Large weapons, smoothbore vs Rifled

okay, we should all know the benifits of rifiling in small arms. But recently I found out the British Challanger 2 MBT uses a rifled 120mm Main gun, compared to the M1A2 Abrams 120mm Smoothbore. which is better, or prefered? I talked to a crewmember and they say it is more accurate then a smoothbore, but then why are most 120mm tanks out there using it?

btw, i think i know the reason why, but I want other peoples input on it

My understanding (i'm no expert) is that rifled guns can't handle as much pressure. The smooth bore is therefore necessary for firing Kenetic Energy rounds as well as anti-tank missiles. The advanced fire control systems in modern tanks can still be deadly accurate at 1 or 2 kilometers, so the advantage of rifling is diminishing.

Rifled guns can fire HESH though- a small advantage in urban environments because it is so effective against concrete. I think that NATO nations should standardize to smooth bore. The Chally is a good tank, but logistics are ultimately important. It would be a huge advantage if they could use KE rounds and missiles from their allies in the field when necessary. They're ammo choices are just too limited for my taste I'm afraid.

An excellant question Jehosephat and one that has posed all sorts of technical problems for gun makers and master armourers for hundreds of years.

Let's take a trip back through time to the days of the Pilgrim Fathers. Firearms then, were mostly 'Long Rifles' but really they should have been called 'Long Barrelled Muskets' because they were smoothbore and bullets were smooth 'balls' of lead - i.e: .58 or .64 calibre depending on manufacturer.

The length of the bore, increased range but not by very much. The smoothbore musket served the British Army for centuries and skilled musketeers were reputed to get off 6 to 8 aimed shots a minute!

I forget who realised that if you drilled grooves along a barrel, you caused a projectile to 'spin', but he or she realised that range was greatly increased.

Everybody knows (I hope) the basics of the 'Theory of Small Arms Fire' - Flight Path, Line of Departure, Trajectory, Mean Point of Impact, Estimated Scoring Zone - but, simply put - as the projectile spins, it moves very much like an arrow - it flies away from the target then, because of gravity, falls back on target.

If you think of a smoothbore weapon, the most obvious choice is the shotgun. When you fire (discharge) a shotgun, wadding flies off the shot which then disperses throughout a wide arc. (A Civil Ware smoothbore cannon firing cannister [tin can containing 100s of ball (smooth) shot] works on the same principle, as does a modern claymore mine!)

When mounted on a tank, the only advantage in the smoothbore, is the ability to fire both normal ammunition andmissiles from the main gun.
These gun barrels have a longer life as there is no 'rifling' to wear out.

Rifled barrels on the other hand, increases the 'lethal range' of a tank gun. All ammunition types are fired during exercises and 'range' shoots. This excludes 'war shots'. This ammunition is of a superb quality to standard rounds and because of this, the range can be as much as 6.5 - 7.5 kilometers, depending on ammunition. Chally 2 firing APFSDS can hit targets with ease out to 7-7.5 Ks. (Just over 4.5 miles to you and me)

All types of ammunition cause tremendous pressures within the breech block and barrel - be they smooth or rifled but with a rifled barrel under wartime conditions, it would have to be replaced after about 400 -450 rounds.

It may be of interest to you to know that, at the height of the cold war, British Aerospace (BAe) was re-borring Russian tank barrels at the Birmingham Royal Ordnance Factory. (Must have been Glasnost!)

Sorry not much to add apart for cost and service service were a factor in the preference of smoothbore over rifled for US and Germany.

Brit may now be going down that route for commonality with NATO stocks

Excellent topic Jehosephat

Brillant post fritz

Can rifled guns shoot laser guided rounds? If the rounds are spinning, can they still home in onto laser designations?

IIRC the British army are going to be changing to smooth bore guns on the C2. I think this is due to the cost of developing new ammunition as the current stuff is nearing the end of its shelf life and not because of any problem with the rifled barell itself.

I was always told one of the main factors behind going rifled was the HESH ability which the British army were very fond of, and the problems of mating an APFSDS round with a rifled gun have obviously been overcome already as they have been being used by the Brits for ages.

As far as accuracy being increased with rifling, i think this is largely an irrelevance with modern FCS's on western MBT's nowadays.

The Abrams rounds don't need to spin they mostly open up in flight and are just long rods with the exception of few. Its like an arrow, it does not need to spin that's that same thing wit the Abrams rounds.

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[edit on 1-5-2005 by WestPoint23]

Reports for the Gulf war states that the Abrams normally engages the enemy at 2000m but was able to effectivly engage at 4000m. The the fact of Rifling being more accurate doesn't hold much wieght, especailyl with Ballistics.

