Different casings affecting seating depths?

oilmanjd

Well-Known Member
Guys, I am new to the relaoding game and experimenting with the press and dies etc.
I have used the lock-n-load gauge and comparator (0.308) and obtained the distance to the lands/ogive etc and therfore the required bullet (ogive) length.
Now my question is, does using differing manufactures brass casings affect the desired bullet seating depth or is there something I am doing wrong?
I have some Winehester brass and get 90% consistency in seating depth, however, when changing over to Privi and Federal brass, without changing any set up I have, the bullet seating depth is quite a ways off.....any advice greatly appreciated.
Thanks, Jd.
 
Muir, I have measure COAL to be 2.284, backed off to 2.264 for the jump, this is what I set die for on the Winchester casings, then when using PP and Federal the seating depth is much greater, COAL in the region of 2.235 to 2.245 dependant on whether it was a Privi or Federal (all once fired cases). Maybe this is acceptable QA but I would have thought the tolerance to be a little tighter than that.
Thanks, Jd.
 
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They should be tighter. That is too much. Are you certain that you have the does set correctly? It should be within a few-four thousandths.~Muir
 
Are you using the "ogive length" for the COAL values you report, or are you using the bullet tip? If you are using the ogive length, then "something's rotten in Denmark". There's no mechanical mechanism for changing the OAL if the bullet doesn't change. HOWEVER, is there a possibility that you have mixed batches (lots) of bullets or even manufacturer? Different lots of bullets CAN have slightly different ogives, and small ogive-angle differences make big ogive length differences. Second, different bullet manufacturers OR even bullet types within a manufacturer WILL have VERY different ogival lengths.

So...

1) Are we discussing changes in ogival lengths OALs or "tip" OALs?
2) Have you mixed batches of bullets (same type but from different boxes)?
3) Have you mixed bullet types - flat-base for boat-tail for example, or 150 for 130?
4) Have you mixed bullet maufacturers?

These differences in OAL are too great IF the the ONLY component changed is the bullet, AND if you have not mixed batches of bullets.

Regards,
Paul
 
Just a thought Paul - Muir , and I might be 'way-out here. If the different cases are of harder brass or have thicker necks, but the bullets are all of the same manufacture and model but the ogives fairly soft, might this cause the bullet seater to require to exert more pressure and dig in or distort the ogive a bit, thus giving a slightly different seating depth.
The average bullet seater is not shaped to conform with every ogive pattern, and in some instances the push might be on the tip of the bullet whilst in others it will be the leading edge of the 'cup' which will force the bullet home.

I've seen ring marks left in bullet ogives before now.

Do you think that there's any possibility of this ?

Ken.
 
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Just a thought Paul - Muir , and I might be 'way-out here. If the different cases are of harder brass or have thicker necks, but the bullets are all of the same manufacture and model but the ogives fairly soft, might this cause the bullet seater to require to exert more pressure and dig in or distort the ogive a bit, thus giving a slightly different seating depth.
The average bullet seater is not shaped to conform with every ogive pattern, and in some instances the push might be on the tip of the bullet whilst in others it will be the leading edge of the 'cup' which will force the bullet home.

I've seen ring marks left in bullet ogives before now.

Do you think that there's any possibility of this ?

Ken.

It's a possibility that what you describe could be a contributing factor but I doubt it could account for .020 to .030" of seating depth variance. I would venture that a variance in neck tension combined with linkage slop might account for a bit of variance. It just seems to me that this is excessive. I once tested bench mounted gear against the Lee Classic (In line) loader and found that with same lot brass for both (simultaneous loading starting with new brass) the bench gear averaged +/- .006" over-all-length with over the counter bullets, and the Lee in line averaged +/- .003 inches. ~Muir
 
Exactly what Muir said including the measurements.

While my sources and circumstances were different, I find it almost impossible, even with a "micrometer die" to consistenty do better than about 0.003", and for most dies, 0.005" in ogival length.

The source of that variance is tedious to ascertain. It can have a variety of origins including all you mention.

Regards,
Paul
 
Thanks both - just a thought. I'll add that the 'dents' were more often seen in round nose bullet models.

Cheers Ken.
 
Just a thought - my reloading press is a Wamadet which is a cantilever system pressing the die downwards and it would appear, no chance of body flexing. It seems pretty tight in the joints so I'll do a bit of measuring and see what my cartridges come up with.

Ken.
 
It will be interesting to see those results. Just for the sake of this thread, I'll do a similar exercise using my 'regular' RCBS JR press and Lee .308 Win dies, AND my RCBS mic die. I haven't done the measurements in a while, but I am pretty sure the two won't be too far apart.

Regards,
Paul
 
So yesterday afternoon I stole a few minutes and loaded 10 rounds of .308 Winchester - five each with my RCBS "micrometer" die, and five with my Hornady die. I used the bullet I use most in my .308 Win - the Speer 130-gr HP #2005. Here are the results - all dimensions in inches.

Hornady: 2.2106, 2.2106, 2.2114, 2.2114, 2.2122, 2.2122
Mocrometer: 2.2165 x5

The results were a bit surprising because they didn't jibe with results I got with 150-grain Nosler BallisticTips. I assumed, apparently incorrectly, that the variance observed with the Noslers was due to the dies. This data, sparse as it is, suggests the variability was due to the bullets, not the dies.

Setting the middle value as "0", the variation observed with the "regular" Hornady die was minus 0.0008" and plus 0.0008". (If these numbers appear "oddly similar" it's because the mic I use is a metric mic and I convert to "English" using a 25.4mm/in conversion factor.) The 'spread' is less than about 0.0016 inches. That's good.

The RCBS "micrometer die" showed no measurable variation. That's "REAL good".

Now before anyone jumps to too many conclusions about the precision reported here, let me point a couple of 'things' out. Most importantly, because I was only interested in the variance, I didn't try to achieve a specific length. In other words, I simply set the dies in the press and let the final lengths 'fall where they might'. Were I to try to "hit" an exact OAL value, it would be MUCH more difficult to hit that exact point with 0.0015" precision. Not impossible, but more difficult for sure. Still the variance around whatever value I settled for would likely be close to that recorded above for the Speer 130-grain bullets.

Second, this sample size is small. I think it is 'representative' of what might be expected, but it is still 'small', so don't get too aggressive in drawing conclusions.

Third, someone, ;) should do this with several makes and models and see what the variance is between bullet makers and bullet types within a maker. And, the ability to MOVE exactly 0.005" from one setting to the next also needs to be examined.

The point was to see how realistic it is to expect to adjust COL to a precision of plus or minus 0.005" or less. This modest look, using these bullets, suggests that it is not unreasonable to have that expectation of precision for one setting with one bullet type.

Regards,
Paul
 
Hello all - I'm back and hope that you didn't all wait - holding your breath - - - - .

The measurements were taken from a quick sample of nine .270 Win. reloaded cartridges using the same bullets and brand of cases. These were done on a Wamadet press which has seen at least 20 years of service.
3.257 ", 3.258", 3.2575", 3.256", 3.258", 3.257",3.257", 3.257", 3.2565".

On the guage I detected a slight base roll on a couple of the cartridges and suspect that there was the slightest influence of a primer protrusion, so this might have accounted for the larger figures.

The various pieces of advice by Paul do not require to be embellished-upon.

Ken.
 
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