TargetTalk

I'm making a new tube and I have a piece of carbon fiber that is 18". My barrel is 16.5". My current tube is about 9". When I slipped the CF tube on at first, it seems comically long. So has anyone done any testing (anecdotal or otherwise) to find out if there is such a thing as too long? Assume weight is not a limiting factor.

As the tube gets longer (assuming you have the front sight on the end of the tube) your front aperture diameter will need to be bigger. I think that would be your first limitation ... how big of an aperture can you get.
Next, would be the trajectory of the bullet. You don't want it splashing around against the tube. If you had a 1/2" diameter tube, I think you'd bang the tube at about 4-5 feet. (22LR Std Vel)

Both of these cases would be ridiculously long.

My oldest daughter shoots a 15" tube which I think is too long, but she has learned to like it.
What did I know, it was the first tube I bought. Figured I could always cut it down, but she won't let me......

As above,

whenever you increase sight radius, it takes time to readjust. That said the sight radius you get from a 16.5in barrel + 18in tube isn't that actually long, it's only a fraction shorter than a standard 27in Anschutz barrel + 8in tube, which isn't uncommon. Your current set-up (16.5 + 9) produces a sight radius that's a tad shorter than a standard barrel + no tube, so naturally the longer tube will look very different.

Normally the factors that affect tube length are the stillness of your hold and weight. A longer tube will make any movement in your hold more visible. The more steady your hold, the longer the tube you can use, as seeing wobble can affect your shot timing. Prone shooters often use quite long tubes, but I see standing shooters who have tubes slide the foresight back along, or they swap to a very short tube, or even remove the tube totally. Even in prone, tubes over 12in don't seem common (at least where I am) on standard barrels, which suggests they are recahing diminishing returns .

Weight may not be an issue with lightweight Carbon Fibre, but it can be with aluminium. A 12in tube can weight 8-10z, which on the end of a 27in barrel can make the rifle quite muzzle heavy. The folks I know who use tuner tubes (heavier still) have had to add weight to the butt to re-balance the rifle.

If as you state your barrel is only very short you will be taking it out to roughly where most Bloop tubes end up. As stated you will need a firm joint for that length of tube.

I'd drill and tap a series of holes along the entire top of the tube, so you can try any sight radius before you decide where to cut it. Maybe even mill a 3/16" slot through the top of the tube and use a metal keeper inside the tube, just like how MEC Contact series butt plate height adjustment works. Your welcome to stop by and use my mill anytime.

Andre

Andre wrote:I'd drill and tap a series of holes along the entire top of the tube, so you can try any sight radius before you decide where to cut it. Maybe even mill a 3/16" slot through the top of the tube and use a metal keeper inside the tube, just like how MEC Contact series butt plate height adjustment works. Your welcome to stop by and use my mill anytime.

Andre

Except that tubes cannot be perforated, see rule 7.4.1.5.

A dovetail cut into the tube body, or a long dovetail block bolted atop would fulfil the same function within the rules.

Tim S wrote:

Andre wrote:I'd drill and tap a series of holes along the entire top of the tube, so you can try any sight radius before you decide where to cut it. Maybe even mill a 3/16" slot through the top of the tube and use a metal keeper inside the tube, just like how MEC Contact series butt plate height adjustment works. Your welcome to stop by and use my mill anytime.

Andre

Except that tubes cannot be perforated, see rule 7.4.1.5.

A dovetail cut into the tube body, or a long dovetail block bolted atop would fulfil the same function within the rules.

What is the thinking behind the anti-perforation rule? I can't understand it, not that I am affected by it. I know a little of the supposedly beneficial - but disputed - effects of porting in shotgun barrels, such as reduced recoil, but what unfair advantage is gained by any number of holes in an extension tube? I would have thought that, if anything, they might possibly de-stabilise the bullet in its transit. Puzzled.

As I see it, perforations in the tube wouldn't help in reducing muzzle lift - the bullet has already left the barrel if the propellent gasses are exiting holes in the tube.
The advantage to perforating the tube would be in dispersing the high pressure gasses and reducing any buffeting that the bullet experiences from the turbulent chaos around it while in the tube.

I could be wrong though.

I too have a 500mm length of carbon fiber tube that I intend to use with my new barrel - mainly to see if there is an optimum tube length for any particular length of barrel (AKA the Tony Purdy, PRX theory)...

K.

KennyB wrote:As I see it, perforations in the tube wouldn't help in reducing muzzle lift - the bullet has already left the barrel if the propellent gasses are exiting holes in the tube.
The advantage to perforating the tube would be in dispersing the high pressure gasses and reducing any buffeting that the bullet experiences from the turbulent chaos around it while in the tube.

