6br high pressure

[fdshuster]

jaybray: Sounds like you're doing all the right things, and getting excellent advice here. My standard load with the 95 gr. Bergers and Sierra MatchKings is 31.5 of Varget with no signs of pressure.

But another factor: Krieger makes both .236" and .237" bore diameters available. Do you know which yours is? My bores have always been .237", just recently had my first .236" chambered, but have not been able to do any serious work with it, due to the lousy weather. If yours is .236" that could contribute to higher pressures, I would think(?)

I know it's very basic, and do not mean to insult you, but are you sure you are throwing or weighing the exact powder charges you want? Could they be a little on the heavy side from what you wanted?

And yes, you are correct with the bullet seating depth. You will be sitting on top of the donuts that will form at the neck/shoulder junction.

And finally, if your fired case neck measures .271", then your chamber neck diameter is .272" + or minus a few ten thousandths. I've always found there to be .001" of springback and I'm able to compare the dimension difference with my reamer print drawings. That springback has held true for every cartridge from 204 Ruger to 30-06, that I've loaded over the years.

 

[jaybray]

jaybray: Sounds like you're doing all the right things, and getting excellent advice here. My standard load with the 95 gr. Bergers and Sierra MatchKings is 31.5 of Varget with no signs of pressure.

But another factor: Krieger makes both .236" and .237" bore diameters available. Do you know which yours is? My bores have always been .237", just recently had my first .236" chambered, but have not been able to do any serious work with it, due to the lousy weather. If yours is .236" that could contribute to higher pressures, I would think(?)

I know it's very basic, and do not mean to insult you, but are you sure you are throwing or weighing the exact powder charges you want? Could they be a little on the heavy side from what you wanted?

And yes, you are correct with the bullet seating depth. You will be sitting on top of the donuts that will form at the neck/shoulder junction.

And finally, if your fired case neck measures .271", then your chamber neck diameter is .272" + or minus a few ten thousandths. I've always found there to be .001" of springback and I'm able to compare the dimension difference with my reamer print drawings. That springback has held true for every cartridge from 204 Ruger to 30-06, that I've loaded over the years.

im very gratefull for all this advice and the speed of it to As for the scale I thought that maybe it was out so I weighed a bullet and it came out to 95 grains,so should be good, and no offence taken! For the bore diameter, I phoned the guy I bought the barrel from and he said it was what Krieger recommends for the 8 twist, so im not shure. When my throat grows from erosion enough that I can start seating the 107 above the shoulder junction, being a heavier bullet, and popping the primer with the 95 berger at 30.2, ill never make 30 grains of powder. I tried 29 grains of varget with the 107 and it was safe, but if I do have the tighter bore diameter, maybe go up im .01 incriments?

 

[Shynloco]

....just recently had my first .236" chambered, but have not been able to do any serious work with it, due to the lousy weather. If yours is .236" that could contribute to higher pressures, I would think(?)

Sorry, don't mean to jump the thread Jay...BUT FD, did the blue box Lapua fit into your new .236 chamber or did you have to use a small base die to resize them to fit? Just curious...I have a new Krieger ordered (probably get it in Jan 2014-YUCK!) and was curious about the brass fitting alright. Thx.

Alex

 

[CJ6]

You can also make a Cast of your chamber with Cerro-Safe. This may help with understanding your chambers dimentions. I do this with ALL my rifles.

 

[ragsflh]

change your primers to cci 400.magnum primers raise pressure. then work up your load

 

[jaybray]

change your primers to cci 400.magnum primers raise pressure. then work up your load

Thanks ,maybe ill try that.

 

[jamesh]

CCI 400 are standard primers the 450s you are using are the magnum primers and what you want.
It sounds like you have a carbon ring, pretty common with the 6 Dasher I haven't seen as much problem with the BR though. Thoroughly clean the throat area, you may need to use some JB or Iosso to get the carbon out.

James

 

[jaybray]

CCI 400 are standard primers the 450s you are using are the magnum primers and what you want.
It sounds like you have a carbon ring, pretty common with the 6 Dasher I haven't seen as much problem with the BR though. Thoroughly clean the throat area, you may need to use some JB or Iosso to get the carbon out.

James

This rifle has only 100 rounds through it. Could I see a carbon ring so soon?

 

[fdshuster]

jaybray: There are those who compete in our local match's who have said that the .236" bores are better suited to the long, heavy weight bullets, whether that came from Krieger or not, I don't know, but you may very well have the tighter bore diameter. I always have the gunsmith save and return the chamber end cutoffs & they remain with the barrel. Pictured are 2 recent 8 twist Kriegers, one with a .236" bore (on the left) and the other at .237". It would seem to make sense that the tighter bore would result in more pressure. Can you check with the gunsmith to see if he may still have the cutoff section?

