Bolt vs semi auto velocities with a 22

[mjbskwim]

So the scenario is a m39 marlin,22in barrel and a 10/22 with a 16in barrel
Distance is say 75 yards.
Both guys are shooting good and putting all hits in a baseball sized group
The guy with the m39 ores a hole thru the plywood but the other did not.
I said it would be the extra length of barrel not so much the semi auto action robbing gas. One of the guys figured it would be the action.
Has anyone cronoed? (Is that a word?)this?
Could be both or which one is the big factor?
Thanks
Mike

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[Andy54Hawken]

Accordingly to the NRA Firearms Fact Book , "the .22 Long Rifle cartridge seems to develop its maximum velocity in a barrel 20" long or less and the use of longer barrels actually results in lower velocities."

That being said I don't think a 22 inch barrel is going rob much if any velocity from a .22
Having shot against many a 10/22 with various .22 bolt and lever action rifles it seems to me that a .22 with a 20 to 24 inch barrel hits "harder"
Harder meaning hitting the gong with a louder "smack" or drilling a deeper hole into a target.
This is my memory and far from a scientific study , so take it with a large dose of salt.
Andy

 

[The Heretic]

It depends on the load. There are so many different .22RF loads that you would have to test with them. I have seen the same load in gel tests between a pistol with a 2" barrel and the 10/22 and the pistol of course was several hundred FPS less - the difference in the performance of the CPHP projectile was significant also - from the pistol it mostly did not expand at all, but gave really good expansion from the rifle.

As we say in my profession (software engineering); if you don't measure you don't know and the devil is in the details.

The action of most .22 RF semi-autos, including the 10/22, is blowback where the action stays locked until after the projectile has left the barrel, so while the pressure in the barrel is used to work the action, it won't affect the velocity of the projectile.

 

[tac]

Funny you should ask this stuff, as we did some testing a while back with some Eley standard 40gr ammunition, with an on-the-box stated velocity of 1040fps.

Using one of these fancy new magnetic doo-da's that you strap on the barrel, we shot ten shots each time from -

1. 16" bbl b/a Anschutz = 997 fps - es of 20 fps.

2. 29" bbl BSA Martini International MkII = 1051fps [!] - es of 17 fps.

3. 24.5" bbl Walther s/a in semi-auto mode = 976 fps - es of 23 fps.

4. 16" bbl Lantec AR s/a = 930fps - es of 9 fps [!].

Seems pretty definitive to me.

tac

 

[The Heretic]

Funny you should ask this stuff, as we did some testing a while back with some Eley standard 40gr ammunition, with an on-the-box stated velocity of 1040fps.

Using one of these fancy new magnetic doo-da's that you strap on the barrel, we shot ten shots each time from -

1. 16" bbl b/a Anschutz = 997 fps - es of 20 fps.

2. 29" bbl BSA Martini International MkII = 1051fps [!] - es of 17 fps.

3. 24.5" bbl Walther s/a in semi-auto mode = 976 fps - es of 23 fps.

4. 16" bbl Lantec AR s/a = 930fps - es of 9 fps [!].

Seems pretty definitive to me.

tac

I don't think that tells us anything except that those particular rifles give us those velocities. The Walther with the longer barrel than the Anschutz had slightly less velocity. That could be the chamber, the throat, the rifling or a combination of that.

Another saying we have in my profession, is that when testing/measuring/diagnosing, change one variable at a time. A different rifle model/make/style with a different barrel length equals at least two different variables changing. It would be more valid if someone took the same rifle, and gradually shortened the barrel to see the effect on velocity.

As I recall, American Rifleman did that with a centerfire rifle or pistol once, or maybe it was Guns & Ammo?

Ballistics By The Inch has charts for different cartridges, but they are calculated (and therefore theoretical, not empirical). The do have empirical data, but for different guns, not the same gun with the same barrel, being shorter and shorter.

BBTI - Ballistics by the Inch :: .22 Results

http://ammoguide.com/myag/articles/tloc54/Length_Velocity_Pressure.pdf

FWIW, while not all blowback actions are delayed (do not start moving) until the projectile leaves the barrel, almost all do not let any gas escape from the action until after the projectile leaves the barrel. I don't see how a blowback action would have any significant effect on the velocity of the bullet vs. a bolt action. There are devices for the 10/22 that will hold the action locked to eliminate the action noise with suppressors.

 

[tac]

'The Walther with the longer barrel than the Anschutz had slightly less velocity.'

Note that the Walther was also a semi-auto.

I take your point from a scientific POV, but the 'assumption' made here is obvious to a simple layman like me - shorter barrels = lower velocities in both semi-autos and bolt-action, for whatever reason.

Your comment about blow-backs is an interesting one. I've not actually encountered any blow-back semi-auto .22 rimfire calibre firearms that have the breech-block moving at the same time as the bullet. With the velocity [and mass] of the gas and the bullet coming nowhere near the mass of the breech block - by design - I don't understand how this can happen, even if for some reason there is no recoil spring. Surely, the only way that could happen is if the breech block actually weighed the same as the stuff going the other way? Equal and opposite reaction - that kind of stuff?

