Discussion in 'Practical Precision--PRS, NRL, ELR' started by VaRandy, Apr 21, 2017.
for barrels to answer lingering questions to a build problem I have.
That would be WILLIADA on OZFclass
May consider "Varmint Al". Here is a link to his website and contact info: www.varmintal.com
Recreational Software, Inc. (RSI)
Williaida will have your head spinning !
Post your Question on Ozfclass.com !
Call Eric Bostrom at RAS tuners. He wrote the book.
If anyone is interesting in Williada's teachings,Go to
ozfclass.com. Today there is a thread under Equipment and Technical
referring to Barrel Tuner's posted by PGCPTY ( my friend in Australia)
that lists a compendium of WILLIADA postings.
If you can't find out about tuners there, you are lost!
Keep coming back to this one. Really want to know what the question was.
There are some pretty knowledgeable people here. Ask away.
It is too complex to explain without phone or Skype session.
Here's a link to another thread:
Post #28 lists web sites/pages with good information. Some pages explain how positive compensation of barrel whip to bullet exit makes accuracy at longer ranges better than at mid ranges.
I've done a few tests at 1000 yards shooting 308 Win and two 30 caliber magnums slung up in prone chronographing each shot. 'Twas interesting to see some bullets strike above call with slower velocities 10 feet from the muzzle than others. And some of the faster ones struck below call. Not much in either direction; only 5 to 8 inches from call. With a hold area of 5 to 7 inches diameter, add those numbers to get the group size in best conditions for environment as well as shooter skills.
I think the small spread in bullet BC caused by the normal, microscopic unbalance they all have that made some nutate their tips a bit more about trajectory axis than the really well balanced ones. More unbalanced ones will have more drag and lower BC so they'll strike lower than perfectly balanced ones leaving at the same fps number with highest BC; all relative to the point of call.
Of course, none of us shoulder a rifle exactly the same after reloading each shot and that causes bullets to leave in a greater cone of fire. Match rifles shot from machine rests or F class positions may shoot half MOA at 1000 yards; best us humans can shoot them slung up in prone without artificial support (bags and bipods) is 1 to 2 MOA in good conditions.
Makes me wonder about the balance of any bullet. Some of Hornady's .308 match bullets are as much as .0004" out of round on the bearing surface. Definitely not for precision, just an example, I was looking at some 7.62x39mm bullets. My SKS is not vary accurate at any time but some ammo shoots much worse than others. Notably the Wolf FMJ. (a pattern, not a group) I cut a few apart and was surprised to see the lead was not distributed equally producing a heavy side. All 3 of these are the same weight, so the longer one has a much larger cavity in the nose allowing the mass to be more off center and out of balance. Probably to some degree all bullets suffer from this, especially any HP design. How much does this alter the path of the bullet when it's spinning maybe 170,000 rpm?
Years ago, a friend (7X Nat'l Champ) spun a few hundred Lapua 30 caliber D46 185-gr. rebated base FMJBT bullets in a collet chucked in a Dremel Moto Tool. An ampmeter was connected in series with the power cord. Bullets out of balance spinning 30K rpm drew more current than those perfectly balanced. They loaded the bearings with more centrifugal force. As I remember, a tool and die maker at Sierra Bullets made the collet to fit the Moto Tool. Some bullets were enough out of balance they flew out of the collet then bounced off walls and ceilings before coming to rest on the shop floor.
He took several dozen of the "perfect" ones to test in his Win 70 Hart barreled 308 Win match rifle clamped in a machine rest pointed at the 600 yard target. He shot several 10-shot groups ranging from 1.5 inch down to .7 inch. Then put one 40-shot group into 1.91 inch. The few unbalanced ones he shot ranged from 3" groups to about 15" ones. No wonder there were several fliers in each 100-round box.
Most interesting was his using a 50X optical comparitor looking at bullet ogive shapes across all. Four distinct different shapes were seen. Proof that four different bullet ogive forming dies different machines were used making that lot of ammo; no tool maker's bullet forming dies are exactly the same for a given bullet. Not surprising as Lake City and Frankfort arsenal's 30-06 and 7.62 match ammo had 3 or 4 different lots of bullets in each lot of ammo. No wonder the National Match lots shot just under 2 MOA in 600 yard accuracy tests. The best bullet machine's lots would shoot groups half that size if they were the only lot used in the ammo lot. No wonder military teams pulled the 173's from their arsenal match ammo then replaced them with Sierra 168's or 180's and get 4" test groups from their semiauto service rifles.... at 600 yards.
Interesting. I wondered how you could test them. You're right about the forming dies. Here are 2 lots of .308 bullets from Hornady, the Match 168 grain BTHP. I measured them from each end using their bullet comparator. The insert inner diameter is .299". Still you don't know if they are out of balance. I plan to try the Alco premium bullets sometime this year.
In spite of the fact that some rifle barrels whip and wiggle in the vertical plane such that slower bullets leave at higher angles relative to the LOS than faster ones positively compensating for their greater drop at target range and therefore are more accurate at longer ranges, some claim that's impossible.
Certainly not impossible, I've seen it.
I use a 208g A-max, (now ELD Match) bullet with 41.5 grains of Varget for long distance (loaded hot, not dialed in for accuracy) in my thin barreled Savage .308. About 2,430 fps. In testing with the same ammo, I got a 1-7/8 group out of 10 shots at 100 yards. (embarrassingly poor). At 215 yards it still shot 1-7/8". I moved out to about 500 yards and shot a 2-1/8 " group with 7 shots. I would like to try 1,000 yards but have no place close with the room. Harmonics? Bullet going to sleep? I want to repeat this with the Hornady ELD bullets which should be very close. Have to wait until the corn is harvested to get out to 500.
Good bullets go to sleep by the time they're 100 yards down range. But they don't change their trajectory path when that happens. The stay on the same path to start out but have higher BC's because their tips are not nutating (spinning in circles) about the trajectory axis.
It's harmonics; more correctly "positive compensation."
This calls for another test!
Get ahold of Mike Ezell. He is a very competent gunsmith and knows a lot about barrel harmonics and tuner related questions.
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