How far back from muzzle to stop taper, for highest accuracy?

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by Max Heat, Sep 10, 2013.

  1. Max Heat

    Max Heat Well-Known Member

    Messages:
    385
    Joined:
    Feb 26, 2012
    I have a 32" barrel on order that will taper down to 1.00" at the muzzle (from 1.20 at the chamber). But it looks like I have the option to terminate the taper at some point BEHIND the muzzle, going straight cylinder (NO taper) to the muzzle from there. I'm thinking somewhere between 1, and 2 to 3 inches max?

    The length that best dampenss out the harmonics Is what to use, I presume. Too long taper setback, it that's what to call it, will result in some stiffness lose though.
    But I don't have even the slightest idea. Highest possible accuracy is the goal. Any ideas on what "setback" length might yield the highest accuracy potential?

    Is there anyeasymethod to "calculate" the optimum value for this paticualar dimension? (It is 0 right now, but I don't think that is optimum.)

    Cal is 7RUM w/9 twist, & muzzle will have 11 degree crown, WITHOUT a brake. Due to the backlog, I should still have plenty of time in which to make changes to the order.
     
    Last edited: Sep 10, 2013
  2. Fergus Bailey

    Fergus Bailey Well-Known Member

    Messages:
    219
    Joined:
    May 3, 2001
    The "best" is no taper. Why not keep it straight parallel couture from breach to muzzle? Sounds like you are planning on minimal taper anyway, so why not just keep all the material there.
     

  3. Max Heat

    Max Heat Well-Known Member

    Messages:
    385
    Joined:
    Feb 26, 2012
    With NO taper it will exhibit a stronger tendency to resonate, which is presisely what I wish to eliminate, as much as possible That's why THAT apporach doesn't go over so well with me..
     
  4. Fergus Bailey

    Fergus Bailey Well-Known Member

    Messages:
    219
    Joined:
    May 3, 2001
    I thought you wanted the best accuracy, not a theoretical discussion.

    My answer is based on actual results in competition in both short range and long range matches over 12 years.
     
  5. Max Heat

    Max Heat Well-Known Member

    Messages:
    385
    Joined:
    Feb 26, 2012
    You have a point there. Are you saying that a straight 1.20" cylinder will ALWAYS [noticably] trump out, over 1.20 to 1.00" taper, when it comes to accuracy?

    If so, I do need to give that option serious consideration.
     
  6. Fergus Bailey

    Fergus Bailey Well-Known Member

    Messages:
    219
    Joined:
    May 3, 2001
    Short answer, I think there is a very strong body of evidence that a straight taper is a better option from an accuracy perspective. You need to bear in mind here though that in ultimate accuracy, there are a lot of different, incremental elements that all lead to accuracy. Its not as if you can isolate any one of these variables and see an immediate difference on the target (at least in many cases - some are obvious". So I cant guarantee you a "noticeable" improvement - just a better chance to shoot accurately and maintain an accurate tune.

    When the cartridge in a rifle is detonated, there are a lot of forces at work, and no barrel contour is going to eliminate these effects. The best you can hope to do is minimise the vibrations and tune the best that you can. I believe the straight taper is the best outcome for this.

    I shoot a lot of short range benchrest, and in may classes, a barrel taper is required under the rules. However in unlimited (as the name of the lass suggests), there is no limit on the barrel taper. If you take a look at an unlimited barrel, you will see 99% of entries in the class have a straight taper. Likewise in F Class and long range BR where there are no contour restrictions, the vast majority of competitive shooters will be running a straight taper.

    Like I said earlier, based on my shooting, and discussions with very accomplished shooters, a straight taper is a better, more consistent, option than any taper. Its just a matter of whether your circumstances (eg governing rules in a competition environment - or equipment & tactics in a hunting environment) allow its use.
     
  7. Max Heat

    Max Heat Well-Known Member

    Messages:
    385
    Joined:
    Feb 26, 2012
    Thanks, mate! An american yankee redneck bloke like me doesn't normally use words like that, but I want to convey how much appreciation and interest I have in what you have to say.

    Since it will not be a pure BR rig, being taken "afield" quite frequently, I think I will stick with minimum taper. But I still haven't heard any suggestions on how far back from the muzzle to end the taper . I'm thinking 2.25". But that's basically for no other reason or rhyme than looks, aside from trying to avoid having it be a dividend of the overall length. Especially a low, even dividend. I'm try to avoid getting too technical, like I frequently do. But with ANY taper it is very difficult, without having to solve complicated differential equations, to come up with a solid [mathematically proven] solution for the optimum setback # that I wish to go with.

