Bullet runout

[Kevin1990]

So I finally got my Sinclair concentricity gauge. (Backordered for 4 months.) I went to measure some of my 6br reloads, and to my surprise I had maybe about 1 thou run out give or take. Measured a few more and they were about the same. Figured I'm doing something wrong. So I took some 6.5 Grendel American Gunner ammo, and it was getting like 6 to 7 thou run out.

They never shot great out of my gun. I know there could be a million reasons why, but could that kind of number degrade accuracy? What exactly is the end result if your concentricity is off by a good bit?

 

[Big Mc]

So I finally got my Sinclair concentricity gauge. (Backordered for 4 months.) I went to measure some of my 6br reloads, and to my surprise I had maybe about 1 thou run out give or take. Measured a few more and they were about the same. Figured I'm doing something wrong. So I took some 6.5 Grendel American Gunner ammo, and it was getting like 6 to 7 thou run out.

They never shot great out of my gun. I know there could be a million reasons why, but could that kind of number degrade accuracy? What exactly is the end result if your concentricity is off by a good bit?

The gun should tell you if you have too much run-out. Some will shoot 0.006 others will not.

 

[BoydAllen]

So I finally got my Sinclair concentricity gauge. (Backordered for 4 months.) I went to measure some of my 6br reloads, and to my surprise I had maybe about 1 thou run out give or take. Measured a few more and they were about the same. Figured I'm doing something wrong. So I took some 6.5 Grendel American Gunner ammo, and it was getting like 6 to 7 thou run out.

They never shot great out of my gun. I know there could be a million reasons why, but could that kind of number degrade accuracy? What exactly is the end result if your concentricity is off by a good bit?

I think that knowing what sort of rifle your 6.5 is would be useful.

 

[jelenko]

Over on National Match forum, a fellow tested ammo sorted to < 3 thousandths runout and 3/> 3 thousandths. Saw no difference in 600 yard groups. That said, the group sizes were on the order of 1/2 +/- MOA - so might not apply to benchrest typical groups.

Generally, 1-2 thousandths for non benchrest shooting is considered fine.

 

[Bronsin]

If it's a sloppy factory chamber, .006-.007 will be a problem.

 

[wildcatter]

.001" is about as perfect as one can expect being very particular with your reloading practices. I doubt anyone can maintain under .001" runout if the truth was known.

One thing is for sure, with ammo having no more than .001" and under runnout, any accuracy issues are coming from somewhere else,,,, in any cartridge!

 

[Bill Norris]

Erik Cortina said he had tested up to .015 runout and seen no difference in his groups.

 

[Tesoro]

I used to be a big 'run out measurer' to test the quality of my reloads. And then I wised up. And I used to weigh to the kernel and then I wised up!! But i do use my sinclair concenticity gauge every now and then to check neck run out when wildcatting brass, Not sure why. Live and learn. The fun of it all!!

 

[Bill Norris]

I used to be a big 'run out measurer' to test the quality of my reloads. And then I wised up. And I used to weigh to the kernel and then I wised up!! But i do use my sinclair concenticity gauge every now and then to check neck run out when wildcatting brass, Not sure why. Live and learn. The fun of it all!!

About the only time I use the concentricity gauge is when setting up a new die to see if it is straight.

 

[Tesoro]

About the only time I use the concentricity gauge is when setting up a new die to see if it is straight.

I have some saved post somewhere made by name brand shooters on here they stated 'within a 10'th' and 'concentricity variances are corrected by the chamber' was good enought for me to follow! These were intermediate and LR pro shooters. Not BR. My quickload 40gr calcs run out at 95% powder burn so....

 

[One Eye Pete]

I shoot F-Open. When I reload for a match I am fanatical about headspace and bullet seating depth as they go hand in hand and are critical to accuracy. I trim cases to +/- 0.001 and carefully chamfer. I uniform primer pockets, weigh and sort my primers. I use a Sinclair priming tool and seat my primers within +/- .001. I sort my bullets by OAL trim and point them and then resort by OAL. I measure powder to 0.02 gn. or 1 kernel whichever comes first. Am I nuts ABSOLUTELY. But being really fanatical with this along with a lot of luck has eliminated flyers and allowed me to shoot a few 600 scores. The one thing I do not do is measure bullet runout. If your dies are working properly BULLET RUNOUT doesn’t matter. If you really want to eliminate any effects of bullet runout do as most of the benchrest shooters do and slightly jam your bullets.

 

[BoydAllen]

Erik Cortina said he had tested up to .015 runout and seen no difference in his groups.

I forget, did he chamber the crooked ones, remove them and measure the runout a second time? I would guess that his chamber and loaded round dimensions combine to do a lot of straightening of crooked rounds as they are chambered. On the other hand, with factory ammo. a relatively loose chamber, and seating well short of the rifling, it may be that the result would have been a lot different.

Years ago, working with a .262 neck 6PPC, with about .0015 neck clearance on a loaded round, I used a gauge that was designed to straighten to make a round more crooked, .0035 supported on the ogive and near the head. I chambered the round and then unchambered and remeasured the runout. It was .0015. The bullet was seated a few thousandths into the rifling, but shorter than jam.

 

[Bill Norris]

I forget, did he chamber the crooked ones, remove them and measure the runout a second time? I would guess that his chamber and loaded round dimensions combine to do a lot of straightening of crooked rounds as they are chambered. On the other hand, with factory ammo. a relatively loose chamber, and seating well short of the rifling, it may be that the result would have been a lot different.

Years ago, working with a .262 neck 6PPC, with about .0015 neck clearance on a loaded round, I used a gauge that was designed to straighten to make a round more crooked, .0035 supported on the ogive and near the head. I chambered the round and then unchambered and remeasured the runout. It was .0015. The bullet was seated a few thousandths into the rifling, but shorter than jam.

