Maltby Project Update

[CINDERS]

I use 46Gns AR2209 or 4350 in your land in all my 303's No.4's, MkIII's and my T it works the powder your using is our equivilant of AR 2206H its to faster powder for the 303's from my experience the fastest powder I used was AR 2208 or Varget where you are found the recoil harmonics to sharp. I played with seating depth and crimp with Taipan .312 HPFB, SMK's, Highland's, Hornady 150 .312 FBSP and The bullet factory 174Gn till all the rifles groups were acceptable it took a few years to get it all together. I used 760 Win at one stage and had a bad experience as in one round as I reckon I suffered a flash over from a low density loading and yeah was not a good experience I was lucky.
I shy away from low density loads now though going to have some fun with some trail boss I have for some light hearted fun at 100M.

I do not think fast powders are the go with the 303's rather they like a constant harmonics not an event so to speak I use 06H in my 308 but never in the 303's there is so much to ponder working out loads/groups I would conduct a ladder test find the weight of powder that the group is tightest there is plenty of info on the web for a ladder test. Then when you have the weight play with one thing at a time dont go crimping and changing a projectile along with a primer as the group could blow out again and you'll be puzzled what caused it.
So my load with what ever projie I tested is the same except for the crimp as I made them the same length as a POF MkVII COAL I fls & TTL each case except in the T just neck and TTL all cases are neck annealed with my AMP machine.
I use RP cases CCI BR primers the load data with the AR 2209/H414/4350 you should go 5% under and work up to it as I cannot accept any responsibility in others using it this load/powder works in my rifles but you may have to tweak it I worked it out from load data to give me 90%+ case fill with 2440fps* projected.
Also modern projies fly allot flatter so say to hit a 100M target your ladder may be at 175-200yd setting anyway I have told you what I do I have won comps with that load my best was defeating 40 other shooters timed multi position over 3-200-100yds at the SASR range in Perth, I have done allot of time like we all do with our rifles just change one thing at a time.
I fell into a trap multi powders & loads and in the end just confused myself

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[22SqnRAE]

I use 46Gns AR2209 or 4350 in your land in all my 303's No.4's...

I do not think fast powders are the go with the 303's

Agreed, Ron. AR2208 and AR2209 are the 'go to' more relaxed burners than the rapid AR2206H.

Having serious consideration of the exercise, no one can reproduce the Mk VII round as a standard until they can use the open based, rear-weighted Mk VII bullet. And no one is or will be making them again.

So the best one can do is approximate.

The most important thing to do is match a tight recipe for each rifle. If you have 4 x .303's you will have 4 x 'standard' loads, if you're seeking a higher level of consistency and accuracy. If you're simply out for a hit and a giggle, then go with one load to suit all and be happy at 100 yards/metres.