short vs. long actions
 

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?

RE: short vs. long actions
 

The stiffest action I've seen is the Remington 788, it has a minimum of cuts of the smallest posseble size. A single column magazine, and just an opening for ejection, not the whole top of the action being cut away. It is made of heavy tubing, and the barrel seats a whole lot deeper than normal. It has the same internal barrel seat the Mauser 98 has, but with no extractor cut, and it is a short action. Additionally it has a very fast lock time. How come every precision shooter doesn't have one?

RE: short vs. long actions
 

I like only ONE short action,and thats a .308,I only like long actions.

RE: short vs. long actions
 

I am not going to say more accurate, but, but much easier for me to work up a load. I beleive its the powder ignition mostly. I am sure other factors go into play. I can almost watch a chrony and know which load is the best iwith a 308 or 7mm-08. Std dev go down down, then up, up as the load goes up. With my 300RUM or others like that, its hard telling.

RE: short vs. long actions
 

I agree. I've never heard that short actions were more accurate, only faster due to the shorter bolt throw. And to be honest, it's hard to agree that a few milli-seconds is going to make a difference. Just my humble opinion.....

RE: short vs. long actions
 

Short tube is going to be stiffer then a long tube..now whether 1/2" makes a difference that is hypothetical. It would also have faster locktime as some one else pointed out.

RE: short vs. long actions
 

It’s rigid by the very shortness of the action itself. It’s similiar to bending arrows that are equal in every way except for length. For an example, one is 24” and the other is 30”. The 30” arrow will be easier to bend. 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 know most benchrest guns have sleeves installed over their short actions, to make them even stiffer. So, it must improve accuracy. Finally, the unbelted case design means head spacing will be on the shoulder, which is more exact than head spacing on the belt of a belted cartridge. This also increases accuracy. However, the difference will not be seen in all rifles.

RE: short vs. long actions
 

If we look at it from a pure machine design aspect this becomes a bit more clear for a couple of reasons.

If we study how loading occurs once the firing pin has fallen we see a couple of things. Begin by examining how the whole system is loaded once the ignition occurs... the inertia of the firing pin acting on the case for sake of argument is a negligable force.

Once the round "goes off" the you have a radial pressure resulting in a hoop stress of the barrel. at the same time you have a linear force pushing on the bullet, chamber (assumption bottle neck cartridge) and the bolt face (assumption that headspace is correct ). Assuming both the radial stress and the linear occur simultaneously we can deduce that the bolt face is acted upon and barrel channel under chamber first. The whole action flexes to some point due to barrel expansion and the bolt thrust tries to seperate the threads. The bolt thrust being the major line energy transmission thus transfers the "recoil" force to the barreled action and thus to the stock and finally shooter. The recoil is transmited through the bolt, to the bolt lugs which are an integral portion of the receiver. Since the stock is clamped (thru bolted) to the receiver the friction between the two sets off movement of the stock. This gives way to some minute amount of movement between the action screws and recoil lug then loaded against the stock.

Now considering this scenario lets look at some of the geometry within the system. Right off you have a moment in the system which flexes the action. Barrel lifts and naturally causes deflection of the stock downward. The action screws stretch to some extent and the tang is forced against the stock. Exaggerated the action would look like a U. Naturally a shorter moment arm (receiver) would be stiffer and deflect less. Next is the relationship of the bolt to the recoil lugs and bolt face to the actual case. If none of these are square you don't evenly transmit the energy down the C/L of the action. This also results in a bending moment on the receiver. IF both recoil lugs do not have contact (as say many remingtons don;t) and the bolt face is not square to the head of the case the bolt will be loaded in a moment. Now assume both recoil lugs are in contact but still a non square bolt face... the case will put pressure off center and still result in a bending moment , using the bolt as the lever arm.

One thing that a long action has going for it is the length of the bolt and distance between the raceways. For a given clearance a bolt will have a greater angular defection as the supports are moved closer together. Once the sear falls away and the firing pin falls there is nothing but the bolt face relationship to case head and bolt lug to receiver lug relationship holding the bolt in alignment.

In the case of attempting to stiffen a long action, or even a short a one piece scope base is beneficial if securely bedded to the receiver.

Reckon this was a quick and dirty synopsis and there are many more factors to take into account.. but the main point is that a short action will deflect less due to length and stiffness for a given load imposed in the system.

Jamie

RE: short vs. long actions
 

Well all of that would be a great answer if the tang was actually taking any recoil. It's not. The recoil is transfered through the recoil lug to the stock which is in the front of the receiver. If the stock isn't fit properly and the tang does transfer any recoil to the stock you end up with a split stock right behind the tang.

Basically every part of the receiver and bolt behind the front ring just sits there during firing.

Don't assume.;) The chamber preessure has to build inside the case before the bullet starts to move. Only after the pressure has signifigantly risen is the bullet released fron the case mouth and begins moving to the lands of the barrel. And then only after the pressure has risen to 60,000 psi +- does the bullet continue down the barrel.

The radial forces in a chamber happen way before the linear forces do. As "way" as you can get in a milisecond.;)

The action screws do not play any part in the recoil of a gun. They are only there to keep the firearm inside the srock. There is signifigant clearance 360 degrees around them so that they do not contact any part of the stock.



A short action does not necessarily have a faster lock time. The firing pin is smaller and lighter yes but the spring is also smaller and weaker than a spring in a long action firearm. Thus canceling out the lighter firing pin. They both have to be cocked the same distance to get sufficient momentum to dent the primer.

