Ideal difference between case ID and bullet OD?

There's a discussion on TargetTalk about loading .32 ACP and the use of T&Bs new 60 LSWC.  A comparison is being made between this bullet and Hornady's 60 gr XTP both in performance and diameter.  The T&B bullet has an OD of .314 as opposed to .312 for the Hornady.  Both are my measurements.  The new cases I'm using have an ID of .306.  Is there an ideal difference between case ID and bullet OD?

Hi besser,
I have an Erma in .32acp with a .311 barrel, so my diameters are different from the Pardini barrels at .314+. 
My set-up:
The expander for Hornady XTP's (they measure .311-.3115) is .310" OD.
The expander for .312" lead bullets is .311 OD.
At this moment I am casting with soft lead and gooey lube and have only tiny traces of leading in the lead angle, none in the rifling (using a bore scope).
I'd like to hear what others are doing also.
Wes

It sounds like I should be expanding my .306 ID cases to .312 or .313 for the T&B .314 bullets.  Is that correct?  And if so, how do I go about doing this?

Also, why does the Hornady XTP bullet perform so well when it's at least .002 less in diameter than the barrel?  And why wouldn't a similarly sized cast lead bullet perform as well?

I'm beginning to maybe understand now why Starline has been so cautious about introducing a .32 ACP case and why they were asking some of us what diameter bullet we intend to use.

A lead bullet should be AT LEAST 0.001" larger than the actual barrel groove diameter. Thus, a 0.356-0.358" lead bullet will be "right" for a 9x19.
For a .32, I find that lead bullets of 0.313-0.315" work well.
Expanders: Ideally the case ID should be 0.001" smaller than the bullet OD. 0.002" is fine. This means that many folks who are trying to get the best accuracy from lead bullets will order an over-sized expander.
Let's say I have a 0.308" expander plug and have 0.312" bullets. After case expansion, the case ID is 0.307". This tells me that the case ID will be about 0.001" smaller than the expander after expansion. As I have 0.312" bullets, I want the case ID to be 0.310-0.311", so I order a 0.311" expander, which should give me a case ID of 0.311"--just to eliminate having some cases expanded too much. Ideally, if EVERY case had an ID that was 0.001" smaller than the expander plug, I would want a 0.312" plug, but I also don't want to worry about loss of bullet grip from some case being expanded too much and actually being 0.312".

I can tell you that the Magnus 32 wadcutter bullets give an ever so slight bulge to my RP and Lapua cases.  Enough to cause them to fail to chamber on occasion in my Walther GSP-C.  They shoot well and are attractively priced but I'll have to find a slightly smaller caliber bullet.  (I noticed that Dardus gives you a choice of .312", .313" or .314" calibers.  I only wish they sold a sampler pack).

Kelsey: what brass bulges?  I know most of this thread is on ACP but for S&W-L, you have to watch out on the brass; it isn't all straight wall.

 The expander or the bullet can bulge the brass where it tapers to a thicker cross section.

Softer bullets tend to swage down inside the case.

Solved my leading and accuracy issues.

regards

Thanks for your insights.  As you noted, the case walls become thicker deeper within the case.  The hollow-base wadcutters that I have tried are either soft enough or, because of the hollow-base feature, are more able to compress slightly to accommodate the smaller inside diameter without bulging the case.  My .314" Lapua HBWC's create no case bulge whatsoever.  However, Magnus .314" wadcutters (not hollow-base) are either harder lead or less able to deform due to the lack of a hollow-base, thus they leave an ever so slight bulge (barely visible, but measurable with a micrometer).  This is the case on both R-P and Lapua cases.

I don't have any unloaded Lapua HBWC's left, but I expect that they are actually longer than the Magnus non hollow-base bullets since they are both 98 grains.

My simple solution is to find a different bullet (which is easier than resizing bullets, and then having to touch up the lube to avoid leading).  I've ordered .313" and .312" Dardus wadcutters to see how they work as an inexpensive practice load.  I'll use Lapua HBWC's for matches (as they function flawlessly).  (Has anyone noticed that reloaded 32 S&W Long's are only a very small amount more expensive than 22 rimfire now!  I have mine down to 11.9 cents per round including shipping of components etc).

