.264 bullets fit loosely in a .268 case, how important is neck tension?

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Lahti

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Hello,
I got one of the recent imports of carcano and decided to try some .264 bullets to start. I know the oddities of carcano bore diameter, and that this may or may not shoot well in my rifle but I thought I’d give it a try. My issue is that even with my seating die (Hornady) set to give some crimp, I can still turn the seated bullet with my fingers and slide it back and forth with some effort. I know that under recoil there’s a good chance OAL will change and would be unsafe to use, but if I were to singly load into the chamber is there a safety issue with this and is there any reason to expect this would dramatically hurt accuracy?

I know there’s purpose built crimp dies to fix this going forward, and .268 bullets as another option but I was wondering if there was any reason this wouldn’t work as a stopgap/experimental measure? Not looking for laser accuracy, just trying to get an idea if my rifle will tolerate .264 bullets before I get the crimp dies/give up and switch to .268 and thought the general discussion on neck tension could help others with this caliber or situation.

Thanks,
 
If you’re just playing; try sizing the cases without the expander ball. It might be enough difference for the cases to grip the bullets at least. How they shoot is anyones guess; but for what its worth there were .303 British loaded with .308” bullets. Might happen.
 
Most reloading books I read suggest that you want the bullet to expand the case neck by about 0.002" when the bullet is inserted. 0.002" case neck "tension". You are proposing "0" tension - needing a crimp to even hold the bullet in place. Kind of out there inventing stuff for yourself. Maybe it will work, maybe there will not be enough "bullet pull" to allow your powder to burn properly? Hoping that you can tell us what you find out in your experiments? I just can not come up with a single reason to want to try .264" bullets in a cartridge calling for .268" bullets. At very least, and not sure at all it is a good idea or not, but you can reduce the diameter of your expander ball in the die to get a .262" inside case necks when you re-size them?

NOTE: EDITED after reading Post #2 - not certain any expander ball even needed? Might want to try as suggested there - most dies size the necks "too small" and then "open them up" when pulled back out over the expander ball.

I doubt very much that jacketed bullets are going to "slug up" to fill your bore - I am struggling with exactly that in a rifle with a perfectly good and normally dimensioned 270 Win chamber, a 0.270" bore and 0.282" lands - the lands, for whatever reason, are .005" oversize for a nominal .277" bullet - 4" to 5" groups at 25 yards with multiple loads and bullet weights. And using 7mm (0.284") bullets will not fit into that 270 Win chamber neck.
 
You'll have poor ignition/low pressure and risk squibs with 0 neck tension. I ran into a similar issue with Lee 7.62X54R dies with a .310" expander (that should have been .308 ish for .310 bullets) and bullets sold as .311 that measure .3095. I had 2 squibs using a mid range load of H4895 under a 180 gr. Speer FBRN. The other rounds did not fire form the cases and they were all sooted up quite a bit right down to the rim. The rifle was filthy. Turning the expander down to .308" provided proper neck tension, good es/sd for unprepped brass, proper fire forming of cases and very clean burning.
 
Hello,

Interesting feedback so far, for what it’s worth I’m using the Hornady manual, dies and projectiles, only foreign component is the ppu brass so I wasn’t expecting any issues at all. Is it possible the techs at Hornady used a .264 expander ball when making those rounds to get the data? I load 6.5 arisaka and Swedish so have that size expander ball to try, unless I’m misunderstanding?
 
I looked through my Hornady 9th Manual and it seems to agree with you - FYI - they report they used Prvi Partizan brass - that is the PPU that you are using. They used a rifle that they identify as an M41 - not certain what that is compared to the one that you are using. None the less - I just can not see anything good coming from firing off cartridges that have "0" neck tension. The Hornady 9th manual simply has nothing, at all, to say how they loaded these .264" bullets versus how they loaded their .267" bullets - nor do they mention their loading techniques in almost any other cartridge that I skimmed through. If it was me I would be reverting to the 0.002" neck tension "general idea" or close to that, but I was not there to know how they came up with their data. Note their statement on page 279 about the 6.5x52mm Carcano, "The rifles are, by virtue of this (.257" bore and .268 groove"), not generally accurate with conventional .264" 6.5mm bullets".
 
I used to remove the sizer button in the sizing die after depriming and run the .303 British through the die once more to allow me to shoot .308 size bullets.The the seating die could then grip the slightly undersized bullets.May also work with the 6.5 Carcano.
 
Fill them with black powder it was common to seat the bullets by hand in an unsized case.

Or paper patch your bullets to size. Then they will fit the case and the bore. And you can use normal ole printer paper or loose leaf.
 
A uniform bullet pull weight is important to accuracy, and if you can turn the seated bullet with your fingers, or slide it back and forth in the case neck, the situation is less than optimum. A different manufacturer of brass might have a thicker neck, which increases neck tension. Polishing the expander ball while spinning it in an electric drill effectively reduces its size and increases neck tension. There are a number of cheats you can try if you don't want to polish your expander ball. Removing the expander as Dogleg suggested is one. Using a long seating depth so the bullet jams into the lands uniforms the bullet pull weight, but might prevent you from loading rounds from the magazine, and creates the potential of sticking the bullet in the chamber lead, and dumping the powder in your action if you unload a chambered round without firing it. You can also crimp your bullets, although I'd just crimp lightly on bullets without cannelures to prevent distorting the shank. That will still be enough to uniform the bullet pull weight.
 
Neck tension is very important for safety and good ignition.

After sizing the brass, remove the decapper rod and re-size. This may make the neck tight. If the brand of die uses a ball on the decapper rod, take the ball off.
 
Paper patching is a science all unto itself if you don't know how to do it properly.Have an article somewhere in G+A that the author was paper patching a .275 H+H with .284 bullets as the groove was bastard size.The undersized bullets had to first have their jackets roughed up with a bastard file rolled on a steel plate to grip the patch.Then there's cutting the correct patch shape and length as well as making sure it's wrapped in the right direction so it tightens with the rifling when shot .Other than that it's easy? High speed cast can be accomplished wrapping the bullet with teflon plumbers tape in the correct direction.
 
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