What is the recommended barrel length for .22 rimfire?
Is there a "best" barrel length for accuracy? I understand max velocity is reached in 16" to 18".
Does that imply "optimal" length for best accuracy using a scope?
Donít know what the optimum length is, but most agree it isnít at maximum velocity length.
Have you ever notice how longer barrels are quieter than shorter barrels?
Thatís because thereís more area for the gas to expand into reducing the base eroding, bullet upsetting pressure when the bullet exits the muzzle.
So ?? What length is best 18 inches or is it longer???/ garrisone.
I get the longest barrel that the blank will allow. Seems the longer barrels will assist in stablizing the bullet better in the wind. I think you will find most BR 22RF barrels will average to be 24" in length. Why not attend a match near you and see what is being used by the competitors.
Last edited by Fred J; 09-14-2010 at 06:33 PM.
If it's anything like buttstocks, then you'll need Ĺ" longer than you trim it to!
Many years back Anschutz and others ran a bunch of experiments regarding barrel length, optimum velocity, and accuracy; as it pertained to position shooters ( some time in the 80's). The general consensus at the time was 18-19" + but shy of 20". Somehow over time this 16" size started to appear, ( which just happens to be the ATF minimum rifle barrel length), Perhaps some confusion occurred as the match air rifle barrels are set at 16"( again optimum length for the .177 pellet size/velocity used in competition) There was a definite relationship( 22rf) of lower velocity /inch of barrel from apx. 20" on. Crown placement and weight are more of the controlling factors in the BR game. The testing was written up in one of the NRA monthly publications. I suppose I have just muddied the waters further.
Blade: Thank you for a most informative answer. The 19+/<20 answer fits with a coaches clinic (Benning) which recommended shorter barrels and a bloop tube that I received in the 80s. Can you clarify "Crown placement" for me? Not sure I understand that concept.
My four BR .22's have barrels from 24" to 26".. I have seen longer and shorter, but this length works for me..
Crown placement = Basic, slugging the barrel to find the tightest point at the muzzle end of the barrel when installing new.
The reason that smallbore position shooters prefer the shorter barrel is that one has less "barrel" time until the round is in free flight, and thus unaffected by movement in standing and kneeling. The extension ("bloop") tube extends the front sight back to, or further than original location for proper sight radius.
Originally Posted by blades
Air rifle barrels are essentially the same, but I seem to recall after 12" or so the pellet starts to slow down.
My first post here at Benchrest.com
We recently had this discussion on rimfirecentral. To clear a bit of possible confusion over the long vs short barrel accuracy question, the long average of 25" for benchrest appears to work nicely in bolt-actioned rifles like turbos and anschutz, etc. The short barrels tend to have the accuracy edge in blow-back actions, like the 10/22.
In fact, a couple of us plan on doing an experiment to see if 12" is, in fact, the best in accuracy in a 10/22 rifle as was suggested by a respected member and specialty parts manufacturer/designer.
Why the big difference? First, check out the graph, half-way down this page titled "22LR Pressure Curves from Strain Gauge Data" http://varmintal.com/a22lr.htm The example is of a Benchmark 24.75" barrel on a bolt gun shooting a standard velocity bullet.
Peak pressure of 7500 lbs/sq.in. is reached between 5 to 6 ten thousanths of a second after primer ignition, then drops quickly and levels off at about 500 psi at 16 "tenths".
The bullet departs at 26 tenths from that 24.75" barrel with still nearly 500 psi behind it. Because the pressure remains quite steady after 16 tenths, the bullet continues to accelerate somewhat and generally in bolt guns to the end of the barrel. I noted comments from those who submitted chrony data on bolt guns indicating speeds continued to increase slightly up to his longest barrel in the 26 inch range.
Something different happens in 10/22s, persumably because of the blow back of the bolt during the firing sequence. I was informed that the 10/22 bolt does not even begin to move until the bullet is 2" down the barrel at which point it has already accelerated to 60% of its maximum velocity. The bolt never travels faster than about 80 mph, which is 0.13" per ten thousandth of a second ("tenth" for shorthand). As data is scarce, let us assume for rough figuring, that the bullet breaks free of its case just before maximum pressure is attained, say at 3 tenths after ignition and reaches 2" down the barrel at say 8 tenths. It is still accelerating at this point at which the bolt begins to blow back. The gas release at the rear might then occur "starting" at about 14 tenths after primer ignition based on accerating bolt speed average travel at this time-frame of 0.1" per tenth.
