PC Neck Tension Questions-HV Rifle

[Bama]

Up until recently I had been using standard dies and flaring case mouth on HV rifle loads using PC. I had to pull 50 due to velocity after going up one grain made bullets turn to a cloud 15 ft from muzzle. Upon pulling found bullets were necked down as much as .003+ due to neck tension. I have searched posts and tension recommendations go from .001 to .003 on standard lubed bullets. I know that there is a certain amount of spring back of the neck even using the NOE pin type plugs in a lee expander die . Questions are:

1. How much smaller should the diameter of the pin portion be in relation to the final sized diameter of the bullet to account for spring back and recommended neck tension on PC bullet? Most rounds are shot from bench at longer ranges.

2. Has anyone seen any accuracy considerations with PC bullets that differ from conventional lube bullets in regard to neck tension?

[popper]

Most of my expander/die plugs are ~ 0.003" smaller than I size. BO takes 3085/0.305 Lee expander plug. 308W takes 310/0.307 plug. Isocore/WW alloy. Both run near max jacketed fps from ARs. Other lubes were LLA, Recluse, veggie oil. Only the veggy oil worked, no difference in accuracy.

[OS OK]

This is a bit of a juggling consideration…there's the BHN of the PC'd cast and standard neck tension from the case alone and there is the Lee Factory Crimp Die that I think will offset standard neck tension and allow a good starting pressure from a tiny ring taper crimp that would deform the cast the least amount when using an oversized expander.
Some cast harder than necessary, PC or Lube, and the standard way of having proper start pressure using the J-type boolits expanders…I think the harder cast are less affected even though they might be .002"+ larger in size but are still swaged to some extent.
With 12-15 BHN I would expand at .001" smaller than the cast and use the LFCD. With spring back and it being different to some extent from one brass mfgr. to the next…I would expand at the same size as the cast allowing the variable in the spring back to do the undersizing of the case mouth for me. Thats a hard one to wrap your mind around as the annealing plays a part of that also.
I am waiting to get the NOE inserts for the Lee expansion die…using these will allow me to actually load with different neck expansions and then take them down a week later and measure what swaging really has or has not happened. I want to try to prove that we can shoot softer alloys at pressure along with not going grossly oversize with the cast with a quality PC'd jacket around it…allowing the cast to obturate yet be protected by the PC.
Does that make any sense to you?

OS OK

[runfiverun]

even with naked lead I hate the too big boolits thing.
controlling diameters and neck tension is where we really gain accuracy.
getting everything lined up with the centerline of the barrel takes a lot of effort.
mucking it up by jamming too much lead in there [destroying the shape under pressure]
or ruining the perfect castings by squishing them down in the loading proces doesn't make a whole lot of sense.
neither does not using enough neck tension or a batch of inconsistent annealed brass to allow a consistent burn on the powder we chose.
I strive for .0015 to .002 neck tension and a consistent seating feel [you can also feel it over the expander ball]
sometimes this means I have to anneal a batch of brass and then neck size it 2-3 times to get everything settled back down again.

[popper]

Gee Bama - you always ask difficult questions.:smile: Like R5R says and no carbide rings in rifle die.
1) brass sizing down boolits is NOT what you want. I started casting for 40SW, results were terrible until I got a 'proper' M die.
2) Bore/groove slightly sizing down you DO want - usually.
3) alloy should withstand neck tension. Gets worse for low Sb alloy.
I load cast in semi-auto, only get set back when I get a nose slam.
I load with a single stage press and I can feel tight necks, hard/soft brass. I have pulled boollits with my normal alloy and checked for swaging - don't get any I can measure.
IMHO, boolits don't disintegrate due to neck tension.

