FPS of .22 LR ammo bolt gun vs. semi auto.

[Mike38]

Will the feet per second readings of .22 LR ammo be lower in a semi auto rifle vs. a bolt action rifle, all other things (such as barrel length) being equal? The results I'm getting are around 100 FPS lower in the semi auto than a bolt action. Does that sound about right?

Thanks for the replies.

[tangolima]

.22lr auto loaders have direct blow back action. Its MV should be little or no different from bolt action. Having said that it is close to impossible to have everything the same except the he action type.

-TL

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[mikejonestkd]

the barrel inner dimensions in the semi auto are negatively affecting the muzzle velocity.

[Sharkbite]

I think the variations between different guns will be greater than the variation between bolt vs semi.

[FrankenMauser]

My son and I shoot Precision Rimfire competitions of various types (and organizations). Though he *mostly* shoots the same 10/22, I constantly bounce between a dozen bolt action and semi-auto rifles. (For various reasons - including different rule sets for each organization, which let me shoot different rifles in the class(es) that I prefer.)
After much testing, we gave up differentiating.
We now use the same data for all 16" barrels, the same data for all 18" barrels, the same data for all 20" barrels, etc. Unless a rifle is known to be an outlier, we only have a few DOPE charts that we use.

They shoot the same. We have found absolutely no reason to differentiate semi-auto data from bolt action data.

Some rifles are faster/slower than others, given the same barrel length. Extreme examples need their own data. But most are so close that it doesn't matter.
It is within the 'noise' and atmospheric changes that occur during a match.

If you have a semi that is shooting slower, it is just a slower barrel.

In centerfire rifles, it might be a measurable difference. But with typical rifles chambered for .22 LR, it is less than the noise within ES and SD. (Even with premium ammo.)

Slow barrels are outliers. But most barrels do the same thing, based on their length.

Temperature, HOWEVER, does matter.
A 15 degree difference between test days will show a change in your velocities. A 90 degree difference (very possible here, we shoot all year in the high desert) is MASSIVE!

[stagpanther]

I'm a hard core 22lr shooter like Franken--but I don't do 22lr comps so I view this question a bit differently than he does. First thing I'd say is the whole barrel length vs velocity thing in 22lr is virtually irrelevant because; well, there's only so much you can do with 3 to 5 grns of powder. In addition to that I personally have yet to discover conclusive proof in my shooting that high velocity 22lr ammo has any repeatable consistency advantage over sub-sonic or slightly over supersonic; although there are pro 22lr shooters who claim otherwise. I'm not aware of any high velocity which I define as 1,250+ fps that is placing consistently at or near the top at comps--maybe Fraken would know that better.

IMHO velocity variations are going to be due mostly to how fast the gun fouls (regardless of whether it's auto or semi-auto) and how long it can hold "it's sweet spot" before fouling out of the game. That's going to rely on more factors than simply barrel length or action type IMO.

[gwpercle]

Just pick the action type you want ... when it comes to 22 LR there is little or no difference in velocity .
In fact the inner dimensions after rifling will give different velocities at times ...
barrels near the Min. tolerances will give faster velocities than a barrel near the maximum tolerances ... with the same type action ... Choose a 22LR by the action you wish to shoot and hope a barrel with Minimum dimensions , it all evens out in the end .
Gary

[jmr40]

Minor differences in the tolerances of a barrel will result in different speeds even with the same length barrel. Generally, a barrel with loose tolerances will be a little slower. If a semi-auto is manufactured with loose tolerances to enhance reliability it could be a little slower.

But that's not because it's a semi-auto. A semi-auto can be had with a target barrel and chamber and a fixed breach rifle could be made with loose tolerances.

[Mike38]

Thanks for the replies everyone. Learning something new is a good thing.

[10-96]

It wouldn't be all that hard to get numbers on that if someone had a Savage Model 87(?) which can be switched from semi to non-semi and a chrono. I'm guessing that would be about the truest test a guy could hope for in the OP's parameters.

[44 AMP]

The difference in velocity is due to the different barrels. Blowback semi autos don't open up any before the bullet is out of the muzzle, and no gas is "tapped off" to work the action, either.

The difference in velocity you are seeing has nothing to do with the action type it is well within the range of variation from one barrel to the next.

