6.5 gas gun fine tuning

[WildRose]

loaded some more today. 87 gr vmax using h4350, superperformance, and rl 17.
found out new empty brass necks measured .271 and after seating .2735 at an oal of 2.650.
Was going to shoot earlier reloads but winds picked up to 10-15 mph. Expecting 2# of hybrid 100v tomorrow.
So is .0025 enough neck tension with out a crimp you all think?

I wish I could give you an intelligent, positive answer. It very well may do the trick but hard for me to say definitively.

I settled on very little neck tension to the point I could actually seat a bullet in the case with my fingers and then crimped. That seems to give me the best consistency in all of my bolt guns.

The only AR I've loaded for is my DPMS/Krieger .260 Remington. That was before I really even knew the difference in bushing dies and SAAMI spec dies. At SAAMI Spec some bullets did walk, those I'd loaded with a compressed load walked as much as 1/4" just sitting in the box so I had to reseat them all and apply the crimp.

Once I'd done that I never had any more issues but again, I only did that for the AR10 and doubt it would be safe in a bolt gun.

Those were rounds so tight they were hard to pull bullets on even with a bullet pulling die it still took considerable force.

 

[Shawn Carverelli]

I wish I could give you an intelligent, positive answer. It very well may do the trick but hard for me to say definitively.

I settled on very little neck tension to the point I could actually seat a bullet in the case with my fingers and then crimped. That seems to give me the best consistency in all of my bolt guns.

The only AR I've loaded for is my DPMS/Krieger .260 Remington. That was before I really even knew the difference in bushing dies and SAAMI spec dies. At SAAMI Spec some bullets did walk, those I'd loaded with a compressed load walked as much as 1/4" just sitting in the box so I had to reseat them all and apply the crimp.

Once I'd done that I never had any more issues but again, I only did that for the AR10 and doubt it would be safe in a bolt gun.

Those were rounds so tight they were hard to pull bullets on even with a bullet pulling die it still took considerable force.

ordered a Lee factory crimp die for my 6 and 6.5 creed along with 6.5 rcbs competition micrometer seater die with the open window in front. I inherited a few old vickerman seater die from my grandpa and they make seating bullets a breeze.
The crimp die(s) will hopefully take the guesswork out of the bullet tension scenario...thanks for the help, wildrose

 

[QuietTexan]

So is .0025 enough neck tension with out a crimp you all think?

Enough in terms of based on my experience you likely won't get setback while shooting, yes. In terms of tuning to a setting that shoots better than another setting with everything else being constant, too many variables to know until you shoot them.

To go back to the top for a minute:

Question is....have you'll found neck tension variables will change groups sizes and SD?

Yes, very much so. But in combination with several other factors, to the point that I don't think there's a way to say "yes that will work" without experimenting. Sure there are common settings like 0.002" that a lot of guys say works fine, just like 0.020" off the lands works fine, but I think that's more a factor of averages than an actually precise setting that's optimized.

Talking with Mike in another thread, the theoretical optimal neck setting would be where you can run a mandrel the same caliber as the bullet in and out without the neck expanding. That would mean the brass is springing back to the previous state and is holding the bullet, rather than the bullet expanding the neck. I don't know how feasible that is yet, but I'm trying to set up something to find out.

 

[Shawn Carverelli]

me to say definitively.

I settled on very little neck tension to the point I could actually seat a bullet in the case with my fingers and then crimped. That seems to give me the best consistency in all of my bolt guns.

Those were rounds so tight they were hard to pull bullets on even with a bullet pulling die it still took considerable force.

that sounds like a scenario where a guy would want to start with a lower powder charge and work up like one would for safe load development to veer away from overpressure, especially in a gas gun. Whats one more variable. I'm learning a lot..thanks again

 

[QuietTexan]

Whats one more variable.

To be entirely fair, averages are averages for a reason. That's why book COL, 0.020" off, -0.002" mandrel, etc, all work for so many people.

You can always pick a setting and if it doesn't make the groups worse keep it there until the time comes to tweak it. That's the only way to stay sane sometimes when there are so many things to change up. Plenty of guys use mandrels to push into the case for final expansion rather than pulling a button out against the shoulders, the purpose there is to reduce runout rather than tune neck size, and never once tune it at all with good success.

 

[Shawn Carverelli]

I can take my fired cases BEFORE any resizing is done and reseat a fresh bullet with my fingers and the brass neck will hold the bullet, but just barely. This morning I bought a rcbs fl bushing resize die and matchmaster seating die set.
I'll check but I have several redding bushings on hand. My 6-284 has a tight neck (.268 I think).
My guess is a .271 bushing would give me a .272 neck, with springback, and hence .0015 neck tension before and slight crimping