neck tension changes with time?

[CZ550]

Had an interesting experience yesterday. I put a 6.5 barrel on that I havent shot in over a year. I had a few loaded rounds from the last match about 13 months ago and decided to pull one bullet and weigh the charge because I failed to keep my notes. I use a hammer (inertia) puller and much to my surprise with one very light tap I was able to move the bullet far enough to pull it the rest of the way by hand. I figured they would have taken considerably more effort. Neck tension was still very light after one year.

So heres what I am thinking, Is it possible that the brass just below the edge of the last point of contact on the bullet over time or whatever forms a tight spot, there for causing a considerable about of force to seat deeper after a period of time. If you look at a loaded round with say .005 neck tension and the bearing surface is above the neck shoulder junction you will get a visual of what I am saying. You can see where the brass expands around the bullet and below that the neck is smaller in diameter.

Just thinking out loud here. But I can say for sure my 12 month old bullets were not bonded to the cases.

 

[BoydAllen]

Good thought, but the amount of additional effort that we are talking about is impossible to create by any amount of neck tension. One of the problems with written, or for that matter verbal communication is that words have different meanings, depending on who is reading or listening to them. Keep up the good work. When you share, we all learn.

 

[shanmoll308]

Just a thought but, maybe it is the salt in the perspiration in ones fingers contaminating the bullet heads just before seating that contributes in some way to the reaction between the bullet and the brass?

As I wear surgical type gloves when reloading and shoot my rounds usually within a few days of loading I would not encounter the pop sound you are referring to.

Again just more unproven theory but I do like CZ550 explanation.

Adrian.

 

[bozo699]

Adrian,
Your theory has been discussed in Boyds thread I re-posted, and i very well could be I don't know, what I do know is the ammo doesn't have to sit for long periods of time before the "POP" occurs, I loaded my rounds that it first happened too on a Wed and reseated on Sat afternoon for my Sunday match and they all popped, and they were mollied and had .001 neck tension so go figure,... ???
Wayne.

 

[lpreddick]

i am more preplexed than ever now. i thought time had a big part in causing a change in neck tension, so i drug out some 22-250 rounds i loaded 10 yrs ago! some were new brass and some fireformed. seated both .010 and NO POP! there was a very slight hesitation before the bullet moved. i am starting to wonder if the surface conditions of the inside of the neck has a big factor, if not the main factor in determining the amount of "bonding" that takes place. powder residue particles would act to very slightly seperate the brass from the copper. i once highly polished some bullets and the inside necks and this combo resulted in a very tight bonding. i will load some without doing anything to the inside neck and some after really brushing the inside and wait awhile then seat both batches .010 ? have we heard from the ultrasonic cleaners, since the inside of their neck are very clean.

 

[bozo699]

i am more preplexed than ever now. i thought time had a big part in causing a change in neck tension, so i drug out some 22-250 rounds i loaded 10 yrs ago! some were new brass and some fireformed. seated both .010 and NO POP! there was a very slight hesitation before the bullet moved. i am starting to wonder if the surface conditions of the inside of the neck has a big factor, if not the main factor in determining the amount of "bonding" that takes place. powder residue particles would act to very slightly seperate the brass from the copper. i once highly polished some bullets and the inside necks and this combo resulted in a very tight bonding. i will load some without doing anything to the inside neck and some after really brushing the inside and wait awhile then seat both batches .010 ? have we heard from the ultrasonic cleaners, since the inside of their neck are very clean.

lpreddick,
I now brush my inside necks with a nylon brush on a RCBS power case prep station, 10 strokes exactly on every case I use in matches, my seating pressure is almost identical on a K&M force seat arbor press, I anneal everytime and I am meticulous with brushing the necks, after our championship shoot in Aug two years ago when I had the "POP" I tried all kinds of things figuring out necks, with all other factors the same squeaky clean necks seat harder then ones that have just been brushed but still have some carbon left in them, I believe it acts as a lube so to speak. When I had the loud POP and it took a lot to get the bullet to move I was shooting 6*284, Lapua 6.5*284 brass necked down, a little less then .001 neck tension mollied 107 SMK bullets done myself but I did not wax them, and I think the key to the pop was I used 0000 steel wool to polish the inside necks, I thought I cleaned all the residue ( small steel particles ) from the inside of necks but perhaps I didn't do a good enough job, I think a combo of several things may have came into play, Aug, so it was hot!! and my hands were sweaty probably, squeaky clean necks but with micro pieces of steel possibly left or embedded in the necks and un waxed molly bullets. All I know is these bullets seated so hard or rather they initially seated like butter but I seated them way long and when I did a final seat at the match I thought I was going to break the gear in my arbor press, thank God I took my 21st century and not the Sinclair or I think I would have! I have since played with different degrees of cleanliness on the inside necks and switched to a K&M arbor press with the force seat indicator on it and you can most definitely see a difference on the gauge with differences in inside neck conditions, for instance if you anneal it leaves a scale for a lack of a better term on the inside and outside of the case, I have found if I don't re tumble it I get inconsistent shoulder bump and if I don't really brush the inside neck they seat much harder and also inconsistent! If you or anyone else on here doesn't believe me, take some old brass or some range brass and just do some playing with it, try different things and you will find there is differences, if it is important to you, then change your routine if it isn't then continue on with what you have always done, but don't say it can't happen because it can, and one last thing if your shooting 300 yards or less this may not apply but if your shooting 600+ and one case has .001 neck tension and another has .0025 and another has .004 I assure you they wont go where you expected them to go unless the wind Gods help you out! so the same thing applies with inconsistent seating pressure, again we could argue terminology, is it neck tension or bullet grip or something all together different,....who really gives a crap you know what were implying! best of luck to all of you with your neck tension and inconsistent seating force issues.
Wayne.

P.S Boyd I saw you called yesterday, I was repairing my roof in 106* : ??? I will call you this evening if I get in on a reasonable time