Thread: "Air space" in 303 British and 308 Winchester caseloads...Dangerous?

Originally Posted by Kiwi Sapper

having fired a lot of WW 2 303, I am now VERY conscious of a click.....bang

Or even worse, a click.......

Consequently the latter causes me to freeze for 15 seconds then eject and "peer myopically down the long hollow thing." :>)

I'd suggest waiting a tad longer. NRANZ requirement on their ranges is 30 seconds and that's for modern ammo not cantenkerous old milsurp.

Originally Posted by Kiwi Sapper

Ah, thank you.
My ponderings were something along this line but as it is not an issue over which I have any control, ( apart from buying suitable projectiles) I disagree with winaa's view. I believe I have more ability to affect accuracy with projectile seating depth.

Seating depth and concentricity are related.

Consider why people seat just off the lands. ON lands may of course cause a pressure spike, so just off lands is desirable. But why try and get as close as possible to the lands? It is for out of a desire to have the projectile engage concentrically. A long throat risks the bullet having too much time and space to misbehave (deviate from concentric) before it locks into the rifling.

Originally Posted by zimmer

I'd suggest waiting a tad longer. NRANZ requirement on their ranges is 30 seconds and that's for modern ammo not cantenkerous old milsurp.

Good point..........I can count to ten, add in the fingers and then do the toes.:>) Sweet as. :>)

Originally Posted by Cordite

Seating depth and concentricity are related........

Yup, so that is why I will try to follow mimms2 golden rule, ".....the golden dimension for me has been 0.02 ogive to lands.


Am I wrong?

Originally Posted by Kiwi Sapper

Good point..........I can count to ten, add in the fingers and then do the toes.:>) Sweet as. :>)

Yep, if you open that bolt and a hangfire does go bang you may end up less 5 or more of those counting aids.

At least with a smle you can manually recock without opening the bolt and try again.
Although I've generally found if they don't go off with the first strike they won't go off at all.

Originally Posted by mimms2

I've heard this story before. Maybe even from you. How do you know you got "double detonation".... and what exactly is that, anyway...

(some keyword searches are SEE, secondary explosive effect; and detonation, which is the super-sonic propagation of "an explosion" which afaik is impossible in this scenario as powder is rather carefully engineered to deflagrate (burn at subsonic speed)...rather than detonate. And the transition has been carefully studied by folks clevererer than me. And if they reckon it ain't too likely, I'll reckon it aint too likely.

BA....Boom definate pause between them....really made a fella flinch something aweful.

Originally Posted by Micky Duck

BA....Boom definate pause between them....really made a fella flinch something aweful.

Greetings Micky,
I find your description of the Ba...Boom sound quite interesting. Setting aside any discussions about SEE and it's acronyms it sounds to me that you may have had a delayed ignition. I have seen this described as a pressure spike in a series of identical loads. This seems to happen in well worn barrels with slow powder. The theory is that the cap goes bang and the powder takes a wee while to get going. In the mean time the projectile has entered the worn throat and slows down just as the pressure rises causing a pressure spike. About 20 years ago loads for the .243 Win and 7mm Rem Mag and some others were reduced after the introduction of electronic pressure testing equipment. The new equipment showed pressure spikes that the old copper crusher test equipment could not detect. Both these cartridges are noted barrel burners sometimes blamed on their short necks. Thought you might be interested.
Regards Grandpamac.

Without being there it can only speculation on my part. But my first think is lazy lock time.

Did it happen every time?

Cannot remember without reading back but wasn't it a reasonable load of ball powder?