By the way, if you are loading flush-seated wadcutters in 38 specials (e.g. for S&W 52's) you'll find that you'll usually bulge the case when you load it into a 38 Spl +P case, but not in a non-+P case.  I was told by a rep from an ammunition manufacturer that +P cases are simply truncated 357 Mag's and consequently have a thicker case wall and smaller inside diameter.  I've found that every brand of +P 38 Spl case that I've tried will significantly bulge with a wadcutter and none of the non-+P cases will bulge.  It makes a big difference in getting your S&W 52 to function reliably.

Try unresized brass and see what happens; the crimp holds the bullet in place. I am puzzled that RP brass does that; mine was verified as straightwall (as are the Lapua brass). I used ball micrometers.

I also had an expander plug that was 0.315 and if it went too deep, that, not the bullet bulged the case.

Your observations above are correct about the Lapua being longer AND the bullet base compressing; I pulled some and it was obvious.

A too small hardcast bullet diameter bullet solves one problem but causes another; leading. Three bears solution: you need just right.

regards

 am

Good thoughts.  Thanks.

I fired 90 rounds of Lapua HBWC's today; no malfunctions and shot a couple of points above my average (850).  So at least I have a good match bullet.  I'll play around with your suggestions to see if I can get a less expensive combination to work as a practice load.

Dr. Darius Young used a .308 barrel with his Erma in .32 S&W long. It produced satisfying groups for him. A fellow named Dave Wilson reportedly makes fast twist barrels in .32 S&W long. If I were going to go the .32 caliber route, I'd consider him.

Back to my dilemma with loading for .32 ACP ....

Here's the skinny on the situation as it now exists:
The brass cases have an ID of .306".
The Dillon expander with powder fill has an OD of .308.
The Pardini barrel apparently has an ID of .313".
The T&B LSWC bullets have an OD of .314".

The prevailing opinion is that the cases are swagging the bullets down to a less desirable diameter and causing leading of the barrel and accuracy issues.  The solutions that I've come up with are as follows.

Open up the case ID with a reamer to .311".
Expand the case ID to .312" or .313" with a separate die without reaming.
Expand the case ID to .312" or .313" with a separate die with reaming.

The brass cases have a wall thickness that is about .002" thicker than other cases I've measured so reaming them about .004" seems to make sense if expanding the case alone to .312" or .313" doesn't allow it to fit the barrel chamber.

Thoughts?

Find some different brass. I've heard good things about Magtech, they sell new ammo too if you can't find just their brass.

- Dave

dronning wrote:Find some different brass.  I've heard good things about Magtech, they sell new ammo too if you can't find just their brass.

- Dave

It would still have to be expanded to ????

beeser wrote:

dronning wrote:Find some different brass.  I've heard good things about Magtech, they sell new ammo too if you can't find just their brass.

- Dave

It would still have to be expanded to ????

I thought I read in another of your posts that you had Fiocchi brass and indicated it had thicker walls and a smaller ID than other makes of .32acp brass.

- Dave

dronning wrote:

beeser wrote:

dronning wrote:Find some different brass.  I've heard good things about Magtech, they sell new ammo too if you can't find just their brass.

- Dave

It would still have to be expanded to ????

I thought I read in another of your posts that you had Fiocchi brass and indicated it had thicker walls and a smaller ID than other makes of .32acp brass.

- Dave

That's correct.  The wall of the Fiocchi brass is .002" thicker than Hornady brass, from factory ammo. for example.  I have some Magtech brass coming my way but if it's the same as the Hornady the ID is still only .310".  Based on noylj's comments the ID should be .312" or .313" for the .314" bullet.  So the brass will have to be expanded with an over sized die either way.  Incidentally, the expander on the Dillon combination expander/powder funnel is .308".  I just purchased .312" and .313" expander dies from CH Tool.

Get a new expander.  Far easier.  If it isn't available from Dillon, any decent machine shop could make one.