Problems with primers on new 6BR build

[stomp442]

Ok, so a friend and I are having similar issues with pierced primers and excessive primer cratering/flow in 6mmBRs built on Savage model 11 Actions.

First a little history. I built my wife a BR to shoot in our monthly local matches. Build went together fine broke in the barrel and found a sweet shooting load with 30.3 grains of Varget under a Berger 105gr VLD. Primers showed a bit of cratering with that load but pockets remained good and tight and the gun grouped in the .2's when she did her part. Fast forward a couple months and it was now time to order some more Varget because we were out. Had a match last month and the last two shots of the string pierced primers. We only fire ten round strings. I figured it was due to having a different lot of Varget and it was running a bit hotter than the last batch which I have read is a common problem with Varget. So I went down to 29 grains and was going to work my way back up to a good node and every primer was pierced. There were no other signs or feeling of excess pressure with easy case extraction and primer pockets remain good and tight. I did some research on the FAQ page here and find that the optimum firing pin protrusion is .037". Mine was set at .056" which from what I gather is factory spec. I followed the tutorial and fixed my protrusion so that it is now .037" and while I still have some primer flows I have have not had a pierced primer and my groups are great at 29 grains of H4895. I decided to try some H4895 to rule out Varget as my problem and I am glad I switched.

Now while the wife's rifle was shooting well I had a friend ask if he could build a 6mmBR as well because he was so impressed with it. I said sure and we got all the required components ordered and assembled about two weeks later. He went ahead and purchased a brand new Savage model 11 hunter xp with bottom bolt release in .243 for his donor action. We screwed on and head spaced the McGowen 26" varmint contour barrel, mounted a scope and loaded some rounds with AA4064 for break in. First three shots at 28 grains pierced primers. We checked his protrusion and it was set at the factory spec .055" problem is with the new bolt style of the new action there is no way to adjust the protrusion like there is on the older bolt. He has since tried moving to Benchmark powder and using start loads with one of every three piercing primers and the others showing excessive flow. My question is this. Is there a problem with our bolt heads firing pin holes being over sized allowing the excessive primer flow and if so, how do I fix it? Is there a different bolt head we should be using because we are shooting a cartridge with a small primer hole in a .473 sized head? Sorry for the excessive post but all help will be appreciated. Thank you.


We are both running the same components:
Norma Brass
CCI Small rifle primers No. 400


Here is some pictures of his cases he sent me last night.

[LongRange]

something to consider doing...

http://bulletin.accurateshooter.com/...r-performance/

[darkker]

LR has a good resource for you to read-up on.
Another is actual Pressure. You mention powder weight, but never velocity. Without a system to actually tell you, velocity is the only way of reasonably knowing what pressures are. The charge weight is completely irrelevant.
Also, extruded powder had its burning rate controlled by geometry, meaning size. Loading by a consistent volume should give you better results than a weight, which will allow for fluctuating BR's.

[stomp442]

The wife's 6br is running the 105s at 2855 in a 26" barrel according to my chrony. Nothing excessive or out of the ordinary that I have seen.


I see that PTG sells a bolt head for the PPC cartridges for about the same price as a bushing job would thos be a simple viable option?

[LongRange]

The wife's 6br is running the 105s at 2855 in a 26" barrel according to my chrony. Nothing excessive or out of the ordinary that I have seen.


I see that PTG sells a bolt head for the PPC cartridges for about the same price as a bushing job would thos be a simple viable option?

I would call PT&G and talk to dave kiff...ask for him and you may have to leave a massage but he will call you back...or try sending him an E-mail.
personally id just have it brushed as I think you will have a better finished product.

[short round]

Before changing bolt heads, give some CCI 450 Mag primers a try. They have a stronger cup than 400.

[short round]

Before changing bolt heads, give some CCI 450 Mag primers a try. They have a stronger cup than 400.

[darkker]

The wife's 6br is running the 105s at 2855 in a 26" barrel according to my chrony. Nothing excessive or out of the ordinary that I have seen.

Well, that is 200 fps above Hodgdon data, so it is excessive pressure wise.
You can try a different primer, like Short Round suggests.

[bythebook]

Before changing bolt heads, give some CCI 450 Mag primers a try. They have a stronger cup than 400.

I had this problem with my 204R and switched to CCI 450 primers and it cleared up.

[stomp442]

I have heard the 450's are better just can't find any locally. Once I do I will definitely try them.

[stomp442]

Well, that is 200 fps above Hodgdon data, so it is excessive pressure wise.
You can try a different primer, like Short Round suggests.

Most of the data found on Accurate shooter in the 6mmBR cartridge guide is running 29-30.5gr of Varget and H4895 using 105-108gr bullets and they are showing velocities over 2900fps with 28" barrels. I would say I am right in line with that data with my 26" barrel.

[darkker]

Most of the data found on Accurate shooter in the 6mmBR cartridge guide is running 29-30.5gr of Varget and H4895 using 105-108gr bullets and they are showing velocities over 2900fps with 28" barrels. I would say I am right in line with that data with my 26" barrel.

Not saying you are the only one doing it, but it is still over pressure.
If the speed limit is 70 mph, but the traffic is going 75, does that mean you aren't speeding? No, just speeding with company

I don't know how well it would translate to all other cartridges, but from pressure testing the Creedmoor and a 308; for an additional 200 fps you need 20-30,000 psi extra push.

[stomp442]

I'm not saying your wrong at all so don't take this as combative, but I have not read or heard about any 6mmBR running at 2650 with 105 class bullets. Looks like Hodgdon data was using 24" barrels as well which could account for a bit of velocity loss.

[stomp442]

Just as an update, my friend found some Remington primers to try and he reports very little cratering on those primers. So while the firing pin hole may be slightly oversize it seems the primers are also playing a role. He's going to do some load work up and let me know what happens. I will update the thread as we go. Thank you everyone for your help so far.

[homefrontsniper]

Its the cci 400 ! Get cci BR or cci 450 !!!

[DanSavage]

Did you look over the firing pin tip? I had 6 pierced primers when I tried Remington primers and it ruined the nice radius tip on the firing pin. I had to fix the tip with a file and emery cloth, and reset the pin protrusion to .038. Switched back over to the Federal primers and haven't had anymore problems.

[memilanuk]

I'm not saying your wrong at all so don't take this as combative, but I have not read or heard about any 6mmBR running at 2650 with 105 class bullets. Looks like Hodgdon data was using 24" barrels as well which could account for a bit of velocity loss.

Dig a little harder... I posted a fair bit about it back in '06-07 or so over on (then) 6mmBR.com. Had the same problem you're having, with a SSS Douglas 26" 6BR tube... shot GREAT, but maxed out @ 2670 fps with a S107MK and a little over 29 gn of Varget. Anything more cratered the heck out of the primers. 'Everyone' else was claiming 2900-3000 fps. Had people tell me it was 'because I was using a factory action' and other things of that nature. Later I ran into the same problem with a 30" Lilja on a 40X receiver... got that firing pin hole bushed, and the problem went away and I was running mid 2800s no issues. Unfortunately I had long since sold that original barrel, so I never had the chance to go back and try the fix on that original barrel. That bolt did get the firing pin hole bushed, as I was unable to run any heavy-bullet .223 loads for it otherwise when my wife started shooting F/TR.

[stomp442]

The primers seemed to be the culprit. My friend has since moved to Remington primers and not having any more issues. The firing pins on his bolt and mine look to be fine and neither of us is having pierced primer problems currently. Adjusting the firing pin protrusion on my bolt seemed to fix my problem and the primer change fixed his. Thank you all for the help and I will continue to update this thread if any more problems arise.