50cal sniper rifle question

[planeman]

Keep hearing how self-loading sniping rifles are less accurate than bolt action ones. How come no one has made an optionally-self-loading version?????? ie. you can select self-load or manual cocking just like assault rifles flip between semi and fully auto?

Maybe have a valve setting on the exhaust port?

[Bro Jangles]

why would you want to? the accuracy is relative, semi autos are still fairly accurate.

[UKWolf]

From what I know of physics and ballistics (which, admittedly, is limited), to enable you to be able to choose between semi and bolt-action, you'd have to have a seriously strong valve, if you're going to restrict it via gas parts. Plus, you'd also have the problem of having a mechanism inside the gas parts, which are small in themselves, and cleaning it would be a hell of a task...

Plus, straight-pull bolt action rifles (as a design like this would have to be) aren't popular. I use the L98A1 cadet GP rifle, which is a straight-pull, bolt-action version of the SA80, and it's horrible. It jams very easily and it's nigh on impossible to keep a good zero with it. Most bolt action rifles have a rotating bolt where the user themselves rotates the bolt, instead of a mechanism inside the bolt carrier, as semi-automatic, rotating bolt firearms do. This is because it's a more comfortable way of cocking, allowing a zero to be kept more easily. Finally, in a semi-auto you would require a spring under tension to act as a recoil buffer and return-spring to force the bolt back forwards to collect the next round. Turning that into a smooth bolt action would require some serious out-of-the-box thinking.

[DeltaWhisky58]

Some semi-autos are more accurate than others, take the relatively new Accuracy International AS-50 for example, compared to AI's bolt Action AW-50 it is less accurate, but would probably compare very favourably to some lesser bolt action rifles.

The AS-50 is capable of around 1.5MOA accuracy whilst the AW-50 can boast 1.0MOA and the AW-50F perhaps even better.

Other semi-auto .50BMG rifles are perhaps less accurate. The bolt action is still king for all out accuracy.

UKwolf - I don't understand why you have brought up the subject of straight-pull bolt action rifles in this context, all bolt action .50BMG rifles are turn-bolts, plus ... ... the L98A1 isn't strictly speaking a straight-pull bolt action as it's a manual adaptation of a gas-operated semi-auto. Real straight-pull rifles are the likes of the Swiss Karabiner 31, the Schmidt-Rubin 1911, the Mannlicher M1895 and the Blaser R93 series.

[UKWolf]

UKwolf - I don't understand why you have brought up the subject of straight-pull bolt action rifles in this context, all bolt action .50BMG rifles are turn-bolts, plus ... ... the L98A1 isn't strictly speaking a straight-pull bolt action as it's a manual adaptation of a gas-operated semi-auto. Real straight-pull rifles are the likes of the Swiss Karabiner 31, the Schmidt-Rubin 1911, the Mannlicher M1895 and the Blaser R93 series.

Fair point. After posting I actually went to see if I was right about straight-pull and I realise what you're talking about. I think I'm actually talking about something else but don't quite know how to describe it.

[DeltaWhisky58]

I'm not sure in reality that you're sure what you're posting about. I don't suppose cadets have much use for .50 calibre sniper rifles.

[planeman]

lol.

Yeah L98 isn't a good benchmark for anything. But you do raise an interesting angle - making the bolt action natural and yet compatible with auto-reload.

How about a split bolt, as in the cocking handle only moves in the manual mode but is left behind by the auto action? In my head I can see how that might work << warning: I am talking out of my arse

[DeltaWhisky58]

This thread had lost its way before it started, now it's totally lost.

[Greek soldier]

lol.

Yeah L98 isn't a good benchmark for anything. But you do raise an interesting angle - making the bolt action natural and yet compatible with auto-reload.

How about a split bolt, as in the cocking handle only moves in the manual mode but is left behind by the auto action? In my head I can see how that might work << warning: I am talking out of my arse

I'm not a gun or an engineering expert, but bolt-action with semi-auto option sounds peculiar. Semi-autos have coil springs for recoil, bolt-actions don't (manual recoil).

Do you mean that? Put a coil spring behind the bolt and use it as semi-auto(when bolt's opened)?

[SMGLee]

Bolt action as in a simple turn bolt design has A LOT less moving parts compare to a semi auto rifle, from a rotating bolt to a recoil spring, not to mention the gas system. the reason why a semi auto gun tend to be less accurate than a bolt gun is because the bolt gun with manually operated action can be made with a lot tighter tolerance than a semi auto gun. so the question you had should had been researched better in terms of mechanical operation of the two systems.

Other than a tighter tolerance, with a bolt gun, once the trigger is pulled, your system is still locked...but a semi auto, as soon as the bullet begin to pass the gas port inside the bore, the gun begin its cycling phase. the nano second that the gas starts back toward the gas tube, or the piston, you start to get some difference in accuracy...

To make a bolt/semi auto gun, it is kind of like a oxyimoron.....you can not do that without giving up the tight tolerence advantage of the bolt gun...to be able to have a semi capability.. you still have to have all the mechanical of semi gun...thus by locking the gas system would only give advantage in suppressed operation, but not able to gain more accuracy.

[jango]

Keep hearing how self-loading sniping rifles are less accurate than bolt action ones. How come no one has made an optionally-self-loading version?????? ie. you can select self-load or manual cocking just like assault rifles flip between semi and fully auto?

Maybe have a valve setting on the exhaust port?the british have made a semi automatic 50cal that is now in use in afghanastan and it is as accurate as a bolt action

[DeltaWhisky58]

the british have made a semi automatic 50cal that is now in use in afghanastan and it is as accurate as a bolt action

Says who?

The British-made Accuracy International AS-50 which has been adopted by US Navy SEALs is perhaps the most accurate semi-auto .50cal rifle, but it is certainly not as accurate as the best bolt actions such as the AW-50F, Timberwolf, McMillan etc.

No semi-auto .50cal rifle is as accurate as the best bolt actions, but the AS-50 is certainly more accurate than many of the lesser bolt action .50cals.

[Likvid]

...To make a bolt/semi auto gun, it is kind of like a oxyimoron.....you can not do that without giving up the tight tolerence advantage of the bolt gun...to be able to have a semi capability.. you still have to have all the mechanical of semi gun...thus by locking the gas system would only give advantage in suppressed operation, but not able to gain more accuracy.
Well, those moving parts are quite big factor in affecting accuracy, so by turn it off, you certanly can improve accuracy - practical example is SKS, which is notably more accurate with gas valve in "gas-off" position (however point of impact is also changed). But I agree, that you can't make it as good as dedicated bolt action.

[martinexsquaddie]

the l98 is possibly the worst rifle ever made.
just to make you jeolous my 9 year old niece runs round with an m16 some variation on royal marine cadets based out of portsmouth:)

[brainplay]

I seem to remember firing some .22 rifles that were closed bolt single shot/semi-autos back in the day. You would pull the trigger and it would fire, but continue pulling the trigger back further and the bolt would eject and extract a new round. Felt sort of like an old switch-blade stilleto.

While the concept is sound my concerns would be for the complexity of the mechanism and the ****e to failure of minor parts when using higher caliber rounds than a .22 Long.

[DeltaWhisky58]

There were certainly semi-auto (i.e. blow-back) .22 rifles on which the bolt could be locked. My late Father-in-law had a .22 semi which could be locked by pushing the cocking knob inward so that it locked into the other side of the action (rather like the way a cross-bolt safety functions) and thus the blow-back bolt didn't cycle. It was US-made, but I can't remember the make, possibly Savage or Stevens?