HMR, legal barrel length

johngalway

Hi folks,

What's the legal length for a rifle barrel, in this case HMR?

I am going to change my Sako .22lr barrel for a HMR barrel later this year. I want to get it shortened to something like 14" - 16" for handiness sake. Just wondering what's legal.

Regards,

John

Kramer

50cm minimum rifle barrel length in CJA '06 but this refers to "shortening" a barrel.

Something already under 50cm from the factory like a CZ should be OK.

65:- The following section is inserted after section 12 of the Firearms
and Offensive Weapons Act 1990:
“Shortening
barrel of shotgun
or rifle.
12A.—(1) Subject to subsection (2), a person
who shortens the barrel of—
(a) a shot-gun to a length of less than 61
centimetres, or
(b) a rifle to a length of less than 50
centimetres,
is guilty of an offence.
(2) It is not an offence under subsection (1) for
a registered firearms dealer to shorten the barrel
of a shot-gun or rifle to a length of less than 61 or
50 centimetres respectively if the sole purpose of
doing so is to replace a defective part of the barrel
with a barrel of not less than 61 or 50 centimetres,
as the case may be.

Rovi

In the CRIMINAL JUSTICE BILL 2004 there is mention of "It is an offence for a person (except a registered firearms dealer) to possess without lawful authority or reasonable excuse—" "(b) a rifle the barrel of which is less than 50 centimetres in length", while leads me to surmise that it IS legal to have a shorter barrel provided you have "lawful authority or reasonable excuse", whatever they may be.
I suppose "lawful authority" would be some sort of licence/cert for the short barrel, but the word "or" before "reasonable excuse" seems to state that you don't need the " lawful authority" once you have a plausible "reasonable excuse" for possession of said short barrel. I doubt that 'because I want one' qualifies.

There's talk of a maximum legal length (of the whole firearm) of some sort in the fabled 'Restricted List', which might or might not have a bearing on this too.

It would appear, on face value, that you can have a rifle barrel shorter than 50cm (19.7ins) provided you get "lawful authority" from whoever, the Gardaí/DOJ presumably; I'd check it out and get the okay in writing before going ahead with the project, though.


edited to add-
Of course, I should have referenced the CRIMINAL JUSTICE ACT 2006 for the above, but it all appears to have gone in as described [Section 65-(6)(b)].

johngalway

:eek:

50cm = 19.68 inches...

Thanks for the info lads.

Bloody rubbish law :mad:

dimebag249

So, for the sake of arguement, should one purchase a shotgun with a ten inch barrel, wouldn't the firearms certificate issued for the gun be "lawful authority"? No guard has ever asked me for the barrel length of any gun I've applied for. To me the situation here appears much like it is in Canada, it is illegal to shorten a barrel below a specified length, but perfectly legal to buy a new gun with a short barrel.

Edit: Needless to say I'm not going to be the one to argue this in front of a judge, but the law is sufficiently vague that you might get away with it. (?)

rrpc

johngalway wrote:

Hi folks,

What's the legal length for a rifle barrel, in this case HMR?

I am going to change my Sako .22lr barrel for a HMR barrel later this year. I want to get it shortened to something like 14" - 16" for handiness sake. Just wondering what's legal.

Regards,

John

You're going to lose a good deal of accuracy by doing this. The round will leave the barrel in a very unstable manner causing it to be heavily influence by wind and the likelihood of considerably widened groups.

20" has been found (in the case of .22") to be the shortest you can go without affecting accuracy.

freddieot

I've just checked the 2006 Act and it looks to me like less than 50cm for a rifle is not allowed. ( See Sec 65, 6, b).

Maybe I've picked it up wrong. However, I would say that just because the local cops are unaware that someone has a shorter barrel does not mean that they have authorised it in some way. I suspect it would be a hard job to convince a judge of that but it would depend on the judge and the general circumstances. The cops would argue that you should have asked for special permission and that you deliberately tried to decieve the State and all that s*i**.

since when has ignorance of the law really been a best defence.

If you really want a shorter barrel then explain why to your local sargeant.

freddie

thelurcher

rrpc wrote:

You're going to lose a good deal of accuracy by doing this. The round will leave the barrel in a very unstable manner causing it to be heavily influence by wind and the likelihood of considerably widened groups.

20" has been found (in the case of .22") to be the shortest you can go without affecting accuracy.

Do you have more info on this? I always hear different opinions on it 12" 16" etc.
For your last statement to be true it would mean that anything over 20" would NOT improve accuracy.