Alex: Sorry for my confusing post, I do that sometimes. I have my own chambering reamers (all PTG), and except for the differences in freebore, they are so close in dimensions that brass is interchangable, so no, no difference when chambering any Lapua or Norma 6BR brass.

 

[jaybray]

He is not around at the moment but, I have another spare Krieger being shipped that will be here Monday, from the same guy I bought the last one from and he said it is the same as the one I have on right now. I never knew about the difference between the two till today so, it is what it is I guess. If this problem is due to the tighter bore, then ill just have to deal with it until the throat wears so I can shoot the 107 match kings. Again, thank you all for your help!!

 

[jaybray]

Hey guys, for me to get the 107 match king out of the neck shoulder junction, id have to jam 25 thou into the lands . would this be advisable if I started low and worked up watching for pressure to find a node?

 

[fdshuster]

jaybray: With a jam of .025" would not the bullet be pushed deeper into the case neck, (with hard bolt closing), and end up at the time of firing close to the neck/shoulder junction? All you would be doing is fully seating the bullet by chambering the round, and it would still be sitting on top of the donut.

And, if you should ever have to remove a live round from the chamber you will be left with the bullet stuck in the throat, and powder spilled in the critical locking lug area, putting the rifle out of commission.

If the short throat is causing seating problems, have you considered having the freebore length increased with the use of a throating only reamer?

 

[rogn]

I am wondering if the neck lenght is proper for the application. The tiny differences in sizing set back are hard to explain. As is the seeming excess pressure. It may be worth the simple trick of magic marker painting of the case mouth and chambering of unsized case. If the coating is marked, then the neck is infact too short. Just looking for the simplest answer.

 

[jaybray]

Thanks for your help guys . I marked the case mouth chambered a empty, tight case and marking was not touched . AS far as a .025 jam with the 107 goes, even at that it is still in the donut area,so I guess its either lengthen the throat, or shoot the 95 Berger's till it erodes, then use the matchkings. I tried the Berger seating depth method, while it does shoot these bullets good, but I can seat no deeper than .040 jump from the rifling or the bullet will disappear into the case. That seems like a very short throat to me. Someone mentioned it could be a soft lot of brass causing the tight cases. The only brass I have is the old gold box lapua, and I have 800 pieces un fired so I hope not.

 

[Shynloco]

Hi Jay,
Based on your last post, have you considered having the barrel re-chambered to better accomodate a range of bullets you want to shoot? If I recall you said this was a relatively new rig so it wouldn't be a huge issue to have your gunsmith rechamber her and not really a huge expense. Just something to consider.

Alex

 

[fdshuster]

Alex: Much cheaper, and the original chambering is saved, by simply lengthening the throat with a throating reamer.

I've had several done & for me it was the best solution.

 

[jaybray]

Hi Jay,
Based on your last post, have you considered having the barrel re-chambered to better accomodate a range of bullets you want to shoot? If I recall you said this was a relatively new rig so it wouldn't be a huge issue to have your gunsmith rechamber her and not really a huge expense. Just something to consider.

Alex

The problem is that it would be at least 6 month wait . are there any other bullets besides the 95 berger that would get me out of the donut area? The 75 v max will but it has to be jammed. What about the 80 grain bergers?

 

[jaybray]

Just want to say thanks to you all for the help. I went to the range today and at 200 yards accuracy was poor with both bullets. My cooper 22 250 will outshoot this rifle easly. Blew two primer at 29.5 grains so ill send it back to the smith, Thanks again!!

 

[Shynloco]

Alex: Much cheaper, and the original chambering is saved, by simply lengthening the throat with a throating reamer.

I've had several done & for me it was the best solution.

Thx FD...thats what I actually meant...extending the chambering...I just didn't write it correctly. Sometimes dummie me knows what to do, but uses the wrong terminology. Got a great gunsmith to bail me out though.

Jaybray....how about doing what FD wrote...matter of days proposition??

 

[Old Navy]

Why are you worrying about donuts that you don't have. If you use two hundred cases you might never get donuts before you wear the barrel out. I have 185 Lapua cases I cycle through my 6BRX. I am up to eleven reloads with no donuts. I use a FL Redding bushing die. The bushing does not quite make it to the neck/shoulder junction. Good luck with what ever you decide to do. Later! Frank