Pierced Primer question working up a load

[fella5]

Okay here is a newbie questions I have.... Just wanted some input on your though about my primers, velocities, etc.

So far I have 100 rounds through my Savage 12F 6 Norma BR 1-8 twist with 30" barrel. After fire forming some Lapua brass, I started to work up some loads. So what I have is once fired Lapua brass, CCI BR4, Varget, Berger 108 BT. My starting load was at 29.6gr to 31.7gr of Varget and the bullets were seated on the lands and had 0.0015 of neck tension. I made three loads of 29.6, 29.9, 30.2, 30.5, 30.8, 31.1, 31.4 and 31.7. Here are some pics of my cases after firing... the left most case is 29.6 and right most case is 31.7.

Here are my velocity:

29.6 - 2680
29.9 - 2693.5
30.2 - 2719
30.5 - 2752.5
30.8 - 2781 pierced primer
31.1 - 2802 pierced primer
31.4 - 2834.5 pierced primer
31.7 - 2854 pierced primer

If you look at the Side view, you can see the primer sort of lifted on the 2nd - 4th case. Also the only time I had a hard bolt lift was on the 31.7 case. I have read that this might be caused by the firing pin and not so much by pressure....

29.9gr and 30.5gr gave me my tightest group... in between those two were not bad at all. By the way... temp was around 65F.

Top

Angled

Side

 

[spclark]

Pierced primers are more a result of "factory" tolerances between the firing pin diameter and the FP hole in the bolt face than any other factor alone.

If best accuracy is with a load that you can shoot without piercing primers (or worse) why load any hotter?

Check your FP with a decent magnifying glass or loupe to determine if it's been eroded by gas cutting. Once primers have been pierced it's often the case a pin has been damaged, likely to result in further issues.

You can have your bolt FP hole bushed to reduce the tendency for primers to crater or pierce. Send Greg Tannel <greg@gretanrifles.com> an e-mail or visit his website. He's the specialist in this operation & well respected. Cost at the end of 2008 was $64 with return shipping included.

Be mindful of how far back you bump your case shoulders too when resizing. Primers should NOT be backing out even under higher-than-advisable pressures. You may want to have your Savage checked for excessive headspace....

 

[fella5]

Spclark,

Thanks... I will take a look at the firing pin to see how it looks. So if I load up some 29.9gr and I have no issue with pierced primers, does that rule out a bad firing pin and that the loads I was working up was too hot?

 

[madmixerman]

I had pierced primers using 30 grs Varget. Sent bolt to Gre-Tan & had firing pin turned down & firing pin hole bushed ,no problems since.

 

[fella5]

Thanks... I will send them an email.

 

[6BRinNZ]

Hi Scotty,

the view of the primers side on, is it the primer has moved or is it actually the cratering of the primer you can see - sometimes before primers pierce you will get primers within the same load or the loads leading up to the piercing will have a severe "crater".

If it is severe cratering then even these loads are possibly too hot...Bushing the bolt face will definitely help the cratering as well. Something I have found that will produce the same symptoms (I think it is talked about on this site somewhere as well) even though the load has been fine - loading the rounds and leaving them to sit for some time (week or more), I think it is something to do with a bond forming between the case and projectile (?).

 

[hardrock6]

In my gun the cases with the pierced primers would to hot. 30.2 would be about right.

Gary

 

[fella5]

The Sierra manual for their 107gr starts at 25.5 to 29.4. So should I start around 26-27 and work up? Also, I made the ammo the night before so they weren't sitting around. I will make some tonight and go out to the range tomorrow and report back

 

[RonAKA]

Suspect my Savage LRPV 6BR has the same action as yours. I have not seen any issues using the same powder and BR-4 primers. Max bullet weight in mine is 80 grains due to the 12 twist, so I can't give you a direct comparison. However for 80 grains Sierra has a max load of 30.5, while Hodgdon says 32.5 as max. I've loaded to 32.8 and not seen any evidence of primer pull out, crater, or pierced primers.

In your case Sierra says a max load of 29.4, while Hodgdon says 29.0. You are starting at 0.6 over the maximum Hodgdon load and going up from there. Normal practice would be to start much lower and slowly work up to the maximum, not up from the maximum. I think the primers are telling you that your pressures are too high -- and quite a bit too high.

