infoman jr.":3qv22hfe said:
I think many online claims of "cloverleafing" rifles are largely unsubstantiated.
Getting factory ammo to cloverleaf is highly dependant on barrel length, provided the barrel is a shooter to begin with. In other words, a poorly rifled barrel or one that is shot out isn't gonna shoot anyway.
Factory ammo is usually loaded to obtain a barrel time that is close to optimum in a certain length barrel but close on other length barrels. For instance, My 300 Win Mag likes 72.5gr of RL22 with a 200 Accubond .020" off the lands. That load has a barrel time of 1.405ms per QuickLoad. I worked this load up using the OCW method 2 years ago and had only heard of accuracy nodes and the science of barrel harmonics. Fast forward to this year and I look back at that load in Quickoad and find that it fell EXACTLY on a node for my 28" barrel. If I were to try that cartridge in a 27" barrel with the same throat, it would likely not shoot as well because the barrel time would be 1.376ms and the accuracy node for the 27" barrel needs to be 1.355ms. In order to hit that node, the charge would need to be increased to 73.2gr provided you didn't hit pressure first which would yield a barrel time of 1.357ms. For a 26" barrel, the load would be near 71.0gr in order to achieve the barrel time required at 1.388ms. A 25" barrel would require a barrel time of 1.335ms which would be a charge of 72.0gr. A 24" barrel would require a barrel time of 1.281ms which would be a charge of 72.5gr. A 23" barrel would require a barrel time of 1.228ms which would be a 73.5gr provided you didn't hit pressure first. If that happened, you would need to drop to the next lower node at a barrel time of 1.345ms and a charge of 69.3gr. From that data we just observed, the load for my 28" barrel would also work in a 24" barrel. Of course, it could be shot in other barrel lengths but accuracy wouldn't be very good. This is what makes it so tough to make factory loads that work in a variety of barrel lengths and throats.
That said, as you go thru a charge progression, groups will likely go from horizontal to a clover to vertical so when you are on the sweet spot of the harmonic node, the group will be a clover leaf.
Kyle Pittman and I were recently testing his new Pittman Accumax 275gr high BC jacketed 40 cal ML bullets in my new Savage/Rock Creek 40 cal Smokeless Muzzleloader and I was able to hit 3 different harmonic nodes with 3 different charges of the same powder. We only had a limited number of the test bullets to confirm their accuracy before production began. Therefore, all 3 loads had never been shot. They were hatched in Quickload and shot with absolutely NO tuning at all. You can see the 3rd group at 3288fps was vertical so the charge needs to be lowered a couple tenths of a grain. Also notice the distance between the harmonic nodes. 65gr Varget at 2577fps, 83gr Varget at 2925fps, 99gr Varget at 3288fps.
http://hanksmessageboard.freeforums.net ... in-testing
This is cool stuff. I'm having a blast learning and just thought I would share a little.