Case web growth and head hardening

[Harvey_NW]

I'll start by saying I'm aware of the Sherman SAUM based cartridge brass/reamer spec discrepancy, but I'm already waist deep so I'd rather discuss topics that will apply to reloading in general. Recently received my custom rifle chambered in 7 Sherman Max and fired 47 pcs of the fully formed ADG brass at a low charge recommended by Rich Sherman to "harden the case head" and finish form. Upon taking some measurements with calipers I was getting an expected .002" shoulder growth, but at roughly .200" above the case head I was getting consistent .006" web expansion. Unfired cases measure .545", all fired cases were .551" +/- .0005". I realize this was done rogue and with an improper tool, but my concern lies within the fact that it's consistent, and measurable. After chatting with the gunsmith and Rich, they said that growth is normal and the chamber/reamer measurement at .200" is .553". Too tight of a chamber causes clickers in the 7 SAUM based cartridges.

Both of these topics have extremely conflicting views. There are some gunsmiths that say .0005" web expansion is an indication of excessive pressure and you should stop immediately. Some claim any web expansion is a direct link to loose primer pockets, other say it depends on the headspace or shoulder growth. Rich and many others claim that firing at a low charge first firing will finish form and harden the case head and primer pocket, and from there you can do load development to find pressure and should get multiple firings.

Just looking to get some feedback instead of reading conflicting theory.

 

[BBob]

There are some gunsmiths that say .0005" web expansion

That figure does not refer to the case dimension @ .200", it refers to expansion at the base just above the extraction groove in an effort to watch for excess pressure. This method requires a blade micrometer to measure correctly since the area you need to measure is narrow. If you're trying to use calipers for this then forget it. This is also not an absolute so you can't totally hang your hat on it to look at pressure. Most I know don't even look at it anymore.

As to case measurements @ .200". Depending on the cartridge size the reamer (finished chamber) is generally recommended to be .002-.004" over the size die dimension for proper sizing. You also cannot have a size die smaller than the original case head and expect it to work. This is why many like Sherman offer a particular reamer and a size die for sale. It is also why some well known gunsmiths offer up open source reamer designs and refer you to a particular die to work with it. They also generally tell you what make brass the combo was worked out for too. It's a fine line between brass, reamer and die for it to all work properly. When I set out to do a new to me cartridge the first thing I do is source the brass I want to work with, then source a die and then pick or design a reamer last.

 

[Cahunter805]

Rich is a very smart guy and I’d be inclined to trust his judgment on the cases. Only way to really tell is size and fire a case over and over and see how many firings you get from it.

 

[WeiserBucks]

I want someone to explain to me how the 1st firing hardens the case head and primer pocket. I've never experienced this myself and at this point I'm confident that its pure bullshit.

 

[Harvey_NW]

When I set out to do a new to me cartridge the first thing I do is source the brass I want to work with, then source a die and then pick or design a reamer last.

Hard lesson learned, but there was information about changes in brass size by the manufacturer that was not disclosed until recently, which leaves me with this issue.

 

[Harvey_NW]

I want someone to explain to me how the 1st firing hardens the case head and primer pocket. I've never experienced this myself and at this point I'm confident that its pure bullshit.

Same here, but I am perplexed. A good friend/mentor of mine is a national long range competitor and a scholar in metallurgy, he claims it is in fact bs and the pocket is going to blow out regardless at a given amount of pressure. Conversely, there are tons of guys on the Sherman page that followed the recommendation of using a low charge for the initial firing, then do load development and find pressure, and are getting multiple firings. The guys that are losing primer pockets put their standard load in new brass.

So is that coincidence, or evidence?

 

[Harvey_NW]

Rich is a very smart guy and I’d be inclined to trust his judgment on the cases. Only way to really tell is size and fire a case over and over and see how many firings you get from it.

I have so far and intend to proceeding, just wondering if others have had similar experiences in different chamberings, and what the general consensus of these theories are from shooters I can ask questions or discuss with.

