7mm-08 pressure signs with Varget

[Tom3006]

I just got back from the range where I shot some hand loads with my son's Remington 700 SPS Youth in 7mm-08. I had previously done some load development using 39.1 - 40.0 gr of Varget pushing 168 gr Berger VLDs and found an accuracy node at 39.4 gr. I don't recall seeing any pressure signs at the time. I loaded up some more of the 39.4 gr loads to see if I could get repeatable results and to my surprise it seemed like I was getting some definite over pressure signs. Some of the cases (2 or 3 of the 10 I shot) were really difficult to extract and looking at the primers they all seem cratered (what do you think?). I use the Lyman calibration weights before weighing my powder to make sure my RCBS M500 scale is reading accurately. I measured all my case lengths and neck sized using my Lee Collet neck sizing die. Cleaned the pockets, chamfered and deburred. Primed with CCI 200 and seated 0.020" off the lands with my Hornady OAL gauge and Lee seater die. If anyone has seen this before or has some ideas on what's going on I'd appreciate the feedback. Thanks!

 

[Tom3006]

Oh, and for MV's I recorded 2,472 - 2,557 fps with a median of 2,507 fps using my Labradar. Seems in line with Hodgdon's load data.

 

[ImBIllT]

Those primers don't show pressure signs. I see two different brands of brass. You could have two very different case capacities. The stiff bolt lift could be coming from soft brass, although I didn't see any signs of brass flow into the ejector. Was it equally hard to close the bolt? Was this brass ever fired in a different gun?

Accuracy nodes are based velocity, not powder charge. When you use brass of a different capacity with the same powder charge, you will no longer on your node.

 

[gotcha]

Your primers are showing classic signs of the need for having your firing pin bushed. ..................... measuring the extractor groove before and after firing is the most effective method of determining that a load is actually over pressure. If you don't have the specialized caliper necessary to do this measuring the case body just ahead of the groove will yield similar results. Your load doesn't appear to be over pressure. ................... Do a google search for measuring cases to determine over pressure........... then send your bolt to Gre-Tan to have it bushed. You'll be glad you did ............ Almost forgot. check "similar threads" below; Titled; pressure signs from two guns.

 

[ImBIllT]

I've used bolts with the same issue without any negative effects, but yes, that buldge is from the primer going into an oversized firing pin hole. A perfectly centered firing pin can reduce SD and ES in some circumstances as well. Again, I've never felt the need.

 

[Comrade Terry]

What gotcha said. You've got a typical Remington big fat firing pin hole. The 'cratering' is just the primer flowing back into that big fat hole.

 

[msinc]

I posted a thread a week or so ago titled "To bush or not to bush???" search on here and you will see exactly what I did...had the same identical problem. Just took a quick look...it's on page 3 of the main message board. There are some pretty good, up close, detailed photos you can compare to.

 

[gotcha]

I posted a thread a week or so ago titled "To bush or not to bush???" search on here and you will see exactly what I did...had the same identical problem. Just took a quick look...it's on page 3 of the main message board. There are some pretty good, up close, detailed photos you can compare to.

Matt, You may want to retitle your post "hill billy engineering" Just sayin'

 

[T-shooter]

I had trouble with PPU brass. The worst was CBC (Magtech) NATO. After a few firings it wouls stick and I would have to tap the bolt handle to extract them. This was with mild loads.I even dropped below the minimum load listed in the manual and they still stuck. I threw them away. I stick to Lapua and Hornady brass. The Hornady seems to handle higher pressure a bit better.
I don't worry about a little primer cratering. Picture (#1) is excessive with a flattened primer. I look for signs on the case. With a bolt gun, when you see the slightest trace of an ejector mark (#2) where the brass starts to flow into the hole, it's time to back off a little. (#3) show a severe overpressure. The only one I had like that, the primer fell out. (These pictures may not have had the primers shown when they overpressured.

 

[Tom3006]

Thanks for the replies. I didn't realize brass made such a difference (only been reloading 7-8 months), but good to know for sure. I marked the really difficult to extract cases with a sharpie at the range and looking at them now they were all PPU. None of them have the have an ejector mark that I can see on the case. I guess I'll stick to Hornady or Winchester brass from now on or maybe splurge and buy Lapua brass.

Gotcha: thanks for the tip about Gre-Tan. I'm actually in Denver so he's only 3 1/2 hr drive on I70 from me. I've been looking for a good gunsmith for another rifle I'm building anyway.

 

[XTR]

Make sure you don't have any lube left on your cases, it will give you heavy bolt lifts because the case doesn't grab the sides of the chamber and you get more bolt thrust.

As stated above, those primers are not showing pressure, just a fat firing pin hole.

 

[Homerange]

Thanks for the replies. I didn't realize brass made such a difference (only been reloading 7-8 months), but good to know for sure. I marked the really difficult to extract cases with a sharpie at the range and looking at them now they were all PPU. None of them have the have an ejector mark that I can see on the case. I guess I'll stick to Hornady or Winchester brass from now on or maybe splurge and buy Lapua brass.

Typical learner mistake, seen it on my range too. Use only one make of brass, preferably from one batch.
A guy here that made the same mistake was told to get Lapua for his 308 and now shoots bug holes.

 

[gotcha]

[QUOTE="

Gotcha: thanks for the tip about Gre-Tan. I'm actually in Denver so he's only 3 1/2 hr drive on I70 from me. I've been looking for a good gunsmith for another rifle I'm building anyway.[/QUOTE]
If you don't mind struggling over Eisenhower pass more power to you I'm sure an Inquiry here about Denver area Smith's would be fruitful...................... PM sent

 

[Shaggy357]

How was the temperature on the days you shot? I have several guns that favor Varget. I do have to be careful when it gets really hot. My 6BR shot a home grown 107gr bullet really well at 60-70 degrees. When I got in a match at 90+ the jackets started coming apart. My 7-08 is same way. Shoots great in the fall, but can be temperamental in the summer if it gets too hot. WLR primers and Varget go together like peanut butter and jelly.

 

[Racebannon3855]

Gre-Tan is the way to go. Oversize firing pin holes are not just a Remington issue, they helped me out with a Ruger 77.