Hugnot
Well-Known Member
Thanks for responding.
I had some cases that were loaded with near max loads but upon trying to slip fit a bullet into the fired case it would not fit without considerable force applied. Brass sides and bolt face were dirty with powder residue. A measurement of case OAL showed they were over .010 spec.& jammed into chamber hard with bolt camming force. Trimming the cases to recommended trim length fixed the problem. Case head space on shoulder was close to zero but OAL exceeded spec (long necks). Accuracy sucked.
Your fired brass showed signs of excessive pressures but unexpanded necks - my guess is the brass OAL was excessive & strong bolt camming forces jammed brass into chamber preventing neck expansion.
The detonation effect can occur with both slow burning single base powders (no NG) & double base powders (NG) with greatly reduced loads. Accurate 5744 , a real fast burning double base powder is sometimes used for reduced rifle loads having large volumes of empty case space. 46 Grains of 5744 would make for lots of unused space.
Double base ball powders, like W760, are very dense and occupy less space per weight than extruded powders having similar burn rates. Less case filling would make for the detonation effect. IMR & H 4895, medium burn rate extruded powders, are sometimes used for light bullet loads in large capacity cases like the the .264 Win Mag.
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