I could be wrong though.

I too have a 500mm length of carbon fiber tube that I intend to use with my new barrel - mainly to see if there is an optimum tube length for any particular length of barrel (AKA the Tony Purdy, PRX theory)...

K.

Yes, that explanation makes sense, though I'm a bit surprised that there is enough science in this area for the ISSF to act upon. I should have added that presumably the holes would have to be exactly and symmetrically placed to even out any de-stabilising effects, and who knows where they ought to be precisely placed for them to be truly advantageous, especially as the bullet will be on a slightly loopy trajectory, so different holes would have different effects. How anyone could tune the holes, as on a musical instrument, is entirely beyond me. Still it has obviously given the ISSF a bit more useful legislation to enact.

It's all quite interesting, however, especially for those of us - and there do seem to be few - engaged in making our own extension tubes. Mine has the twin aims of cheapness and lightness. I'm using fairly thin aluminium tubing, having considered carbon fibre, which would, however, probably require aluminium pieces at either end for fastening and affixing purposes, or so I concluded. I am currently revising my method of affixing the foresight. Bolting an Anschutz dovetail onto the aluminium tube is none too easy, I find, so I'm now going to machine a 4 inch strip of dovetail and glue it in place. All good fun, keeps me off the streets, and it might even work, if I'm very lucky.

I think the subject of too long is a matter of preference and the ability of your hold. I have been using a ten inch tube on my anschutz 1907 for the last few months now; this is the first time I have used a tube beyond a trial test in the 9 1/2 years I have been shooting. So, my sight line with barrel and tube is 36 inches long. Personally, I love the tube in prone, it has helped my prone be more consistent and I am more likely to shoot a deep ten as opposed to a scratch ten. It is somewhat nice in kneeling, although I do not like the 10 inches in offhand as my hold is not very good. I think a total sight line, if I am using the correct term, would be good at about 32 inches or so, just from my personal opinion, and only that. The tube does help you see more movement and can make your aiming more precise, but if it causes you to overhold, than there is no point. There are many top shooters who do not use them (more international, they are very common in the U.S.), which was part of the reason why I have stayed away from them for so long. I do see a reason for them now. At the very least, I would bring your sight line up to 26inches. As for the matter of too long, I did a trial run for a practice and just for fun with a 14inch tube, so a total sight line of 40 inches. This was way too long; I could still shoot okay, but it put a tremendous strain on my eye. Bloop tubes can help vision problems, but I know now that at least for me, there is such a thing as too long.

-Zach

I very much apologize for steering this thread off topic.

His sight base does not mount with a dovetail, it's screwed on. So to follow the anti-perforation rule and still have adjustable sight radius he'd have to get a new sight base. (Get a FWB one!!!)

You don't have to follow ISSF rules if you don't shoot ISSF competitions though. Even NRA allows those flat bars.

My 10" one has a series of holes in it so that I can try the foresight at varying distances. He had a supply of Anshutz threaded cap screws so that all holes are capped, this works well. He went this way as he has had problems grooving the Aluminium, with it deforming when the sight was fitted.

Cumbrian wrote:

Tim S wrote:

Andre wrote:I'd drill and tap a series of holes along the entire top of the tube, so you can try any sight radius before you decide where to cut it. Maybe even mill a 3/16" slot through the top of the tube and use a metal keeper inside the tube, just like how MEC Contact series butt plate height adjustment works. Your welcome to stop by and use my mill anytime.

Andre

Except that tubes cannot be perforated, see rule 7.4.1.5.

A dovetail cut into the tube body, or a long dovetail block bolted atop would fulfil the same function within the rules.

What is the thinking behind the anti-perforation rule? I can't understand it, not that I am affected by it. I know a little of the supposedly beneficial - but disputed - effects of porting in shotgun barrels, such as reduced recoil, but what unfair advantage is gained by any number of holes in an extension tube? I would have thought that, if anything, they might possibly de-stabilise the bullet in its transit. Puzzled.

ISSF rule 7.4.1.5. is if I recall correctly there to ban the fitting of a muzzle compensator system, as seen on many centerfire caliber pistols. Mind you there is a lot more recoil on a CF pistol, and given the way that they work they also tend to still have substantial barrel pressures at the muzzle and even for a short period after the bullet has exited the muzzle. The rules are worded to prevent any holes in the barrel behind the apparent muzzle, so that there is no wriggle room for compensators. The ISSF are very anti any active systems for aiding shooters accuracy too, so the rules are not surprising)

Alan