Not real sure Boyd if he re-measured after chambering the rounds.

 

[Straightshooter1]

So I finally got my Sinclair concentricity gauge. (Backordered for 4 months.) I went to measure some of my 6br reloads, and to my surprise I had maybe about 1 thou run out give or take. Measured a few more and they were about the same. Figured I'm doing something wrong. So I took some 6.5 Grendel American Gunner ammo, and it was getting like 6 to 7 thou run out.

They never shot great out of my gun. I know there could be a million reasons why, but could that kind of number degrade accuracy? What exactly is the end result if your concentricity is off by a good bit?

From what I've gathered from listening to some top competitive shooters, if you're lead angle is like 3-4° (like what's often found in factory barrels), then >.005 TIR can have an effect on consistency due to how the bullet is being engraved. In custom barrels with lead angles at ~1.5°, it will usually help the bullet to straighten out before the engraving.

 

[Pres100]

I shoot F-Open. When I reload for a match I am fanatical about headspace and bullet seating depth as they go hand in hand and are critical to accuracy. I trim cases to +/- 0.001 and carefully chamfer. I uniform primer pockets, weigh and sort my primers. I use a Sinclair priming tool and seat my primers within +/- .001. I sort my bullets by OAL trim and point them and then resort by OAL. I measure powder to 0.02 gn. or 1 kernel whichever comes first. Am I nuts ABSOLUTELY. But being really fanatical with this along with a lot of luck has eliminated flyers and allowed me to shoot a few 600 scores. The one thing I do not do is measure bullet runout. If your dies are working properly BULLET RUNOUT doesn’t matter. If you really want to eliminate any effects of bullet runout do as most of the benchrest shooters do and slightly jam your bullets.

Just curious, why would you have to re-sort by OAL a second time after trimming your bullets? Wouldn't you just trim to the OAL you wanted and they would all be alike? I'm not an F-Classer or trimming bullets ... just interested.

Disregard ... for some reason I missed the part about pointing them after trimming ! Makes sense

 

[One Eye Pete]

Just curious, why would you have to re-sort by OAL a second time after trimming your bullets? Wouldn't you just trim to the OAL you wanted and they would all be alike? I'm not an F-Classer or trimming bullets ... just interested.

Disregard ... for some reason I missed the part about pointing them after trimming ! Makes sense

After pointing I found the OAL varied slightly and it is easy enough to resort into groups for each stage of the match using the Accuracy One OAL comparator. It’s probably not necessary but I’m retired and have nothing better to do.

 

[Dave M.]

So I finally got my Sinclair concentricity gauge. (Backordered for 4 months.) I went to measure some of my 6br reloads, and to my surprise I had maybe about 1 thou run out give or take. Measured a few more and they were about the same. Figured I'm doing something wrong. So I took some 6.5 Grendel American Gunner ammo, and it was getting like 6 to 7 thou run out.

They never shot great out of my gun. I know there could be a million reasons why, but could that kind of number degrade accuracy? What exactly is the end result if your concentricity is off by a good bit?

If you can make ammo with only 1 thou of TIR at any point on the bullet, you are doing something very RIGHT. I stopped using my concentricity gauge years ago when it started telling me I was making horrible rounds, but the target was telling me otherwise. Don’t get hung up on that new gauge. I have conducted testing of my lowest vs highest TIR rounds against one another and statistically, I saw no difference. I shoot all bullets loaded into the lands and perhaps this explains what I saw; but I would highly encourage you shoot you best runout rounds versus your worst runout rounds, and then make up your own mind. You may just find that your new gauge starts gathering dust like mine does. lol.
Dave

 

[Dave M.]

I shoot F-Open. When I reload for a match I am fanatical about headspace and bullet seating depth as they go hand in hand and are critical to accuracy. I trim cases to +/- 0.001 and carefully chamfer. I uniform primer pockets, weigh and sort my primers. I use a Sinclair priming tool and seat my primers within +/- .001. I sort my bullets by OAL trim and point them and then resort by OAL. I measure powder to 0.02 gn. or 1 kernel whichever comes first. Am I nuts ABSOLUTELY. But being really fanatical with this along with a lot of luck has eliminated flyers and allowed me to shoot a few 600 scores. The one thing I do not do is measure bullet runout. If your dies are working properly BULLET RUNOUT doesn’t matter. If you really want to eliminate any effects of bullet runout do as most of the benchrest shooters do and slightly jam your bullets.

Are you inside my brain??? Because you wrote exactly what I do in my OCD reloading practices and what I stopped caring about with regard to concentricity a long time ago.
Dave

 

[bozo699]

If you can make ammo with only 1 thou of TIR at any point on the bullet, you are doing something very RIGHT. I stopped using my concentricity gauge years ago when it started telling me I was making horrible rounds, but the target was telling me otherwise. Don’t get hung up on that new gauge. I have conducted testing of my lowest vs highest TIR rounds against one another and statistically, I saw no difference. I shoot all bullets loaded into the lands and perhaps this explains what I saw; but I would highly encourage you shoot you best runout rounds versus your worst runout rounds, and then make up your own mind. You may just find that your new gauge starts gathering dust like mine does. lol.
Dave

Gathering dust like most all of us that bought one!… like Bill I use mine when setting up a new die or a new chamber after that I don’t use it.
Wayne

 

[Bc'z]

I sold my Sinclair concetrisity gauge couple years ago once I figured out it didn't show up on paper.
Just the other day I bought a new to me concenrisity gauge because a buddy told me they work great for coloring tips with a sharpie for testing.
Ymmv