6x47 Lapua Peterson Brass - first observations

[urbanrifleman]

Both are really great cartridges but yes both with LRPs are totally the way to go.

Back around 2005-2007 or so when I built my first 6x47L I had problems with hang fires and uneven velocities and that lead me down a path of investigation to resolve. I spoke with Tubbs about it who spoke with Obermeyer about it and I ran into Salazar down at Perry one day. It was unanimous that SRPs would result in the exact problem I was having and LRPs would be the solution.

Knowing what I know now, I would sooner let a friend drive drunk than run SRPs in a 6x47L.

What problem are you having? I shoot SRP and it was 25 degrees yesterday.

 

[PracticalTactical]

What problem are you having? I shoot SRP and it was 25 degrees yesterday.

I'd like to see your chronograph data over a wide range of temperature swings.

I personally no longer have any problem... as long as I use large primers with 6x47L.

LRPs work so well for me that I do not have the will to enter a rabbit hole trying to find a way to make SRPs work. I gave up that effort long ago. For me that effort is pointless. I get low single digit ES velocity spreads and consistent velocity over a wide range of temperatures. In fact, I have had to turn off my chronograph between shots because it so frequently produces the exact same speed that I start to think the chronograph missed the shot.

FWIW I settled on and have been running 38.3 grains of 4350 with 115s for roughly 10 years and have no reason to change that... 1:7.5 twist.

My first test was done using 22-250 cases that I resized with my 6x47 die and even that was phenomenally better than SRPs in Lapua cases.

 

[Kracken McGraw]

I'd like to see your chronograph data over a wide range of temperature swings.

I personally no longer have any problem... as long as I use large primers with 6x47L.

LRPs work so well for me that I do not have the will to enter a rabbit hole trying to find a way to make SRPs work. I gave up that effort long ago. For me that effort is pointless. I get low single digit ES velocity spreads and consistent velocity over a wide range of temperatures. In fact, I have had to turn off my chronograph between shots because it so frequently produces the exact same speed that I start to think the chronograph missed the shot.

FWIW I settled on and have been running 38.3 grains of 4350 with 115s for roughly 10 years and have no reason to change that... 1:7.5 twist.

My first test was done using 22-250 cases that I resized with my 6x47 die and even that was phenomenally better than SRPs in Lapua cases.

Have you tested this srp vs lrp in cases such as the 6.5x47L or the 6.5 Creedmoor?

 

[urbanrifleman]

I'd like to see your chronograph data over a wide range of temperature swings.

I personally no longer have any problem... as long as I use large primers with 6x47L.

LRPs work so well for me that I do not have the will to enter a rabbit hole trying to find a way to make SRPs work. I gave up that effort long ago. For me that effort is pointless. I get low single digit ES velocity spreads and consistent velocity over a wide range of temperatures. In fact, I have had to turn off my chronograph between shots because it so frequently produces the exact same speed that I start to think the chronograph missed the shot.

FWIW I settled on and have been running 38.3 grains of 4350 with 115s for roughly 10 years and have no reason to change that... 1:7.5 twist.

My first test was done using 22-250 cases that I resized with my 6x47 die and even that was phenomenally better than SRPs in Lapua cases.

Might be the undersized flash hole in Lapua brass.

 

[PracticalTactical]

Have you tested this srp vs lrp in cases such as the 6.5x47L or the 6.5 Creedmoor?

No I haven't.

I know there are people who gravitate to small primers for some traditionally LRP cartridges so they can run hotter loads. I can see why an FTR shooter might be drawn that way since they are caliber restricted to 308, but I fail to grasp why anyone would want to go that way with a 6.5 Creed. If you want more speed then just run a 260.

The guys I know on the Canadian F Class team never use small primers in the cold, its a strictly summer time load for them. That at least makes sense even if such a restricted operational parameter is not my cup of tea.

The problem with running the ragged edge of poor ignition is in testing at the extremities of the operational range. Under ideal conditions and on a single day of testing, you may get pretty good results. But when you objectively track those results over a wide range of weather conditions and evaluate how much velocity varies over such conditions, the wheels fall off.

Professionally I have been involved in R&D for many years and the analysis of performance is what I do every day. I always try to watch out for cognitive bias and keep an open mind. With that in mind, I do not test ammunition as part of my career and if you are getting results that are acceptable to you, then I'm perfectly ok with that. For me, I'm required to stress test systems and perform failure mode analysis. I exaggerate parameters to the point of failure, but that depends upon how we define failure.

I also understand marketing has a primary interest in generating sales and much like most fishing lures catch more fishermen than fish, the same can be said for many popular shooting products.

 

[rijndael]

Did you ever try a SR Mag primer like the 450 or 41?

 

[PracticalTactical]

Did you ever try a SR Mag primer like the 450 or 41?

Late response, but yes. Results with any SRP was not as good as the worst LRP.

 

[PracticalTactical]

Might be the undersized flash hole in Lapua brass.

Late response, but yes, I also tested cases where the small flash hole was enlarged. Using 6XC brass for 6x47 was absolutely the best way to go. The difference was not even close.