Any experience with this Primer pattern???

[SG4247]

photo 1.jpgphoto 3.jpg

Noticed some interesting primer extrusions on a 6.5 AR using CCI #41 primers.

No ejector swipes and the primers are not really flattened.

Not sure what to make of this..

Any ideas?

[explorecaves]

What is the load? Looks like the primer is flowing around the firing pin into the hole in the bolt. May be on the verge of a pierced primer...

[LRRPF52]

What is the load? Looks like the primer is flowing around the firing pin into the hole in the bolt. May be on the verge of a pierced primer...

This. The heat and pressure are to the point that the primer is literally molten in that area, and flowing into the firing pin hole.

[SG4247]

It is 28.5 grains of Varget behind a 123 scenar in a Lapua 6.5x47 case.

[LRRPF52]

Ok, Varget is right next to Vihtavuori N140 on a burn rate chart. There aren't any powders loaded that low even for a 100gr in Lapua's data for start loads.

The start load for N140 with a 123gr Scenar is 33.2gr, giving 2520fps from a 27.5" barrel. I'm not saying to use N140 and Varget interchangeably, but that load is way low. Where are you getting data from for the 6.5x47 Lapua?

[SG4247]

My mistake 38.5 gr of Varget. It's been a long day!

That's the trouble with these 6.5s, good load data is really hard to get.

Vihta is a common reference for the cartridge, conversions from their powders to others, is not so simple.

[explorecaves]

For the 130 VLD's I found this:

http://forum.snipershide.com/snipers-hide-reloading/162271-varget-6-5x47-lapua.html

"A lot of Varget gets burned up in the 6.5L I have burned up about 24 pounds, anywhere from 34.8 up to say 38 grains will work, approach the upper end with caution."

I would say you need to back off of the charge a bit.

[SG4247]

That's a good read, thanks for that!

The rig was making 2920 fps from a 22" Krieger tube with this load.

Sounds like this is pushing it. I will back it off until the primers look "normal".

[LRRPF52]

The 6.5x47 Lapua is rated for over 63,000psi SAAMI MAP, which is within 2000psi of the .270 Winchester. Depending on the primer, you can start seeing cratering at 50,000psi with the softer, thinner cups, whereas the thicker, stronger cups might not show any signs until they hit 70,000psi, and they might be ever so subtle.

What did your chronograph give you for ES and SD? How many shots?

[SG4247]

The 6.5x47 Lapua is rated for over 63,000psi SAAMI MAP, which is within 2000psi of the .270 Winchester. Depending on the primer, you can start seeing cratering at 50,000psi with the softer, thinner cups, whereas the thicker, stronger cups might not show any signs until they hit 70,000psi, and they might be ever so subtle.

What did your chronograph give you for ES and SD? How many shots?

I ran six shots thru the Chrony at 2922, 2888, 2889, 2909 ,2930, 2921.

[SG4247]

image.jpg

This load shot 3 touching at 300 yards.

Fluke? Probably.....

[LRRPF52]

How many of the primers exhibited those signs?

Achieving 2900fps with a 123gr from 6.5x47 Lapua is well within the cartridge's capabilities, but I think Varget might be limited if it burns like N140, since N140 maxes out at 36.4gr in VV's data. N540 produces the best velocity with 123gr Scenar, and 140gr pills as well in my experience with that powder/cartridge combination.

My sniper partner for FinnSniper 2010 was pushing 140gr Berger VLD's at over 3000fps from a 25" barrel, but primer pockets were getting loose very quickly. He was dropping 900m and farther targets like it was easy though, 1st-round hits, one right after the other.

[SG4247]

They all had some cratering, which doesn't really bother me.

A handful were extruded back into the bolt face like the photo.

No pierced primers ever with CCI #41 primers, but I may be getting close!

So is Varget safe load like this in your opinion? or should I consider it maximum?

Or should I go to N540?

[LRRPF52]

What's your firing pin hole diameter on the bolt? There's no way for me to determine safety without seeing the pressures on instrumentation.

[Klem]

Looks like the primer is flowing into the gap between the firing pin and hole because there is too much space.

Pacific Tool and Gauge sell Rem700 bolts with a smaller than spec primer holes for F Class ,223 shooters. Their smaller diameter pins are 0.062" whereas a standard pin is 0.075" The hole in the bolt is machined smaller and the gap between the firing pin and hole is less. This is is so that higher pressures with magnum primers can be reached for situations like F Class shooters using .223 to reach 1,000yds. For that you skate on the edge beyond SAAMI but with quality components it is safe to do so. With the smaller, tighter hole there is more primer support and less chance of do-nuts like in your photo occurring. There is more chance of the narrower firing pin piercing the primer however if you use magnum primers which have harder cups this mitigates that problem.

Perhaps in your case the firing pin hole diameter relative to the pin diameter might be too sloppy for the loads and primers you are using in that caliber. They might not necessarily be too hot loads for the chamber but are not being supported enough at the pin hole.