The UK's Finest Independent Forum for Shooters and Gun Owners. Est 2010.

Sim G wrote:About 12 years ago, Guns & Ammo magazine did an article on this using standard velocity ammo. 14" was the conclusion. The evidence was very convincing.

That's what I'd have expected with SV .22LR. 12-14 inches has been quoted as being ballistically optimum for many years with this ammo.

What many people forget though is that the rimfires have greatly varying powder charge weights depending on type. SV .22LR is 1.3-2gn of a very fast burning grade and is consumed in a very short barrel length, standard HV variants will likely double that weight and need slightly slower burning powders and might benefit from a bit longer barrel, and hyper-vel types use a longer and higher capacity case form stuffed full of very much slower burning propellant. I don't know where subs fit in - same as SV I'd expect, so a very short barrel will work fine.

the .17HMR is a very different animal using the longer .22 WMR case as a base and it's nearly filled, so its powder charge and characteristics will be very different from the low velocity .22 Short and .22LR loads suggesting that a considerably longer barrel is needed for full velocity.

SimG, I had a feeling wet suppressors were as much about sound reduction by dampening/deadening the structure as anything. The suppressor is just means of reducing the sound signature by cooling and slowing down the gasses as they leave the muzzle and I have often wondered about the use of a thermal jelly or paste to act as some form of heat reducing medium however I have no idea how to apply it and keep the can to a sensible size.

John MH wrote:Suppressed semi-autos also suffer from more fouling than unspressed with more powder residue being blown back into the action.

John, do you know the reason for that? Is it something that could be factored into a moderator to reduce?

I don't read my own signature!

So all the Olympic shooters that have 26- to 30 inch barrels are wasting there time on there 5grand rifles and should stick to a 10/22 with 14 inch barrel

Regards Jack

Jackmanuk wrote:So all the Olympic shooters that have 26- to 30 inch barrels are wasting there time on there 5grand rifles and should stick to a 10/22 with 14 inch barrel

Regards Jack

As was mentioned earlier - sight radius is a reason for longer barrels.

BBTI for 22LR - http://www.ballisticsbytheinch.com/22.html

Freebore boost effect - a couple of articles on it,

https://www.tactical-officer.com/articl ... 4TIh3YzS8A

http://emptormaven.com/2007/03/freebore-boost-effects/

Jackmanuk wrote:So all the Olympic shooters that have 26- to 30 inch barrels are wasting there time on there 5grand rifles and should stick to a 10/22 with 14 inch barrel

Regards Jack

If you look at modern smallbore prone competition rifles, they don't necessarily use these barrel lengths anymore. Many use a short, fat, stiff barrel plus a 'bloop tube' to take the foresight out another ten or twelve inches to get the required sight radius. Anschutz pioneered this a couple of decades ago. (It's not as simple technology as it seems as the extension tube will spoil the rifle accuracy if it's not very well designed.)

The US research done donkeys years ago that involved starting with 25 or 26-inch barrels and cutting them down and recrowning them by a inch at a time, found that 25/26-inches actually reduced the MV of a standard velocity 40gn match .22LR, and the initial shortening cuts produced a modest increase.

In 'The Ultimate Ruger 10/22' Mark White includes some data where a 10/22 and a 77/22 had their barrels progressively shortened, with velocities being measured after each cut:

10/22 77/22 They found the 16" gave the highest velocity but also that until they got below 10", velocities were maintained to within 4% of the peak. So a UK minimum 12" barrel typically give only about 30fps lower than the maximum. It would be interesting to look at at the spread of velocities at these two barrel lengths . . . I guess in theory the higher velocity in the 16" tube means that all the powder's been burnt so it should have a more consistent velocity.

Triffid

Target pistol ammunition is designed to burn in 6" barrels , if pistol ammo ( free pistol ) was used in a 12" rifle barrel there wouldn't be much unburned powder would there ?

So in theory it is possible to drop below 16" without a serious loss of MV. I will start the barrel at around 16" and chrono with a couple of types of ammunition then work back to the desired 12-13" and add a suppressor. If things really go pear shaped I can re-barrel to a longer length.

Triffid, thanks for posting the tables, I had not seen these ones before.

No problem.
I'd be very interested in your results, particularly if you can do some extreme spreads and SD's at different barrel lengths . . . I've got a Finnfire with a 22" bull-barrel that I'd like to get cut to something a bit more wieldy/lighter.
Triffid