7mm RSAUM powder burn rate choice

[rossneder]

I've been working on this platform for a year. Most of the issues are resolved except what seems like a over pressure load. I'm using RL19 and 175 MK's, quick load claims no pressure issue and I'm only running at 2809 f/s. Yet the primers are flat (CCI) and occasionally they are pierced. There are ejector marks although very hard to see.

The barrel is a benchmark, 32" with brake. I had overgas issues for awhile and have the adjustable block nearly shut off, at this point is cycles and feeds perfectly.

I wonder if RL19 is to slow for this gun and there is just too much pressure in the barrel for to long. I ran some calculations with QL and at 15" RL22 is at 21607#, RL17 - 18832#, H4350 - 18647# and Varget - 17537# all these loads run the MK at about 2970 f/s.

I don't know what a goal is for pressure at the barrel block but it seems like Varget would be easier on my brass and primers since I'll have a much reduced pressure to cycle and less pressure on the brass while extracting.

What do you think about powder choice?
Thanks

 

[blksno]

Re: 7mm RSAUM powder burn rate choice

I don't have much to say, except that I have my adjustable PRI block 100% shut off and I still cycle smooth with my 300 SAUM.
Maybe try closing it some more...or all the way.

I've had great results with RL17, but I don't know jack about burn rates.

 

[MLC]

Re: 7mm RSAUM powder burn rate choice

I think in AZ I would be running a slow single based powder like H 1000 or Retumbo. You'll get an analogous velocity with less pressure variation due to temperature.

*edit* that being said I have no idea if the port size on your rifle is the correct size for the amount of pressure generated by the 32" barrel.

 

[rossneder]

Re: 7mm RSAUM powder burn rate choice

Me neither on port size.

I just took it apart and checked headspace, it is perfect.

I pulled a few bullets and replaced them with 162 AMAX and 140 CT.

The AMAX also was flat and cratered, the 140's were perfect.
I loaded a single round with 4350 with about 52 gr, again flat and with ejector marks.

The firing pin hole measures .081, is that too big?