    I'd like to know more about BR rules and regs though, since I'd like to try my hand at it some time soon. I'd like to start out at around 3hun, then maybe move out to 6. Are there any "standardized" BR classes out there that are NOT open to the straight taperers, but ARE open to a 32 or 33" barrel, with 7RUM chambering? P.S. - Overall weight will probably be between 20 and 22lb..
     
    Last edited: Sep 12, 2013
  8. Fergus Bailey

    Fergus Bailey Well-Known Member

    Messages:
    219
    Joined:
    May 3, 2001
    Hi Max

    No worries. Glad you are finding it helpful. There is a lot in some of your points. Firstly, to the contour question, as that is relatively easy (short answer - more is better).

    I believe you benefit from the heaviest contour that you can find to fit within your weight constraints. Quite simply, the less material you remove, the better off you will be. The only counter-point to this is staying within your weight limit. So for accuracy and all round shootability, I would rate a #7 contour over a #6, but better again would be a #8 over a #7. Likewise, if you needed to cut a barrel, I would rather cut the muzzle than the chamber end (retain the heavier, stiffer section over the lighter section).

    I defy anyone to prove a theory that a given contour or barrel length is going to give you an advantage. A number have come forward with hypothesis, but none have been proven. For example in the early to mid 2000s, Bill Calfee (who is a very fine rimfire BR rifle smith) advocated a process of "ringing" a barrel to determine the best point to cut the muzzle and install a tuner so as to minimise any negative harmonics. This was debated on a number of accuracy forums for a some years. But when several very good BR gunsmiths tried Calfee's approach, they could never replicate the results Calfee claimed. There are plenty of theories out there, but the results in the winners circle are the only meaningful measure in my opinion (I have beaten people in competition, and then they explain to me why in theory they have better equipment than me!).

    Regarding benchrest, I would very strongly advise you to find local matches and go visit them. You will learn a lot and it will really help you decide what you want in terms of a discipline to shoot, and also the equipment you want to invest in. I believe too many beginners wait to attend a match eg "I am not ready to compete yet so I will practice for a month/year". This does them a real dissservice because they can learn any umber of bad habits on their own, and miss out on the really rich learning experience that comes with competition. Far better to get to a match early, have an open mind, and absorb the information that will come from very experienced competitors.

    Also, a lot of people that are new to the sport will invest in equipment (sometimes at considerable cost) that is not as well sited to competition as they had hoped. If you get in there with nothing, and see what successful competitors are actually using, you will be far better placed than doing research at arms length.

    I can tell you how much good stuff I have learned from competition. It REALLY helps all the other shooting I do.

    Benchrest comes in a number of flavors, but I will limit this to two primary categories. What is often referred to as "short range" BR, and is generally shot at 100 & 200 yards, with very limited matches at 300 yards, has light class (10.5 pound rifle) and heavy class (13.5 pond rifle). These classes have limits on barrel contours (amongst many other rules) that would limit the use of what you are currently building, and the caliber choice would also work against you (IE you will not be at all competitive).

    Perhaps a better option based on what you ave mentioned would be 600 yard BR. This has a light class which permits rifles up to 17 pounds, then a heavy class which goes from >17 pounds to unlimited weight. You will see the vast majority of competitors using light rifles at these events.

    Another alternative given some of what you have mentioned may be F Class open, which is shot from a rear bag and front rest, has a maximum weight rifle of 22 pounds, and is shot a one hundred yard increments from 300 yards to 1000 yards (and sometimes out to 1200 yards) from prone.

    I would encourage you to attend some matches, talk to some competitors, and see what looks lie your "thing". I am sure you will get a lot out of competition shooting if you put some effort (and unfortunately $$$) into it.
     
  9. Max Heat

    Max Heat Well-Known Member

    Messages:
    385
    Joined:
    Feb 26, 2012
    I'm trying to absorb everything you are saying. Sounds like there is a lot of wisdom behind it. I think the F class that you mentioned is probably the way I would want [and have] to roll, due to the weight issue. I AM really thinking about going completely untapered now, if it's unrealistic to think that I could have any chance at being competetive otherwise. But you say it best to first attend some matches, strictly as a spectator. They do happen to host 1000yd BR competition matches about 45 minutes away from me. I'll have to find out what the name of the club is, then download their match schedule.

    I did order the rock (not the BR version though) front rest 3 days ago, because I know I need to ditch the bipod, due to it's adverse effects on accuracy (with a sporter barrel, anyways). My budget IS limited, but it does make sense that I should see what equipment the highest scoring shooters are using, before I buy anything else, without having any idea what it's potential is. OK, I gotta go mull over this barrel taper thing for a while.