timing barrel

[PWS]

It's not even up to the level of a SWAG but I have a hunch that barrel curvature is tied directly to POI shifts when doing load ladders with cast bullets.

Most often when working up small game loads in sporter weight barrels, the groups move with increases in velocity, typically with both vertical and horizontal changes. The hope is that a light load will print on some useful aiming point within the scope when zeroed for a full powered load but they rarely do. Perhaps a 12:00 indexing will favor POIs along the vertical crosshair but I haven't taken the time to investigate whether there is any correlation between the direction of "barrel curve" and the line of dispersion? Probably be frustrating anyway...

 

[Stan Taylor]

My first blank was a Douglas almost exactly 30 years ago. I was a student at CST then and pretty sure we all used a Douglas that year. I still have that rifle today.

That's absolutely gorgeous thanks for sharing.

 

[Stan Taylor]

Dusty an Donavan you guy's won't give me a break at all.LOL

 

[Dusty Stevens]

It's not even up to the level of a SWAG but I have a hunch that barrel curvature is tied directly to POI shifts when doing load ladders with cast bullets.

Most often when working up small game loads in sporter weight barrels, the groups move with increases in velocity, typically with both vertical and horizontal changes. The hope is that a light load will print on some useful aiming point within the scope when zeroed for a full powered load but they rarely do. Perhaps a 12:00 indexing will favor POIs along the vertical crosshair but I haven't taken the time to investigate whether there is any correlation between the direction of "barrel curve" and the line of dispersion? Probably be frustrating anyway...

Like i said above, all you gotta do is change the bullet speed and itll exit on a different spot of its swing- its all about perfect timing of the exit not the static barrel itself

 

[tobnpr]

Not trying to beat a dead horse, but did want to provide the scientific evidence behind my opinion that muzzle "timing" is irrelevant. Models show the barrel's muzzle not only whips, but twists as well. Interesting stuff.
Some of you may have seen this before...I'll be the first one to confess that as a non-engineer, confirming their conclusions (or not) is above my pay grade.

According to the article, Butch used to make the tuner used...

http://www.varmintal.com/amode.htm

http://www.varmintal.com/aeste.htm

 

[Alex Wheeler]

I dont like getting into these discussions online. But theres some pretty serious testers as well as a very large barrel manufacturer that would highly disagree with the statement that timing is irrelevant.
Out of anyone I know thats tested it, none have said it didn't matter. I have seen enough, that I wont chamber one without timing it.

 

[zeke06]

I’ve played around with indexing barrels on rimfires. The picture shows 6 different positions I test fired the barrel. Almost always the best shooting are around 6 and 12 o’clock. I’d say about 65% of the time they shoot better groups at the 6 o’clock position. Every barrel is different too. The one in this test fire clearly showed the different indexes, sometimes it looks more egg shaped and others look like one big group.
I’ve only done this with rimfires and have seen enough of an advantage that every barrel I chamber gets indexed. It doesn’t take that much more time to do it anyways.

 

[Alex Wheeler]

Isolating one thing in any test is hard. But whats interesting is that different guys with different rifles types and calibers all have ended up with very similar test results.

 

[dmoran]

@zeke06
Myself have only spin tested center-fires (in fact only 6Dasher's), but can agree with your input well, to what I've seen also. One aspect I feel I definitely see is bad positions, where I definitely would not want the barrel timed at. Which were not near 12 o'clock on any barrels I've tested.

 

[butchlambert]

I'm curious as to how these were tested. Was the barrel clocked at different places of the clock or was the rifle rotated?
Gene Beggs did some testing in his tunnel years ago clocking the barrel in different positions. Gene figured out an attachment between the front ring and the barrel to allow him to rotate the barrel while maintaining headspace. I'll see if I can get Gene to elaborate on this.
On the tuner on Varmint Al's pages, Al did some tests with my tuner. The bottom of the last page on the link is the Shadetree Tuner. I kinda think the results that he was showing here are with another tuner.

 

[dmoran]

I'm curious as to how these were tested. Was the barrel clocked at different places of the clock or was the rifle rotated?

See my Reply #18 for pictures of my "spin testing chassis" setup.
From which the barreled action is clamped into the chassis, then rotated and shot in the different rotational positions desired.
I shoot groups in 12 positions, the same pattern of all 12 hours of a clock.
Have done it at both 100-yards and also at 450-yards (preferred the 450-yard results).

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[butchlambert]

See my Reply #18 for pictures of my "spin testing chassis" setup.
From which the barreled action is clamped into the chassis, then rotated and shot in the different rotational positions desired.
I shoot groups in 12 positions, the same pattern of all 12 hours of a clock.
Have done it at both 100-yards and also at 450-yards (preferred the 450-yard results).

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Donovan, My question is if it is the same just rotating the barrel as rotating the barreled receiver. Not doubting your word.

 

[tobnpr]

Gene figured out an attachment between the front ring and the barrel to allow him to rotate the barrel while maintaining headspace.

