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Thanks. I think people (me in particular) have been confusing the issues around barrel harmonics (barrel whip, oscillations etc) with nodes, thinking they "cancel out" at some certain velocities. The S&L has a very slim barrel, and powder choice (and the corresponding effects that has) as much as anything predicates how it will shoot.
A thin barrel of very high quality will have less "barrel whip" (hence induce less cross velocity) than a poor-quality thick barrel
Here is the ladder shot today with the LVR, just no comparison or group but worth including to give a full picture. It has one more round cause I don't really trust some of the ball type powders, hence starting a bit lower (relative to the 2206H)
Attachment 269873
Whats that 26/26.3 grn velocity about? 300 fps jump for .3grn
I'd guess transcription error. 2963.
Oops - yup. 2963Quote:
Originally Posted by gimp
You are not including the other very important factor in equation.the one that can have,and often does have the most impact on impact destination ( see what I did there lol) the nut behind the butt will change things by huge amount or you either having a bad day of just not in the zone. I know personally if my back is sore I can't shoot for shit.a mild headache or tired eyes do the same. A wise man once said to call it honestly. If you think your wobbling around 2" you sure as shit won't group tighter than that.
Quite right MD, that with enviromental considerations . . . I always make a call on how good my "hold" is for that day, in good morning light when my eyes are at their best I reckon I can hold to about 0.5 MOA but as the day goes on so does my concentration and eyesight and my hold can easily balloon out to over 3/4 MOA, and being a bit tired or grumpy and some wind, then a 1.00 MOA hold is as good as I can do.Quote:
Originally Posted by Micky Duck
If I'm shooting someone else's rifle I always take something of mine I know is going well as a "control", both for myself and them too sometimes.
Been thinking this through at idle moments - all things being equal I'm not sure barrel 'quality' will have that much effect on how the tube performs for 'whip' or resonance.Quote:
Originally Posted by gimp
Quality of the barrel work will have a huge effect on how the barrel performs for accuracy, cleaning and velocity sure, but as far as I can work out the type of steel used for barrel construction is fairly equivalent (cro-moly vs 416 stainless - maybe one or two options with other construction methods like carbon wrap but for the purposes of this I'm happy to ignore those). So all things being equal, and both options being the same caliber and length the barrel with the most mass will be stiffer and have less whip (thicker walled). Two barrels of the same mass but different lengths, the shorter will have less whip (thicker wall section on the tube). Two barrels of the same mass but different lengths (longer one fluted) the shorter barrel will be stiffer but if they have the same length and mass but one is fluted the thicker wall section should be slightly stiffer (but not as stiff as if it wasn't fluted).
More mass = stiffer + less whip and I'm not sure that there is any way around that. The quality issue comes in to the repeatability of the barrel where things like how concentric the bore is (did the driller get it in the middle of the stock), smoothness of the rifling, general quality and accuracy of the machining work and also how good was the heat treatment/stress relieving was. That's a major which effects how evenly the barrel shifts as it heats up and again all things being equal the heavier barrel heats up slower so shows less variation here. But that still doesn't affect 'whip' as such.
The slimmer tube might heat up quicker and show more effect with temperature, and will have more barrel whip than a more cheaply machined but thicker walled barrel. But I'd say it is a fair assessment that barrel whip is only one factor that affects performance and repeatability - trying to shoot some rifles in freezing temperatures shows a huge difference in POI and 'zero' as the bedding tensions have changed. A rifle that shows this sort of variation is a good candidate for bedding work...
Barrel whip is largely a function of straightness and concentricity of the bore. Bore diameter consistency also affects principle axis tilt of the projectile.
Regardless, if we zoom up one level - it's sort of immaterial. If you want good results consistently, you want to get a very high quality barrel. It is observable that good cut rifled match barrels of thin contours provide the sort of precision that loses benchrest matches. It's in the same ballpark. I'm getting benchrest-match-losing 5rd group sizes with factory match ammo from a sporter weight barrel. Whatever characteristics are providing that precision is sort of irrelevant. Consideration of the game you want to get involved is probably wise, if you really want to compete in benchrest you may as well use up every gram of the weight allowance and get a fat tube.
Quality barrels simply do not move measurably with temperature, inside the kind of use cases that are actually practical. Yeah if you sat and continuously fired it for 200 rounds the precision may degrade. Precision degrading in 3 rounds due to "barrel heat" is a joke. 10-20 rounds with most cartridges doesn't seem to be a problem. If your group "opens up with heat" it's one of 2 things - your barrel is defective, or you are not measuring your precision properly in the first place and misinterpreting that.
Bedding problems are a defective rifle. Don't get or keep a defective rifle.
No expert but 23.3-23.6 seems to be the smallest gap in velocity. I would have done that ladder 3x to see if it was repeated. Then go middle of road and do a seating depth test for groups
