Concentricity issue with 185 Juggs in a 170” freebore FTR barrel.

[jlow]

This combo shoots great with higher MV and no pressure signs, but it seems like the loaded rounds have more concentricity issue than I am used to ~4-5 thousands.

Same bullet, same neck turned Lapua cases, in the same gun except with the new barrel now loaded longer due to the freebore and about 10 thousands off. The longer freebore means less of the bearing surface in the neck and I wonder if this is the cause. Any similar experience?

Does not seem to affect precision but I still wonder....

 

[rifleman700]

Yes, if there is not enough bearing surface / neck contact. This is where a lot of people end up when they think they have to contact the lands with the bullet and are then left with minimal bearing surface / neck contact. Not knowing what you have in the way of contact I would suggest more neck tension as a possible remedy.

 

[jlow]

Yes, if there is not enough bearing surface / neck contact. This is where a lot of people end up when they think they have to contact the lands with the bullet and are then left with minimal bearing surface / neck contact. Not knowing what you have in the way of contact I would suggest more neck tension as a possible remedy.

Thanks for the response, but my guess you don’t reload for F-class – thus the confusion.

Loading long in this case is pretty much SOP and intentional and not to get the bullet in the lands – I am 10 thousands off.

BTO is 2.360” and the point is to increase case volume to allow more powder and MV without pressure. MV is important for long distance F-class. This is the whole reason for the long freebore.

I have 3 thousands in neck tension and at least 135 thousands of the bearing surface in the neck. So I do have less than say if I was loading for mag length where my BTO is more like 2.282”.

 

[rifleman700]

Thanks for the response, but my guess you don’t reload for F-class – thus the confusion.

Loading long in this case is pretty much SOP and intentional and not to get the bullet in the lands – I am 10 thousands off.

BTO is 2.360” and the point is to increase case volume to allow more powder and MV without pressure. MV is important for long distance F-class. This is the whole reason for the long freebore.

I have 3 thousands in neck tension and at least 135 thousands of the bearing surface in the neck. So I do have less than say if I was loading for mag length where my BTO is more like 2.282”.

You are correct, I do not reload for F-Class but I do reload for ELR - 1500 yds+ and IME concentric loads trump everything else. With only 135 thou of contact I would still look at more neck tension. I hope you figure it out.

 

[XTR]

I wouldn't worry about it too much. I've sorted by most and least runout and most and shot groups and I can't see the difference on a target with my F-TR rifles, though in the past it has made me feel better about my loads at a big match to sort them.

Are you measuring your runout at the same distance from the mouth that you used to or are you measuring at the same point on the ogive, i.e., further from the mouth. With a long bullet seated long what was a slight variance at the mouth is multiplied.

Something else to consider with our long .308 freebores, if you stick a crooked bullet in there it will get straightened, it has to.

I switched to a Wilson seater and I quit checking runout, there is nothing more I can do about it anyway.

Oh yea, We had a BR shooter in Oak Ridge who has held more than s few records. He told me he can't see any difference in groups up to .004. If he can't see .004 I'm betting I can't see 4x that.

 

[jlow]

Thanks guys!

As to not to worry about runout, that is where I am actually leaning myself. I measure runout at the neck.

Honestly I have been pretty anal about this in the past. A personal conversation with Dan Newberry (of the OCW fame) earlier this year started to push me away from worrying about concentricity – his opinion, a total waste of time…

Started to shoot loads without checking and they shot well….. My current load is shooting about 0.3” three round groups consistently so.

But mostly just wondering if others seating this bullet long is seeing the same increase in runout as I am – kind of a curious thing.

 

[watercam]

There is always the 'jam them into the lands no matter what' train of thought that seems to work for a lot of folks.

 

[jlow]

There is always the 'jam them into the lands no matter what' train of thought that seems to work for a lot of folks.

Yes but I really don't want to do the jam thing as that leads to "chasing the lands" which is something I rather not do....

 

['Freak]

How do the numbers compare when concentricity is measured still on bearing surface but further out, away from the case mouth?

 

[jlow]

How do the numbers compare when concentricity is measured still on bearing surface but further out, away from the case mouth?

I have not done that. No loaded rounds now for a while but can check next time when I am loaded up. I think the run out will be worse up by the ogive, is that what you are thinking?

 

['Freak]

Thinkin’ if rolling on the same two points either end of the case body, if reading .004” to .005” bullet runout at the case mouth, and if runout is notably greater after moving the reading out away from the case mouth, then the bullet’s got to be not only offset from but also seated cockeyed relative to the outside of the case body.

The necks were turned but were they turned down far enough to give ‘em all a consistent neck wall thickness end to end and all around? Were the necks given an offset and/or sent cockeyed relative to the outside of the case body during sizing? Did the bullet because of what happened during sizing or for some other reason enter the neck bad cockeyed during the seating operation? Either way it’s gotta be squirreling with neck tension and putting a misaligned case and/or bullet in a bind inside the chamber, or so I thinks, FWIW ...

 

[jlow]

Thinkin’ if rolling on the same two points either end of the case body, if reading .004” to .005” bullet runout at the case mouth, and if runout is notably greater after moving the reading out away from the case mouth, then the bullet’s got to be not only offset from but also seated cockeyed relative to the outside of the case body.

The necks were turned but were they turned down far enough to give ‘em all a consistent neck wall thickness end to end and all around? Were the necks given an offset and/or sent cockeyed relative to the outside of the case body during sizing? Did the bullet because of what happened during sizing or for some other reason enter the neck bad cockeyed during the seating operation? Either way it’s gotta be squirreling with neck tension and putting a misaligned case and/or bullet in a bind inside the chamber, or so I thinks, FWIW ...

Run out could be greater at ogive, impossible to tell without measuring.

However as mentioned earlier, the gun is shooting in threes consistently. Yes, I have turned necks for a long time, consistency in the 2-3 ten thousands – Lapua brass with final thickness in the 13 thousands so just skimming. Very good consistent neck tension as measured with K&M arbor seater with force dial, seating pressure around 0.4 “ unit so good tension, and variance about 0.05 inch unit which is about as good as it gets (at least for me...). Seated with a Wilson inline seater.

In the end, I think the reason for runout is because the neck is only holding a small amount of the bearing surface. It is only logical that the less bearing surface you hold, the less control you have in terms of getting the round to sit concentric to the case, regardless of how straight the case or bullet is.

Appreciate all the comments thus far but I wish more people who actually shoot this bullet in the configuration i.e. with a long throat and bullet seated long would comment with their actual experience - thanks!

 

['Freak]

It evidently still shoots well enough to suit its purpose, so …, and I’m just some ‘Freak mostly pondering other folks’ hands on experience, and some of my own, with what’s left of this thinker thang inside me ‘Freakin head. Might even learn a thang or two… Carry on.