6 BRX velocity vs pressure

[nfa1eab]

This afternoon we were doing some load testing with a 6mm BRX. We were trying loads with Varget and VV140 using bare 107 SMLs amd 105 Bergers.

Using loads of Varget anywhere from 32.7 to 33.2, there were always ejector wipe marks on the rear of the Lapua cases. Not real bad but enough to cause a bolt "Click" at the top of the opening. Velocities were anywhere from 2980s to 3011 fps,measured over an Oehler 35P). This rifle is a Rem 700 that still has it's ejector installed.

In order to get to 3030 fps with either of these bullets and keep pressures safe, it would seem that some sort of friction proofing is in order.

What have you BR case shooters found out about this?

Bob

 

[swglenn]

Why are you looking for 3030fps? Usually 2950 is a pretty good number to look for accuracy.Every gun is different but let it tell you where it ts to be. Good Shooting.

 

[nfa1eab]

Well, accuracy just a little over 3000 was very good. ES was down around 12 fps and SD was in single digits 2-6.

Pressures were too high with naked bullets and I figured that I could maintain a higher vel sweet spot with less pressure using a friction reducer like Moly or the such.

One of the reasons I went to the BRX was for the additional velocity over the standard BR.

Bob

 

[techshooter]

nfa1eab:

You might try RL-15 instead of the Varget/VVN140. Both of the latter powders definitely shows pressure signs in my 6 Dasher at velocities well below what RL-15 delivers. I am getting about 3080 with bare 105s and 33.0 grains RL-15 in the 30" barrel length Dasher, and this is definitely a very broad and accurate node. If the BRX reamer that you are using yields a smaller case capacity than the Dasher,~40.6 grains H2O), you may not be able to get to those velocities with any powder. However, RL-15 has clearly been proven as a top performing powder in the 6BR improved cases.

Cheers,

 

[MarkS]

Bob,

I shoot a 6BRX for 600 yd benchrest. In my old barrel I shot 105 Berger's at 2975 f/s with varget. Don't worry about the speed! Run them where they shoot. My new barrel I have tried RL 15, it will get you more speed. But I have not ticked my final load.

Are you resizing every time? The last click, means you are tight in the butt of the case. I F/L every time I fire. The old barrel I sized the butt with a 7mm-08 F/L die, then bumped the shoulder with a 6BR body die.

With the new barrel I had a custom F/L die made.

Also what primer are you using? The Remington larger firing pin hole may show pressure sooner, than a tighter custom, Like my Hall action does, CCI BR4 helped in this case.

If you are running 3000 f/s with ES of 12 with good accuracy, you are there.

Mark Schronce

 

[Bob3700]

Mark,

We are shooting Rem 7 1/2 primers and the Remington action has had it's firing pin bushed to .062. The Remington primers may be a bit on the "Hot" side compared to say Russian SRMs. The ES and SD numbers are good over the chrono and the groups were decent as well.

Moly'ed up a bunch of 107 SMKs and 105 Bergers and will try a couple of the same loads to see if the pressure drops while keeping the rest of the good results.

RGDS

Bob

 

[Dubya]

Have been using RE15 at 33.0 to 33.6 gr.,in 6BRX) with 105 VLD Bergers and am getting 3040 to 3060 fps. depnding on the temp. with very good accuracy. Also try the CCI450 magnum primers.

Gary.

 

[Bob3700]

Gary,

I have run RL15 thru Quickload and it does produce higher velocities with the same pressures as Varget or VV140.

If it will produce the same small groups and low ES and SDs, that will be the best of both worlds.

Bob

 

[Dubya]

Bob,
Quick Load is a nice reference point, but does not give the actual results for a given piece of equiptment,ie; barreled
action). Real world testing is what will give you the best result.

Gary.