• This Forum is for adults 18 years of age or over. By continuing to use this Forum you are confirming that you are 18 or older. No content shall be viewed by any person under 18 in California.

6br high pressure

Hello all, first off this is my first post . Just want to say thank you to all the knowledgeable people who contribute to this forum. Other then reloading manuals, this forum is where I have learned most of what I know to the point I am at on the subject of reloading,thanks. My issue is this. I have a new 6BR, 8 twist Krieger,bat sv action,272 no turn neck. I have been working up a load with 95 Berger hunting vlds with varget, 15 thou of the lands and started at 29.5 grains and went up in two grain increments . No pressure signs at all until 30.2. At 30.2 the cci 450 primer had a black ring of residue around it . The primer never blew out of the case. Should note this is only 2nd firing on new gold box brass. It also left a very small divit in the bolt face . Of course I stopped continuing firing higher charges. There was no hard bolt lift or flattening of the primer, or ejector marks. From what ive read this seems like a light load for this bullet. The loaded round measures 1.629 to the ogive touching the lands.Could I be seeing high pressure at so low of a load? Sorry for the long post but help would be appreciated, thanks!.
 
Hello, my fired cases measure 1.155 to 1.156 with the hornady headspace gauge. I bump them back to 1.554. one thing I notice is I can not close the bolt on a once fired case at 1.155, but bumped back to 1.1554 the bolt closes easy . Every fired case needs to be bumped even some brand new cases need to be bumped. The cases that measure 1.156 , if you did close the bolt, galled lugs for shure.
 
Make certain that you are not head-spacing on the primer, as opposed to the case-head; in other words, the seated primers should not protrude above the case-heads (shallow primer-pockets are not uncommon). Make certain that you are not including a potentially protruding primer in you initial "head-space measurement - de-cap before measuring your fired cases. Good shootin'! RG
 
Sounds like you have minimum headspace and can cause higher pressures.I would decap the case that leaked and see how a new primer seats in it.If it glide's in the case is junk. I would back off alittle bit and find a slightly lighter load and proceed with that as speed isnt always the answer in every firearm which all act like tempermental kids at time's.So in retrospect it may be one piece of brass that had a bad pocket to begin with.I would try a different powder to be sure the varget isnt the problem.I know I will get slayed for saying that as I have tried varget and it isnt the holy grail of gunpowders.
 
Another thing to check is the legnth of your brass, have you ever trimmed it? Its a long shot but...you say the extra thousanth will allow the bolt to close....it could be possible that you do not have the true headspace reading and the case is a little long and you are going off feel of the neck hitting the end of the chamber. Also if your brass was long and the neck is interfering with the chamber it will cause it to pinch on your bullet which could cause a pressure spike.

Just another thing to check...
 
Well I have to admit that I have been taking headspace measurements with spent primer still in ::) Learned something new and will stop doing that!. I decaped one and the measurements were the same with the primer in or out. I decaped the case and inserted a new primer, and it was just as tight as the other ones. If I do have a minium headspace chamber I guess ill have to live with it. 29.5 grains varget 10 thou in the lands was 4 shots 3/8s of an inch at 100 yards so ill play around with seating depth and see. If varget is the problem I'm in trouble cause I have 28 pounds of it and nothing else available in BC . One more thing, when I first started working up this load I started at 29.5. I have read lots about the 95 Berger and most people end up around 31 or so. Ive been reloading for a year and I was getting impatient and almost started at 30.8 like some threads on other sites suggested. Things may have turned out bad for me and rifle!! I have learned that this is why you always work up to max!! Thank you all for the info. :D
 
How certain are you that your rifle has .272" neck diameter. I have this same problem when I first developed load for my 6.5-47 Lapua. I did not bother to measure the diameter of my loaded round because I assumed I have the standard .292" diameter chamber. Well, I'm getting erratic pressure spike even with starting load. I measured the loaded round and it's exactly .292". When I measured the fired case, I was getting .291" on average. The fired case is tight enough that it will hold the bullet without resizing the neck.

I measured the neck wall thickness of my brass and it varies from .0125 to .0135. I neck turned the brass to .0125, removing just the high spot. I use .288" bushing to size the neck. My loaded round now measured .290" and the erratic pressure spike was gone.
 
Hi desert fox, .272 neck is stamped on the barrel and that's what I asked for but I don't have the proper tools to actually measure it. my loaded rounds measure .268 and a fired case measures .271,this is just with digital callipers . My fired cases can hold a bullet also, I can get them through with a little help. Maybe I need to neck turn? I hope not, but I'm pretty leery now going above 29.5. 29.5 gave pretty good groups at 100 but haven't tried farther. Funny thing is I was firing groups of three and it was the third case that popped the primer. Not shure what to do.
 
jaybray said:
I have been working up a load with 95 Berger hunting vlds with varget, 15 thou of the lands and started at 29.5 grains and went up in two grain increments..

