6mm br help

brad555 said:
The scuff marks I was refering too are very light and you have to look close to see them. My biggest concern was why the primer had deep distinct marks in them. In my .223 I had experienced this but I knew the loads were getting to max. In the case of the 6mmbr this started right off the get go and only 28.5g charge of Varget. I am going to back them off the lands and try them when I get time and see what the results are. Thanks for all of the great help guys, please feel free to keep it coming.
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The scuff marks could be from the brass flowing into the ejector pin and the cratering of the primer both indicate too high a pressure, which you get from 28.5 and plus grains of Varget with 100+ grain bullets. Your velocities top out around 2850. Try a slower powder. I get 3050...but I have filled in the ejector and use 450's.

NormB
 
NormB said:
The scuff marks could be from the brass flowing into the ejector pin and the cratering of the primer both indicate too high a pressure, which you get from 28.5 and plus grains of Varget with 100+ grain bullets. Your velocities top out around 2850. Try a slower powder. I get 3050...but I have filled in the ejector and use 450's.

NormB
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Norm, where are you getting these numbers from?

Cartridge : 6 mm B.R. Norma
Bullet : .243, 105, Berger VLD
Cartridge O.A.L. L6: 2.440 inch or 61.98 mm
Barrel Length : 28.0 inch or 711.2 mm
Powder : Hodgdon VARGET

Chrg Wt.: 28.50 / Vel. FPS 2724 / PMax Prsr PSI 48191

Max pressure for a 6BR Norma is 59,000 PSI. 28.5grns of Varget doesn't even come close to that.

Running the info through Quickload (With a 28" Barrel) I come up with a "suggested" max load of 30.51 grains of Varget @ 58,714 PSI
2890 FPS
99.9% Load Density
99.84% of Propellant Burnt
Of course, variations in bore diameter from one barrel to the next would change the dynamics completely.

I would like to know how you are achieving 3050 with a heavy bullet, slower powder and not running the pressures out the roof.

EDIT:
A 6BR Rem, OTOH, is a whole other field of corn. 28.8g of Varget would technically be overpressure.
 
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About the only thing 'upgrading' firing pins do is cause light primer strikes.

The cratering is definitely a byproduct of pressure.

Not sure why 6BR Rem would be any different from 6BR Norma. Dimensionally, they are almost the same.

Rem 6BR/7BR brass is actually very well made and some batches of 7BR made way back when is still coveted for its construction and durability. I have had the pleasure of shooting some of this stuff and it is really good brass.

We need to put perspective on the performance that some are getting with their 6BR. Pretty hard to say that a case using 2/3 the powder of a 243 is equalling, even exceeding that larger siblings performance without excessive pressures.

There is no free lunch. Just because the action opens without undue force, does not mean the pressures are low. I have proof load cases that definitely reached 80,000psi. There are absolutely no outward signs of pressure and the case was easily extracted from the factory rifle it was fired in.

This is not a negative against Kreiger as other barrel makers do the same thing. There are undersized 6mm barrels out there. I have had a Gaillard. Loaded with typical amounts of powder, the pressure signs were obvious and accuracy was poor.

A switch to a narrower bullet solved that issue and the rifle shot like a champ.

The cratering and other indications even with 'low' amount of powder may indicate you own an undersized barrel. Just keep an eye on things if you decide to increase powder amounts.

Jerry
 
I have read that the Lapua 105 are a narrow bullet and like the tight chambers. I might have to try some I guess, the only crappy thing is I just bought 2000 rounds of Burgers.... ugggg oh well just my luck. What about the 107 match kings are they a decent option?
 
I forgot to mention that I tried a few tonight again, I allready had some loaded at both 29.5 and 30.0 grains so I bumped them back so they were just in the lands and had close to the same results. I am going to order a box of Lapua 105 and give them a try.
 
brad555 said:
I forgot to mention that I tried a few tonight again, I allready had some loaded at both 29.5 and 30.0 grains so I bumped them back so they were just in the lands and had close to the same results. I am going to order a box of Lapua 105 and give them a try.
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50,000 lbs of pressure bumps up every bullet to barrel dia, bullets .001 over size don't make that much difference either, it swages them down.,. But, the rise of the pressure curve does make a difference. Your 105 Bergers are fine. VLD's like to be into the lands. Try for starters 31 gr. Reloader 19,(its double based), CCI 450's. You should be able to move up to 33.5 or so. Should be Lapua brass... not Norma tooo soft.

Where did I get my numbers. I tested Varget and got rubbed brass, ejector marks with low velocities. Went to slower powder and problems went away. I could get higher velocities. I used a standard Rem 700 with 30" MacLennan barrel. I have since taken the ejector out and plugged it.

NormB
 
brad555 said:
I have read that the Lapua 105 are a narrow bullet and like the tight chambers. I might have to try some I guess, the only crappy thing is I just bought 2000 rounds of Burgers.... ugggg oh well just my luck. What about the 107 match kings are they a decent option?
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Hey Brad,

I'll take those crappy "Burgers" off your hands. Must be at a substantial discount though, as they are just too fat and cause those nasty pressure problems. PM me:D

NormB
 
I'm Shooting a hotter load than brad in my shilen 24'' barrel using federal 205m primers. There is no divot around the firing pin mark on the primer , which is odd being that federals are supposed to be softer, they are flattened out though. I'm going to lower my load as I have had stiff bolt lift on a few rounds. 30.6 gr varget 105 berger vld 2860 fps chronied.
 
One thing you can do to check your head space with your brass is remove the firing pin and ejector pin+spring from the bolt. Load an empty re sized brass and check the foreword and aft movement of the bolt. I set mine up to have a couple of thou of clearance. Side note check the bolt movement with no brass first its usually around 15 thou. Helps to have a dial indicator to.
Stephen

Stephen
 
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