.  I doubt most competition shooters, even with the most precision made "sporter weight" firearms shoot well enough realize the difference.  The theory is there, no question.  Question is, are our manufacturing processes and shooting abilities exacting enough to take advantage of the theory?

AMEN.