|
Forum Rules | Firearms Safety | Firearms Photos | Links | Library | Lost Password | Email Changes |
Register | FAQ | Calendar | Today's Posts | Search |
|
Thread Tools | Search this Thread |
January 16, 2019, 05:00 AM | #1 |
Member
Join Date: November 20, 2016
Posts: 76
|
Bullet Concentricity important?
I have just drilled my seating stem to fit vld-bullets. It is probably not as precise anymore. How important for accuracy is bullet concentricity when seating the bullet?
|
January 16, 2019, 05:05 AM | #2 |
Senior Member
Join Date: June 23, 2013
Location: Central Taxylvania..
Posts: 3,609
|
Very important.
I'm sure others will be on here shortly to give you the scientific explanation/aspect of it. Lol
__________________
When our own government declares itself as "tyrannical", where does that leave us??!! "Januarary 6th insurrection". Funny, I didn't see a single piece of rope... |
January 16, 2019, 08:47 AM | #3 |
Senior Member
Join Date: September 2, 2010
Location: Plainview , Long Island NY
Posts: 3,863
|
J
Your loading low drag bullets for long range shooting 300 yards and out . Making our reloads as accurate as possible . You would have been better off calling the die company to send you a VLD stem . I see posts on drilling out the stem but the bit has to be dead center , not many can do that with regular home tools . How far are you shooting and how much runout are you getting ? |
January 16, 2019, 11:53 AM | #4 |
Senior Member
Join Date: March 1, 2009
Posts: 4,232
|
bullets are like people, electricity and water. When being inserted into a case neck that is smaller in diameter than the bullet itself it will follow the path of least resistance. If the neck is concentric so shall be the bullet unless you can make your neck go oval instead of round
__________________
“How do I get to the next level?” Well, you get to the next level by being the first one on the range and the last one to leave.” – Jerry Miculek |
January 16, 2019, 11:54 AM | #5 |
Senior Member
Join Date: February 7, 2009
Location: Southern Oregon!
Posts: 2,891
|
You mentioned bullet seating die modification and concentricity of bullets. Are you talking about bullets being out of round or concentricity of finished cartridge?
__________________
My Anchor is holding fast! I've learned how to stand on my own two knees... |
January 16, 2019, 02:15 PM | #6 |
Member
Join Date: November 20, 2016
Posts: 76
|
Finished cartridge. Shooting distance up to 1300yards. Just ordered a new vld stem.
|
January 16, 2019, 02:27 PM | #7 |
Senior Member
Join Date: November 6, 2001
Posts: 1,125
|
The old rule of thumb for seated bullet concentricity is .002" or less for targets and .004" or less for hunting rounds. Of course zero would be best if possible.
|
January 16, 2019, 05:05 PM | #8 |
Senior Member
Join Date: February 22, 2014
Posts: 868
|
Im with 308 and rg1
|
January 16, 2019, 07:06 PM | #9 |
Senior Member
Join Date: March 1, 2009
Posts: 4,232
|
http://www.nielsonbrothersarms.com/2...centricity.htm
some hard numbers from a test using .22 LR in a test facility
__________________
“How do I get to the next level?” Well, you get to the next level by being the first one on the range and the last one to leave.” – Jerry Miculek |
January 19, 2019, 01:53 AM | #10 | |
Senior Member
Join Date: April 10, 2012
Location: San Diego CA
Posts: 6,876
|
Quote:
I've since bought a new die with interchangeable stems but the old die works just fine still . The interesting thing I've founds since doing all that is realizing how different the ogives of bullets are in shape and length resulting in some fitting well in the stem while others kind of rock back and forth . Having one custom fitted/molded to your specific bullets would be the best idea I'd think . I kind of remember reading there is a seating die manufacture that does that very thing . You can buy a stem for the 190gr smk specifically or any other popular bullet . Forget the brand though , sorry .
__________________
If Jesus had a gun , he'd probably still be alive ! I almost always write my posts regardless of content in a jovial manor and intent . If that's not how you took it , please try again . Last edited by Metal god; January 19, 2019 at 02:05 AM. |
|
January 19, 2019, 06:51 AM | #11 |
Senior Member
Join Date: February 6, 2014
Posts: 128
|
Whidden will make custom stems, though I don't know if they will fit other dies.
they seem to be $40 per. |
January 19, 2019, 08:19 AM | #12 |
Senior Member
Join Date: November 17, 1999
Location: NW Wi
Posts: 1,671
|
Lacking a concentrically tool/gage, am still using the roll the loaded cartridge on a flat surface technique. If wobbling is evident, may want to consider evaluating why.
Concentrically may be one of the top accuracy concerns leading to buying a good Match seating die. |
January 19, 2019, 08:36 AM | #13 |
Senior Member
Join Date: June 21, 2016
Posts: 148
|
Back when we were loading for long range the rule of thumb was if it don't go in straight it don't come out straight.
|
January 19, 2019, 10:44 AM | #14 |
Senior Member
Join Date: May 15, 2012
Location: Texas
Posts: 2,566
|
Concentricity is important. At least it is to bench rest and thousand yard shooter, the rest of us, not so much.
|
January 19, 2019, 01:48 PM | #15 | |
Senior Member
Join Date: April 10, 2008
Location: Alaska
Posts: 7,014
|
Quote:
Houndogs link is truly amazing amount of work (astonishing actually).
__________________
Science and Facts are True whether you believe it or not |
|
January 20, 2019, 05:41 PM | #16 |
Staff
Join Date: March 4, 2005
Location: Ohio
Posts: 21,063
|
The results vary with the bullet. In the '60s, A. A. Abbatiello measured concentricity on samples from, IIRC, 42 lots of National Match ammo and got 1 moa wider groups from 0.004" of tip-tilt off-center. Beyond that much tilt, additional tilt made little additional difference, as the bore straightened out anything much more than that. This was 30-06 ammo using the 173-grain M1 Type bullet. When Harold Vaughn did it with stubby 6 mm bullets, the same amount of tilt gave only about half the dispersion.
The differences include how many calibers the bullet bearing surface is (longer is straightened out more by the bore) and how far forward of the geometric center of the bearing surface (where the tilt is centered) the center of mass of the bullet lies. The further forward (or behind) the center of mass, the bigger the orbit it has around the bore line for a given degree of in-bore tilt, so the greater is orbital speed. When the bullet exits the bore the bullet is tossed at that speed radially away from the mean trajectory path in a direction tangent to the bore where it is nearest to the center of mass at the moment of release. The drift due to that tangential toss was on the order of half a foot per second with the National Match ammunition, and that is too slow for drag to have much effect on during bullet time of flight, and thus it stays with the bullet all the way to the target.
__________________
Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle |
|
|