 

[WeiserBucks]

Same here, but I am perplexed. A good friend/mentor of mine is a national long range competitor and a scholar in metallurgy, he claims it is in fact bs and the pocket is going to blow out regardless at a given amount of pressure. Conversely, there are tons of guys on the Sherman page that followed the recommendation of using a low charge for the initial firing, then do load development and find pressure, and are getting multiple firings. The guys that are losing primer pockets put their standard load in new brass.

So is that coincidence, or evidence?

People fall for Sherman bullshit like a blind roofer. If they load their rounds to "normal pressure" they get normal brass life. If they load em up to "Sherman pressure" they lose primer pockets prematurely. Rich is constantly spewing his designs as handling pressure better, being faster with less powder ect. It's all bullshit, higher pressure makes more velocity, period, it's physics.

I'm not bashing Rich, but his rabid followers are going to get someone hurt with their insane reloading practices. Many of the 7SS shooters brag about their little short mags running at 28 Nosler speed.

harvey_nw, I sincerely hope you get your rifle sorted out and enjoy it. Please be realistic and don't drink the 40,000 FPS Sherman Kool-aid. Rich has some nice designs that are great for the intended use but they're not magic.

 

[Harvey_NW]

harvey_nw, I sincerely hope you get your rifle sorted out and enjoy it. Please be realistic and don't drink the 40,000 FPS Sherman Kool-aid. Rich has some nice designs that are great for the intended use but they're not magic.

No Kool-aid for me, I like mild loads and accuracy nodes. The only reason I ended up with a Sherman is because 7 SAUM brass has been unobtanium for a few years and he had all components in stock when I was gathering parts for my build. I almost didn't even mention the chambering in attempt to keep the discussion on track but I know someone would ask..

 

[WeiserBucks]

Back to fire-hardening the case head/primer pockets, it's bullshit. Every time you fire a cartridge the primer pocket gets bigger. Quality brass is typically harder and thicker in the case head to begin with, which results in less primer pocket growth and less pressure signs. The pressure is there, but quality brass can hide it pretty well.

Perfect example, I used to have a 26" 300 Norma. With Norma brass I'd start to see pressure signs at 2950 FPS with 230's and the brass would last 3 firings before it wouldn't hold a primer any longer. After switching to Peterson or Lapua brass, it would send the 230's at 3080 FPS with zero pressure signs and the brass lasted 15+ firings before the necks started to split, primer pockets were still good. The pressure was there in the good brass, it just took me a longer than it should have to realize that my load was likely unsafe.

If firing the brass made the primer pockets harder or not grow, nobody would ever have to throw away brass due to stretched primer pockets.

 

[Harvey_NW]

After switching to Peterson or Lapua brass, it would send the 230's at 3080 FPS with zero pressure signs and the brass lasted 15+ firings before the necks started to split, primer pockets were still good.

If firing the brass made the primer pockets harder or not grow, nobody would ever have to throw away brass due to stretched primer pockets.

If the necks split before the primer pocket loosened up that kind of contradicts the exact point you're trying to make though. Based on what I've read I think there is some merit to the theory, but also why I wanted to start a discussion here. I think the primer pocket can potentially grow every firing because of high pressure, but it can also stay tight at optimal pressure and ability to springback, which would be work hardening. If I proceed with this cartridge I'm going to try it because Rich and many others recommended it, and it's kind of like a barrel break in procedure, it can't hurt.

 

[BBob]

If the necks split before the primer pocket loosened up that kind of contradicts the exact point you're trying to make though

Neck splits happen because of the work hardening that results from repeated manipulation of the brass. You size it, you fire it, you size it, you fire it and so on….. this is one reason some choose to anneal the neck/shoulder.

 

[WeiserBucks]

If the necks split before the primer pocket loosened up that kind of contradicts the exact point you're trying to make though.

You completely missed the point. Let us know how the primer pocket hardening goes.

 

[Wrench]

Brass work hardens. If it were not true, necks would only split on the first firing if they were going to split. Does case head hardening occur controllably? Dunno.....but it does happen.

I just built two 300wsm's and fired a load at 2.2grs over book max. My web expansion is .0005" with a caliper, safe to say sub one thou. I was about 2 to 3 tenths deeper on the second barrel and web swell on it is a tenth or two larger. Both of these tubes were cut on the same lathe, same day, same reamer and me spinning it.

