School me on concentricity

[Branxhunter]

I haven't yet found a load I am happy with for my Parker Hale .243. I have a few loads that have shot groups under 1" but the only one that shows any consistency is 70gn TNT HP. I have a number of projectiles between 85gn and 100gn, and I would be happy with consistent grouping at or under 1".

While reloading yesterday I rolled the loaded rounds across the bench top, and the gyrations of the projectile tips were a bit disconcerting. Some were barely discernible while others were waving a round wildly. While I realise a factory Parker Hale is no benchrest rig I don't expect this poor concentricity of loaded rounds is helping.

The dies I have been using are Super Simplex 5/8" neck dies, or 7/8" Lee and RCBS standard FLS and seating dies.

Interested in everyone's thoughts.

Marcus

[mick_762]

I would assume you have checked twist rate of the tube - plus / minus seating depth and charge weights?

"Usually" the pope isnt toooo hard to get shooting well - 55gn to 90gn has been my usual limits though.

What powder are you using?


As for dies - Forster are "my" preferred but Lee collet dies are bloody good too.

[trevort]

Marcus I read a lot about concentricity early on and decided that I couldn’t be stuffed trying to measure it so I would use the dies best reputed to minimise it. That means the sliding sleeved seaters that capture the case in a chamber before the pill is seated. That was the Redding to start with but I buy Forster seaters now as they are cheaper and just as effective


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[LoneRider]

mate i use a simplex press for seating.
something about em sometimes puts the pill in on an angle [sometimes ]
so after ive seated the pil i drop the arm down a little,spin the cartridge 180 and seat it again.
but ive found it to be like towing a trailer,your better off not looking

ok
schools in,go sit in the corner and face the wall

[Branxhunter]

I would assume you have checked twist rate of the tube - plus / minus seating depth and charge weights?

"Usually" the pope isnt toooo hard to get shooting well - 55gn to 90gn has been my usual limits though.

What powder are you using?


As for dies - Forster are "my" preferred but Lee collet dies are bloody good too.

I haven't checked twist rate.

Have tried a range of charge weights for each projectile, have tried flat base and boat tailed projectiles. Have used the split case method to determine OAL to the lands for each projectile. For many of the lighter ones they are less than a caliber in the neck if loaded just short of the lands. One thing I have noticed is that the velocities for a given projectile weight and powder charge is usually 150-200fps down on those in the ADI manual, and that this rifle will digest loads over ADI max.

With the 55-58gn projectiles I have tried AR2206H, and with 70-90gn projectiles I have tried AR2208, and 85-100gn projectiles I have tried AR2209.

Marcus

[kickinback]

Expander balls can cause neck eccentricity.


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[mick_762]

I pretty much stuck with 2208 until I "found" RL17.

2/3's of the caliber in the neck is "the generally accepted" minimum so nothing new there for those light pills.

I have always found ADI book data to be low on cronographed numbers too - so I started loading to velocity not "gn weight". In my rifles I found best accuracy when the pope was pushed fast.

My current 87gn Hornady s/p load with RL17 is pushing just over 3300fps in a Ruger 77 VT.

[curan]

mate i use a simplex press for seating.
something about em sometimes puts the pill in on an angle [sometimes ]
so after ive seated the pil i drop the arm down a little,spin the cartridge 180 and seat it again.
but ive found it to be like towing a trailer,your better off not looking

ok
schools in,go sit in the corner and face the wall

I'll sit next to ya!

[trevort]

Expander balls can cause neck eccentricity.


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Yes, remove the expander balls from bushing neck dies

[frakka]

Interested in everyone's thoughts.

With a standard set of "delux" Redding dies I tried mightily hard to increase the percentage of concentric ammo, made sure the die aligned with the ram, used a floating carbon sizing button, floated the decapping rod with an O-ring under the lock nut, turned the case when seating etc etc. The best average total runout I could manage was:
0-1 thou 37% )
1-2 thou 27% )
2-3 thou 18% )
3+ thou 18%
To increase the percentage of 0-1 thou rounds, competition dies are a must, but only after you have tried every other avenue first

Edit: Redding not RCBS

[trevort]

I was looking for the Facebook like button


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[Camel]

Don’t need all that flash gear, the barrel will get the bullet pointing straight, that’s what it’s for

[macca]

Don’t need all that flash gear, the barrel will get the bullet pointing straight, that’s what it’s for

Made me smile and laugh a bit. Needed that today.
Maybe people should ask exactly how less or more concentricity actually effects accuracy.
Also what concentricity are we measuring case, case neck, projectile. Not much point of a concentric neck if the case is a banana.
If you haven't cleaned the necks up????
So many variables.
If you only want a sub 1 inch group powder and seating depth or a change of pill should get you there without all the bench rest preperation.
Cheers

[frakka]

Macca,

“If you only want a sub 1 inch group”........I guess Branxhunter posted the original question as he may apsire to better than that, or to eliminate flyers ?

the etc etc in my post covered the other easily achievable steps eg spotlessly clean dies, necks, shell holder....not a grain of dirt to misalign.

I was spooked some time back about the “banana case” but it is easily measured to discount and have not encountered it. I find it hard to contemplate it happening in the small Lapua cases considering the relative thickness of them, it must take some impressive pressure ? Or crops up more with large capacity cases ? crook die ? crook chamber ?

Accuracy........in the past, up to 3 thou total runout (ie 1.5 thou off axis) I have found no discernible difference out to 400m, others write that it shows up at longer distances than this, I don't know, but if tighter runout tolerance is easily attainable to remove another variable........why not ? even identifying the loads "out of tolerance" is a step forward.

Camel is a Philistine (but a good one)

[macca]

Macca,

“If you only want a sub 1 inch group”........I guess Branxhunter posted the original question as he may apsire to better than that, or to eliminate flyers ?

the etc etc in my post covered the other easily achievable steps eg spotlessly clean dies, necks, shell holder....not a grain of dirt to misalign.

I was spooked some time back about the “banana case” but it is easily measured to discount and have not encountered it. I find it hard to contemplate it happening in the small Lapua cases considering the relative thickness of them, it must take some impressive pressure ? Or crops up more with large capacity cases ? crook die ? crook chamber ?

Accuracy........in the past, up to 3 thou total runout (ie 1.5 thou off axis) I have found no discernible difference out to 400m, others write that it shows up at longer distances than this, I don't know, but if tighter runout tolerance is easily attainable to remove another variable........why not ? even identifying the loads "out of tolerance" is a step forward.

Camel is a Philistine (but a good one)

Fair enough. Good preperation does sometimes prevent piss poor performance.
I have a box of blue lapua 6br cases that have one wall considerably thicker then the opposite side(I can't remember the correct term in a circle.) Never saw it it the brown boxes.
Does it affect accuracy. With the brown cases this barrel does .100s. With the blue .300s.
Never assume Lapua don't make some duds.
Your advice and methods seem sound to me.
Branxhunter do you have anyone near you with a concentricity guage. Or you could post some resized cases to me and I will check them for you. That way we could eliminate the sizing die, or blame it.
Cheers