Long range .303

[BritishBeer]

I'm new to this forum but hopefully you all can help me.

I mostly shoot Fullbore Target Rifles to distances of 1000m and I have a No4 Mk 1* to play with when I've finished my normal shooting. It holds a good group up to 600m but when I shoot at 900m and 1000m targets it is horrendously inaccurate and the butt markers say they can hear the bullet tumbling.

Is there a fix to this or am I trying to over-reach with a 70+ year old rifle? As far as I can tell it has a good bore with correct headspace and no muzzle wear from pull-throughs. It is a two groove original barrel should that make a difference.

I normally shoot 174gr Privi Partisan and do well enough with my other rifles!

Cheers!

Information

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[mrbungle]

i am no expert my any means. but a 5 groove barrel might give you better accuracy. but a 175 grain bullet should be good to a 1000 with 303, i would think.... i am shooting at 500 with a scope and around 300 with irons. on a no 4 mk 1 2 of them. but i have not taken it out pass 500 yards.

[Beerhunter]

The PPU .303 is not the same as the ammunition it was designed to shoot. PPU is boat-tailed and the Mk.VII was flat based.

I have found that PPU works OK on some rifles some of the time but I have seen the groups tighten up on all my Lee-Enfields by the use of a flat based bullet.

BTW, tests over the years have shown the 2 groove barrels to be perfectly good.

[mrbungle]

interesting to know about the flat based bullets. is this still using 175 grain?

[Bruce_in_Oz]

The boat-tailed bullet was introduced to service .303 way back in the 1930s. The whole idea was to extend the useful range of the bullet.

At supersonic speeds, the boat-tail DOES reduce the base-drag a LITTLE, but most of the drag on ANY bullet travelling faster than sound is from the "shock" or "compression' cone formed at the NOSE of the bullet.

However, as the bullet approaches the trans-sonic speed range, two things happen: the shock-cone moves BACKWARDS and the airflow becomes more laminar and starts to generate base turbulence, and thus, drag.

A boat-tail WILL reduce base drag a little during supersonic flight, but it really comes into its own in the trans and subsonic zones.

The boat-tailed Mk8z bullet as in the commonly available PPU stuff is essentially machine-gun ammo. The BIG problem with ALL boat-tailed bullets in ALL rifles is base blow-by.

This is especially a problem in Lee-Enfields because of the rifling dimensions: .303" bore but the grooves can often run out to .318 or larger and still be in factory spec. Thus, at launch, the bore/groove "hole' is NOT fully obturated (sealed) because the bullet is smaller than the groove diameter by a few thou. Thus, some gas will leak around the base. If the base is a boat-tail, then there is NO way it will "bump-up" to completely seal the grooves. Not only that, but the truncated cone that is the boat-tail, tends to act as a wedge to force the gases AROUND the rear of the bullet. If the seal is not perfect, there WILL be blow-by and consequent gas-cutting of the throat. This is NOT a good thing in your trusty, collectible Lee-Enfield.

Furthermore, because the Boat-tailed bullet is of almost identical length to the Mk7, the presence of said boat-tail also reduced the effective bearing length of the bullet in the rifling. The trick with same length / heavier bullet was achieved by the simple expedient of swapping the light "nose filler" in Mk7 bullets for a tapered (boat) tail on the Mk8. The Mk8 bullet/ cartridge HAD to be the same length as the Mk7 or the entire inventory of machine-gums would have required re-engineering of their feed mechanisms..

This was a continuation of the matter from when the round-nosed, heavy .303 Mk6 was supplanted by the spitzer, 174gn Mk7. As it was, the change to Mk7 ammo meant that the entire RIFLE inventory required new MAGAZINES because the ones built around Mk6 ammo would not retain or feed Mk7 ammo reliably enough.

As for the "tumbling" noise at 100yds: at that range the bullet id DEFINITELY subsonic. thus the target-pullers will not hear the CRACK heard at 800 yds or shorter. The "crack" is a "baby" sonic boom. Bullets that "whizz" are subsonic.

The other thing that happens is that the bullet is Spun VERY fast by th w1:10" rifling twist. Whilst "linear" speed drops dramatically with range, ROTATIONAL speed does not. Rotational speed provides stabilization, which is all very handy, except that the trajectoryis not a straight line, but more of a parabola. Thus a bullet launched at, say 15 degrees above level will attempt to maintain that angle all the way down range. The problem is that the nose of the bullet SHOULD be following the parabolic flight path. So, the rotational inertia (spin) tries to keep the nose pointing at say, 15 degrees, whilst the aerodynamic forces ate trying to make the bullet follow the parabolic path. Eventually something has to give.

