unusual bullet seating issue

[taliv]

my question is what could possibly make a bullet seat deeper in one group of cases than another? i mean, what physical force

assume same cartridge (6.5x47), bullets (140hybrid) etc. in this situation, 3 different seating dies (wilson, redding, forster) were used and without changing anything on the seating die, bullets in one group were seated consistently .020" deeper than another group. Very repeatable.

There is a difference in the cases between the two groups (number of times fired) but put that aside for a moment.

I can see how a couple of things could cause this:
1. bullets sticking in the seater and being pulled up slightly before releasing - but in this case, there is no mark from the stem and i'm using moderately light neck tension, and i would expect the consistency of the depth to vary much more than it does

2. compressed powder pushing the bullets back up - but in this case, these are nowhere close to compressed loads


so what else am i missing?
bullets are either being pushed to the same depth, and one of them is coming back up
or one is not being pushed as far as the other.

is it possible that the brass is springy and the brass itself is moving in the seating process? given the original use of wilson hand seater and small arbor press, i don't think i'm using enough force to move the brass 20 thou

thanks for any thoughts

 

[dantiff2]

Check to make sure the cases that are coming out with a shorter OAL are sitting flush on the bottom of the case head and not being supported by the taper in the extractor groove of the case.

Dan

 

[Shaggy357]

Where is the base of the bullet setting in relationship with the neck/shoulder junction? Those cases that end up with the "dreaded doughnut" at the base of the neck may allow the bullet to retract during the brass spring-back. Check neck thickness on your brass. I would bet neck thickness varies between the lots of brass and the doughnut build up is causing the difference.

My guess based on the info provided.

Steve

 

[Comrade Terry]

2. compressed powder pushing the bullets back up - but in this case, these are nowhere close to compressed loads

That would've been my first guess, but you said that's not the case.

 

[Fotheringill]

Not my caliber, but did you measure the "test" bullets before you seated them? Are they each exactly the same?

 

[ireload2]

There is no magic. Some where there is a difference in the die or the shell holder or the press.

 

[jlow]

[[/QUOTE]

my question is what could possibly make a bullet seat deeper in one group of cases than another? i mean, what physical force

assume same cartridge (6.5x47), bullets (140hybrid) etc. in this situation, 3 different seating dies (wilson, redding, forster) were used and without changing anything on the seating die, bullets in one group were seated consistently .020" deeper than another group. Very repeatable.

If you are using 3 different seating dies, the question is have you adjusted all three initially to seat the bullets to achieve the same BTO length for the round? If you have not, that's your problem. Each die does not push down on the bullet at the same location on the bullet and so each must be adjusted to give the same BTO for the round.

 

[CharlieNC]

Different seating dies. For a given die, differences in neck tension can easily give several thou range. This was apparent when I started annealing. You could feel the seating force vs unannealed, with up to .005" difference.

 

[X-Caveman]

I have a Lot of 140 hybrids that are tapered about .0008" along the bearing surface. By comparison other lots and my Berger VLDs have about .0002"-.0003" taper. I was getting inconsistent seating depths with the fatties. I couldn't figure it out. Finally I measured the bullets and it sense. They would "fall" after the fat portion passed the part of the neck that was being sized with my Forster bushing. The brass wouldn't spring back enough to grab onto the tapered shank. My solution was to size more length of the neck (float the bushing less).

I called Berger and they said not to worry about it/ they were in spec. Get some micrometers and measure the bullets. You may have a similar situation.

 

[Joe Salt]

Taliv do you use any lubricant on the inside of your necks, if not you should.

joe Salt

 

[mikecr]

If the bullets are actually of the same lot(same ogive radius), then it would take a huge difference in neck tension to consistently cause 20thou shift. It's more than I believe you could work with and not notice as an obvious difference.
You ruled out dies in your scenario.

20thou is way more than normal issues cause.

 

[taliv]

shaggy, donut is definitely something i didn't think about. i'll check that.
brass is all same lot, same neck thickness.

fother, not 'test bullets'. i didn't measure them. i loaded 250 or so rounds for a match (using wilson die) using half 0x fired and half 3x fired brass and was surprised to see the 3x fired were 20 thou deeper

jlow and charlie, after discovering the above, a friend and i tested 2 more seaters and they both did the same 20 thou deeper. we initially adjusted them so they would seat to the higher depth on the 0x fired brass, and then tried the 3x fired brass and they seated 20 thou deeper.

alloy, very interesting. i'll look into that.

joe, no lube. i've tried lube in the past but never figured it out. it always drives my extreme spreads up. but i think you may be on the right track, as i tumble but don't completely clean the carbon out of the neck prior to anneal.

mike, right. thus the confusion. bullets are same lot. i'm stumped. was planning to figure out some test that could help me rule out carbon inside the neck as the culprit (maybe ultrasonic cleaning on my 3x fired, but i'd have to borrow a cleaner)

 

[243winxb]

The 3x fired brass needs a smaller bushing. More neck tension. Even turned necks need a smaller bushing after a few loadings.

 

[500Stroker]

Easy, trust the Wilson die and get rid of the others.
Many people I shoot with and myself use Wilson seater dies and have had no funny issues and are always very accurate no matter how you measure the results.
Good Luck

 

[taliv]

243, i'm not following you. let's take your example to the extreme and say there was nearly no neck tension at all. what would cause one bullet to seat deeper than the other, given the bullets are the same and the seater die hasn't changed?

500stroker, please read more carefully. the issue happened using the wilson die. all 3 dies give exact same results. they all three seat some 20 thou deeper than others.

 

[JohnKielly]

Has it something to do with a dimensional change in the case bodies after being prepped allowing the cases to enter the die further?

 

[243winxb]

Its just a suggestion to see if it makes a difference.

 

[tenring]

Probably neck tension. Are you sizing with a expanding ball type die or with a bushing die? If the first, remove the ball; if not try smaller bushings.

 

['Freak]

Brass is work hardened a little more every time it’s subjected to dimensional change. A case more times fired then reloaded and fired again so more so work hardened isn’t going to spring back the same so isn’t going to try to hang onto the bullet on firing, or resist the bullet’s insertion into the neck, the same as a case that’s been work hardened to a lesser degree.

 

[taliv]

how could differences in neck tension and spring back cause this?

are you suggesting both bullets are being seated to the lower depth, and it's actually the new brass that is springing the bullet back up 20 thou?

my sizer is redding s type, with bushing, no expander ball.