Turn the necks down until the tension is where you want it.

Neck tension is about the most variable thing there is in any reload. The reasons are several.



Compare the necks to a rubber band. That's how it functions. The thicker the neck given the same stretching, the tighter the tension.



You also have a difference in the ductility of the brass. It gets work-hardened. Naturally the harder brass gives a different tension than recently annealed brass. Same difference in a stiff less elastic rubber band than one of the same dimensions only more elastic.



In work hardened brass you will note a change in accuracy as the necks get work-hardened. Sometimes it can be for the better but usually it is for the worse. I notice it in most cartridges at about the third reload, and surely the fourth and after. I therefore anneal cases at that point. I've noted a marked improvement in accuracy for the same shot sequence as with newer brass. That is likely because the load was originally developed with ductile brass and the tension changed as the neck hardened, became less elastic and had a tighter grip on the bullet than when the load was developed.



Sealing of the neck and bullet isn't necessary for a discharge but consistent pressure in the powder chamber at ignition is necassary for accuracy. Tension on the bullet insures ignition of the powder consistently and any variance in that can affect accuracy.

Bob, until you wrote insures complete ignition of all the powder I was with you 100%. From what you wrote prior to this statement I see that you understood the point I was trying to make. You certainly covered it much better than I. roger

bill smith,....you measure a sized neck and then measure a neck after the bullet is seated in it. The difference is the neck tension.

ex. a sized neck measures .292" and a loaded round neck measures .294",..there is .002" neck tension.

My general rule is to shoot for either .001"-.002" neck tension,..this works well for me. This is also where bushing sizing dies are worth their weight on gold.

"ex. a sized neck measures .292" and a loaded round neck measures .294",..there is .002" neck tension."

If I'm understanding what you have said so far your neck thickness is about.016" That's a lot. Now if it were .011" that would be closer to were it normally is. From what I understand you to say with either thicknees the way you are measuring it you would still get.002". Now .002" with .016" has to have a different TENSION than with.011".

If you can shot it and it seals OK with moderate pressures you have a working combination. If it doesn't seal turn the necks down to about .012" for starters. That is neck wall thickness and not a diametral measurement. Roger

. . .and if you're questioning "complete ignition of ALL the powder," I agree with you. ALL the powder is NEVER ignited. I understand the industry accepts around 3-4% never igniting, and that is variable, propellant to propellant, and load to load. Should have not included ALL and I'll edit and remove it.

how do you measure neck tension to know what it is and how do you know what is correct?? is this just a matter of "feel"..?? or are there some tables or charts or other reference materials to tell you what amount of tension is correct??

A while ago, I loaded 20 .30-06 cases of 20 different manufacturers with the same load.
The group on the target was not great, but better than expected. After the fifth reload I had the impression that group size was shrinking, and after the tenth reload (group smaller again) it was clear: there was an egalization process - I think due to case neck hardening.

3-4% not burned, I'll buy that. Not the same as "3-4% never ignited." Sometimes it's a lot more than that that doesn't burn, in an inefficient load of slow burning powder. But I think it'd be unusual to find so much as a single grain that never ignited. What you get is a progression of ignition through the charge initially, but by the time the pressure's high enough to start the bullet the fire's surrounding every grain and they all will burn to some extent. They may not burn all the way through, especially the last ignited ones.

Do the rounds chamber easily ?

I just got my varmint rifle rebarreled to 6-284. I plan to use the Lapua 6.5-284 brass necked down to 6mm and the Sierra 107 Matchking bullet. This combo produced a loaded round neck diameter of 0.276�. The chamber neck diameter is 0.278�. I have not shot it yet but it seems like the neck tension is probably higher than ideal for best accuracy (the neck gets thicker after sizing it down from 6.5mm to 6mm and therefore neck tension is higher). My question is this: Should I buy the Redding full length bushing die in order to reduce neck tension or should I just go ahead and shoot it and see how it works? Thanks, Rufous.