I'm not a physicist or engineer; my MSc and BSc are in remote sensing and GIS-related areas.

Thanks.

tac

 

[Certaindeaf]

I wonder if a feller could take a few readings from his semi-auto and then take a few more with his thumb keeping the bolt home. Probably not though.. seems pretty hard.

 

[The Heretic]

Blowback (firearms) - Wikipedia

 

[tac]

I wonder if a feller could take a few readings from his semi-auto and then take a few more with his thumb keeping the bolt home. Probably not though.. seems pretty hard.

Feel free to experiment and advise us of the results.

tac

 

[The Heretic]

Feel free to experiment and advise us of the results.

tac

Video and pics please.

 

[Stomper]

I wonder if a feller could take a few readings from his semi-auto and then take a few more with his thumb keeping the bolt home. Probably not though.. seems pretty hard.

Not as hard as putting your thumb over the muzzle to keep the fired boolit from getting out!

 

[The Heretic]

Not as hard as putting your thumb over the muzzle to keep the fired boolit from getting out!

I have seen people put their hand over the muzzle at gun shows.

The inevitable result was...

You guessed it - somebody shot themselves in the palm of their hand. I was at the show (WAC in Puyallup) and heard the shot. Their hand did not stop the boolit. I guess they learned that lesson?

 

[Stomper]

Stupid is as stupid does....

 

[The Heretic]

Not slow enough to really compare.

 

[Mark W.]

'


Your comment about blow-backs is an interesting one. I've not actually encountered any blow-back semi-auto .22 rimfire calibre firearms that have the breech-block moving at the same time as the bullet. With the velocity [and mass] of the gas and the bullet coming nowhere near the mass of the breech block - by design - I don't understand how this can happen, even if for some reason there is no recoil spring. Surely, the only way that could happen is if the breech block actually weighed the same as the stuff going the other way? Equal and opposite reaction - that kind of stuff?

I'm not a physicist or engineer; my MSc and BSc are in remote sensing and GIS-related areas.

Thanks.

tac

I have a blow back semi auto .22 its my Winchester Model 55 a semi auto single shot. It fires from an open bolt and once fired the bolt flys back to be caught by the sear and the casing drops out the bottom of the rifle. Sometimes right into your palm (but usually only once) Great rifle for kids as the safety is engaged as you press down on the top mounted loading gate. So if its loaded the safety is on until clicked off each time. I killed hundreds of squirrels and rats with the one my dad had. SO when I found a nice one for sale I bought one for myself.

 

[Certaindeaf]

Feel free to experiment and advise us of the results.

tac

I've done it.. no chrono though.
Here's a chap that did also.. no chrono

 

[mjbskwim]

'The Walther with the longer barrel than the Anschutz had slightly less velocity.'

Note that the Walther was also a semi-auto.

I take your point from a scientific POV, but the 'assumption' made here is obvious to a simple layman like me - shorter barrels = lower velocities in both semi-autos and bolt-action, for whatever reason.

Your comment about blow-backs is an interesting one. I've not actually encountered any blow-back semi-auto .22 rimfire calibre firearms that have the breech-block moving at the same time as the bullet. With the velocity [and mass] of the gas and the bullet coming nowhere near the mass of the breech block - by design - I don't understand how this can happen, even if for some reason there is no recoil spring. Surely, the only way that could happen is if the breech block actually weighed the same as the stuff going the other way? Equal and opposite reaction - that kind of stuff?

I'm not a physicist or engineer; my MSc and BSc are in remote sensing and GIS-related areas.

Thanks.

tac

Would not the force or energy produced by the round being fired replace the weight or equivalent mass needed to match the bolt weight?
And I ain't gots no fancy letters to put behind my name
I was hoping one of yalls had a crono.
@The Heretic ,I saw some test were the performance was the opposite of what the tester thought it would be with a 22 rifle and a pistol. It's been a while but I'll try it o find it
Was it the wound channel or was better with the pistol but better penetration with the rifle?
Like I say it's been a while since I read the article

 

[The Heretic]

The gel test I saw showed the penetration and expansion better with the rifle than with the little Beretta Bobcat.

Beretta:

I thought the same guy did the same test with a rifle but I can't find it.

Obviously, velocity has an impact on expansion and there is a minimum velocity that any given expanding bullet will expand at, so a person should understand the capabilities of their ammo.

Most of the .22 LRN ammo I have seen gel tests for do not expand in gel regardless of the velocity. The various HP ammo does to one degree or another. I have LRN and HP .22 RF ammo. The LRN ammo will be for practice and the HP ammo for hunting unless I want the bullet to not expand - mostly I think I do want it to expand - I think.

 

[Member 5605]

Next time I go to the range I will chrono..

I'll use an XT-22 bolt and a Model 60 semi. 18" on the Model 60 and 20" on the XT.

Will post results of you'd like... not sure how long you want to wait though may be a bit.

 

[Certaindeaf]

Next time I go to the range I will chrono..

I'll use an XT-22 bolt and a Model 60 semi. 18" on the Model 60 and 20" on the XT.

Will post results of you'd like... not sure how long you want to wait though may be a bit.

You need to cut the barrels down in 1/4" increments. We'll wait.
lol