[Jim Watson]

A weird gunzine experiment. The author took a Ruger Mk II and built a fixture to hold the bolt closed when fired. Strangely, he reported LOWER velocities with the bolt locked, HIGHER with it left free to cycle in blowback. His theory was that as the case started to move in the chamber, it kind of rubbed itself into closer fit, better seal.

[44 AMP]

Strangely, he reported LOWER velocities with the bolt locked, HIGHER with it left free to cycle in blowback.

Without numbers, in fps or as a percentage of velocity change, there is no useful information. How much higher or lower?? 15fps? 150fps? more? less??

A significant difference is always detectable, but a detectable difference is not always significant.

[stagpanther]

Got my own crazy theory about that--(FrankenMauser might want to contribute). My opinion is that cartridge conformity to the chamber and bolt headspace are probably the biggest factors in determining consistency in 22 lr shooting. The tolerances are so far smaller than anything in the centerfire world you can't compare what works in centerfire cartridges to what works for 22LR IMO. I'm talking in the 10,000 ths of an inch realm can make a big difference in the way the pin/striker hits the rim and ignites the primer and subsequently how the ignition drives the bullet.

[Jim Watson]

Without numbers, in fps or as a percentage of velocity change, there is no useful information. How much higher or lower?? 15fps? 150fps? more? less??

A significant difference is always detectable, but a detectable difference is not always significant.

True, but I can't be much help on the minutae, it wasn't even in this century.

My Weatherby XXII has a "single shot" setting but I believe it still auto-ejects, not much help in this sort of comparison.

[FrankenMauser]

(FrankenMauser might want to contribute)

I tend to agree with your opinion.
In my experience and opinion, it is priming and rim support that are most important in the rimfire world.
Pretty much everyone (except Winchester and Remington) have powder charges *really* dialed-in for everything but bulk ammo, and they're consistent to roughly less than 3 milligram. (Which, I believe, is less than 0.05 gr?) (And much of the bulk ammo reliability issues seem to come back to cracked or broken priming compound from rough handling - but that is another discussion.)

As long as you have good rim support (which may require good headspace) and are shooting a quality brand with good priming, .22 LR should do well.

I have not previously considered chamber sealing, so I am hesitant to offer an opinion on that yet. I need to think about what I have seen; and, perhaps, solicit some valued opinions. But with a surface-level pass, I don't think that theory is reasonable.

That being said: I have seen and experienced the difference between "Match", "Bentz", and "Sporting" chambers.
It really does matter.
Sure, some people get 'Sporting' chambers that shoot really well, I am currently shooting a Bentz chamber in some matches (NRL22 with a Marlin 880SQ), and that same Bentz chamber got a class win in my last match. But, overall, it seems that the tighter you can get the chamber, the better any .22 LR will shoot. --If you have good rim support! Without good rim support, it doesn't matter what chamber you have. Performance will be erratic without good rim support.

[stagpanther]

That being said: I have seen and experienced the difference between "Match", "Bentz", and "Sporting" chambers.
It really does matter.
Sure, some people get 'Sporting' chambers that shoot really well, I am currently shooting a Bentz chamber in some matches (NRL22 with a Marlin 880SQ), and that same Bentz chamber got a class win in my last match. But, overall, it seems that the tighter you can get the chamber, the better any .22 LR will shoot. --If you have good rim support! Without good rim support, it doesn't matter what chamber you have. Performance will be erratic without good rim support.

Thanks for your insightful input. I have and shoot all three types of chambers. The chamber size and headspacing probably accounts for why rifles have different "tastes" for the type of ammo you can optimally shoot IMO. Take a high-velocity jacketed cartridge (1,250 fps+) and fire it in a match-chambered barrel headspaced to a precision cartridge like Eley or RWS you run the risk of picking small pieces of brass from your face (don't ask me how I know).

[stagpanther]

Without good rim support, it doesn't matter what chamber you have. Performance will be erratic without good rim support.

I think that's why we're starting to see custom 22lr actions that are doing away with "traditional" slotted barrel extensions in favor of totally supported rims and case head immediately above the rim. But these often require a new approach to feeding from factory magazines. But new development energy seems to be headed in that direction--it's great to see IMO.

[TruthTellers]

Originally Posted by Sharkbite

I think the variations between different guns will be greater than the variation between bolt vs semi.

Exactly.