When does a bullet get to small?

[17nut]

I got a fine Danish Krag-Jørgensen rifle that is supposed to be .323" bore, but in reality is more like .327".
When does a condom bullet get to small and accuracy fall off (rapidly)?

[madsenshooter]

There's a lot of variables there. It might somewhat depend on what the bore diameter is, your .327 is groove diameter, I imagine. I've dealt with US Krags that have a oversized groove diameter of .311 vs the nominal .308, so three thousandths oversized. Despite the oversize groove dimension I've got 1moa groups with .308 j-words at moderate velocities. As parashooter explained it to me, the oversize bullets ride on the rails of the rifling with a bit of gas sometimes leaking past the base and supporting the bullet, with luck equally around the bullet. That theory leaves out obturation which is going to occur if the chamber pressure is high enough. Get enough pressure, the base of the bullet is going to expand into the grooves, again depending on variables, jacket material thickness and hardness, for example, or if the bullet has an open or closed base. Give whatever you can get a try, that's about the only way to see for yourself. Maybe you'll find bigger is better, maybe not. And an undersize bullet that shoots good at full pressure might not shoot so good at lower pressure due to lack of obturation. Even though I said that, I've found otherwise.

[17nut]

My bad!

Bore is .316 and groove is .32675".

I asked because i'm a bit broke and buying 100pcs of several different designs, to use 10 and use the rest as paperweights is not my kind of fun.

I have loaded the first 40 cartridges with the Lee 329-205 sized .328" and nose sized .315" masuring @ .316".
Sunday will tell.

[Multigunner]

Depends on how thick the jacket and how sharp the kick in the pantaloons the charge gives to the projectile.

Many early smokeless rifles used an undersized bullet that depended on upset to fill out the grooves. This was an effort to reduce chamber pressure when bores were badly fouled or rusted from corrosive primers. Early smokeless with a high nitro content had a higher initial impulse than later single base powders. An example would be some Lee Enfields with oversized bores that still shoot tight groups when using cordite loads, even if the bullet is also undersized, but keyhole when using single base loads.

[Good Cheer]

When jacketed first became all the rage with European powers there were some designs that used jackets that the bases bumped up to fill the grooves. Not meaningful to your current application, just (to me) an interesting tidbit on how things were once done.
Best of luck on the Lee. It might just be the cats meow.