7-08 pressure problem

[MrMagumba]

It was the brass! I had a thread going in gunsmithing because I thought I might have a gun problem. But it turned out to be the brass. I had some PPU brass that cycled in my Weatherby Vanguard just fine new, but caused a sticky bolt on retraction after the brass was once fired and resized. Lots of ideas from the gunsmithing forum, but I got to the point of buying some new Starline brass and it worked perfectly on first firing and after resizing.
Not sure what could be going on with that PPU brass. On my last range trip today to try the resized Starline, I also loaded 5 of the PPU but instead of full length sizing, I gradually raised the die a few thou. The #3 and #5 round functioned quite a bit better. So there is something about the fluid dynamics of that PPU brass that causes a bulge on firing (I think right where the body meets the shoulder) and creates a sticky bolt. Not sure if I will mess with that PPU brass anymore.
By the way, my Starline test consisted of increasing loads from 35.0 - 39.5 H4985 in .5 gr increments behind the Hornady 139 FB SP. The last 5 shots produced a 1 MOA group. Not bad for 5 different powder loads over a span of 2 grains.
Lessons learned: There was no overpressure as my original title suggested. Primers were starting to flatten, but not that bad.
Brass can be finicky. A slightly different "metallurgy" can affect gun function.
Careful analysis and testing beats jumping to conclusions.

 

[tightgroup tiger]

They may just need the neck trimmed on them. Trim one and try it in the chamber.

 

[horsemen61]

I’m not a fan of PPU for this reason I had a similar issue once I switched it went away so I think it was the brass and I haven’t had that issue since

 

[tightgroup tiger]

I’m not a fan of PPU for this reason I had a similar issue once I switched it went away so I think it was the brass and I haven’t had that issue since

I don't really care for PPU either.

 

[troy fairweather]

Never had any problems with ppu, it's better then most us commercial ammos brass.

 

[AJC1]

Sounds a lot like a poor sizing die/chamber mismatch. If your happy with the results of a different brass then use that.

 

[Larry in wyoming]

I'm having a similar problem with my savage in 308. Shoots good at 42 gr of mp540 and 2520 but at 43gr extraction is very sticky. Bolt lift is fine but primers are getting flat. Max load for 2520 is somewhere between 41.5 and 45gr depending on which book you use. Brass is Lc 97 match bullet is 168gr amax velocity is, coincidentally 2520. I was hoping to push them a little faster but I may be maxed out. I'm going to change primers and go to commercial brass and see what happens.

 

[MrMagumba]

Yeah I am a little slow to condemn PPU brass all together. I have used it before without problems, but in all my loading I have never seen such dramatic problem between new and once fire brass. Plus the problem persisted from once fired to twice and three times fired. Starline works good so I don't think there is anything wrong with my Redding dies or Weatherby Vanguard. I'll just move on and probably not buy PPU again. I'm assuming it was a bad batch of brass or some unknown incompatibility with my setup. Been loading casually for 30 yrs and this was a new one. Thanks for all the ideas. At least it looks like I found a way to navigate through this mystery.

 

[Larry in wyoming]

Loaded some test rounds in commercial brass at 43gr of 2520. They extracted easily. 41.5gr in LC brass also extracted fine. Apparently the LC brass has a lower volume and it feels like it is less malleable than the commercial, thus raising pressure. No surprise.