[Bama]

Popper, like you I load 50 at time single stage. Even with neck flared, I can feel each grease grove as bullet goes into place, and have seen slight indentations at groves on necks at times. I know this is wrong and should not occur. I have tried collet sizer and it tightens up groups but is not consistent from lot to lot of Lake City brass. Changed groups to almost perfect vertical lines. That is reason I am going to pin type like the NOE which can be used in Lee die. This type should give consistent inside diameter regardless of neck thickness. The NOE expander plug come in .001 increments. I have had good luck with .310 in 308W and .285 in 7-08 and want to get the "Proper" expander plugs for these sized bullets. I am cheating by making my own as an experiment but even then I want to get it right on the first tries. I have made a set .001 smaller than sized diameter to try. I have been playing with the alloys going from 100% WW to 50/50 with Linotype an can see no major difference in accuracy when PCed. PCing seems to have altered a lot of what I thought I knew in past years. I did not mean to imply I though neck tension was a factor in bullet disintegration. Twist rate and velocity compared to alloy strength are the factors. In past I could not even approach the velocities I normally shoot today without leading. Now I get "0" leading even when driving fast enough to disintegrate in flight with PC.

[popper]

slight indentations at groves on necks - neck spring back - not bad unless it resized your bases. Same with GC, you can feel them 'bust' through the shoulder.

[HangFireW8]

You have discovered that jacketed oriented dies have poor dimensions for cast accuracy- or jacketed accuracy, for that matter.

I shoot for .001 to .0015" tension, with maybe a little tighter at the gas check for 30/30 to help prevent setback. Short neck cases fed from a magazine might need a little more tension and/or a little crimp.

[clearcut]

If all the neck tension is the same with out change to the diameter of the boolit the POA should be consistent.Just MHO.
CC

[runfiverun]

should be unless you have ignition inconsistencies.
this is pretty common with reduced powders especially medium burn rate rifle powders.

one other thing that will cause those inconsistencies is when the boolit hits and engraves the throat.
this changes when the pressure spike occurs that makes the powder burn quicker.
change the timing from shot to shot and you change the velocity.
change the velocity from shot to shot and you get vertical stringing.

neck tension suddenly becomes a little more important when you see it's affects on paper at 100yds.
this same thing can be caused by ignition inconsistency's because the powder is just not igniting properly from shot to shot, neck tension won't help this so much except to hold things together better and knock those affects down.
the real cure is a powder change or a case filler so that you hold the powder against the primer and buffer the base of the boolit from taking the primer blast and moving forward until pressure builds enough to release it.

[243winxb]

Plug .0015" smaller then bullet diameter. Measure neck area before and after seating a bullet. The neck should not expand more than .002" Bushing dies give better control over sizing necks then standard dies, because some standard die size as much as .010" smaller then needed. Then brass wants to return to that diameter. No experence with PC. http://i338.photobucket.com/albums/n420/joe1944usa/2015%20Reloading/th_45acp%20NeckTension%20A_zps2nhf4njc.jpg (http://s338.photobucket.com/user/joe1944usa/media/2015%20Reloading/45acp%20NeckTension%20A_zps2nhf4njc.jpg.html) http://i338.photobucket.com/albums/n420/joe1944usa/Firearms%20%20and%20%20Reloading/th_BulletPullNeckTension.jpg (http://s338.photobucket.com/user/joe1944usa/media/Firearms%20%20and%20%20Reloading/BulletPullNeckTension.jpg.html) Click photo for larger view. Near pure lead, comparded to Lyman #2 may make the biggest difference when bullets get sized smaller in diameter. Use Linotype. 22 BHN :wink:

[popper]

Bama - interesting comment you make about PC. I found it takes more force to pull coated boolits than using a camming puller on jacketed. Alloy doesn't seem to make much difference. I had to pull a bunch of BO cast, I know many cases seated too easy. All the boolits were hard to pull. Alludes to 'neck tension' is much different for coated.

[blikseme300]

Bama - interesting comment you make about PC. I found it takes more force to pull coated boolits than using a camming puller on jacketed. Alloy doesn't seem to make much difference. I had to pull a bunch of BO cast, I know many cases seated too easy. All the boolits were hard to pull. Alludes to 'neck tension' is much different for coated.

This mirrors my experience when pulling PC CB's. In my mind PC is not slick or a lube it is merely a barrier between the alloy and the barrel and that is why it works.

The feel when seating CB's is important especially when there is a variance as this is an indicator that things are not right when striving for consistency no matter what lube or coating has been applied.

The relatively low velocities of pistols compared to rifles and the positive experiences for pistol PC shooters clouds the reality that PC does fail in certain respects at higher rifle velocities due to stubborn fouling build-up and as a result drop-off in accuracy. Yes, PC does have a place for CB shooting but it is no nirvana solution for CB's overall.