If you're growing 5 thou you're killing brass imo. Tight isn't necessarily right, but a hotdog in a hallway is not the way either.

If I cut one 5 over, it would be because I got a bum reamer or my tailstock was not square.

 

[Harvey_NW]

That figure does not refer to the case dimension @ .200", it refers to expansion at the base just above the extraction groove in an effort to watch for excess pressure. This method requires a blade micrometer to measure correctly since the area you need to measure is narrow.

I know it's not the proper tool but last night I remeasured just above the extraction groove with the blades of the caliper and got completely different numbers that are much less concerning, and they were consistent.

I just built two 300wsm's and fired a load at 2.2grs over book max. My web expansion is .0005" with a caliper, safe to say sub one thou. I was about 2 to 3 tenths deeper on the second barrel and web swell on it is a tenth or two larger. Both of these tubes were cut on the same lathe, same day, same reamer and me spinning it.

This is the info I was looking for. So as said above, I remeasured using the blade of the caliper just above the extraction groove I'm getting .001" growth. Unfired cases .545", fired cases .546" some maybe +.0005". Is that where I should be measuring?

 

[Wrench]

.2" above the head is typically the edge of the web. That's where chamber size shows up. The area below that is case head, full thickness brass. If you split a case it is easy to understand. It's not a bad plan to split one after 5 or so loadings and monitor brass flow. The case will move brass forward.

 

[Harvey_NW]

.2" above the head is typically the edge of the web. That's where chamber size shows up. The area below that is case head, full thickness brass. If you split a case it is easy to understand. It's not a bad plan to split one after 5 or so loadings and monitor brass flow. The case will move brass forward.

Thank you. I will keep an eye on everything and continue taking measurements. I'd love to offload these components and go a different route but I couldn't morally without making someone fully aware of the issues, at which point I would assume they wouldn't want it either.. So I guess I'll test some theories!

 

[BBob]

I fail to see why there are “issues“ with what you have. Can you resize the fired brass, load it, fire it and extract it without clickers? If so and you can do this after multiple cycles then you don’t have a problem IMO. I personally could care less if the brass expanded .006” over the unfired case dimension as long as the size die sizes it correctly. What is the case dimension at the .200” line after resizing?

 

[Harvey_NW]

I fail to see why there are “issues“ with what you have.

The issue is guys are complaining about losing primer pockets on the first firing of ADG brass in the Sherman SAUM based cartridges. The excuse is that Gunwerks got a batch of tight 7 SAUM reamers that caused clickers with ADG, so they worked a deal out to downsize the case head and web area by .0023". The current Sherman reamers are .555" at the case head, .553" at .200", and the cases are .545". He is now having his reamer size adjusted so all chambers and dies from here on out are exclusive and will either have this issue or need fireformed 7 SAUM brass at Norma dimensions. I think the .008" difference is where the problem lies. I have yet to fire them all and get to the resizing process, but the only people that seem to not have issues are the ones that listened to Rich and initially fired them all at a low charge, at $2/pc I'm willing to try whatever works but I wanted to hear opinions on the theory from people that aren't googley-eyed over the topic.

 

[BBob]

I don't really buy into the chamber being so big to where it causes head expansion to the the point that primer pockets are blown out. I buy more into that batch of brass is too soft. GAP had the same issues with the first batch of dedicated head-stamped 6.5 GAP (6.5 RSAUM) brass. The second gen was better and 3rd gen the problem pretty much went away. Had nothing to do with reamer dimensions at the back end. There were no issues with Rem 7RSAUM brass in the same chambers and I don't think cases were much different dimension wise. I'd have to go back and check though.

Case heads are unsupported by the chamber so I've been puzzled as to why anyone thinks a tighter chamber is the cure for loose primer pockets. Once upon a time lots of benchresters thought that and designed really tight chambers but we all now know all that did was create what we all call clickers these days. Pretty sure the word clicker as applied to cases first came from short range benchresters, at least that's when I first heard it to describe the issue.