Reading some comments from former tankers, specifically a Master Gunner, one downside to rifling is the increased dispirsion of the explosion on impact. Thus robbing the progectile of some prenetration ability



I seem to also recall that there was a problem of getting the ammo for the rifiled main gun and that the supplier was overseas on not domestic. So instead of having ot rely on foreign sources for the rifled ammo they went to a NATO standerd

Correct, the spin imparted by rifling reduces the effectiveness of shaped charged warheads considerably. The jet ( as you said ) is literally spun apart to some degree.

This has been a particularly educational thread for me. Fritz and Jehosephat both just got WATS votes from me
Way to go guys.

Ahem, just where did you come across this information. APFSDS rounds actually do not spin - the Charm 3 round has to use an anti-rifling collar ( as do all APFSDS rounds fired from rifled guns ) so as it does not spin. Spin is highly detrimental to the lethality of sabot rounds. Note that FS in APFSDS stands for Fin Stabalised not Spin Stabalised.
Therefore rifling has absolutely no effect on the accuracy of APFSDS rounds.

PS. Please do provide some information on these hit ranges of 7km, just because you say it does not make it true.

Good post Fritz, but nothing I didn't already know though.

As stated before, HESH rounds are the main reason the L-30 barrel is rifled so they can be delivered accurately.

Smoothbore barrels allow for more velocity since there is no friction to slow the round down while Rifled barrels afford more accuracy.

However the Challenger 2 has one of the most accurate guns out there, however it's FCS wasn't as impressive as some other modern tanks.

Smoothbore guns achieve a higher velocity and are better for firing APFSDS and KE penetrators. They can also fire HEAT.

Rifled guns are more accurate at longer ranges and can fire HESH and HE better.

I'll say this once more rifling makes absolutely no difference to the accuracy of APFSDS shells, if anything it is detrimental to accuracy ( hence the reason the Brits had to fit an anti-rifling sleeve to their sabots ). The US MPAT HE is also as accurate as any conventional HE shell fired from a rifled barrel.

As for velocities that is dtermined by barrel length and weight of the propellant behind the shell. Having a rifle or unrifled barrel makes almost no difference.

AS for HESH rounds there really isn't any need for them these days, the Brits as far as I know are the only ones who still bother to use them. HESH shells have bugger all effect on modern tanks and have no greater effect than HE shells.

As has been said, the primary reason to select smoothbore over rifled barrels is in a wider range of ammunition from which to select.

Anyone who owns a sturdy shotgun knows this. You can fire just about anything out of a good duty shotty. Including, but not limited to: dragons breath, flechette, door breaker, AP, pit bull rounds, gas, pepper, rock salt.

There appear to be other considerations, in terms of maximizing the effectiveness of shaped charge rounds, and perhaps others. However, I would say the main attraction to using a smoothbore gun is versatility.

Ok you guys may believe this or not, but when I was watching a show on the History channel out the Abrams tank they said can hit a target the size of a basketball form a mile away. Is the Abrams gun really that accurate?

westpoint.. yes

concidering the abrams effectively engaged the enemy in combat at 4000 meters, that isn't a stretch.

All guns are near that level, how the hell do you think they can hit a tank size target at 4km ? Don't forget that a computer actually calculates the angle for a the gun.

The Isaraeli's during the Water War with Syria hit a bulldozer at 11km and that was with 1970's tank gunnery.

Although modern armor won't spall much (thus making HESH virtually worthless as an anti-tank round unless pitted against older/inferior tanks) it is extremely useful against concrete, which is nice and brittle, abd will break into nice little chunks and enter the enemy's face at a high rate of speed if he happens to be hiding inside of the concrete target in question.

It's really too narrow of a use to be viable on an MBT though. I wouldn't mind seeing it show up on a heavy IFV, but I have a feeling it wouldn't get used much. Civilians don't like seeing their military level buildings on the news for some reason. Apparently they think that there's a safe way to fight a war- play by the rules and nobody gets hurt, or something like that.
It's kind of a shame that we can't have it both ways. In urban situations I think I trust the mechanics of HESH over HE FRAG. I'm no expert, but it seems to me that a frag round wont hurt you if you have adequate cover, whereas HESH essentially uses your cover against you.

Perhaps if the need ever arises they will devise an arrangement of fins which can impart the necessary spin to fire HESH from a smoothbore cannon.

"(thus making HESH virtually worthless as an anti-tank round unless pitted against older/inferior tanks) it is extremely useful against concrete, which is nice and brittle, abd will break into nice little chunks and enter the enemy's face at a high rate of speed if he happens to be hiding inside of the concrete target in question."

A HEAT round will do pretty much the same thing.