RE: short vs. long actions
 

I have also heard more accurate but at what range,between my 300 WSM and my 300 Ultra mags,the diffrence I could not tell under normal hunting conditions or off the bench shooting side by side out to 400 yds,when you have a miles of stubble feild behind your house I shot both to see how far they would go befor they hit dirt and tell you what,they went farther than I can kill anyting accurately.

As for short vs long,there is probaly some truth due to better groups to a more solid action and less metal to flex under presure.

BBJ

RE: short vs. long actions
 

Yeah, but that's exactly what I am getting at. All of the linear energy (recoil) is transfered to the stock at the front ring.

It never has a chance to flex the rest of the receiver if it's sitting properly in the stock.

RE: short vs. long actions
 

Actually... in a closed chamber pressure is equal in all directions at the same time... therefore the radial and linear aspects of force generation are the same, force varying souly due to surface area. Since the recoil lug is below the C/L of the barrel & receiver where the lug bears against the stock and the bottom of the receiver is constrained from rotation by the bedding in the stock you have a bending moment which will deflect the receiver and barrel joint, moreso the action across it's length since the barrel is free to rise. The bolt is the transmitting member of the force to the receiver and the receiver / barrel / recoil lug assy imparts the force due to good ole mr newton's laws of motion... the barreled action will actually slide a very minute amount within the stocks inletting and bedding... even if there is zero contact between the recoil lug and the recess the wood will still compress an amount greater than the steel...

what i was hitting at for the tang and action retaining bolts is this. The tang at the rear of the receiver is constrained because it rests on the stock. It is securely clamped by the rear action bolt. since the barrel wants to lift due to swell from 60 ksi of pressure in the chamber and the rear tang cannot move you set of a lever type of situation. Now the front action bolt is imparting a clamping load to hold the front of the receiver / barrel in the stock against the bedding... since the barrel is pushing downward on the stock in turn the barrel wants to rise.. the front action bolt has to stretch which imparts another constraint on the assy. The tang at the rear of the receiver is clamped and bedded and won't want to move downward, call this the pivot point. therefore you end up with a U (exaggerated) shaped deflection of basically the receiver....

i guess if i took the time i could grab the calipers, mics and such and model a long action 700 in solidworks and do some FEA to see just how much deflection we're talking about... might take me a couple of weeks to complete... i'm actually curious enough to tackle it just for the heck of it...

Jamie

RE: short vs. long actions
 

I would have to agree with rootsy on this one also. The bolt face has force acted upon it before the recoil lug. The recoil pulse doesn't come until something is accellerated down the barrel, this acceleration is caused by pressure exerted on the chamber and boltface. Without out pressure on the chamber and boltface, you don't have accelleration and no recoil. I would hink theis would be the reason why in accurizing a rifle, you would wan to make sure the locking lugs are bearing evenly, or lap them until they are bearing evenly to make sure the cartridge doesn't misalign when fired and to eliminate any other accuracy killing gremlins in the process.

As far as the 788 goes, its a decent action and lends itself to accuracy and has a fast lock time, but there are other problems with it that can negate any advantages.
The bolt itself doesn't lend itself to durability. If shot with mild loads, there isn't too much of a problem, but if handloaded hot, the bolt is prone to setback not to mention the bolt handle is pretty fragile which has frequently in the past broken off when shooters tried to extract cartridges.
I would actually build a preceision rifle on a mauser 96 action long before I would consider doing one on a 788.

RE: short vs. long actions
 

I understand what you are saying about the chamber radial pressure making the front ring area want to "jump" out of the stock and impart bending forces on the action. I guess that the extremely small amount of flex could effect accuracy to some degree.

I didn't think about the "jumping" of the front ring area.

Just to keep this going;) let me also ask this. Wouldn't the shorter distance from the chamber area to the tang of a short action receiver lend itself to allowing the chamber area to "jump" higher since it wouldn't have as much leaverage as a longer action would?

If you tackle the Remington project I would be very interested to see your results.




I agree that the 788 is actually one of the least stiff actions made. The lugs are in the rear and therefore the bolt is highly succeptable to bending and flexing. Especially with hot loads it can bend badly enough to become inoperable.

RE: short vs. long actions
 

read four times...


mental insanity setting in

RE: short vs. long actions
 

sooo.... If that little bit of length makes a short action inherantly more accurate..... a ruger No. 1 or browning high/low wall would be even better right?

RE: short vs. long actions
 

A short action seems stiffer,it not it just that the bolt has less distance to travel and is supported in the rail guides for a shorter distance.A longer action the bolt will have less support at the rear just because it is longer. Just the nature of the beasts.On the shorter action being more accurate is a bunch of hog wash!! The action has nothing to do with the accuracy in that respect. Whom ever started that is reading to many comic books vangunsmith

RE: short vs. long actions
 

vangunsmith said
"On the shorter action being more accurate is a bunch of hog wash!! The action has nothing to do with the accuracy in that respect. Whom ever started that is reading to many comic books"

How true. I think you guys are forgetting that accuracy is directly related to consistency. Doesn't matter if you make your receiver and bolt out of rubber bands and it does the watusi after every shot. Accuracy and precision won't be affected as long as it does the EXACT SAME watusi after every shot. All the talk about the inherent accuracy of short, fat cartridges is because they burn powder with more precision, not because of the action length.