Why the UK legal minimum is .240 not .243.
- Thread starter Sinistral
- Start date
And why the use of ".240""? Well that's what it said on the box back then!
Not usually, I think...
Ronin
Distinguished Member
Groove diameter is usually a tenth or two under bulket diameter
Has to be otherwise no obturation
A tenth of what? I thought bullets were usually about the same as groove diameter - since the the material displaced by the lands has to go somewhere. Perhaps a thou or two larger might not hurt - though I think the groove diameter of the .243Win is meant nominally to be the same diameter as the bullet - at .243".
What I was saying is that the dimension of a barrel which is known as the 'bore' is usually (for historical reasons, I guess) the land diameter - since in cut rifling, that is the diameter it was actually bored to before the rifling was cut
Smellydog
Well-Known Member
6&1/2lbs
Ronin
Distinguished Member
Tenth - 1/10000”
Bullets are usually the diameter of the base of the grooves
As I said before there wouldn’t be any obturation otherwise
Sinistral
Well-Known Member
This might be of interest to some, so I've pulled it out of an old lever-arch file and scanned it.
Decades ago when I was ordering SR20N LH rifles from Heym GMBH I asked for details of the barrel twist rates they used. Generally I've always been a nosy parker interested in figures, but was taken aback to receive a chart of their engineering dimensions for each calibre. Heym explained that it wasn't usual to publish the barrel twists in their catalogue, presumably because they didn't think any of their customers would be interested. Would this do?
Everything was in German and metric, with some mindbending technical terms. With the help of my trusty Collins 2-way I converted the whole thing into English Imperial, during the night shift at work IIRC. After all these years this may not be what tolerances they currently work to, but it's an accurate and faithful translation of what they sent me.
In my defence, I'm less of a geek now than I was then.
'No. Grs.' = No. of Barrel Grooves
'Int. Circ.' = Internal Circumference (Linear)
Std. Twist = (used then in U.S. - added for comparison)
There is an error on the bottom line of this for .470 NE bullets, which are .474" diameter not .470".
Decades ago when I was ordering SR20N LH rifles from Heym GMBH I asked for details of the barrel twist rates they used. Generally I've always been a nosy parker interested in figures, but was taken aback to receive a chart of their engineering dimensions for each calibre. Heym explained that it wasn't usual to publish the barrel twists in their catalogue, presumably because they didn't think any of their customers would be interested. Would this do?
Everything was in German and metric, with some mindbending technical terms. With the help of my trusty Collins 2-way I converted the whole thing into English Imperial, during the night shift at work IIRC. After all these years this may not be what tolerances they currently work to, but it's an accurate and faithful translation of what they sent me.
In my defence, I'm less of a geek now than I was then.
'No. Grs.' = No. of Barrel Grooves
'Int. Circ.' = Internal Circumference (Linear)
Std. Twist = (used then in U.S. - added for comparison)
There is an error on the bottom line of this for .470 NE bullets, which are .474" diameter not .470".
Ah - unfamiliar prescision-engineer's jargon. Every day's a school-day!
That's what I think, yes: wider then the bore by 6thou or so for .243Win, for example
You are confusing nomenclature with one of two diameters
The law is an ass
In Scotland the passing of legislation on minimum “calibre” stems from a group of select Estate owning Lords looking to create a law that would allow lasting prosecution of poachers using much more widely used rimfire and .22 centrefire rifles when taking game from the Laird!
The written “transcript” of the meeting is available online.
I have it saved somewhere
The law is an ass
In Scotland the passing of legislation on minimum “calibre” stems from a group of select Estate owning Lords looking to create a law that would allow lasting prosecution of poachers using much more widely used rimfire and .22 centrefire rifles when taking game from the Laird!
The written “transcript” of the meeting is available online.
I have it saved somewhere
Well imagine the problem a friend had.
Wanted to get some suitable bullets to reload his .300 Savage and the shop said it had none it that diameter.
Also wanted some to reload his .303 Savage as well. They'd got none in that diameter either.
Shop owner asked if could "get by" with some from a cancelled order for another customer with a 7.82mm Lazzeroni.
And swage them down if needed to? My friend said he smiled and he'd see if he could "make do" with them.
So that it was. He took the lot at a much reduced price as they were, as he persuaded the shop owner, "useless for anything else".
Well when my friend related all this I told him straight if you asking for bullets for a proper calibre, .308 Winchester, you'll not have this issue with retailers.
Anyway I'm off. Just off to reload for my new, to me, .307 lever action. Lovely it is. If I can find a shop that can tell me it has in stock a box of bullets for it of course...
Wanted to get some suitable bullets to reload his .300 Savage and the shop said it had none it that diameter.
Also wanted some to reload his .303 Savage as well. They'd got none in that diameter either.
Shop owner asked if could "get by" with some from a cancelled order for another customer with a 7.82mm Lazzeroni.
And swage them down if needed to? My friend said he smiled and he'd see if he could "make do" with them.
So that it was. He took the lot at a much reduced price as they were, as he persuaded the shop owner, "useless for anything else".
Well when my friend related all this I told him straight if you asking for bullets for a proper calibre, .308 Winchester, you'll not have this issue with retailers.
Anyway I'm off. Just off to reload for my new, to me, .307 lever action. Lovely it is. If I can find a shop that can tell me it has in stock a box of bullets for it of course...
Last edited:
So if you made a .22 centrefire that could fire a 100gr bullet at over 2807fps, you could use it? Why haven't I heard of anyone trying?! I mean it's not the most practical idea, but I'm the sort of person who would want to just because...
Heym SR20
Well-Known Member
Yes you could use a 100gn .224 diameter bullet provided it has a muzzle velocity of over 2450 fps and a muzzle energy of 1750 ft lbs (I think so but might be incorrect).
Who? Me?
Read old early 1960s "Shooting Times" "Notes from the Hill". The .220 Swift was quite popular with some as what'd be maybe now known as a "canyon rifle".
I bet it was! Just like the .22 Hornet for woodland roe - perfectly capable but the law thinks otherwise. Quite why I will never fathom, because a bad shot with a .308 won't kill them either.
jthyttin
Well-Known Member
There's been 100gr 22cal bullets in early 2000's but I'm not sure how usable they would've been. Designed for subsonic ARs etc.
But more currently, 100gr bullets have been made for 224 Valkyrie. Federal seems to have changed to 90gr and I'm not sure who else has been making 100gr. I think you'd need something like 1-6" fast twist barrel, and bigger cartridge than Valkyrie. And it would be inferior to larger diameters in every way. I guess same would go for lighter non-lead (if Scotland drops the weight requirement to 80-85gr) since they're also long for caliber and require fast twist.
.220 swift was popular with a few Highland stalkers, it was also used on stags by Bell when he retired from Africa to his Highland Estate.