 

[fella5]

RonAKA,

Yeah I looked at that.. I guess my issue was researching other's accurate loads to find my starting point. I'm planning on a starting load of 27.0 and working up 0.3 grs to aroun 29.4. Does that sound okay?

 

[jonbearman]

you might want to try a different powder as well.I use h322 for my light bullets and varget just didnt work.

 

[rocketron]

not 100 % sure....but if you look at the case specs in the manual they are remington cases and the trim length is shorter than 1.550.....

i believe the loads in the manuals are for the 6 br remington.........not the 6 br norma

again not 100% sure on this but thats what it seems like to me....

Ron

 

[hardrock6]

Yeah I looked at that.. I guess my issue was researching other's accurate loads to find my starting point. I'm planning on a starting load of 27.0 and working up 0.3 grs to aroun 29.4. Does that sound okay?

Good choice

 

[fella5]

Thanks... I will post my findings tomorrow. Then I'm shipping my bolt to Gre-Tan

 

[RonAKA]

I'm planning on a starting load of 27.0 and working up 0.3 grs to aroun 29.4. Does that sound okay?

Yes, I assume you are looking for the most accurate load. It may not be the maximum possible load. You really have defined your maximum load already with the existing bolt. As 6BRinNZ, asked has the primer in the 2, 3, 4 loads actually popped out of the case or is that the crater we see from the side. If that is a crater that is major, and not acceptable in my view. If the whole primer is popping, then I wonder about headspace being a little high. That is quite easy to correct if not right.

 

[fella5]

That is not the primer backing out. It is the crater that is showing. If you run your finger tip over the base of the case, you will feel the sharp edge of the crater.

 

[spclark]

30 grains of Varget behind a 105 - 108 grain bullet is kinda the "benchmark" load for the 6BR; if a given rifle won't shoot that accurately there's likely something wrong somewhere.

You mentioned you'd gotten the best accuracy from the two loads on either side of this @ 29.9 & 30.5 grains which adds support for the rule of thumb above.

Primer cratering isn't normally something that affects accuracy & some folks ignore it.

I'd go with the bolt bushing operation (I had a Quadlite bolt done two years ago) then tune the load that you know works. 30.5 grains is likely the high end anyway for your rifle & conditions, particularly if you're using bare bullets & want some safety margin for shooting in warmer weather.

 

[deadlyswift]

Scotty,
If it was me, here is what I would do. STOP!!!! Go back to Square 1. First I would send my bolt to Gre-Tan and have the firing pin bushed and shaved to .062. It will cost you $82 turn key, and the bolt will be back to you in most likely 5 days. Even if that doesn't fix the piercing problem it will be well worth the $82! Things will be right with your firing pin, and you will be good to go. Trust me it's worth the $82! How far do you plan on shooting? 100, 300, 600, 1000yrds? Are you shooting for your own personal enjoyment? Witch by the way. I do enjoy that myself. Regardless If you want to shoot at 300 or futher, and you are able to. I would read this article. http://www.6mmbr.com/laddertest.html I will say that this article is probably one my favorite articles. You will be able to find your max load for your chamber as well very clearly see exactly where your accuracy nodes are with your barrel. You will only need max vol if shooting at long distances, 600 or more. If your under that you can shoot a lower end vol. node and save barrel life. Just my 2 cents, and something to think about. Keep us informed. Hope this helps!
Mark

 

[fella5]

deadlyswift,

My range allows me to shoot out to 600 yards. I will start at the 100 yard and then go to the 200 and then 300 before I start shooting the 600. I guess I was worried about the low velocities 2600-2700 and the drop I would be getting out to 600. I shoot for fun, but I shoot with a member who got me into this sport. I spoke with Greg at Gre-Tan and I will be shipping my bolt to him tomorrow or Friday. He will do what you mentioned about the firing pin bushed and shaved.

I did look at the ladder test a couple weeks ago and read many others. I think eventually when I find that perfect load, I will be shooting more in the 200 yard and 600 yard.

 

[fella5]

By the way.... I'm seating the bullet on the lands. Now how I measured this is I took a dummy round and seated the bullet around 1.8370 and then chambered the dummy round. I measured it and it was 1.8220 consistently with 5 dummy rounds. So is this considered into the lands or soft jam??? I see the land making on the ogive of the bullet. The rounds that I just made are seated 1.8210.... should I adjust this?