I'd like to see a study where they take say a 24" barrel and correctly shorten it 1" at a time firing groups at each increment.

Rovi

freddieot wrote:

I've just checked the 2006 Act and it looks to me like less than 50cm for a rifle is not allowed. ( See Sec 65, 6, b).

Maybe I've picked it up wrong.

Check my post #3 above.

CRIMINAL JUSTICE ACT 2006
Section 65-(6)(b)
"It is an offence for a person (except a registered firearms dealer) to possess without lawful authority or reasonable excuse—" "(b) a rifle the barrel of which is less than 50 centimetres in length"

I read that to mean that you can possess such a thing, provided you have "lawful authority or reasonable excuse".
What constitute "lawful authority or reasonable excuse" is another matter entirely.

Clare gunner

Which you do with your firearms cert. How many Rugers out there with 16.5 in barrels?It is up to the lawmakers to be clear on the law they propose to impliment.
The ten in shotgun barrel is a conomdrum here.It is illegal as a smoothbore,but if you were to get just a pistol grip on the gun with a rifled slug barrel,you could possibly register it as a large calibre pistol.Albeit a very inaccurate one.Dolphin arms did this awhile in the UK to sanction bust the big cal semi rifle ban.Before the pistol ban came in that is.

FLAG

Lads to put you all of your misery.

In the original form that the proposed legislation took we would have had a prohibition on barrel lengths shorter than 16.5" this was unintended.

We noted this during discussions and the very points made in the posts were brought to the attention of the legislators and the wording added to ensure that lawful possession of rifles with barrels shorter than 16.5" would not be an issue.

The original intent of the legislative change was to outlaw the unlawful shortening of rifle and shotgun barrels save by a RFD, posession of a factory or RFD modified rifle with a barrel lenght less than 16.5 inches as long as one has a firearms certificate or appropriate authorisation is within the law.

Vegeta

rrpc wrote:

You're going to lose a good deal of accuracy by doing this. The round will leave the barrel in a very unstable manner causing it to be heavily influence by wind and the likelihood of considerably widened groups.

20" has been found (in the case of .22") to be the shortest you can go without affecting accuracy.

Why does it become unstable??

Jonty

It goes unstable, because it is not in contact with rifling for long with a short barrel. The bullet needs to spin to be accurate. Its the rifling that causes the spinning.

Vegeta

Jonty wrote:

It goes unstable, because it is not in contact with rifling for long with a short barrel. The bullet needs to spin to be accurate. Its the rifling that causes the spinning.

Ok for a .22lr with a 1 in 16 twist and a 20 inch barrel the bullet gets rotated 450 degrees. Does that extra 90 degrees of rotation when compared to a 1 in 16, 16 inch barrel really make such a huge difference?

rrpc

Vegeta wrote:

Ok for a .22lr with a 1 in 16 twist and a 20 inch barrel the bullet gets rotated 450 degrees. Does that extra 90 degrees of rotation when compared to a 1 in 16, 16 inch barrel really make such a huge difference?

Yes it does. The bullet when it leaves the gun is not actually spinning in a straight line, the nose is rotating slightly around an axis from the centrepoint of the tail. This can vary from bullet to bullet and manufacturer to manufacturer. I have seen bullets strike a target at 25 yards sideways, i.e there is a long cut in the paper as opposed to a small hole.

It takes some time for the bullet to 'settle down' in flight. The longer it stays in the barrel the quicker it settles into stable flight on exit. While it is unstable it is much more affected by the wind and hence the overall accuracy is affected.

With the .22lr round the optimum performance is achieved within a 20" barrel. Some disagree and maintain that although this may be true for 50 metre shooting, a longer barrel is required for greater distances. This is a different argument however and other variables such as barrel 'flip' come into the equation.

Vegeta

rrpc wrote:

Yes it does. The bullet when it leaves the gun is not actually spinning in a straight line, the nose is rotating slightly around an axis from the centrepoint of the tail. This can vary from bullet to bullet and manufacturer to manufacturer. I have seen bullets strike a target at 25 yards sideways, i.e there is a long cut in the paper as opposed to a small hole.

It takes some time for the bullet to 'settle down' in flight. The longer it stays in the barrel the quicker it settles into stable flight on exit. While it is unstable it is much more affected by the wind and hence the overall accuracy is affected.