Interesting, would like to see that...that would certainly go a long way in terms of limiting variables that would also change. Similar to what Jmoran posted early in the thread.

I agree there would be validity with the rotating barreled action; for me, an immovable fixture with mass that could rotate with extreme precision that eliminates the aiming process (a variable) altogether would be an improvement to test the theory. Make sure that sucker can't move so much as thou in any direction under recoil, makes me wonder if such a thing would be possible (or advisable)

Good discussion.

 

[jrm850]

Someone could externally thread a donor action and make a collar retainer kind of like an AR. Either bush the internal threads or cut them out so you could make a precise fit with the tenon.

 

[butchlambert]

Here you go:

Hi Butch
Yes I came up with a differentially threaded bushing that fit in between the threads of the receiver and the tenon threads which permitted one to 'clock' the barrel in any position without changing headspace. The first action I tried this on was my drop port Viper which has 18 tpi threads 1.062 diameter. I had to reduce the barrel tenon to 1.000 and thread 28tpi. The bushing looked somewhat like a helicoil and was threaded 18 tpi on the outside and 28 tpi inside. It worked great and I shot it quite a bit in the tunnel.
Although it worked well, I decided not to pursue it further. For one, it complicated things and I don't think you would want to turn the average shooter loose with it. Someone like you would have no trouble dealing with it but I shudder to think what some would do with it.

I still have one barrel on the shelf with the bushing installed. If you're interested, I'll send it to you at no charge. If you want it, it's yours. It's fun to play with and most people just scratch their heads and say, "I see it but I can't believe it." If you have a Viper or Panda action It would be easy to fit it up. Of course, the Viper has a Remington type extractor and a flat breech. It cannot be safely used with a cone breech. It's also chambered in 6Beggs .269 neck.

The jury is still out as to whether or not it's worth it to carefully 'clock' a barrel in the receiver. To most shooters it would just be something else to worry about. I haven't fooled with it for years but you might have better luck than I did. It adds a lot of work to installing a barrel and I don't think people would be willing to pay what it would cost.

I had Bill Meyers fit up two new Turbo rimfire actions with my bushing system. One of them is now owned by Landy Landercasper and the other by Pete Waas. Bill and I both agreed that barrel clocking works. Is it worth it? I'm not sure.

 

[jrm850]

Here you go:

Hi Butch
Yes I came up with a differentially threaded bushing that fit in between the threads of the receiver and the tenon threads which permitted one to 'clock' the barrel in any position without changing headspace. The first action I tried this on was my drop port Viper which has 18 tpi threads 1.062 diameter. I had to reduce the barrel tenon to 1.000 and thread 28tpi. The bushing looked somewhat like a helicoil and was threaded 18 tpi on the outside and 28 tpi inside. It worked great and I shot it quite a bit in the tunnel.
Although it worked well, I decided not to pursue it further. For one, it complicated things and I don't think you would want to turn the average shooter loose with it. Someone like you would have no trouble dealing with it but I shudder to think what some would do with it.

I still have one barrel on the shelf with the bushing installed. If you're interested, I'll send it to you at no charge. If you want it, it's yours. It's fun to play with and most people just scratch their heads and say, "I see it but I can't believe it." If you have a Viper or Panda action It would be easy to fit it up. Of course, the Viper has a Remington type extractor and a flat breech. It cannot be safely used with a cone breech. It's also chambered in 6Beggs .269 neck.

The jury is still out as to whether or not it's worth it to carefully 'clock' a barrel in the receiver. To most shooters it would just be something else to worry about. I haven't fooled with it for years but you might have better luck than I did. It adds a lot of work to installing a barrel and I don't think people would be willing to pay what it would cost.

I had Bill Meyers fit up two new Turbo rimfire actions with my bushing system. One of them is now owned by Landy Landercasper and the other by Pete Waas. Bill and I both agreed that barrel clocking works. Is it worth it? I'm not sure.

I don't know about everybody else, but I would be on the edge of my seat waiting for your results if you decided to resume his experiment.

 

[GenePoole]

I'm still trying to figure out how that bushing would work. The barrel must register off something besides a standard type shoulder.

 

[jrm850]

I'm still trying to figure out how that bushing would work. The barrel must register off something besides a standard type shoulder.

I'm guessing that the inner bushing floats so to speak and the barrel shoulder still butts the action. 51° turn of the bushing should rotate the barrel 90°. I'm guessing he went with a 28tpi tenon thread more for space constraints than anything else. Would love to see pics.

 

[greisdor]

Zeke06 - do you have pictures of the result after you timed the barrel ? Did it shoot the same tiny hole ? Proof that it did work....

 

[GenePoole]

I'm guessing that the inner bushing floats so to speak and the barrel shoulder still butts the action. 51° turn of the bushing should rotate the barrel 90°. I'm guessing he went with a 28tpi tenon thread more for space constraints than anything else. Would love to see pics.

OK, I think I get it. With the different thread pitches on the inner v. outer of the bushing, you are essentially changing where the effective thread starts and hence where the barrel clocks. Pretty neat.

I too would love to see results!