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

I have a 12" volquartsen barrel on a 10/22 and a SAK moderator - seems to shoot pretty well.

So what is a freebore boost effect then?

Freebore boost effect, the theory is the suppressor extends the barrel length and accordingly the velocity. A 12" barrel +6" supressor would not give the same MV as a 18" barrel however the 6" suppressor will give some increase in MV.

In theory... Downside is some people believe the additional length of supressor will lead to some inaccuracy in a .22LR however this could be attributable to barrel harmonics as much as anything else.

Thanks

ovenpaa wrote:Freebore boost effect, the theory is the suppressor extends the barrel length and accordingly the velocity. A 12" barrel +6" supressor would not give the same MV as a 18" barrel however the 6" suppressor will give some increase in MV.

In theory... Downside is some people believe the additional length of supressor will lead to some inaccuracy in a .22LR however this could be attributable to barrel harmonics as much as anything else.

Is there any evidence anywhere to support the theory?
I know that Eley claimed that with .22lr all the propellant was fully burned in the first 16" of the barrel, and that any additional barrel length in a target rifle was only really beneficial to the shootability/handling of the rifle. I don't know if I like the thought of propellant still burning inside the moderator if indeed it does. I have heard stories some time back in relation to .17hmr rifles of explosions in moderators when accumulated unburnt powder has suddenly ignited. The cause so I was told was the use of unsuitable moderators that weren't designed to be used with this round. I just wonder if you could be risking something similar.

I also wonder about continued combustion inside the moderator being uneven due to the influence of the baffles and distorting the path of the bullet. I suppose what this needs is someone to actually be prepared to conduct some trials and to test the theory out to see the effects on muzzle velocity and accuracy. We already know for instance that a 12" barrel shouldn't be any significantly less accurate than a 16" or for that matter 20" barrel.

Chapuis wrote:Many years ago the club that I belonged to visited Eley as they were then part of the same company and we could buy their ammo at very preferential rates. The guy showing the club members around the manufacturing facilities stated that Eley had done a fair bit of development on optimum barrel lengths for sporting rifles and had come to the conclusion that 16 inches was it. It probably isn't by chance then that several rifle manufacturers offer rifles with that length of barrel.

That and in the US a sub 16" barrelled rifle becomes an SBR (Short Barrelled Rifle) which requires proper paperwork and a $200 tax stamp

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.

I would assume with open sights one of the significant reasons for longer barrels is sight radius however with glass this is of less importance. One thing I had not considered was the potential build up of un-burnt powder in a suppressor. Time for some more research.

ovenpaa wrote:One thing I had not considered was the potential build up of un-burnt powder in a suppressor. Time for some more research.

Was that not one of the reasons for "wet" suppressors? More to do with fire/explosion prevention than suppressing capability....?

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

I own an MP15-22 with 12" barrel and I honestly haven't noticed any difference in accuaracy when compared to the longer barreled .22 semi auto's that I've shot (although maybe I'm just not that good an aim!). I've shot it out to 50M and it can hit 1 inch shootnc patches without too much trouble (weather allowing!)