With the .22lr round the optimum performance is achieved within a 20" barrel. Some disagree and maintain that although this may be true for 50 metre shooting, a longer barrel is required for greater distances. This is a different argument however and other variables such as barrel 'flip' come into the equation.

so what are you saying effects yaw damping, barrel length or rate of twist?

rrpc

Vegeta wrote:

so what are you saying effects yaw damping, barrel length or rate of twist?

Barrel length.

Vegeta

rrpc wrote:

Barrel length.

hmmmm I must ponder on this as that is news to me.

Thanks for clearing that up, I was of the opinion that Yaw was caused by muzzle blast and barrel vibrations etc and the gyroscopic spin of the bullet (along with other things) damped out the yaw. Therefore I couldn't understand where the barrel length arguement was coming in. I am obviously mistaken and need to do more research

rrpc

While you are pondering, think about what is happening to the bullet when you fire it. The bullet is accelerating in the barrel while at the same time the rifling is appplying a spin to it. When the bullet leaves the barrel, it is still accelerating and is no longer confined to the restrictions to it's movement imposed by the barrel. The amount of twist will have different effects, but there is a limit to what can be achieved within a certain barrel length.

Somewhere in my archives I have a full article describing the various tests and effects on the flight of the bullet.

Vegeta

rrpc wrote:

While you are pondering, think about what is happening to the bullet when you fire it. The bullet is accelerating in the barrel while at the same time the rifling is appplying a spin to it. When the bullet leaves the barrel, it is still accelerating and is no longer confined to the restrictions to it's movement imposed by the barrel. The amount of twist will have different effects, but there is a limit to what can be achieved within a certain barrel length.

Somewhere in my archives I have a full article describing the various tests and effects on the flight of the bullet.

yes but an overly long barrel and the gas from the powder will have been expended and the bullet will be slowing in the barrel (due to friction of metal on metal) so I wonder for a .22lr at what length barrel does the bullet begin to slow.

Also I don't want to be pedantic but incase a someone else reads this, how can the bullet be accelerating after it has left the barrell. There is no longer any force driving it forward. Sure maybe for the first foot while still under the influence of gas at the muzzle but after that there is no force driving it forward. Surely 2 chronograhs would highlight this, one at the muzzle and one 20 feet away. Anyway that's a side topic.

Jonty

Vegeta wrote:

Ok for a .22lr with a 1 in 16 twist and a 20 inch barrel the bullet gets rotated 450 degrees. Does that extra 90 degrees of rotation when compared to a 1 in 16, 16 inch barrel really make such a huge difference?

Aren't we talking about a 17HMR with a 1 in 9 twist?

Vegeta

Jonty wrote:

Aren't we talking about a 17HMR with a 1 in 9 twist?

ok then a sako quad with a 22 inch barrel has a twist rate as you say of 1 in 9. That's 2.4444 revolutions.

Cut down to 16 inches it still has 1.777 revolutions

Jonty

Vegeta wrote:

ok then a sako quad with a 22 inch barrel has a twist rate as you say of 1 in 9. That's 2.4444 revolutions.

Cut down to 16 inches it still has 1.777 revolutions

which is a reduction of 27%.

.243

the .22 lr can be no less than 12.5 ins,this it the minimum length needed for the powder to burn,im not sure about the .17hmr but if you look at any of the recent shooting mags cz do a .17 hmr in a 16ins barrel, my last .17 was down to 16ins with no problems,

rrpc

I know Anschütz experimented with barrel length for their smallbore target rifles when they were developing the 2013 model (a marked departure from the previous models). They started with a 400mm barrel, but found that the best accuracy was achieved with a 500mm length. I was on a visit to their factory not long after this and I know they gave me a very detailed run through on the various tests and results they had got, but it being over ten years now I can only remember snippets.

The 500mm barrel only really caught on on the continent, many German shooters and some Americans used it, but the Brits always maintained vociferously that the 20" barrel (500mm) was not as accurate at 100 yards as the 690mm one and they never really took to it. To such an extent that Anschütz had to continue manufacturing the 690mm and in fact at this stage they seem to have dropped the 500mm barrel altogether.

ArthurJ

Vegeta wrote:

Also I don't want to be pedantic but incase a someone else reads this, how can the bullet be accelerating after it has left the barrell. There is no longer any force driving it forward. Sure maybe for the first foot while still under the influence of gas at the muzzle but after that there is no force driving it forward. Surely 2 chronograhs would highlight this, one at the muzzle and one 20 feet away. Anyway that's a side topic.

