Straighten or index

Good test Jackie.

No reason why you should, & I'm not even sure how one could do it, but after a barrel has been fired, say, 500 rounds, is there any runout (difference?) between the individual lands in the throat? I'd be there is. So maybe that's a plus -- if the throat won't straighten a crooked round, neither will it crookify (!?) a straight one.

In the ever-changing world of benchrest fashion, Long-range shooters are beginning to find an advantage to using a seating depth where bullets are jumped. As far as testing goes, I wonder how many short-range benchrest shooters never test a jumped seating depth? I'd have to raise my hand on that one, which is pretty bad follow-the-pack thinking, since and I have done the work & wound up using jumped bullets in some of my 1K rifles.

Just another sheep,

Charles
 
jackie schmidt said:
I will make a bet with anybody who wishes to take me up on it.

Take a case, and full length size it the way 90 percent of Benchrest Shooters do. That means the case will slip in and out of the chamber with no resistance. Seat a bullet, making sure that the bullet is at least .010 into the lands. Before you chamber it, check the runnout. For this test, I would like for it to be at least .0015.

Chamber the round and then take it out. You should be able to see distinct bullet marks on the bullet. Check the runnout again using the same method as before. I will bet good money that it will not be any truer than when you checked it the first time.

The reason I know this is the same reason I know a lot of things. I don't depend on someone else's word, I actually do it for myself.

Saying that a crooked round will straighten out when chambered tells me that who ever makes the statement has never actually done what I said to do..........jackie
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I agree, I have done this and It does not straighten
 
Right. Apparently I put it badly. My point was that the barrel changes with firing, probably unevenly, so it's a good thing it doesn't "straighten" the bullet.
 
I think the better test would be to chamber a straight round and measure to see if it got crooked. If it does, then we've wasted a little time here.
 
Charles E said:
Good test Jackie.

No reason why you should, & I'm not even sure how one could do it, but after a barrel has been fired, say, 500 rounds, is there any runout (difference?) between the individual lands in the throat? I'd be there is. So maybe that's a plus -- if the throat won't straighten a crooked round, neither will it crookify (!?) a straight one.

In the ever-changing world of benchrest fashion, Long-range shooters are beginning to find an advantage to using a seating depth where bullets are jumped. As far as testing goes, I wonder how many short-range benchrest shooters never test a jumped seating depth? I'd have to raise my hand on that one, which is pretty bad follow-the-pack thinking, since and I have done the work & wound up using jumped bullets in some of my 1K rifles.

Just another sheep,

Charles
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Charles...
You make a good point...but having experience working up loads for both short and long range rifle calibers I have found that the long range shooters load their bullets for best accuracy just like we do in short range BR...the big difference is that the VLD type bullets can show a preference for "jump" but can shoot just as well with some "jam" Eric Stecker can vouch for that...I have found that we shoot the seating depth that is the most accurate for the barrel...

Eddie in Texas
 
eww1350 said:
Charles...
You make a good point...but having experience working up loads for both short and long range rifle calibers I have found that the long range shooters load their bullets for best accuracy just like we do in short range BR...the big difference is that the VLD type bullets can show a preference for "jump" but can shoot just as well with some "jam" Eric Stecker can vouch for that...I have found that we shoot the seating depth that is the most accurate for the barrel...

Eddie in Texas
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Eddie,

Yea, but. First Berger, Walt himself, said they had to be touching or jammed. This is VLDs. It was several long-range shooters, Charles Bailey comes immediately to mind, who figured out jumping worked better. And so it has proved -- usually, but as you said, not always. Would it stun you to know that I jump bullets for some 1K barrels, and I've never used a VLD-design?

The point isn't what the current fashion is for a particular discipline, it's that we're too addicted to following fashion. I've already fessed up that I don't even test jumping for point-blank rifles (a practice I'll change). You're saying you have tried jumping for PB with each barrel you use? Never showed up as better?
 
Runout, concentricity, and best seating depths are all seperate and different things.
IMO, best seating is the biggest mystery in reloading. Easy to find. But so far impossible to understand, define, and predict.

It was mentioned here that 'adjusting' a round to concentric means adjusting past concentric(to a point of yield). There is nothing happening with chambering of normal rounds that does this, so it does not reduce eccentricity, much less runout.

There are also theories out there countering Alinwa's belief that concentricity of a loaded round is 1/2 the clearance. I take them as rationalizations w/regard to accuracy seamingly being little affected by runout.
It goes like this:
Firing pin strike drives a case forward to shoulder datum, which centers ammo -that I assume is incredibly sloppy from FL sizing and poor choices in chamber specs.
I don't buy it. I think it's as likely the pin strike driven case would bounce off the shoulder datum inconsistently.
But I do know that new & sloppy fitting cases can perform well enough, so it's hard to argue.
I'l call it another mystery..
 
For the time being

With the run out my loads exhibit according to the sinclair concentricity gauge I will not address the issue which most people contributing to this thread seem to agree is not an issue. For the time being I will leave sleeping dogs lay and keep my eye on the seating depth as the barrel slowly get burned away.
Andy.
 