OK, so what happens when the breech is unblocked at 14 tenths? You now have a "balloon" which is more or less opened at both ends now and more open at the breech end.
The air pressure would drop MUCH faster than we see in the above-referenced graph of the bolt gun which only loses pressure by pushing the bullet out. I would surmise that the pressure drop would "reach" the bullet (perhaps even felt as a slightly destabilizing wave pattern on the bullet) at about 16 tenths after primer ignition. Now, take that information and add it to the fact the bullet will travel no more than 1.4" per tenth at 1170fps and something interesting happens at 16 tenths which happens to coincide with with approximately 12" of bullet travel. The bullet now starts to decelerate at approximately this point as the combined resistive forces of air and bore drag exceed what little remains of pushing pressure, so the bullet goes from accelerating to decelerating in the flash of an instant. This "instant" may be termed the moment of dynamic stability. At this instant and only then, are the forces of the expanding gases behind the bullet "pushing" equal to the forces of drag on the bullet -- the bullet is then and only then "floating" in an equilibrium of tension. If the bullet is released from the barrel at precisely this instant, I would predict it would not only be at maximum velocity, but also poised for maximum accuracy. That is a theory which has yet to be proven in testing. It could be that we haven't seen it proven because of the hassle of class III BATFE requirements and the fact that such a short, light barrel would need a super-stable platform to perform at its accuracy potential.
Anyway, that's one explanation of why 10/22s often do well with short barrels and bolt guns do better with long barrels. I have proven that shortening a 10/22 barrel from 20" to 17.5 inches increased average velocities of all bullets by about 30 feet per second. CCI SV went from 1080 to 1110 fps, for instance. Bolt guns can expect just the opposite trend -- shorten a 20" to 17.5" should decrease its bullet velocity.
I expect over the course of the upcoming year, I may have more data to share on the 12" barreled 10/22 test -- we'll see. Anyone here interested to know the results?
I spend a fair amount of time at our club with a nationally ranked outdoor prone shooter and coach, for what it's worth I do not think he has a barrel any shorter than 27" and most are 28"-29" and he indicates that's typical.
You might need to consider climatic issues with shorter barrels on a bolt gun.
I was shooting prone back when Federal introduced their premium ammunition. In summer their loads would go supersonic about 1 in 4 shots in the Annie 3p barrels with the long bloop tube, with the expected distasterous results on accuracy. I dropped out of the game not long after that, so I'm unaware whether the quicker Eley suffered the same issue.
Maybe they've all learned now.
Scax, Thanks for that great write up. On this forum most of us do not consider the auto loaders in relation to questions like this. Guess we have our blinders on and extended out too far resulting in a real bad case of tunnel vision. I for one would like to read of the rest of your results. I am sure that the people on Rimfire Accuracy forum would also be intrigued.
Yes, that's a good point -- I keep forgetting that when I get pretty fine results from my 10/22, but I agree it's hard to take semis seriously until someone starts beating bolt guns in ARA matches or the like. I believe that day MAY be coming. The precision accuracy some are getting with 10/22 ultimates is getting fairly close now. Great enjoyment. I'll be trying some experiments over the next year with different barrels and set-ups and hope it's interesting. I have to say that when I put hole in hole in hole in hole at 50 yards with a 20" barrel, it makes me wonder if a shorter barrel can possibly do better -- we'll see.
Originally Posted by blades
One thing learned so far -- at least at 50 yard shooting, is that with a 10/22 it IS possible to get a superb barrel from Green Mountain, but you may have to run through a couple of them to find one which is truly great. One of my GM 20" ss fluted shoots the same hole (maybe with .11 elongation) 3 or 4 shots in a row. I did give the barrels a J-B bore compound treatment which likely helped. I'm sure a Shilen would be more assured of greatness with just one to buy, but the GMs were cheap enough on sale that I got a couple and one was very smooth inside. Both shoot, but the smoothie shows greater precision at the target.