First off welcome aboard. According to what you wrote, are you saying you went up at 2 gr increments or .02 increments? A two grain increase is HUGE, let alone twice that amount! One two grain increase in powder would put you at 31.5 on the first increase and that with a hunting VLD bullet. Might I suggest to back down to 29.2 and try a flat base bullet or even a HPBT to see if you still get those preesure signs. Personally I trim all my 6mmbr Norma brass to 1.550 and have none of the issues you reference.
 
Yes I meant .02 grain increments, sorry typo ;) I better try trimming to 1.550,might be the problem. I have tried the 107 matchkings, and at 29 grain start load very good accuracy right of the bat ,problem is the throat is so short that touching the lands the shank is below the neck shoulder junction. From what Ive read the donut thing will cause problems. I have some 75 grain v max ill try. since I don't have any ejector marks, flat primers, or heavey bolt lift , when I increase powder charge, do I keep going up till I blow another primer? The matchkings being a heavier bullet should show pressure sooner ? How do I tell?
 
I trimmed the tight cases down from 1.555 to 1.550 length and still cant close the bolt till the shoulder is bumped back to 1.554. Have to bump the shoulder after every firing. Hard to believe that little bit of shoulder bump can go from an extremely tight bolt close to normal .
 
Evenin Jay,
There are other ways of telling signs of pressure increasing and no you don't just keep going up until you blow primers. One of the simplest forms of beginning signs of pressure is "cratering" of the primer. In other words, run your finger or fingernail across the face of the primer and see if you feel any "cratering". Imagine dropping a rock into water...there is a splash of water to the sides of where the rock entered the water. Hence with pressure, you'll literally feel the contact point of your firing pin stricking the face of the primer and creating a small, so to speak crater. Once that starts, it'll only get worse until you blow a primer. Another way of observing pressure is simply punching out an spent rimer and measuring it with a mic. You can take a new unspent primer and measure it from it's sides and back and from. A primer that had "pressure" signs will now have changed noticeable when measuring it. I occasionally do that at my reloading table, but not at the range. There I just run my fingernail across the face of the spnet rpimer to check each round I shoot for pressure. It's also a way to check and see if you primer pocket have loosened up and maybe time to chuck that particular casing after numerous firings. Good luck and hang in there. Sometimes, no matter how hard you try, some rifle just won't like a specific bullet or not as much as another. Just the nature of the beast. Perhaps your rifle just likes those 107's better than the 95's.

BTW, you might just have a very tight chamber. Do you know what dummie round your chamber was setup for? In other words, some "dedicated" chambers are matched specifically for a certain OAL or even casing/bullet combination. Might I suggest if you have a successful load or even a commercial load that chambers without any bolt heavy issues. Meaure those shoulders and make sure you havenm't gone too far in your bump. I use RCBS Precision Mic's in all my rifles to determine the bump needed. I start with new Lapua brass and make sure it closes easily in the chamber. I then measure each box/lot for a shoulder reading and use that as a reference point on the Precision Mic for my reloading and nothing more.

Alex
 
Thanks shynloco, I will measure some spent primers and compare to new. I looked at the fired primers with a magnifying glass and they look fine. As far as the chamber goes it was set up for the 107 match kings which id rather shoot, but they shot best 20 tho off the lands, and at 20 off, the bullet shank is way past the neck shoulder junction, so if I get neck donuts will I have issues?
 
Are you 100% certain that it is 6mmBR Norma?

I have a McGowen barrel and several of the loads that are published here show pressure signs in my rig. Start low and work up.
 
kelbro said:
Are you 100% certain that it is 6mmBR Norma?

I have a McGowen barrel and several of the loads that are published here show pressure signs in my rig. Start low and work up.
hello kelbro, that was the first question I asked when I had it built, so im thinking it is. At 29.5 grains of varget im getting 3 shot groups around 0.247 at 100 yards so maybe I should just stay there and mess with seating depth.
 

Upgrades & Donations

This Forum's expenses are primarily paid by member contributions. You can upgrade your Forum membership in seconds. Gold and Silver members get unlimited FREE classifieds for one year. Gold members can upload custom avatars.


Click Upgrade Membership Button ABOVE to get Gold or Silver Status.

You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.


To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.

Forum statistics

Threads
166,786
Messages
2,224,009
Members
79,854
Latest member
Mattress09
Back
Top