reloading data for 129 SST and Benchmark

[turnbull]

So I was at Bass Pro Shops the other day and found some 6.5mm bullets, but all they had were Hornady 129 SST. I bought a box, but when I got home I couldn't find any data for those bullets and Hodgdon's Benchmark. Does anyone have any data for these bullets and powder?

[LRRPF52]

Find your acceptable COL, keeping mag length limitations in mind. The 129gr SST is one of the most tolerant bullets for long COL for me and my chamber.

Benchmark appears to do better with the lighter pills, and I don't see any data for it with the 129gr SST, but there is data for the 123gr SMK.

For Benchmark, here is the starting load and pressure ladder I personally would use:

COL: 2.280" (you will have to see what your chamber will allow)

25.0gr
25.2gr
25.4gr
25.6gr
25.8gr
26.0gr
26.2gr
26.4gr
26.6gr

I would shoot through that pressure ladder one-by-one over a chronograph, stopping at each shot, recording my velocity data, then inspecting the brass and primer. Most importantly, the chronograph data will tell me much more what is going on. You should see about a 16-20fps average increase per charge weight. Once you see it depart 40fps or more, you're done. That's how I would approach this. There is no reason to push past a 40fps excursion. Run at least 2 batches of the same ladder to confirm, and use disciplined reloading technique with component selection and procedure, so that you have very consistent loads.

If you get to 26.0gr, and 26.2gr departs from the trendline, that is where you stop, mark the hotter loads that you aren't going to shoot, take them home, and pull them.

If you can get your hands on some CFE223, I would recommend that, but the Benchmark will still spit them out. It's one of the slower powders with the 120-123gr bullets, and there is data for it with 123gr from Hodgdon's and Hornady with the 123gr pills.

[turnbull]

Well that is definitely some useful information and I appreciate it. I am not looking for max accuracy or velocity or anything, I am just trying to make do with what I have. Otherwise I'd go out and buy a powder I actually have data for. I only reload because of the limited availability and relatively high price of 6.5 Grendel ammo. Next time, I'll make sure to buy the right bullets to use with Benchmark. I don't have a chronograph, so I'll just play it safe until I can get my hands on one. Thanks.

[JASmith]

The neat thing is that your bullets will do just fine even when the muzzle velocity is a tad less than the max.

[Whelenon]

I know it's not Benchmark but just for reference, with the 129sst I'm getting excellent accuracy with 25.9g of XBR 8208.