Barrel locking in a long recoil rifle

I am toying around with a sniper rifle for my 3 man scout sniper teams. (They are a different story but relevant to this post is that they need a relatively flexible weapon that is not to bulky)


The weapon will basically be a lighter tighter tolerance, .338 Lapua magnum gm6 Lynx. With the long recoil used to allow a higher rate of fire if the weapon is used as a light anti materiel rifle (can also be used if engaging multiple targets at closer ranges) due to the action the weapon also uses a slightly smaller/less effective muzzle break than usual on .338 rifles (slightly reducing the chance of a dust kick up, target indicator). The action also means the weapon would be less accurate than a fixed barrel design and this is something I would like to be able to counteract (to a certain extent)

Question: The Lynx can already lock the barrel in the rear position for travel, would it be possible to make it able to also lock in the forward position? And to make that lock rigid and consistent enough to make it worth while accuracy wise, to lock the barrel in a forward position if a longer range target is about to be engaged? (This will ofc force the user manually cycle the action, and it will make the maximum recoil impulse higher)

If yes how would such a lock best be constructed?

*edit* before someone suggests it, in case this doesn't work my backup plan is to base it of the leader 50 (that is actually supposed to come in a .338 version at a later stage)

The forces would be similar to the forces on the bolt locking surfaces, and so would need to be of comparable size and construction. There needs to be some sort of hardened surface for the barrel to brace against, but sniper rifle receivers are usually pretty overbuilt to begin with, so none of this is difficult.

What would be tricky is finding a way to re-index the barrel consistently when it gets manually locked forwards.

The consistency of the barrel lock was the thing that bothered me, it would be pointless if I was forced to zero the weapon to gain any increase in accuracy.

Could there be some way to lock the barrel that would "force" it to allign?
Another option would probably be some sort of mechanical linkage between the barrel an the scope, that aligns them without having the scope reprociateing backwards when the barrel recoils in semi-auto...

I would have some sort of moving shoulder that stops the barrel and bolt from moving back. I would guess this has the least interference with the operating system.

True about the operating system but I'm not sure if it will make the "lock" consistent enough. Could work if i had some sort of mechanical linkage between the barrel an the scope as mentioned earlier, but I'm don't how to make that precise enough without having a reciprocating scope smashing into the shooters eyeball...

On a side note I would love to see the leader 50/MD 50 patent for the gas housing allowing a "true" free floating of the barrel...

True about the operating system but I'm not sure if it will make the "lock" consistent enough. Could work if i had some sort of mechanical linkage between the barrel an the scope as mentioned earlier, but I'm don't how to make that precise enough without having a reciprocating scope smashing into the shooters eyeball...

I strongly suspect this would not improve things, at best.

Barrel harmonics are weird with a capital "we". I have a bull-barreled target rifle that will, with 62 grain loads group an inch to the left of where it groups with 55 grain loads.

Also, I don't think that it's the movement of the barrel, per se, that's causing inaccuracy in recoil-operated weapons. Take a glock, ferinstance. The barrel and slide are on the order of two thirds of the mass of the weapon. A human hand is not rigid, far from it. Therefore, a hypothetic fixed-barrel glock wouldn't be recoilling all that much slower than a short-recoil one.

Also, if you look at the mass ratio of the barrel to the projectile, the retreat velocity of the barrel is positively glacial relatively speaking.

But we do know that recoil-operated weapons are significantly, sometimes drastically, less accurate than fixed-barrel ones.

It makes far more sense to me that this inaccuracy comes from the difficulty of exactly re-indexing the barrel with the receiver after each shot. Fixed-barrel designs with quick-change barrels frequently suffer from the same problem.

Therefore, any barrel lock which doesn't mess with the harmonics and change POI (tricky, but probably not impossible) will have to index very exactly to provide consistent alignment with POA. If you can do that with a manually-cycled lockup, why can't you do that within the automatic cycle?

Really, the only way I can see of this is having really tight tolerances, and saying "The designers were really smart, and the barrel goes back to the same place each time"

You don't want to do that. Recoiling barrel action isn't that bad, and due to lower forces it's certainly better than a two-post support that you seem to plan on doing. The only point of a fixed barrel is having the barrel cantilevered with no joints in the line of force transfer.

Where there are joints, there are either clearances or interference. You can manufacture one without either, but it will vary between gap and interference depending on everything down to the time of day. Both gaps and fit friction are variable.

