Longbranch No4 Mark I* 6 groove barrell

[Peter Laidler]

We established during student projects that the amount of grooves didn't matter at all. 2, 5 or 6...., it was pretty well academic. What DID count was that the bullet was and remained stable in flight

\i forgot to add that it was critical that it remained spinning in flight too - but that is part of the stability issue

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[Bruce_in_Oz]

Don't know about RFI, but during WW2, Lithgow plant itself was churning out Bren and Vickers guns, with the rifle-making facilities moved to various "annexes". Last time I looked, the original Bren barrels were six-groove, right-hand twist. Our Canadian cousins certainly fitted barrels with "Bren-style", six-grooved rifling to a few No4s. But were they right or left-hand twist? Apparently there are a few Savage-made No4s floating around with six-groove barrels as well.

Because ALL of the barrels made by the system at Lithgow (and annexes), were single-cut on sine-bar machines, there was a move to make alternate (cheaper/faster) barrels for the rifles, but by the time that idea had done the rounds of committees and "evaluation", the war was starting to get very close to Japan and would likely not last much longer.

Drawing No. A-658 (traced from the original and updated in October 1944 and then amended in 1947), shows the standard, Enfield-style 5-groove barrel for Oz production.

However, it also contains a note:

"As alternatives, a barrel having two grooves diametrically opposite or four grooves equally spaced, would be acceptable."

Were any "alternative" barrels for No1 rifles actually made in Oz?

No idea.

Anyone got one in their sticky paws?

[RJW NZ]

I wonder if the six grooves get more blow by than 2 groovers and a lower velocity as a result?
And on the same/similar question, wouldn't a two groove barrel generate a lot more friction with all that surface area against the bullet case and be prone to problems like build up or faster wear? I realize of course that they went on and performed well over many years, but an experts comments on the possible downsides will be interesting anyway,
cheers

[Peter Laidler]

Good point you raised RJ but in the great scheme of things friction really wouldn't come into the equation in short barrels simply because all friction generates is heat (I realise that this isn't technically/scientifically correct chaps but........) and this absolutely minute amount of friction heat energy is immediately swamped by the propellany heat energy.

2 groovers don't wear faster....... they wear at a slower rate purely because of the greater surface area

[Ridolpho]

By fluke I happen to have one each of Savage and Longbranch six groove barreled rifles. The Longbranch is, of course, a re-furb while the Savage is an early Mk I (no star). My question is- why did manufacturers bother with 5 groove or 6 if there is no theoretical or practical advantage? The only answer that I can think of is that wear on the sharp edges that grab the bullet whilst spinning it up to a zillion rpm is distributed over a much greater length with 5 or 6 groove rifling. A meaningless anecdotal observation- my Savage has a darkened, pitted bore but still shoots very well.

Ridolpho

[Peter Laidler]

To be honest Ridolpho, the number of grooves is pretty well academic just so long as it imparts gyroscopic or stabilising effect to the projectile.

[Ridolpho]

Peter: Indeed, I've seen no reference that suggests any difference in accuracy as issued- but what about longevity? Were there comparisons done after 5000 or 10,000 rounds? I would imagine this might be a bigger issue with machine guns (Bren).

Ridolpho