KHGS wrote:Sounds like a mine field Keith. So when barrel "x" won't shoot and everything else is all top notch ( lets say it's a serious F Open rifle ) does the gunsmith straight away measure the bore ? And if they do how often is a problem found ?
Samples of the bullet to be used should be measured with a mic that measures to .0001", the actual measurement of the bullets will tell you what the accuracy problem (if there is one) is. Smaller diameter bullets are barrel selective, whereas barrels that are .0003" undersized are not bullet selective in regard to bullet size. These barrels will usually shoot all match bullets well. I am always wary of match bullets that are undersized they will shoot well in barrels that suit them, read tight barrels. If you have an accuracy issue with a given bullet the first order of business is to measure the bullet. If the bullet is indeed undersized it can be assumed that the barrel is true to size. If these bullets shoot well in another barrel it can be safely assumed that this barrel is "tight". As you say, this is after a full examination of the rifle does not uncover any. mechanical problem. As an aside, barrels that have shot well and have a low to moderate round count but "go off" the problem will more often than not be traced to carbon fouling or crown damage. This crown damage need only be very slight to create an accuracy deterioration.
Keith H.[/quote]
Sounds good Keith but surely if the boolit is being measured ya really need to be measuring the bore too, both lands and grooves ? I have a serious mic so that's no problem but can u explain the best way for me to get the bore measurements.
BTW I had a big name cut rifled target barrel measured once and the bore dimensions were NOT good. Very uneven cut depths. I got rid of it. My current barrel by the same maker has been very average in performance hence I'm getting to a place where I really want to know what's happening re the bore measurements. I started with the current barrel with Lapua scenars that measured 'oversize' and some very strange behaviours appeared on the range so I changed to another projectile that measured smaller and some of the problems went away and the on-target results improved dramatically.
I wonder too if the bullet to bore fit is excessively interference then that situation might be ok but with a slower powder, whereas running same with a faster powder will get u into excess pressure early ?
So without making this a looooong story about the barrels problems I would love to hear your advice Keith about how I can measure my bore. Regards Rob Kerridge