Interesting test on barrel length and velocity

[Tim s]

i think that he was trying to relate maybe that yeah.. it is going to go to sleep... because it was a bore!

Wow....about a year ago you were'nt sure what end of a 22 to point down range and now a bonafide interweb punster. Impressive.

 

[USMCDOC]

Wow....about a year ago you were'nt sure what end of a 22 to point down range and now a bonafide interweb punster. Impressive.

 

[BobbyJ]

I had two inches cut off my 17 WSM HB SS Bmag when I first bought it. I didn't chronograph it before I had it chopped back to 20in. so there was no base line with my rifle but I have chronographed it with my Magnetospeed since and it Avg. 2990 FPS with the 20gr ammo and the ES, for rimfire ammo, was surprisingly low. This isn't exactly a fair comparison but I've talked to multiple Ruger 77/17 WSM owners who chronographed their Ruger WSM's and those have 24in. barrels, every one of them got slower FPS speeds than I was getting and mine at 20in. shoots as fast or faster than those with factory length 22in. Bmags.

I don't recall where but somewhere out there on the WWW is a chart that shows the results of someone doing this test with a 17 HMR and if I recall it pretty consistently gained speed with every inch cut off with it peaking velocity right around 19in.

Ruger just came out with a 17 WSM with a bull 18.5" barrel. I have a Bmag bull which is longer but a little sensitive to vibrations. I put a tuning ring on the end which tightened by 100 yard groups to under 1/2"

I'm thinking the shorter barrel is going to be more accurate or less fussy. In like three tests I read it showed all things being equal the shorter barrel is the most accurate. The length is used for velocity not accuracy.

 

[Tommie]

I don't recall where but somewhere out there on the WWW is a chart that shows the results of someone doing this test with a 17 HMR and if I recall it pretty consistently gained speed with every inch cut off with it peaking velocity right around 19in.

I think you’re referring to Varmint Al’s test.

 

[Rsadams]

Probably why most aftermarket barrels are 20 inch... That seems to be the sweet spot but I look forward to the finish of this test.... I went with 16 to try it and it hold as good a group as the ammo and myself will allow...

 

[Lefty Trigger]

A while back I bought a CZ 455 Ultra Lux in 22LR and the Ultra comes with the 28" barrel, my thinking was that it should be super accurate with a barrel that long,... I was wrong! It did shoot good but only for awhile then it would go all wonky until I would pull a bore snake through it. Turns out the longer barrel is for sight radius for hunting with a few shots on game not continuous target shooting. When I called about this I was told that the ideal barrel length is 16.5" and most 22LR ammo powder is burnt up by 16" so on that 28" the bullet is just sliding the last 12 inches causing my fouling problem. I ordered a 20" barrel kit and it would shoot awesome groups all day long.

 

[Tim s]

A while back I bought a CZ 455 Ultra Lux in 22LR and the Ultra comes with the 28" barrel, my thinking was that it should be super accurate with a barrel that long,... I was wrong! It did shoot good but only for awhile then it would go all wonky until I would pull a bore snake through it. Turns out the longer barrel is for sight radius for hunting with a few shots on game not continuous target shooting. When I called about this I was told that the ideal barrel length is 16.5" and most 22LR ammo powder is burnt up by 16" so on that 28" the bullet is just sliding the last 12 inches causing my fouling problem. I ordered a 20" barrel kit and it would shoot awesome groups all day long.

Who did you call, 16.5” barrels r us ?
That is simply ridiculous.
Of course, learning how to properly clean the gun could prove useful to accuracy, perhaps.

 

[JohnKielly]

Decades back when the .222 R was benchrest king and Chux disposable washing up sheets were the go on cleaning rods hereabouts, a friend managed to leave a patch in the barrel & subsequently bulged it at around 17". His gunsmith back bored it to 16" or so and it continued to appear in the winners list.

 

[moorepower]

I have a 10/22 book and they did the same test with a 10/22 and a 77/22. If I recall between 14" to 17" were very close to top velocity. Since you want to keep the match ammo subsonic, it matters not if your barrel is longer. What if very strange to "me" is the drift/drop is better on the subsonic due to the turbulence the bullet goes thru going from supersonic to subsonic. On a side note Green Mountain offers a 28" barrel that REALLY cuts the noise down on a 22lr.

 

[mikecr]

It makes sense. Once the bulk of the powder is burnt up,speed will not increase. If there is a significant amount of powder left burning, it will maintain the speed a little longer, but will not increase. After that point, speed will decrease no matter how long the barrel is.

Would like to see reasoning behind the notion. Perhaps math backing it.

My reasoning in contrast:
As long as there is pressure behind the bullet that exceeds it's drag, that bullet will continue to accelerate. Right?
With a standard load for cal and a barrel 200 inches long, I would think the muzzle pressure is still over ~1Kpsi. And that pressure is way higher than drag on a tiny little fully engraved bullet (~14.7psi). So what would cause a bullet's acceleration to stop, or for a bullet to 'coast' while inside a bore?

I check Quickload,, it doesn't.
The MV may go up in ever smaller increments with more barrel length, but it's still going up.

 

[shutinlead]

Mike,
I would like to see the math on this - and not have to do it...

Real time experiments and math may or may not coincide... Point being, I have several 22 RF's I've made, mostly single shots ranging from a DS Cole to a Ballard, a Steven 44 to a few Winchester Low and High walls to different rolling blocks (#2's and #4's) and even a 10-22 with the GM 28" barrel. I shoot most of these in vintage firearm matches with tang sights so I prefer the longer barrels that give a longer sight radius - 28" is consistent but for the Stevens that has a 24".
My latest, is a low wall put together from pieces - some I made, some gathered... I used a barrel blank from RKS. It's 30" SS, left hand gain twist, with an exit that measures to be about 1:15.8 - (don't ask how I measured this, it was a process) - this particular rifle gives me the highest velocity using the same ammo across board, all velocity testing done with LabRadar. This rifle is the longest barreled 22 I have... test data was taken within an hour of each, some were repeated on different days depending on what I chose to shoot (Omitted the 10-22 and the #2 roller). So, does the twist, groove, length, material, cleaning, finish make differences? Is there "fouling" that was slowing the bullet down? cutting the barrel shorter is removing the fouling? shoot a 22rf with cheap ammo and then clean it, repeat with high quality ammo and compare.

Greg

 

[Tim s]

Conclusions like this omit, probably, one of the single biggest factors and thus render conclusions less than valid and why all the velocity testing done on barrel length do so by sacrificing a single barrel for comparisons.
The longest/ highest fps tells us what about all the barrels???
Without knowing the interior dimensions of the bore and/or variances within or interior taper you simply cannot tell.
All things being equal(which they never are) a.2170” bore is going to yield a big difference than one that’s .219”. Then throw in land height, etc.,etc., even roundness of the bore.