It’s a good point you raise and far from being picky. My understanding has always been the same as yours, so now I’m curious.

rrpc will you clarify this matter for us.

rrpc

ArthurJ wrote:

It’s a good point you raise and far from being picky. My understanding has always been the same as yours, so now I’m curious.

rrpc will you clarify this matter for us.

It is still accelerating because the gases are still behind it and driving it forward. I think there are photos illustrating this on one of the sticky threads. It's not for long, but long enough to have an effect on the bullets flight.

What Veg said earlier in his post about the bullet slowing in the barrel is not true. The rate of acceleration is dropping, but it still has an expanding gas cloud behind it. Rifle ammunition is slower burning than pistol ammo in order that the bullet continues to accelerate down the length of the barrel.

I'm not really sure what you want clarified, hope that helps answer your question.

Vegeta

well from my understanding barrel length only effects potential bullet velocity and not accuracy.

I still cant see how a longer barrel is more accurate (despite having a nose around yesterday). Shorter barrels are perfectly capable of making the bullet as stable as longer ones. So if a short barrel and a long barrel can both stabalize the bullet then what is it exactly about the longer barrel which makes it more accurate?

of course velocity helps accuracy, the faster it travels from barrel to target the less time wind and gravity can effect it, but velocity does not equal accuracy.

So what exactly is it about a longer barrel which makes it more accurate? (because its not twist rate and gyroscopic stability)

rrpc

Vegeta wrote:

well from my understanding barrel length only effects potential bullet velocity and not accuracy.

I still cant see how a longer barrel is more accurate (despite having a nose around yesterday). Shorter barrels are perfectly capable of making the bullet as stable as longer ones. So if a short barrel and a long barrel can both stabalize the bullet then what is it exactly about the longer barrel which makes it more accurate?

It's a matter of degree, they both stabilise, the longer one does it better. At least that's what the tests in Anschütz proved. The subsonic .22lr round reaches maximum velocity in about 15", but they found that a 16" barrel wasn't as accurate for 50m shooting as a 20". There are so many variables here. For example, the distance you are shooting will make a difference as well. The Brits maintained at the longer distances (which Anschütz weren't testing for) that the longer (69cm) barrel was better.

of course velocity helps accuracy, the faster it travels from barrel to target the less time wind and gravity can effect it, but velocity does not equal accuracy.

Wind has more effect on a high velocity round, which is one of the reasons why target shooters only use subsonic rounds.

So what exactly is it about a longer barrel which makes it more accurate? (because its not twist rate and gyroscopic stability)

It's a combination of many factors, stability is one of them, the rate of burn of the powder, the relative humidity, air temperature etc. Rifle rounds are designed with a particular barrel length in mind, so that there is a continuous burn until just before the bullet leaves the barrel. Pistol rounds on the other hand are designed to burn quicker.

The original question was about shortening the barrel of a .17 HMR. The arguments against such a course of action insist that loss of accuracy will result.

Vegeta

rrpc wrote:

It's a matter of degree, they both stabilise, the longer one does it better. At least that's what the tests in Anschütz proved. The subsonic .22lr round reaches maximum velocity in about 15", but they found that a 16" barrel wasn't as accurate for 50m shooting as a 20". There are so many variables here. For example, the distance you are shooting will make a difference as well. The Brits maintained at the longer distances (which Anschütz weren't testing for) that the longer (69cm) barrel was better.

I'll take your word for it on this

Wind has more effect on a high velocity round, which is one of the reasons why target shooters only use subsonic rounds.

I don't mean to come across arguementative but this is just plain incorrect. Yes target shooters use sub sonic ammo but the faster a bullet travels from A to B the less time wind can effect it and therefore cannot throw it off course as much.

It's a combination of many factors, stability is one of them, the rate of burn of the powder, the relative humidity, air temperature etc. Rifle rounds are designed with a particular barrel length in mind, so that there is a continuous burn until just before the bullet leaves the barrel. Pistol rounds on the other hand are designed to burn quicker.

Fair enough but barrel length doesn't have much to do with some of the above such as humidity, air temp etc.

The original question was about shortening the barrel of a .17 HMR. The arguments against such a course of action insist that loss of accuracy will result.

The only thing I can think of is that by chopping off a few inches from the barrel is that the expanding gas will be in greater volume at the muzzle increasing yaw angle and taking longer to damp out. Other than that none of the above explain it.

Vegeta

Jonty wrote:

which is a reduction of 27%.

yes in the number of revolutions, which has nothing to do with the rate of twist which governs static (gyroscopic) stability