OzFclass

plumbs7 wrote:

RDavies wrote:I went back and looked at the groups again and it hit me what the issue is. Everyone has been overlooking the most poignant question.

What , what ? I can't watch karate kid now!

What the hell is Matt doing out of his lathe cave and frivolously frolicking around shooting ranges when there is important gun stuff to be built??? Answer me that oh keyboard gurus.

Alan's been posting in his name?

BATattack wrote:Are the velocities your getting from an ET? Is this accurate enough to give reliable measurements?

From what I've seen FO calibers pushing the high BC bullets at high velocity hold accuracy out to 800ish yds even with often poor ES.

Velocity recorded with a Labradar, at this point have no reason to doubt it.
Matt P

I have one myself and testing it against the magneto speed and agreed they seem to be accurate and reliable.

I was just curious what you were using as a chronograph as you have decimal points on your speeds as mine only shows whole units?

If you use the SD card and down load it, there's a lot more info.
Matt

Like I always tell ppl chronys don't win competitions
accurate loads & wind reading do

Hey Matt what twist are you use for the 108?

RB

Raven’s comments are valid ones. It’s what shows on the paper that counts.

With regard to tune, the simulation programs using SD’s do not reveal the full picture in many cases as to what the muzzle is doing.

In this scenario, it is that third point of inertia I have explained before IMO which is responsible for the muzzle chatter. The chatter area will affect all tune types on a micro level compared to fundamental barrel swings. Whether they are the OCW tune which tries to tune out muzzle distortion; a harmonic nodal tune where vibrations are in balance; or a compensation tune where there is an intersection of high and low velocity shots at a specific distance.

Tests need to be repeated at distance in order to clarify the following e.g. a) was the rifle compensating at the short distance. b) Mid point trajectories are a good place to view vertical dispersion in relation to the trajectory characteristic of three distinct tune types mentioned above. c) Was the SD representative of a decent sample. d) How relevant is the SD to the style of tune?

My approach, and I only use a chrono for plotting initial charge tests to trace the fall of low and high velocities on the paper to identify the barrel tune type then to find the best tune on paper for that barrel’s natural condition, then add a tuner to the system to take it through its paces to see what tune type does with the tuner on and whether I can improve things. There are many ways to skin a cat. You could find the load with the lowest SD and use a tuner to change group shape. This usually applies to barrels showing muzzle distortion when returning waves interfere with bullet exit. You can have a low SD, but if the muzzle is being distorted the groups are not as tight as they could be. Bit like a poor crown. Other advanced methods can determine a suitable harmonic length for the barrel, extra muzzle weight to take out torque factors which mainly affect bag handling. Just a perspective.

RAVEN wrote:Like I always tell ppl chronys don't win competitions
accurate loads & wind reading do

Hey Matt what twist are you use for the 108?

RB

Hi Richard
It's an 8 twist Brux.
Matt

RAVEN wrote:Like I always tell ppl chronys don't win competitions
accurate loads & wind reading do

Hey Matt what twist are you use for the 108?

RB

How true that is. Many shooters put too much stock in figures & loose sight of the things that matter. Now before you all jump on me, what I mean is, the figures are a useful guide only, not the holy grail.
Keith H.

Boom boom Keith