At some point (or several points) the "wobble" introduced by the conflict of these two "forces" will result in the bullet going a little "wild" and deviating from the trajectory, usually in e set of spirals called "precession". Once aerodynamic forces have shoved the bullet back onto the nominal trajectory, all will be fine for a few more micro-seconds, until the process is repeated. The "wilder" the precession and the longer it takes for the bullet to restabilize, the more the bullet will deviate from the required trajectory.; i.e. your groups get bigger.

The 1:10" twist in a .303 barrel is required to stabilise a bullet of the LENGTH of a Mk7 from as close to the muzzle as possible. Experienced full-bore shooters will have noticed that their trusty old .303s have "pet" ranges and can be real "dogs" at others. This is all tied in with the process of adjustment "steps" that go on during the flight of the bullet. ALL rifle ammunition does this to varying degrees.

[Thunderbox]

Is there a fix to this or am I trying to over-reach with a 70+ year old rifle?
Cheers!

An average No4 should be perfectly capable of staying in the black at 1,000yds, given the right shooter and conditions. Good No4s are capable of staying in the 4 ring at 1,000.

Try and find some cordite, if you know anyone who has some, or try S&B ammo. Although S&B is boat-tail as well, the bullets are a shade heavier than Privi. Quite often you get a dramatically different performance in a "sensitive" rifle between the two nearly-identical loads.

If you have no luck, its probably worth swapping the rifle for a different one. Your rifle is perfectly good for the average plinking club shooter, but as a long-range TR shooter you'd be better off with one that is good to 1,200 with Privi.

[BritishBeer]

I think it must just be more worn out than I thought. Currently it's more of a fun rifle and one I enjoy for its history so I'll keep it for now and just shoot it to 600.

Need to rebarrel my Musgrave so can't afford to upgrade!

Thanks for the info Oz, think I understand most of it! The butt markers are generally quite experienced and state its tumbling rather than just from far away. Could be a mistake.

Is there any commercial ammo with a flat base that anyone knows is available in the UK? All I've seen are S&B and PPU. Trying to get my head round reloading .308 atm so that's not an option for .303.

[Beerhunter]

Is there any commercial ammo with a flat base that anyone knows is available in the UK?

Not that I know of. In fact its quite difficult to get FB bullets for reloading, at a reasonable cost. Identical copies of the Mk.VII bullet are available in the UK but at a price!

I found a 174Gn. FB South African manufactured bullet a few years ago that performed particularly well but they are extremely difficult to source in the UK.

[Simon P]

Try B&S Products here in the UK, they make facsimile bullets to the original specifications .303 MkVI & MkVIII, these are hand swaged bullets.

They aint cheap but worth a try before you decide the rifle is no good for long range.

They advertise in the HBSA journal:

Tel: 01302 330726

[Patrick Chadwick]

the entire inventory of machine-gums

? Is that some kind of Aussie tree? With clockwork koalas eating the metal-foil leaves?

But seriously, thanks to Bruce for an excellent explanation! To which I would like to add: since the cartridge must have some sideways play in the chamber, the case neck will actually be sitting on the bottom of the neck portion of the chamber. So the gas flow around the bullet is not symmetrical. Result: the bullet is pushed to one side, which will cause it to be engraved with a slight skew.

Before anyone laughs, the amount of skew to produce 1 MOA deviation over the 1/2" cylindrical section of a typical bullet is about 1.5 ten-thousandths of an inch. So when the bullet emerges from the muzzle it is being launched with a small precession that will increase the effect described by Bruce. Somewhere in his books Dr Beat Kneubuehl has a picture showing how precession and nutation can produce a small spiral deviation in the trajectory that worsens the group size as it is a matter of chance where the bullet is in the spiral movement when it hits the target.

BritishBeer, you could try the Hornady type 3130, 180 round-nose, with probably the longest cylindrical section you can get in commercial bullets. They are at least a partial cure if your rifle has a worn throat. Alternatives are the Speer 180gn round-nose and the Sierra 180gn ProHunter spitzer.

And, of course, make sure that you use neck-sized cases for reloading. You don't even need a neck-sizing die, just back off the normal sizing die so that a little unsized ring (1-2mm) is left at the neck/shoulder junction. This un-resized ring will help to keep the cartridge neck centered in the chamber. It's kinder to the brass than full resizing too!

Finally, check that the muzzle crown is absolutely as perfect as you can get it. Any asymmetry (or, heaven forbid, nicks) results in a little kick to one side when the bullet emerges, which also produces the precession/nutation effects.