223 Build - what barrel length??

[bruce moulds]

ian,
if i were persuing ftr, that is the direction i would be travelling for the reasons you mentioned.
i believe that a long barrel, although less stiff than a short one of the same weight, can be quite accurate.
i regularly talk to a californian who is doing this sling shooting 800, 900, & 1000 yd, using re 17 and a special chamber for the job.
laurie from york has done a bit of damage with a 90 gn 223 load.
keep safe,
bruce.

[johnk]

Bruce,

There's a thread that may develop further on the BR Central website where one correspondent suggested that longer, whippier barrels were more forgiving/manageable than shorter, stiffer tubes, claiming Varmint Al's website ( http://www.varmintal.com/index.htm ) prototyping for authority. Reference was also made to Bill Calfee's work with swamped barrels (otherwise referred to as reverse taper) on his XP100 rimfire benchrest pistol conversions ( http://www.hunt101.com/data/500/Calfee_7_8_12_one.jpg ).

All of which got me thinking about my all time best & most consistently accurate field rifle, a Husqvarna .243 built on their small ring Mauser action (not the later model 3000 abortion). It had a particularly robust aft barrel profile & a quick front taper compared to Winchesters & Remingtons of the day.

It might be interesting to poll results of Palma style barrels compared to HV & stiffer profiles.

John

[bruce moulds]

john,
you raise an interesting point.
what i have observed from many ladder tests is that thinner barrels have nodes as do thicker ones, but with thicker ones, the nodes are closer to each other.
this gives the illusion that thick barrels are more accurate, but when the thin ones are in a node, they are equally as accurate as thick ones.
this is for light varmint to truck axle profiles.
reverse taper and barrel tuners seem to come under the same heading to a degree.
following from the above trains of thought comes barrel block bedding. this shortens the oscillating part of the barrel, hence stiffens it.
an experiment i would like to try would be to bolt a 3" wide plate on the muzzle end of a barrel and rest this on the front bag.
the weight of it would dampen muzzle vibration like a tuner or reverse taper, as would the fact that it is sitting on a bag supporting the weight of the front of the rifle.
the plate could be moved back and forth like a tuner.
if it worked, the rifle would require no forend, so the weight of the plate would be somewhat negated.
this would offer a long support base between front and rear rests, and a low centre of gravity.
the possible disadvantage is that it would require an absolutely consistent hold and rest setup for group consistency, the barrel not being floating.
just some thoughts going through an old addled brain.
keep safe,
bruce.

[johnk]

an experiment i would like to try would be to bolt a 3" wide plate on the muzzle end of a barrel and rest this on the front bag.
the weight of it would dampen muzzle vibration like a tuner or reverse taper, as would the fact that it is sitting on a bag supporting the weight of the front of the rifle.

Bruce,

Sounds like the mechanically fitted BP front stuffers now.

Your description there of relative node frequencies (repetitions, not oscillation characteristics) was an epiphany to me. I've never understood what you guys were talking about with nodes, but essentially, what you said describes occasions when the projectile exits when the barrel is vibrating in a desirable range/direction, doesn't it? Of course, a stiff (and/or short) tube would have more "nodal" occurrences than the lazy slow vibrations of a long barrel, but the latter's directional sweet spot would be sustained for a longer duration & perhaps consequently be more forgiving.

The reason that it's taken me so long to get here is that I started playing the tuning game arse about with match rifles. There the aim was to generate the maximum velocity from a .308 with big pills as a first step, then tame the bugger to acceptable accuracy - which is why I'm a fan of tuners. Back in 2002, I found that I could load a 210 grain projectile to high 2600 velocities with a velocity spread under 20 fps (more recently under 12), then fiddle the output with a small barrel tuner (around 2½ ounces) until the load could be induced to group acceptably to 1200 yards. With one exceptional barrel, that tuner setting was valid for a number of projectiles in the 200-210 grain range while I used the same powder. The reason that I went for the velocity spread first was the potential for vertical that velocity variations can (& likely do) have at 1200 yards.

John

[bruce moulds]

john,
bpcr guys tend to try rest the barrel on a null point or a point where the barrel is in a point of no oscillation. (antinode?)
possibly this is what we look for at the muzzle. either that or at the apex of an oscillation.
finding a null point can be done by tapping the barrel in different places with a plastic hammer while listening to it with a stethoscope, or if it has flats, putting flour on it and tapping it with a hammer and looking at the patterns that form. i believe the old dead guys used to hang a metal ring on the barrel and tap it, observing the ring bouncing or not.
this is a most interesting subject.
of course as the range lengthens, so does the importance of velocity s.d., and of course consistent bullet b.c..
then we get changes due to fouling altering in the barrel. the old creedmoor guys solved the latter by cleaning every shot.
i will be offline for a week,starting matchrifle tomorrow, then the hunt, then the queens, 300 shots in all.
keep safe, bruce.