OzFclass

I'm doing some testing ahead of a trip to Bisley, so I'm loading the old sierra 2155.
I've noticed a huge difference (100 thou) in base to ogive measurements between current NRAA loaded bullets and a box of sierra 2155 sourced from a mate.
Anyone else noticed this recently?

Aubrey, if you can pardon me I can give you a little history. Back in about 2002-2003 with early preparation for an Australian TR team competing in a Palma match at Bisley, the decision was made by management to use the .308Winchester Palma round using the projectile you describe, manufactured at Geelong.

Those of us that were testing in project Penumbra were concerned about the irregularities you describe. Winchester was most co-operative and helpful because the Vice Captain and I spent a day at the plant examining the processes, discussing issues with management, the engineers, and operators of the manufacturing equipment.

With regard to that issue at that time, we found Sierra was producing projectiles from 4 different machines and that these were not batched by machine but mixed for bulk manufacture as Winchester received them. There was no way to identify what pills were coming off what machines. Not going into politics or economics, or speculation, but the round was later loaded with HBC which was produced from one machine. I assume the die wear was well monitored.

As a consequence the bullets need to be batched to perform well and I suggest you do separate load development for different dimensions.

The upshot then was Herb McRorie, Max Hedges, and Ray Parker hand sorted 16,000 rounds to take to England. The ammunition proved worthy, because in the Australia Match, the English shot a record score with it. We ran second. Also James C won a Victorian Queens with it before it was issued.

Nothing wrong with the pill.

Thanks for the insight and background. My challenge is to try to replicate the new NRA UK ammo and tune my leade to the bullet, hence need to verify exactly where the ogive really is!

Aubrey, in the past we have trialed UK ammo in Australia to find that it did not meet what was received at the venue. Somehow things can change asI was told such as powder being manufactured in another country with a slighly different performance yet using the same bullet to meet official specification. But the harmonics are out the window unless you are in the know. This sort of thing went back to the days when Perce Pavey told me they had to make changes to barrel length because things changed they were not prepared for. I am also reminded of a story I was told that during an international event the Australian team had a delayed start because their range officer failed to show, yet other teams were permitted to fire on in different conditions for a very long time until arrangements were made to supervise the Australians. You have to be prepared for all contingencies. If you are going to use the supplied brass then maybe a headspace a couple thou over will even pressures with suspect ammo. Its a bit like Australians hosting Davis Cup matches in the bush on grass courts in hot conditions.

I recall reading in an English shooting magazine some decades ago about the gentleman who won that year's Queens after trialling the RG ammunition on issue with every hire rifle in Fulton's shop until he found a screamer....

Just wondering, are you sure they will be issuing the old style 2155s, not the newer 2156s?

Also, do you get issued your ammunition a fair while before the competition? If so, could you throat short in OZ but if need be take a throating reamer to match your chamber to supplied ammo when you get there, then twiddle your tuner as required?

That's their ammo spec. They issue as you get on the firing line.