Some pretty interesting talk here. Seems when all is said and done with discussion the method to fix it should center on where the problem is originating, like some others have said. Tweaking a dogs leg will likely just make more howling.
 
Have done a lot of tinkering with concentricity, including checking runout after the round has been chambered with a 'jam'. Sparing the gorey details, things shook out like this:

- First, work on the gear so the r/o is consistent, even if it seems excessive.
- A loosey-goosey press for sizing (aka RCBS Partner) works great.
- For the double throwdown presses CNC'd from a billet of 7061T6 hand delivered by Swedish vigins in white gauze dresses drinking Perrier, a 25 cent 'o' ring under the die may help.
- Test @ 200 to find the upper limit of r/o where it becomes apparent on target. Most r/o issues are covered up at 100.
- The inside of the necks need to perfectly round.
- Throat angle makes a difference.
- Neck clearance makes a difference.
- Bending necks to 'improve' runout is never a good idea.
- Some barrels are indifferent to runout, some aren't.
- Big r/o numbers can still shoot well if the boltface is truly square.

All of this was done with several Honest-To-Gawd BR rifles chambered in various .30 cal rounds. Any, all or none of this might apply to anyone else's stuff.

Good shootin'. :) -Al
 
Being retired for several years, I can and do spend 5-6 hours daily on reloading matters, about 95% of it involving brass issues.

With each new barrel, I smoke a bullet, put it into an empty cartridge and chamber it to find what seating depth will give me a .020 etch reference mark. If the cartridge I use does not have an almost perfectly concentric neck, the rifling etch marks on the bullet will have different lengths, showing that the bullet, being softer than the barrel, is being deformed by going into the rifling crooked. Had it been a loaded round, that bullet would start down the barrel deformed but I suspect that when it swells under pressure to fill the grooves it would not matter in any measurable way at the target.

I FIRE FORM NEW BRASS AT THE 200 YARD RANGE WITH LOADS WHERE THE NECKS ARE AS MUCH AS .007 OUT OF CONCENTRIC AND THEY WILL GROUP WITH MY BEST EXPERIENCED BRASS. Since my chamber is .004, total, bigger in diameter than the loaded round at the neck, that brass is getting pre-formed a little before firing.

If the brass isn't "straight" after the second firing it probably never will be. I've run "crooked" brass through my annealing machine at luke warm temperatures up to near melting point and then run them back through my dies and they still come out crooked. I've bent them to get them and the bullets straight, fired them, and the cases come out of the chamber crooked again.

ALL BRASS IS BORN FEMALE.

Frank B.
 
You just have to understand the female(yeah, right).
The root cause of runout is case thickness variance(call it hormones).
What brings this evil condition to undeniable measure, is sizing(interaction with a female).
 
macaver1 said:
If the cartridge I use does not have an almost perfectly concentric neck, the rifling etch marks on the bullet will have different lengths, showing that the bullet, being softer than the barrel, is being deformed by going into the rifling crooked.
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Just curious, have you bore scoped your throat to confirm that your rifling isn't 'crooked'? - nhk
 
Good Point, I have scoped barrels that you can easilly see the difference in the length of the lead into the Lands. ............jackie
 
Al Nyhus said:
- For the double throwdown presses CNC'd from a billet of 7061T6 hand delivered by Swedish vigins in white gauze dresses drinking Perrier, a 25 cent 'o' ring under the die may help.

- - Bending necks to 'improve' runout is never a good idea.


Good shootin'. :) -Al
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My favorites!!
 
jackie schmidt said:
Good Point, I have scoped barrels that you can easilly see the difference in the length of the lead into the Lands. ............jackie
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Oh yeah.

I've seen difference of lead start from end of neck in factory chambers from well known manufacturers. Once in a custom chamber but it wasn't a big difference. None of the conditions was caused by shooting the rifle, they were all manufacturing defects.

One lead will start at the step (end of neck), the next a ways back, the next farther still till the opposite lead is the farthest back, then it comes back again. I see this and I think it says the chamber is off center with respect to the bore. I've seen them bad enough that there was almost no lead at all on one side and the opposite side was quite a way back. It would be essentially impossible for a bullet to get a straight start in such a chamber to bore transition. I even saw this coupled with scoops (reamer chatter) around the neck, in a factory rifle that cost > $1,500.00. I told the guy, a range acquaintance, he needed to send it to the factory (not promising since it was 6 years old), trade it in on something else, or see a real gunsmith and have it rebarreled.

He did the latter and just over $700.00 later it's shooting tiny little groups.

Borescopes are very useful tools but they should come bundled with a giant bottle of Mylanta, a lifetime supply of valium, and a clear warning about looking into factory rifle bores and chambers.

Fitch
 
nhkuehl said:
Just curious, have you bore scoped your throat to confirm that your rifling isn't 'crooked'? - nhk
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I did not make my point clear enough. In my tests the "crooked" case (neck) is the issue. When a smoked bullet in a "straight" case is inserted in a new barrel, the rifling marks on the bullet are the same length.... in all my barrels ...thus far. Greg Tannel has done my smithing (at least 2 barrels a year for several years) so I'm not worried about the quality of the chamber.

Frank B.
 
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