High pressure from different primer

[nh15]

First post though I've been lurking for awhile. Searched around and couldn't find anything similar.
Been reloading for thirty years and never seen anything this drastic before.

Both cases are Lake City loaded with 42.0 grains of Imr 8208 XBR behind a Hornady 150 SST.
Everything about the two is the same except for the primer. The one on the left is once fired case with a Winchester large rifle primer and the one on the right is a military primer that came loaded in the brass, that had the bullets pulled.
There was no other indication of high pressure. No ejector marks and bolt lift was basicly the same on both.
Both were loaded at the same time from the same canister of powder and bullets seated to the same length. Rifle is a Remington 700.
Is the difference because the winchester primer is that much hotter causing higher pressure or is the winchester primer that much softer or thinner?
Thanks

 

[Cacciatore]

Another factor is that the primer that was in there is crimped in. The primer you installed is not crimped.

 

[rjacobs]

I'm going to say the winchester primer is quite a bit softer than the mil primer in the other case. I'm not sure about large rifle but I know small rifle has regular, magnum and then an even harder, hotter primer like cci 41's.

 

[SporterII]

Did you have any trouble seating that Winchester primer?

 

[former naval person]

Military primers are a bit harder/thicker to help prevent slam fires in full auto weapons.

 

[nh15]

No, I don't recall any problems seating the primers. Winchester primers usually seem to seat easier than others for me. I use CCI a lot.
There are actually five cases, exactly that the one on the left. I was shooting five shot groups and didn't realize the flattening until after the group. Both groups were similar in size and shot to the same basic point of aim.

 

[bodywerks]

Not sure what primer is in that military round, but it's the same color as Remington primers. Remington primers typically have the lowest brissance of any primer, and Winchester primer cups are a little on the soft side.
Were they all like that?

 

[ksthomas]

The Large Rifle primers used in Lake City ammunition are the #34 for normal combat ammo, and the #43 for Match ammo such as the M72, M118 M852 and M118LR. The #34 roughly corresponds to a Large Rifle Magnum, while the #43 is equivalent to a Large rifle Match primer. Both use thicker or harder cups to preclude slamfires, as has already been pointed out. Recent runs (the past several years) of Winchester primers have been somewhat softer, causing many of us to switch away from what was a long-standing favorite. We went through this with the WSRs, when they thinned/softened the cups to increase sensitivity. Suddenly started seeing serious pressure signs (via the primer) in loads we'd all been using for many years, woth no other changes. Finally had some of these rounds pressure tested in Hodgdon's lab, and found that the pressures were right where they should have been, and not at all excessive despite the appearances on the primer.

Worth remembering that primer appearance is a pressure indicator, but it's just one of several that need to be taken in conjunction with one another. While they will often tell you if when you're into the unfriendly pressure zones, they'll also lie to you faster than a politician running for reelection. I've seen dangerously over pressure (proof load territory) rounds that you'd swear were perfectly safe based on primer appearance, and I've seen what most handloaders would consider signs of serious pressure problems in rounds that were actually quite mild. Combination of factors here, and they need to be taken in as a whole package, rather than focusing on just one facet such as primer flattening. I suspect that that's what you're seeing here, and that despite the flattened appearance, the load is probably within safe limits. Look at the other issues; is the primer pocket staying tight? Is the case life good? Is the case sticky upon extraction? How about velocity? Is it within reasonable limits for this load? Like I said, look at the whole package, and then decide what's valid and what's not.

 

[Pinecone]

FYI, CCI 450 SR Magnum primers and #41 SR Military primers are the same except for anvil seating depth. #41 has a tiny bit more space between the anvil and the bottom of the cup.

 

[turbo54]

Finally had some of these rounds pressure tested in Hodgdon's lab, and found that the pressures were right where they should have been, and not at all excessive despite the appearances on the primer.

Worth remembering that primer appearance is a pressure indicator, but it's just one of several that need to be taken in conjunction with one another. While they will often tell you if when you're into the unfriendly pressure zones, they'll also lie to you faster than a politician running for reelection.

I've seen dangerously over pressure (proof load territory) rounds that you'd swear were perfectly safe based on primer appearance, and I've seen what most handloaders would consider signs of serious pressure problems in rounds that were actually quite mild.

Combination of factors here, and they need to be taken in as a whole package, rather than focusing on just one facet such as primer flattening. I suspect that that's what you're seeing here, and that despite the flattened appearance, the load is probably within safe limits. Look at the other issues; is the primer pocket staying tight? Is the case life good? Is the case sticky upon extraction? How about velocity? Is it within reasonable limits for this load? Like I said, look at the whole package, and then decide what's valid and what's not.

This post is *right* on point. Thank you for it.

 

[nh15]

I too agree with ksthomas.
I think my next move is to load five of each with 10% less grains of IMR8208XBR with Winchester primers, five with CCI # 200, and five of the primed LC brass. Work my way back up to 42 grains, but, this time I'll chronograph the loads as I go.

 

[Boogaloo]

Another thing to do is to accurately measure the case capacity of your brass. Take 5 random pieces and plug the flash hole with bar soap or wax by forcing it into the primer pocket. Use a pic or a Qtip with the cotton removed to scrape away any extruded soap or wax from inside the case so that the soap or wax exclusively plugs the flash hole, but does not take up any space inside the case itself.

Now, measure one case and zero your scale. Then, using a syringe, start adding distilled water to the case while it sits on the scale, and only until the meniscus just bulges over the top of the case mouth. Write that weight value down on a sheet of paper. Repeat the process for the next 4 cases, then average the values out to get an average case capacity for your particular lot of brass.

With this info, you can come back in here and PM me if you don't have Quickload and I will work up your load for you and get you a rough estimate on the predicted velocity, as well as whether or not your current charge weight is questionable, or where it lies on the danger scale.

Like Mr. Thomas stated, I have seen primers flatten like that with no other pressure signs, and on loads where my predicted and observed velocities were within 6 FPS of each other, and well below maximum as far as Quickload or book data was concerned.

If you are not seating the primer all the way into the primer pocket with an ever so slight amount of compression that spreads out the primer cup into the walls of the primer pocket (giving it a "swedged" fit), then the primer can actually back out a bit under pressure, and actually influence the flattened appearance of the surface of the cup as seen in your pictures. Again, as Mr. Thomas points out, this is not necessarily a sign of over pressure, but rather an indication that the primer is "walking" a bit on you, and exaggerating the issue.

Lets figure out if you are on the edge or not with respect to your charge weight first. Also, perhaps a simple adjustment to your priming procedure is in order. They need to be crushed into the primer pocket just a wee bit. (in my opinion).