.22LR Velocity vs Barrel Length

slimjim · Posted: Sun Oct 17, 2010 5:35 pm Post subject: .22LR Velocity vs Barrel Length

I have a Marlin 39A lever action that I really like except for the 24" barrel makes it heavy compared to my other .22s, too long to be nimble in the brush, and a resultant forward weight bias. So, I'm considering shortening the barrel. I've heard other shooters say that 16 inches is the optimum barrel length for .22LR velocity. I had a day at the range breaking in my new AR barrel so shot my four .22s through my chronograph with a variety of ammo while the new AR was sitting idle while copper fouling was removed. The .22s were a:

Browning Buckmark Pistol - 7" barrel
S&W M&P 22 - 16" barrel
Ruger 10/22 - 18.5" barrel
Marlin 39A - 24" barrel

I was surprised by the results.

slimjim

Except for on, CCI Green Tag, all velocities continued to increased with barrel lengths longer than 16 inches. Remington bulk .22 ammo hand significant velocity variation, far worse than any other ammo and its poor accuracy substantiated the inconsistent velocity.

slimjim

Most of the target ammo had low standard deviation. Federal Target that I buy in bulk boxes at Walmart had the best group in the Ruger 10/22. Since my test results did not support a 16-inch barrel as optimum, I will start shortening the Marlin's barrel until I get the balance I'm looking for. I expect that will be 18 to 20 inches.

Pumpkinslinger

Good report! I'd heard at one time that 18" was the "optimum" length but your test doesn't seem to support that. I do wonder how much the action type influenced the results. I think the semi-autos would reduce the velocity some. You've got me curious though, might have to drag out the chrono and some .22s here!

slimjim

I think I'll shorten the Marlin's barrel to 20 inches and run this test again. That would be a more definitive test with only one variable being changed. I'm thinking 18.5 will be where I end up. I have to make sure I still have enough of the tubular magazine left to be useful.

TRBLSHTR

I tried this test about three years ago-with 22lr.I used a chrony gamma master chronograph and printed all results for comparison.I used federal bulk pack ammo,cci mini mags,and super x ammo.Guns were as follows;a 22lr derringer,a ruger slab sides 6" bbl target pistol,a std ruger 10-22,and a ruger 10-22 with a 20"target bbl.My results were that the short bbl's always were lower velocity than the longer bbl's.And that the highest velocityammo was always mini mags in rifle length bbls,and that the most consistant was the federal bulk pack ammo.The super x ammo-really did'nt pass muster with me!!!!!!!!!!!!!!!!!!

chambered221

I wouldn't be surprised to see you gain a little velocity and some consistency with a 20" barrel !!!

slimjim

chambered, I believe you will be shown correct. I initially thought that maybe Marlin's micro-groove rifling might be more efficient and that was why it was faster despite the longer length. However, when all but one round was faster, I had my doubts which only can be proven by shortening the barrel and running the tests again. It will most likely take 2 to 3 months before I have this accomplished. Gives me another item to add to the list of things look forward to.

Ominivision1

Hey Slim, I too took an old Stevens 22 rifle (it was my grandpas) which had a 24" barrel and chopped it down to 18" and re-crowned it. This was about 10 years ago and as this was a single shot bolt action chambered for short, long and LR. It used to shoot ok with the short and LR's, but after cutting the barrel to 18", it shot the LR with better consistency then before, but it would no longer shoot the shorts anymore, no mater what the short group averaged about 5" at 25 yards and the LR's were down to just under an inch.

I asked a local gunsmith about what he thought and he told me twist requirements were different between the short and LR. But over-all I'm happy I did cut the barrel to 18" and use the LR only.

The gunsmith told me that in the early part of the 19th century, these all-in-one 22 rifles were popular and the twist was towards the faster end because of the upcoming popularity of the LR cartridge.

slimjim

Thanks OV1. I think my barrel length will end up being how man cartridges I can get into the tubular magazine. I don't think I want to drop much below 12. I may cut it to 20" shoot it without a crown and decide if I want to go further.

Aloysius

Have a look at some german .22 match guns. Don't remember Walther or Anschütz but they only have a very short barrel inside a long pipe (to get their front side at great distance).
I've been told that a good .22 LR only need about 18 cm, that's about 7".
It's a pity you're commparing semi-auto's with normal bolt guns. So your Golden Boy will get some advantages from the barrellenght, but also because of it's closed bolt (be it from a lever action).
So as an extra when you're cutting down the barrel, maybe you can also compare the 10/22 with the Marlin at the same barrellenght? Then you might see the influence of the semi-auto system? (or will you only be measuring the difference in micro groove and normal groove?)
SJ, I hope you'll still get many years to go. You'll need them to get all your testing done Smile

(that's the stupid thing about shooting and reloading, even when you're already testing for more than 30 years, you still want to try something different to improve...)

Vince

Aloysius wrote:

SJ, I hope you'll still get many years to go. You'll need them to get all your testing done Smile (that's the stupid thing about shooting and reloading, even when you're already testing for more than 30 years, you still want to try something different to improve...)

Not sure about it being the stupid thing mate...but its definitely one of the most enjoyable parts about handloading and shooting.

Do you find that it is really necessary to shorten your barrel mate? I would be loathe to "ruin" a barrel, and possibly reduce the value of the firearm by altering its dimensions. Maybe a re-barreling job would better suit your needs mate.

Slim...don't forget mate that most .22 rimfires have a definite affinity for usually only one or two brands of ammo. What works in one may not necessarily (read usually won't) work in another. What I would be doing first up is finding that brand of ammo that your rifle "prefers", then start your adjusting of barrel length. You may well find that after shortening your barrel, you may have to go right back to "square one" with the different brands of ammo and start again. This is what makes it all so much fun in my mind. Enjoy the process mate.

Cheers, Vince

Aloysius

SJ, if it can help you: I looked in my stock and compared the Marlin 39A with 39M. Besides that the 39M has the nasty square lever that hurts your hand (and the 39A has the nice roundings), the 39A has a 24" barrel and the 39M only 20"
I've learned not to try to invent the wheel again, so there has to be a reason why the people at Marlin gave the 39M a 20" barrel... so I have to support your suggestion for the 20" barrel. If it works for them, little risk that it wouldn't satisfy you.
And don't ask me to measure the difference in fps between the 2 models. I have guns but no chrony, cann't shoot a chrony (and when you do, it's ruined Smile

)

slimjim

I love Marlin's 39A lever action but for one aspect, its too front heavy. Especially when you compare to rifles like the Ruger 10/22 or S&W M&P 22. I thought I would get a noticable velocity increase by shortening the barrel.

Vince, I plan on keeping the gun so its value because the barrel is shorten is not that big of a concern. I'm also trying to replicate on of the Carbine models. I've found 2 examples, 20" 39M and a 19.25" Carbine.

Aloys, there are not many pictures on the web showing how the tubular magazine is configured and where the insertion slot is. It would be very helpful if you could line up you to Marlin lever action 22s or just the 39M and take a good picture of the tubular magazine from the stock forward. Email it to me and I'll use it to figure out how to reconfigure my 39.

I'll redo my velocity test with the short barrel and post. Vince, as you said, I'll have to re-assess which ammo is best. I've got plenty of ammo to choose from since I stocked up on all I could store.

slimjim

I took the tubular magazine apart tonight. It looks pretty simple to shorten. I just need to have the barrel shortened 4.75 inches to get to 19.25 and move the dovetails the same amount while trimming that amount off the inner and outer tubular magazines tubes.