Thread: 303 group-bad bedding?

A lot of worn 303 barrels do not like boat tail bullets. I picked up a tidy PH sporter that was shooting 10" groups at 100 yds with 150 gr. Tried 180 gr Highland (boat tails) 6-8" next, reloads with 180 gr flatbase 4" finally Woodleigh 215 gr flatbase 2.5" groups at 100 yds.

Originally Posted by john m

A lot of worn 303 barrels do not like boat tail bullets. I picked up a tidy PH sporter that was shooting 10" groups at 100 yds with 150 gr. Tried 180 gr Highland (boat tails) 6-8" next, reloads with 180 gr flatbase 4" finally Woodleigh 215 gr flatbase 2.5" groups at 100 yds.

The other factor here is related to weight and boattails: the better grouping ammo types here have the bullet bearing surface increasingly further into the barrel throat when chambered. It may not be the boat tail as such that is to blame - more that a boat tail "costs" you front mass, putting the bearing surface further back, all other things being equal. (a boat tail needs a certain length of cartridge neck to engage with its side to be secure in it, so it needs to be seated deeper).

An engineering workaround the disadvantage of lighter bullets is when Britain replaced the round nose 212 grain Mk V with the 174grain .303 Mk VII spitzer. The Mk VII had a light filler up front which enabled the bullet bearing surface to engage further into the throat of the barrel when chambered. The point of snug/close engagement is that it helps the bullet to travel more concentrically through the bore, thus reducing wobble on exit. The wobble causes the bullet to fly in a spiral path but settles down eventually at some random point in the spiral and flies relatively straight after that - trick is to reduce the wobble in the first place. Imagine if you seat spitzers 1 degree off centre and fire them in a gun with a worn throat... It will make groups shaped like circles with a rare shot in the centre.

If you have a kinetic bullet puller, empty a case for safety and reseat the bullet to its original position, chamber and extract. Pull and reseat to increasing overall cartridge lengths, load and eject, to see how far out the bullet needs to be to engage the rifling lands. Seat your bullets for that gun a bit short of that. This guy here uses a sharpie on the bullets to help read the marks:



But before bothering to do any of this, tighten up and bed the action as advised above. @csmiffy, your groups are not circles, they are being whipped up to the left. You likely have a loose screw.. . (-:

Originally Posted by Cordite

If you have a kinetic bullet puller, empty a case for safety and reseat the bullet to its original position, chamber and extract. Pull and reseat to increasing overall cartridge lengths, load and eject, to see how far out the bullet needs to be to engage the rifling lands. Seat your bullets for that gun a bit short of that. @csmiffy, your groups are not circles, they are being whipped up to the left. You likely have a loose screw.. .

@Cordite good advice-I know about the screw loose-what about the rifle lol
All screws good and tight-I do suspect the bedding and from advice given here, the ammo I have isn't to be trusted.
I don't have a bullet puller but that is something I probably should just get. Or I could put my engineer hat on and make something.
I also think that it isn't just the stability of a boat tail/weight distribution, the theory is more to do with the bum of the projectile not being swaged/obturated against the rifling especially on a worn barrel but good advice still the same.
@Marty Henry I do remember it being the primers as the baddies in the mix for being corrosive-not the powder. I think I will do a bedding job on it. I do need the experience on this project, just was trying not to do it twice.
@shooternz no I haven't slugged the barrel. I was hoping that it might shoot okay with factory ammo and I didn't have to reload at all. in that case 312 is about it.

[QUOTE=csmiffy;750656]I do remember it being the primers as the baddies in the mix for being corrosive-not the powder. I think I will do a bedding job on it. I do need the experience on this project, just was trying not to do it twice.


@csmiffy

Actually, the Cordite was a hot burning powder which by itself caused premature barrel wear, read the history of the Metford rifling. Likewise the contender British powder, Rifleite used by the US Navy in their Lee rifles - same problem. The Metford rifling was not the problem, the propellant was, as evidenced by the Japanese having no problems with their Arisaka Metford rifling but using better, less hot propellant.


As for primers and what's in them, here is a historical progression:U]

Mercury fulminate: 1800s. OK for barrels, but brittling brass, forget reloading. Toxic to eat or inhale. Really bad idea for indoor ranges.

Potassium chlorate: Typical WW1/WW2 primers. Corrosive for barrels and requiring water clean after shooting to prevent corrosion, OK for brass, toxic to lick but not to inhale (OK for indoor ranges).

Lead styphnate: OK for barrels, OK for brass, toxic to inhale - this is the stuff we usually refer to as "non-corrosive primers". Not great for indoor ranges.

You can buy newer compounds - green non-toxic, non-corrosive primers - don't recall what's in them. I'd use only those (or "corrosive" primers) shooting indoors.

I hope this guy is using corrosive primers, or he might get lead poisoning:

Interesting reading this.
I had a 303 Parker Hale conversion that was rubbish best I could get was all on an A4 at about 60 yards.
Used to bush hunt with it.
I put it down to the side mount for the scope but may have been the ammo.

By the way always used to shoot over the bonnet of the ute, with some rifles expected to and had bullets impact where I was aiming.

Originally Posted by erniec

Interesting reading this.
I had a 303 Parker Hale conversion that was rubbish best I could get was all on an A4 at about 60 yards.
Used to bush hunt with it.
I put it down to the side mount for the scope but may have been the ammo.

By the way always used to shoot over the bonnet of the ute, with some rifles expected to and had bullets impact where I was aiming.

And you got the same results as the OP. Neither of you know what wrong with your .303's. Thats what I am trying to say. They have benchrests at ranges just for this application. It's not a girly thing. It's practical.

Originally Posted by Carlsen Highway

And you got the same results as the OP. Neither of you know what wrong with your .303's. Thats what I am trying to say. They have benchrests at ranges just for this application. It's not a girly thing. It's practical.

I have got over it, was over 30 years ago.