Distance from ogive to groves/lands.

[ernierod]

Just how much effect does the distance from bullet ogive to the L/G of the barrel have on accuracy??? Most match grade ammo, shoots superbly,from a rifle,with out regard to this distance. What am I missing experts/ Tnx

[F. Guffey]

What am I missing

The ability to discerning fact from fiction and truth nonsense. The first information dissimilated is about the 'bench rester', do it like the bench rester. Always omitted is the part about the difference between the bench rester gun and the gun used by reloaders. I like what Chuck Yeager said about the difference, same training, same plane, difference results.

I purchased a rifle at the Mesquite gun show, the seller was depressed, no one had anything good to say about his rifle. It was a magnificent 1903 before 1903A3 Remington, it had been modified to a hunting configuration By Santa Fe. I purchased the rifle for $150.00, he threw in two boxes of R-P ammo he purchased when he got the rifle from Sears. I took his old ammo with his rifle to the range. With open sights 'no scope the rifle stacked bullets on top of bullets. Had I been a bench rester I could have improved on the accuracy.

Why did I purchased the rifle? I needed the receiver. I have all the parts from an 03A4 to build a rifle with a 308 Norma Mag barrel that was removed from an 03A4. The receiver for that rifle was removed and then returned to the 03A4 configuration.

I have been informed the 03 Remington receiver is not worth much? Normally that provokes me into tapping and drilling, but there is not much I can do to improve on the accuracy so I applied the 'leaver policy' I am going to leav-er the way I found-er.

F. Guffey

[Bart B.]

It depends on how well centered the bullet is in the chamber throat, the bullet's ogive shape and the leade angle of the rifling. If all's perfect, jump distance doesn't matter much. Otherwise, it usually helps to have the bullet touching the rifling so it's better centered.

Some bullet ogive shapes lets them shoot more accurate with a few thousandths jump to the rifling; others need to be pushed into the rifling. Berger match VLD's often need a little jump to the rifling; Sierra's HPMK bullets do well seated to touch the rifling.

In any situatioin, it takes accurate stuff to tell the difference. Stuff equals rifle plus ammo plus shooter.

[ernierod]

As far as rifle accuracy-I am presuming a runout of less than 3 thousands is OK. I guess about 5 thousand away from L/G is a good place to start-correct?? Tnx for opinions. Cheers.

[hooligan1]

The Berger VLD bullet likes a bunch of jump in the rifles I have tested it in, some of my rifles like the BTip almost touching the lands.

Many loaders experiment with this measurement, try your own test see what you find and make yourself happy.....

F.Guffey, what did that rifle like as far as jump?

[AllenJ]

As far as rifle accuracy-I am presuming a runout of less than 3 thousands is OK.

What rifle are we talking about and what is it used for? For a hunter 3 thousands is more than OK but for a benchrest guy he may want better.

I guess about 5 thousand away from L/G is a good place to start-correct??

I'm afraid to say without knowing how you work up your loads. Typically I go by the book until I find where my rifle is showing pressure signs, then I'll start playing with CBTO to try and find the most accurate length.

[hooligan1]

Taylorce1 has a pretty cool method to find this "sweet spot" quickly, maybe he will post a link, Im not savy enough on a phone to get that done.

[Bart B.]

I and others have shot .308 Win ammo with 3/1000ths bullet runout seated to touch the rifling into 1/2 MOA at 600 yards. Such ammo will also shoot 1/4 MOA at 200 yards if all the other parts of the system are up to it.

[Mosin-Marauder]

How do you tell how far you are from the lands? I seat my bullets for my K-31 fairly deep due to the short throat. They chamber smoothly and extract smoothly.

[OzeanJaeger]

I look at it like carpentry. You get a collar and can calculate the ogive with a caliper, which is the measure twice and cut method, or you can get a headspace gage and push a bullet, which is the hold the board up and mark it with a pencil.

[Unclenick]

Ernierod,

Heres a link to Berger's information on the topic. It is what Taylorce1 reported using for his .243.

Read item 3 on this page for another perspective where a worn throat was involved.


Mosin-Marauder,

Search the forum. There have been numerous posts on this topic. One method is to make a gage by splitting the neck of a case (resized the way you normally size them) with a hack saw so it has a sliding friction fit with a bullet. You set a bullet into this gage case sticking out way too long, then press the case and bullet into the chamber until the case stops against whatever the headspace determinate is for this cartridge (shoulder, belt, rim, case mouth). That uses contact with the throat to finish seating the bullet. Next you push the case and bullet out together gently by using a cleaning rod or wood dowel inserted from the muzzle. This method of removing the two avoids disturbing the bullet position in the neck. You then measuring the COL you get this way. That is your bullet-contacting-the-throat COL. You set your seating die to make the COL shorter than that by whatever amount of jump to the throat you want to experiment with.

You can also buy several different commercial gauges for figuring this out if you want to. The Hornady LNL Overall Gauge plus their bullet comparator is a popular combination. The RCBS Precision Mic has a gage that uses a standard bullet shape instead of your bullet, so it's not quite as precise, but is typically as close as necessary. There is also a tool made by Sinclair.

[Mosin-Marauder]

Ive heard of that chambering a round that is seated way too long, just without splitting the case neck.

