Odd Amount of Power From a Shorter 22lr Barrel

[BigDMT]

Last spring I purchased a Browning Buckmark Varmint pistol with the 10 7/8" bull barrel to have something more handy in the truck than my 1940 Ranger bolt action bull barrel 22LR rifle. The Buckmark is awesomely accurate with any of the American Eagle 22LR ammo be it the 36gr copper plated HP rounds or 40 gr lead solid.

Shortly after I got my Browning, I purchased my son a TC Hot shot break action 22LR. Extremely accurate with all American Eagle ammo as well. Am I sounding like a spokesperson for AE ammo yet??? haha! : ) sorry... it just shoots great for me. The old 1940 Ranger loves it too...ok, I'll stop : )

My son and I went out plinking with our 22's today. We bought a couple 12 packs of strawberry cream soda for targets. Shook them up really good and had a great time watching them explode with a resemblance to frothy blood : ) Then picked up all of our trash!!!
Had to emphasize that because so many inconsiderate people shoot stuff on public land around here then leave their garbage laying everywhere.

Anyhow, the weird thing was that ALL of the explosions from my Browning Buckmark pistol were very noticeably larger even though they were shot from the same distances as the TC Hotshot which has about a 19" barrel. I shot all the guns and my son shot all the guns and good hits were made with all weapons at identical distances using AE 40 gr solids. Just weird how the pistol always seemed to give the best display of destruction???

I have never chronographed my Browning because it never really mattered to me. But now I am sort of curious? Could it be going faster than the TC? I can't imagine so, but I suppose I should check it's speed because that's the only thing that seems to explain the larger explosions. Anyone have any ideas for why this might be, besides speed?

 

[JeffG]

Different barrel twist rates? maybe the browning bullets are still wobbling at short distances creating a bigger entry hole?

set up your chronograph and shoot some paper to see what sort of speeds and impact print you get.

 

[JASmith]

I've forgotten the source, but may have been an American Rifleman article 30 or more years back. Someone did a study of barrel length vs velocity in the .22 rimfire. It turns out that the .22 has very little powder so the pressure is way down by the time the bullet travels 8 or 10 inches. After that, friction between the barrel and bullet tends to slow the bullet down.

It is also possible that your Buckmark has a slightly tighter chamber.

BTW, did you notice that the report in the Buckmark is noticeably louder than the 16" barrel rifle?

 

[boltfluter]

I would imagine that the Browning has a slightly tighter bore. I had a similar thing happen with a Kimber .22LR that was breaking the sound barrier with sub-sonic ammo. Lapped the bore with the Tubbs kit and could watch the velocity slow down as I shot through the chrono. Now it is quiet with the suppressor on. Paul.

http://proprecisionrifles.com/

 

[BigDMT]

Never have noticed any oblong or key shaped impact holes so I don't think bullet stability is an issue.

I was contemplating barrel friction because I have run the AE 36 gr HP bullets through the chronograph using my 1940 Ranger when it had a 26" barrel (have since chopped it down to 24" to make it handier). With a 26" barrel, accuracy was great, shooting 5 shots in a 1" group at 100 yards, but I did notice velocity was only about 1230-1240 fps which is a little lower than the advertised 1260 fps. I remember thinking it was odd that my 26" barrel was pushing them that slow when 26" barrels on my center fire hunting rifles always give me and extra 50-75 fps.
So the small powder charge and friction makes sense to me now. That's definitely a possibility.

And yes, my Buckmark has nearly twice the report of the 19" barreled TC Hot Shot.

So going with the theory, (or perhaps proven fact...don't know) that a 22lr round is slowed after 8"-10" of barrel length...Is it possible that my Browning with a 10 7/8" barrel is producing close to maximum velocity possible for the 22lr round?

I'll have to run the Browning through the chrono this weekend along with the TC and my Ranger with identical ammo to see what's going on. Will be very interesting to see the results since I have a short, medium, and long length barrel for testing.

 

[BigDMT]

Found the info relayed by this other forum member which supports JASmith's idea for my extra velocity in a shorter barrel. It appears JASmith might have hit the nail square on the head : )

Notice how 10" seems to be a high velocity node for the 22lr rounds. It was the fastest in the initial test from the old Guns and Ammo magazine article. And produced the highest velocity in the other referenced test from the 1986 Shooting Times magazine. Only thing faster than a 10" tube was the 22 1/2" Remington factory test barrel. And we all know how manufacturers like to "talk up their products" : )

http://www.kifaruforums.net/archive/index.php/t-6867.html

 

[BigDMT]

So I finally got around to chronographing the various 22lr's.

The first was my Ranger 22lr bolt action target rifle with a bull barrel chopped down to 24"

Next was the Thompson Center Hot Shot break action single shot rifle with a 19" barrel

And third, a Browning Buckmark Varmint semi-auto pistol with a 10 7/8" bull barrel


I fired 10 shots in each weapon using Federal American Eagle 40 gr Solid lead bullets. All bullets were pulled from the same 50 round box in the same brick of ammo to ensure closest production uniformity. My results are below.

Ranger bolt action w/ 24" barrel
High: 1253 fps
Low: 1225 fps
Avg: 1233 fps

Thompson Center break action w/ 19" barrel
High: 1278 fps
Low: 1236 fps
Avg: 1256 fps

Browning Buckmark semi-auto w/ 10 7/8" barrel
High: 1189 fps
Low: 1140 fps
Avg: 1161 fps


So my test seems to disprove the theory that a 10-11" barrel is optimum for speed in a 22lr. BUT, perhaps much of the speed loss is due to power being lost from the blow back action of the semi-auto action??? There's some more food for thought.

So would a 10" barrel from a more stable action like a bolt or break style action prove to be faster? I don't know. All I can say is that a 11" barrel in a semi-auto is much slower than a 19-24" barrel from a bolt or break action rifle.

The 19" barrel was definitely faster than the 24" barrel. But then again, it wasn't much faster, so could bore smoothness be a factor between the two? Maybe not, because we are also talking about 5" of barrel length difference. So many unknowns. All I can show is what my chronograph shows me. Hopefully it gives some insight to this interesting theory : )

 

[500 meter ram]

My 16 " Lilja barrel is definitely faster than my 24" Lilja barrel.

 

[rhbrink]

How about "Dwell Time" meaning the time of the bullet in the target delivering more energy to the target with a slower bullet than a faster bullet? Just guessing but that is something that does seem to have a effect with large diameter cast bullets working on big game especially when they have a large flat meplat.

 

[JASmith]

So my test seems to disprove the theory that a 10-11" barrel is optimum for speed in a 22lr. BUT, perhaps much of the speed loss is due to power being lost from the blow back action of the semi-auto action??? There's some more food for thought.

The reason the earlier tests showed the peak in the 10" region was the small amount of powder in the cartridge. The loads you tested imply a high velocity cartridge with likely more powder. The optimum barrel length increases with powder charge to bullet weight ratio.

We can pull an example from a mistake occasionally made by the hand loader: forgetting to put the powder in the case. There's enough oomph to push the bullet part way down the barrel. So, if the barrel was a bit shorter the bullet would have had a higher velocity than zero ft/sec!

The frustrating thing in this discussion seems to be that all of the observations seem to be correct but contradictory. That's why we need to dig into the physics. Then the apparent contradictions fall into place and are no longer contradictory.