Flash Hole sizes ADI vs OSA .223

[The Raven]

As I'm sitting here going through my brass and prepping it I noted that the ADI and OSA brass (both said to come from ADI) has different size flash holes.

At first thought this may be just a batch issue but the more I checked the more I noticed the ADI brass has a slightly smaller flash hole.

Not having the specialised equipment to measure exactly a test with a few of my specialist drill bits suggested most OSA (and all other 223 brass I had is around 2mm). The ADI a fractionally smaller, which I couldn't accurately determine using metric sized drills.

I wondered what difference the flash hole size would make so I did some googling and turned up this. https://scholarsmine.mst.edu/cgi/viewco ... ers_theses

After wading through it, plus some other sites, it would seem that larger flash holes seem to produce better outcomes. However, some sites also suggested that smaller flash holes would allow for higher loads. This later bit contradicted the theses as they demonstrated that larger flash holes yielded nominally higher pressures.

So in short, I've decided that my ADI brass will be normalised to the standard 2mm (81thou) size for consistency with my OSA. I'm running loads well within spec and get great performance, so see no need to chase hot loads. I just want to be consistent with these two brands of brass.

Any of our competition guys have any thoughts on flash hole sizes and what their preference is? Sure, you're not going to be using 223 like me.

[RDavies]

With 308s, there is quite a bit of evidence of smaller flash holes reducing velocity spread, and hence long range accuracy once they reduce .080" flash holes to .060". However I have also read that this did not translate straight acrodd to the 223. From the small amount I have heard, a slightly smaller, as in .070" flash hole can help, but going down all the way to .060" as in the 308 case did not help for some reason. That said, the ADI and OSA cases are known for being tough and possibly some improvement with the smaller .070" flash hole.

[Camel]

With 308s, there is quite a bit of evidence of smaller flash holes reducing velocity spread, and hence long range accuracy once they reduce .080" flash holes to .060". However I have also read that this did not translate straight acrodd to the 223. From the small amount I have heard, a slightly smaller, as in .070" flash hole can help, but going down all the way to .060" as in the 308 case did not help for some reason. That said, the ADI and OSA cases are known for being tough and possibly some improvement with the smaller .070" flash hole.

From my understanding from what you are trying to say 'rod, is that you LR, both of the BR variety and the F class types, really are tight arses.

[Camel]

Ravon, you really must be bored these days mate, please get out and smell some roses for something different.

[The Raven]

Ravon, you really must be bored these days mate, please get out and smell some roses for something different.

Of course I'm bored, why else would I spend all Easter simply prepping brass that I have no need to reload yet.

I would go outside if the weather allowed

[The Raven]

With 308s, there is quite a bit of evidence of smaller flash holes reducing velocity spread, and hence long range accuracy once they reduce .080" flash holes to .060". However I have also read that this did not translate straight acrodd to the 223. From the small amount I have heard, a slightly smaller, as in .070" flash hole can help, but going down all the way to .060" as in the 308 case did not help for some reason. That said, the ADI and OSA cases are known for being tough and possibly some improvement with the smaller .070" flash hole.

Thanks, I think that pretty much sums up what was in that paper I referenced. The paper specifically looked at 223 and 308. All a bit much for me other than wanting my ADI and OSA brass to be consistently the same, it's bad enough how I separate each brand etc.