I was just trying to load up some .243 95gr Partitions, and found them very loose fitting, I could push them further into the case with my thumb. Thinking I must have screwed up resizing, I tried pushing a sierra and a barnes into the same case, and found they wouldn't go!

Anyway, I then decided to get the calipers on the Noslers, and to my surprise most of them measure .242 rather than the .243 my other bullets measure! A few measure slightly over .242, but not up to .243.

Is this normal? If it is, is there a trick to getting Noslers to seat? Does their smaller size effect accuracy?

Many thanks

63

I would say there undersized. what does the mouth of the case measure?
Do you have a micrometer? you would get a more accurate measure with them.
i just checked some 6mm that are suspose to be .244 and they measure .243 with the calipers and .2435 to .244 with the mic.
just a little on the undersize.
Dave

Two thoughts:

1. What do the Sierras and Barnes actually measure using the same measuring tool? Maybe part of the difference you feel is because the others are also slightly oversized?

2. What kind of sizing die are you using? Usually, the neck-sizing portion of commercial dies create a neck size which provides more than just .001" diameter for neck tension on the bullets....usually something more on the order of .003"...in which case (pardon the pun) the Noslers would still be firmly gripped even at a full .002 undersize.

Sounds to me as if you may have suffered an instance of "tolerance stack" where several normal tolerances in die expander ball, bullet-size, brass "springiness", etc. add up to an unusable combo.

I wouldn't lay all the blame on Nosler just yet, with the facts we have so far....

I've just measured everything again, the Noslers are still coming in at .242 and the barnes and sierra's at .243 precisely. I've measured 10 each of the Barnes and Sierra's and they were 100% consistent, and I've measured half (25) of the Noslers, and they all came out at .242 or .2425.

I'm using a Frankford Arsenal Dial Caliper, I don't have access to a micrometer.

Measuring the top of the cases they are now about .245 but I'm not confident they weren't expanded slightly in my fiddling to pull the bullets out...there was a little resistance.

I'm using a Lee neck resizer (I know, I know, lee gear!), I just ran another case through it and it came out at .241. I may have erred when I set it up last time though, although all the cases that the sierra's and barnes went in were done in the same batch, and they're firmly seated.

I suspect your right, the noslers are definately not as wide as the other bullets (if I set the calipers to the other bullets the noslers will slide through without touching) but maybe my case resizing was a little lax too.

You don't sound at all lax to me. You sound thoughtful, attentive, and competent.

I asked those questions simply to be sure we know what we are dealing with. In particular I asked about the die type (kind) to see if you were using a brand and model which has interchangeable neck bushings. If it did, I was going to suggest going to a .001" smaller neck bushing and leaving out the expander ball and its rod. As it is, depending on the age of your Lee die, you may still be able to leave out the expander ball and its rod the next time you size your cases. That MAY leave the necks TOO small, but it may also leave them just about perfect. Only trial will tell.

Another possibility about which I should have asked the first time...how many times has this particular bunch of cases been fired? If they have been fired more than 3 times, you might want to consider them a possible source of the problem.

As they are fired, resized, fired again, etc., they work harden. Then when they are pulled over the expander ball they will expand, and will NOT spring back as far or as tight as they should, leaving the necks loose on any bullets which may be even very slightly undersize.

There is nothing wrong with Lee dies per se. I use a lot of them myself. But overseas, where American dies are pricey and often hard to get, I usually recommend that people buy dies which use replaceable neck bushings, like some Redding models. They are much more pricey at first, but if you then need to size older brass to smaller diameter, it is much cheaper to just make another bushing locally than to buy a whole new die.

Anyway, best wishes and I hope you find it relatively easy to resolve this problem.

AC

They are certainly undersize! As to what effect this will have on accuracy, you will just have to fire some and see. I have a couple of .311"-.313" caliber rifles that shoot just dandy with .308" bullets, which must be swaging up somewhat to fit the bore when fired. But I am not sure a Partition is as likely to do this.

Regardiong their fit in the case mouth, perhaps you can remove the expander plug form your sizing die, and just seat the bullets in th cases as they come out "squoze down"?? This will work IF the case mouths aren't reduced too much by the squeezing down process. I've done this a couple times when I wanted to use lead bullets in lever action rifles with just case neck tension to hold the bullet instead of crimping....

If by "undersize", you mean smaller than some other makes, they are. If you mean "too small for the rifle barrel", not necessarily so. A typical 6m/m barrel made in the U.S. has a bore diameter of .235" to .236" on top the lands. (That's the original bore size before cutting or otherwise forming grooves in the barrel). So those bullets are definitely going to be grabbed by the lands. They are also likely going to spread enough to completely fill the grooves.

As the areas of the bullets which contact the lands are REDUCED in size by several full thousandths upon entering the rifled part of the barrel, and the metal has to go SOMEWHERE, it is pretty logical for it to flow to the area of the bore with the least resistance....that is, into the grooves.

It is for that reason that very slightly undersized bullets sometimes offer the best accuracy, and almost always produce slightly lower mean pressures. As an example, for many years some bullet manufacturers made it a policy to offer .22 CF bullets in both .223" and .224" diameters. My experience in shooting both from similar chambered guns is that sometimes the .223" diameter bullets would do best in one gun (.220 Swift), while the .224" diameter bullets would do best in another gun of the same nominal chambering (.220 Swift).

Another solution for slightly undersize bullets that you still want to shoot is to use the Lee "Factory Crimp Die".

I've done this with other cartridges....the crimp die will lock the .242 bullets in very securely.

Garrett