I certainly intended to have it locked in the rear of the barrel as I don't want to fuck the harmonics up. The barrel is already essentially free floated and as Epimachus said I think the inaccuracy comes from alignment issues

And I thing those alignment issues are directly related to the fact that the barrel has to be able to move in and out from its forward position, this requires lower tolerances than a fixed barrel, thereby opening up room for a slightly different alignment between shots.

Now to his question

What I was thinking about was something like relatively long (for leverage) handle along the receiver that you move forwards or backwards to lock, when that is done the barrel should be "viced" in place in its usual forward positing reducing the tolerances to such a degree that the barrel would stand no chance of cycling (it will still have to be supported in some way to stop the rearwards motion from tearing at the contact surfaces)

Though I can still ad that I am not 100% something like this would work, and a leader 50 action would probably be a better (but boring) choice. And If I go with that I will be blocked by the fact that the interesting parts of it are still going through the patent process so little or no information exists. Its also not as fun to just do something in the exact same way as a real design even if it is for a different round (a round that as earlier stated they will release a rifle for)

A lot of recoil-operated designs already have a lever in them; the bolt accelerator. I wonder if that could somehow be co-opted to wedge the barrel firmly forwards after each shot. The bolt is on the long end of the lever so it gets accelerated, so it would even have correct mechanical advantage if it were really jamming the barrel up against some sort of index shoulder.

Also interesting to note that in a lot of fixed-barrel designs the barrel isn't, well, that firmly attached. The barrel of an AR-15 isn't threaded into the receiver at all; in fact the barrel of an AR-15 doesn't even touch the receiver. I hear those are fairly accurate

This is an interesting area to speculate upon.

Here's the mistake: it's not. Free-floating barrel means that the whole barrel-chamber-stock assembly is one large beam with one significant support, your shoulder. Any kind of a moving barrel means it's not.

If you understand why free-floating barrels are used, you'll understand where the issues lie here.
Feel free to support the barrel at multiple points, it won't hurt anything. If anything it could help.
The scope is mounted atop the barrel anyway, that is not the issue.

Tolerances are not the issue. Allowance is.
Anything that moves need clearance, anything that doesn't needs interference or other fixed fit. However good your tolerances are, a joint with interference is always more rigid than one with clearance.


Have you thought about essentially mounting a rigid bolt-action rifle on a tripod or bipod+monopod with a chassis that allows for movement? That way you get to absorb the recoil while not introducing inaccuracy.

And that’s why I want to fixate it for the higher accuracy shots... I just want to make sure that the fixation achieves a stricter alignment of the barrel since it can have lower tolerances when it doesn’t have to move.

Couldn't that run the risk of messing with the harmonics? One of the supposed advantages with the leader 50 fancy gas block accuracy wise is supposed to be the fact that it doesn’t touch the barrel, (it can also be closed entirely so that the action doesn’t cycle and none of the powder bleeds of, I don’t know what its third setting is for but it might be extreme cold or fouled weapon conditions)

I suspect you mean on the receiver? Since otherwise it would be painful to shoot when the barrel recoils...

That is very true and it is why I want to "vice" it down when the barrel is locked in the forward position

Though that would certainly work to reduce the muzzle break and lower the recoil but, it would not be the same as a long recoil action since it wont cycle the weapon and it will still move the stock further back during recoil than the bipod. The Idea could be used with the leader 50 though...

Depending on the shoulder design I guess you could get increased accuracy from something like that. And as you pointed out the relative weight of the barrel is immense and its more about how well it is aligned in its forward position that affects accuracy (rather that the fact that it recoils). But as Vault pointed out it must still have clearance in order to move. (I guess a tapered shape could help here, meaning that the barrel has to be inserted from behind and then have its muzzle hider/break attached)

Well the AR-15 might be accurate compared to some AR's but that is not the same thing as a bolt action sniper rifle. But since they have made the m110 of that platform I guess it can be done (though it supposedly struggles accuracy wise vs the m24)

*edit* fixed thanks prae (damned cellphone typing)

You need to fix the close [/quote] in the second quote block.

Through making the barrel able to move relative to the rest of the weapon, the original point of making it free-floating is gone. (Not that harmonics should be your priority here anyway.)
Let me explain:
railgun > tensioned > free-floating > glass bed > conventional > moving w/action > moving w/o action

That's likely to end up counterproductive. It's like usually writing with your left hand, but switching to your right hand for higher accuracy writing.

Except worse. Hands at least have "muscle memory", but here you have two different rifles that also change a little day to day. The most accurate rifle is always your rifle. This is like borrowing another guy's rifle.