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RobB wrote:

WelshShooter wrote:What about the relative temperature while shooting? Some powders are not so consistent during colder weather, for example, Ramshot Tac doesn't seem to perform so well compared to the likes of Varget.

it was only me on the target with no delay in shooting and therefore little temp change between shots. So I'm discounting temp change.


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Actually, I wasn't talking about the change in temperature change between shots. I was talking about absolute temperature. In my example, I am saying that when using Ramshot Tac at "normal" temperature it works fine, but when using at "cold" temperatures I have issues with consistent velocity along with a slight step change.

I've used RS40, RS50 and RS60 and haven't had issues with temperature but I cannot speak for RS52.

What neck sizing die are you using? I have a range of pin gauges that I use to gauge neck tension after neck sizing. I use a Lee collet die and I do find some variation in neck size, depending on how hard you operate the press!

North Star wrote:What neck sizing die are you using? I have a range of pin gauges that I use to gauge neck tension after neck sizing. I use a Lee collet die and I do find some variation in neck size, depending on how hard you operate the press!

REDDING TYPE S-NECK BUSHING DIE.
Redding Titanium Nitrite Bushing/.336

For no particular reason other than they were recommended by someone on the GB F class team


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I'm using the 0.336 Neck Bushing on unturned lapua brass and getting single digit SD - what neck thickness you trimming to? The 0.336 bush gives me 0.0015 tension with a juggernaut - just a thought but you may not have enough tension and may need to go to 0.335 or even 0.334 depending on how much your skimming off.

Haven't trimmed or measured neck thickness yet


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Sorry - got my wires crossed.

My current batch of lapua cases (now down to 92 from 100 due to natural wastage) are on their 10th firing - I annealing every firing - have a Neck thickness of between 0.014 and 0.015 so I didn't bother skimming them.

The cases I bought previous to the current ones and the new lapua cases I bought a couple of weeks ago have neck thicknesses between 0.014 and 0.017 so I have started skimming down to 0.015 and will put my 0.337 bush in to maintain tension - only another 35 to do!

With this slight inconsistency in lapua brass it maybe that you have a batch of cases that vary and give inconsistent/ offset tension.

It may seem like I'm labouring the point but I've been through the same issue your experiencing with muzzle velocity and found the answer was as above - hopefully it'll save you a few bullets!