Click BANG!!!

[Forrest Halley]

Well I figured I'd show up to the thread and kick a man when he was down, but at looks as though I'd have to stand in line. Righteous indeed I'd be in doing that!

I sure hope the OP gets it sorted out. I figured if a man's going to such lengths to rectify the problem and has alluded to the supply chain difficulties that I'd just cheer him on.

 

[Tex .416]

One thing to check is whether the sizing die is setting the shoulder back too much.

The headspace gauges below mount on calipers and measure base to the datum line, which is the mid-point on the shoulder. Starting with the die screwed out a bit long and sizing a FIRED piece of brass, turn the sizing die down no more than a 1/8 turn at a time until it it sets the shoulder back 0.003” - 0.004” at most. Setting the shoulder back more than that creates excessive headspace, which allows the firing pin to push the cartridge forward and which can cause inconsistent ignition.

These should always be used by every one reloading to assure the sizing die is correctly adjusted. Obviously, they are not for straight wall cases the are rimmed or headspace off the case mouth.

Hornady Lock-N-Load Headspace Ga 5 Bushing Set Comparator

The Hornady Lock-N-Load Headspace Gauge is a great tool for increasing the accuracy of your loaded ammunition. The Headspace gauge measures from the...

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[norfolk shooter]

Right the problem has been solved!!

All it was, was too much slow burning powder trying to ignite. I went to my buddies place to test some new loads and they all went off very well and I even shot some outstanding groups. all using the same primers and powder. Albeit i have worked up a load with a faster burning powder too in order to prevent the same happening again.
Time to load up and shoot!!!

 

[fourfive8]

Good deal! Don't say I didn't tell you

Plus going to slightly faster powders will help prevent "exploring" the dreaded SEE phenomenon.

Some don't consider it such, but a big 577 is similar to a big, straight-walled case in many ways including having a generous expansion ratio. That is why those type cartridges usually do best with slightly faster powders. For proper burn and function, the progressive powders (all the smokeless powders we commonly use... from slowest to fastest) require progressive pressure curves for proper burn and cartridges with high expansion ratios don't provide the environment to provide that progressive burn. Progressive powders require some confinement and "self pressurization" for optimal performance and burn. Conversely, black powder requires little if any self pressurization or confinement to burn properly

 

[fourfive8]

The trick is to match the progressive nature of the burn of the powder used to both the case shape which tends to confine the combustion process and the inertial mass and friction of the bullet. Of course a large mass of very slow powder that also has a retardant coating is going to require a good primer to start it but also has to be confined by case shape, bullet inertial mass and friction to get it to burn at a progressive rate to match the force required to accelerate the bullet to desired velocity in the barrel without exceeding the safe working pressure of the case and rifle.

Pic of big carts with relatively large expansion ratios- left to right- 460, 470, 505, 500, 577, 600, 700 and a 264 Win Mag to show a cartridge with a relatively small expansion ratio. That small expansion ratio cartridge does best with very slow powders while all the other larger cartridges do best with various powders that are faster relative to the 264.