Optimim barrel length for velocity, match ammo?

[TimK]

This has probably been covered before, but my Google Fu is weak this morning.

Has anyone looked at the optimum barrel length for max velocity with match type ammo? I have a new Savage MK II with a heavy 21" barrel. I assume the long barrel is designed to try to get max velocity out of high speed ammo. The Wolf Match Target and Eley Target ammo I'm using are both so slow, I wonder if a shorter barrel might actually improve velocity.

 

[9H_Cracka]

Re: Optimim barrel length for velocity, match ammo?

Depends on what your definition of "optimum" is.

Given that your goal is to remain subsonic, plus taking into account a 22LR generates its max velocity in about 12 inches of barrel, three other factors generally drive "optimum" 22 LR barrel length:

- sight radius
- rifle balance/weight
- the tightest spot in the barrel being the last thing that touches the bullet

I own two accurate (as in one won the National 3P Championship 8 times) 54-actioned Anschutz rifles. Both have the following in common:

- 24 inch barrels
- threaded rather than pinned actions/barrels
- trued receivers
- some method of "choke" for the barrel

Rifle #1 has the end of the barrel turned down for about 2 inches, then a barrel diameter metal sleeve on the outside of it. The sleeve was made undersize. In order to fit the sleeve, the barrel was frozen, then the sleeve heated, to fit the two parts together. Once cooled they become one, while inducing choke to the barrel.

Rifle #2 has a Benchmark reverse taper barrel. The barrel is a button barrel, therefore the more metal on the outside, the more resistance the button has on pushing the metal out of the way. A combination of the lapping as well as the reverse taper result in the muzzle being the tight spot in this barrel.

If one were inclined to modify a rimfire barrel they have in hand to achieve an optimum accuracy length, the most important element in doing so would be finding the tight spot in the barrel and cutting it there.

Bill Calfee has written numerous articles on this subject, including a do it yourselfer's guide to slugging a barrel and learning what its interior dimensions are like. The bottom line is, if you have a "trumpet" barrel, that is a tight spot prior to the muzzle, your barrel has a low likelihood of producing good accuracy.

 

[TimK]

Re: Optimim barrel length for velocity, match ammo?

I had no idea the subject was so complex. I was hoping for a few more FPS because I've run out of elevation at 200 yards. I totally forgot about staying subsonic. I guess it's time to break out the chrono and see what I'm getting. Also just ordered a 25 moa base to fix the elevation problem...

Once I get that Eley from you, that is!

 

[9H_Cracka]

Re: Optimim barrel length for velocity, match ammo?

Tim, my experiences with the 17 mach 2 of late have me focusing again on the 22LR and staying subsonic for a long range rimfire platform. At 300 yards I get serious keyholing, though a somewhat predictable POI and about a 6" group. The issue is I also get some serious fliers at that distance.

I'll try to get that brick of ammo in hand later today - when will you be down the hill?

 

[TimK]

Re: Optimim barrel length for velocity, match ammo?

I'll take two if you can get them, and I'll come running whenever you have them. WIll be rolling through COS on Wednesday afternoon if that works out...

 

[Nocalphoenix]

Re: Optimim barrel length for velocity, match ammo?

9H,
I understand the concept of a reverse taper and choking the barrel at the muzzle. Can the same method be used with firelapping? In my revolvers and rifles set up for cast bullets they are all firelapped to both smooth the barrels and to achieve a slight choking effect at the muzzle. The theory being that the abrasive material is most aggressive towards the breech end and less aggressive as it is consumed traveling down the barrel. I have never played with it on a .22 or rifle intended for jacketed bullets but I can say in my revolvers I have seen accuracy go from 6" at 50yards to 2-3" at 50 yards which is about as good as I can hold with open sites. The barrel does have some choke to it, pushing a slug through is definetly tight all the way to the muzzle, but I really dont have any means of measuring it.

 

[VYD]

Re: Optimim barrel length for velocity, match ammo?

I have read somewhere that 16" barrel is the most efficient for .22LR and that there is no gain in velocity with longer barrels. Don't take my word for it though...

 

[9H_Cracka]

Re: Optimim barrel length for velocity, match ammo?

Not a clue Norcal - but if you slug your barrels you can find out for yourself.

 

[frog5215]

Re: Optimim barrel length for velocity, match ammo?

The barrel smith Cameron Dearborn laps a taper into his rechambered/recrowned stock Ruger 10/22 barrels with results that rival expensive custom or semicustom barrels.

 

[TOP PREDATOR]

Re: Optimim barrel length for velocity, match ammo?

i haven't gone down to 16" yet, but...

http://www.snipershide.com/forum/ubbthre...639#Post2137639

 

[TimK]

Re: Optimim barrel length for velocity, match ammo?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: _9H</div><div class="ubbcode-body">
Bill Calfee has written numerous articles on this subject, including a do it yourselfer's guide to slugging a barrel and learning what its interior dimensions are like. </div></div>

Leo,

I searched and found lots of discussion about Calfee and his methods, but couldn't find the actual DIY slugging procedure. You wouldn't happen to have it bookmarked, would you?

 

[9H_Cracka]

Re: Optimim barrel length for velocity, match ammo?

Tim, it was in an issue of Precision Shooting Magazine. I just threw away 7 years worth of them. He publishes on paper, not the Internet.

You might be able to contact the publisher. I believe the article was titled, "Take this barrel and SLUG IT!!"

A friend of mine slugs his barrels. I'll email both of you and see if he has anything in writing.

 

[ipscmaster]

Re: Optimim barrel length for velocity, match ammo?

Please help me understand what good "slugging" a barrel does. It will only tell you what the smallest dimensions of the barrel are.If the bore of the barrel is different in size, I would think it would not have much chance of accuracy. Am I missing something here?
I find it quite interesting to learn of a method to tighten the end of a barrel to help accuracy and would like to hear more about this. Any information would be appreciated. Thanks

 

[TimK]

Re: Optimim barrel length for velocity, match ammo?

If you were to find the tight spot at some reasonable distance from the muzzle, you might consider cutting it there to improve accuracy. I plan to check mine, but haven't yet.

 

[LongArm]

Re: Optimim barrel length for velocity, match ammo?

Does anyone have a write up on how to do this. I am looking to cut my barrel down to 16"