Thread: Pressure Signs in the 6.5x47

Originally Posted by Tussock

I think your theory is sound. By deferring pressure signs, as I said in another thread "sweeping pressure under the rug" you will compress them into less grains of powder. At the same time, when you get there, the size of the loading increment will give you very little gain. Unless you are a muppet and loading 5gr increments, as Gimp said, then everything should proceed as normal.

Now the point I made was that pressure and powder charge are not actually linked. So the issue here with the highest quality brass in individually machined actions is probably extremely trivial compared to people following the loading book with random brass and questionable rifle tolerances.

So you still have to stick to the one thing you have, which is deformation of the case. The case is the weak link. In 6.5x47L it is a very strong weak link. 6.5x47L is a case built from the ground up by wizards. 6.5 Creedmore is a wildcat given a thickened case base as an afterthought (by the same wizzards).

Mostly these things will be in the hands of people shooting them over chronographs in high end actions where you can get to the scary bit and back off.

Mine were doing 2800 with 140s (don't have the rest of the info on hand) and I have dug out 3 of my >300 3X fired brass and I don't have any case head deformation. As I mentioned in another thread I had ejector marks on one factory loading and completely flattened primers on another, when at the range the other day. Wincherster and Sellior and Belliot. Two different rifles. A Sako and a Ruger.

Does the same not also more or less apply to those chamberings based on the 404 Jeffery. That case was used because it can withstand very high pressure safely.

A second load to consider, and if the information on this was more complete, I'd just report the predicted peak pressure along with the pressure signs as before. However that is not the case so here is the the information on which the simulations were based so the missing information and assumptions are clear.

140gr bullet ( AMAX I think), 20" barrel, likely to be 70.5-72mm CoL but not confirmed, velocity: 2810 ft/sec, showed stiff bolt lift in warm conditions, but not in cold, so clearly right at the cusp.
Powder and charge weight not reported.

Given that the powder was not known I ran QuickLOAD simulations on AR2209 and Re-17

The peak pressure to result in that particular velocity with those powders within the CoL range is then predicted to be somewhere in the range of 71.7 - 72.7 kPSI

A lighter bullet (100gr) and faster powder (BM2);
69.5kPSI - 71.9kPSI predicted peak pressures for the onset of sticky bolt lift.

130-140gr bullets, loose primers: 75-77,000 PSI peak predicted.

Just wrapping this thread up from my perspective. I did a bit of testing on my own 6.5x47 - Barnard action so not necessarily a good choice for showing pressure signs, but it is what it is. I pushed the peak pressure up to what I estimate was 68kPSI while measuring case head expansion just above the extraction groove. Wasn't willing to go any further. Multiple firings, multiple cases, and less than or equal to 0.0002" expansion averaged. That would give loose pockets on multiple firings but not immediately, not for a while. My reticence to stuff the cases any further and get beyond 70kPSI and/or a thou of expansion per firing will be understood when I say that this was already a 44gr compressed load giving 3000 ft/sec with 140gr VLDs from a 30" barrel from a slow batch of 2209. Plus I couldn't find any accuracy up above 2900 ft/sec so no real point in staying up there.