Article #6 http://www.swissrifles.com/ammo/reload1.htm

[Unclenick]

The neck split is just a way of letting you adjust the hold on the bullet. You can squeeze it tighter or spread it looser. If you don't split the neck, you have to size it so as to grip the bullet, but not too hard, or you jam it deep into the throat.

[Mosin-Marauder]

Ah, I see now. Thanks for your help, I'll have to try that when I get home.

[Unclenick]

Also, you don't want to use an unresized case unless you are neck-sizing-only, as you will then get a slightly longer COL in the result (by however many thousandths of stretch the case has in your chamber). Hollow point bullets aren't all the exact same length, so you usually want to select one that is average, then set your seating up to achieve that average less any amount of jump you want.

[OzeanJaeger]

Hollow point bullets aren't all the exact same length, so you usually want to select one that is average, then set your seating up to achieve that average less any amount of jump you want.

I did not know that. That surprises me. Is there something in the MFG process that makes it harder to get them to be uniform? I am a cheapskate for handguns and reload mostly hard cast, but I assumed that if I bought expensive HP bullets for hunting they would all be very close to specs.

In my state you can't hunt with FMJ or any bullet that doesn't expand, so I generally by HPs.

[Unclenick]

It depends on the bullet process and applies to pointy hollow points most of all. For Sierra MatchKings, it's not uncommon to find ten or twelve thousandths of an inch length variation in the same box. When you look closely at the tips, you see the final forming of the ogive leaves some straight across and some slightly tilted. It's not enough to affect aerodynamics much, though meplat trimmers are available as are pointing dies to be used post-trim for better symmetry. Some feel it is worthwhile to go to the extra trouble for 1000 yard shooting, but probably not for much else.

Most of the plastic tipped bullets are pretty consistent in length. Some soft points get deformed a little and vary. Some companies put bullets in the same bag that came off different sets of tooling that were not very well matched. So, it's actually worth checking any kind of bullet for that length variation before you depend on COL as a seating depth measure.

The various bullet comparators available seek to eliminate nose length variation by measuring further down on the ogive. But with mixed tooling, even those positions can vary. It seems to me it was about 0.003" variation on some Sierra SMK's I measured, but some Winchester bulk bullets I had at one time were three or four times that, IIRC.

[Bart B.]

In the Sierra hollow point match bullets I've measured from base to tip or a given diameter on their ogive, they have a few thousandths inch spread. My accuracy tests with them at 1000 yards shows that much spread in bullet dimensions probably causes ten to a hundred times that same spread in test group size. But it takes way too many shots per test group to make worrying about those "imperfect" bullets to sort them out to perfectly uniform lots. Just shoot them.

Sierra gets 1/4 MOA accuracy with them in their 200 yard test range. Such tolerances are last on the list of things to fret about for best accuracy.

[old roper]

Lot goes into bullets for match shooting and tools.

Here one that's help win LR 1000yd match at Camp Perry

http://www.sinclairintl.com/reloadin...prod38813.aspx

[firewrench044]

Finding the correct jump to the lands can improve the group size
5% to 20% ( every little bit helps in a match )
That small improvement helps a little a 200 yards and is a big difference
at longer ranges ( you will not see much difference at 100 or 150 yards )

Usually these bullets will be seated too long to fit into the magazine
so they will be loaded one at a time into the rifle

the distance can vary ( rifle/ bullet combination )

In my 308 and 3006 the Sierra 155gr and 175gr bullets shoot best
10 to 15 thou. off the lands
In my AR15 Bushmaster ( Bushmaster barrel made before Bushmaster
was sold ) the Sierra 80gr bullets like to be seated 25 to 30 thou.
off the lands
These rifles shoot best with Sierras, I have tried 4 different brands
to find the brand the gun likes ( the Bergers liked to be at 3 to 7 thou.
off the lands, the Hornadys also liked to be 10 to 15 off )

This is only one of many things you can do to improve Match ammo
when you load it ( making this special ammo can get quit expesive
match dies, comparators, bullet tiping, bullet pointing and finding the
correct combination )

[Bart B.]

That link to Sinclair Int'l's bullet meplat tool made by Whidden may well take 3/4 MOA off the bullet drop and a small amount of drift but so will an extra 25 fps of muzzle velocity. repointing hollow points may well uniform bullet shape to decrease drag and make BC more consistant, but it's not the only way to do it as is often claimed by its maker.

Spinning bullets to measure their out of balance will do the same thing and won't change the bullet's balance like meplatting tools sometimes do by taking off more metal on one side of the bullet than another. Well made and balanced hollow points without meplat uniforming will shoot in the 4 MOA range at 1000 yards as Whidden claims his meplat red ones do.

Note that Whidden's great long range score recently set was in pristine conditions at the range. And the size of the groups shot in the 1000-yard prone matches at the NRA Nationals are at best, 3 times as big as what the rifles and their ammo will shoot.

In either instance of improving bullet's accuracy, it's my opinion that until your 1000 yard groups with regular, not sorted/modified bullets shoot well under 1 MOA (6 to 7 inches, which is what the best of the benchrest rigs do), leave the bullets alone. There's bigger fish to fry.