Extractor tearing rim off 5.56 cases

[smchop]

So I put together a batch of ammo I had spent some time on load testing. What I ended up with is 62gr Goldenwest bullets, with 26.9gr WC844, in LC brass, and CCI 400 primers. Out of two different rifles I had two cases stick and the extractor broke the edge off the case and left the case stuck inside. I prepped the brass as follows. FL sized with Dillon die and deprimed. Cleaned in a Thumblers Tumbler to nice and shiny. Then swaged on a Dillon swager to remove crimp, and trimmed to 1.755. The brass was all once fired that I bought from someone else, so not fired from my rifle. One case shows no pressure signs, a little flat on the primer, but I've seen worse from factory ammo. The other case had a double feed and caved the primer in and pushed the new round down inside the case. So am I dealing with a pressure issue? I had loaded up and shot it in a 100 rd batch before with no problems. But as I type this there is one thing that was not the same as before was that I had my can on both rifles when it happened. Both rifles are AR15's, one is an SBR. Is it possible the suppressor caused a dirty enough chamber to stick the cases? Thanks for any input.

[ray1970]

I'm not familiar with that powder but 27 grains of anything seems a bit excessive to me. Depending on the powder, most of my 55 gr. loads use between 21 and 25 grains.

But, like I said, I am not familiar with the powder you are using.

It sounds like an excessive pressure issue to me.

[Great-Kazoo]

I'm not familiar with that powder but 27 grains of anything seems a bit excessive to me. Depending on the powder, most of my 55 gr. loads use between 21 and 25 grains.

But, like I said, I am not familiar with the powder you are using.

It sounds like an excessive pressure issue to me.


This. The data for that surplus is showing 25 high side, based on an average using 62 gr.

[spqrzilla]

Tearing off rims is a high pressure sign (unless you have an adjustable gas port, in which case you need to dial it down).

[jerrymrc]

That is warm if not on the hot side. I load WC844 at 23.5-24 for 55gr. I bet your primers are flat. In my log book I noted they started showing OP signs @25.5 and again that was with a 55gr FMJ.

I also noted that 25.5 threw bullets like a shotgun at the target. I always start low and go .5 at a time. I have not broken out the crono yet on this load.

[Madusa]

Adjustable gas block, longer gas tube, the case still has pressure when it is being extracted. my first guess

or like everyone else, sounds like a lot of powder (especially for an SBR)

[Not_A_Llama]

That's a pretty warm load, even for a 55gr loading. 62 should be skeery. WC844 is also very temperature sensitive.

I'd dial it back. How does the load chronograph? You getting ejector swipes?

[smchop]

I did break them down by .5 increments, and really had no pressure signs, no swipes, and ran a couple hundred rounds as small batches with no problems. I'll take some pics of the brass after fired. I know there is no denying now that rims tearing is a pressure issue, I need to go through my Dillon and check things over again and see if anything changed but it hasn't before. I'll get the velocities it was running also and post them up for reference.
But the thing that bugs me is I had no problems with the other small batches till I put my suppressor on, but like I said I need to double check powder charge and see if anything changed. Thanks for the input.

[USMC88-93]

Did you do your load work up in cooler temperatures?

[spqrzilla]

The traditional "pressure signs", by which many often mean examining the fired primer, are really mostly bunk. Are you chronographing your loads? Chronographs are really a better way to watch your load development, as erratic velocity or more velocity than expected, are more reliable pressure signs that primer condition.

Also, you are using a non-canister powder, did you change lot numbers in the powder? The above remark about ambient temperature is also a good one.

[Not_A_Llama]

Ditto on the chronograph comment. If you don't have one, you're loading blind. Velocity is your best proxy to pressure.

[Delfuego]

That's a pretty warm load, even for a 55gr loading. 62 should be skeery. WC844 is also very temperature sensitive+1
[Peep]

[SA Friday]

Velocity and pressure do NOT directly correlate as a straight line if graphed for almost all powders. If you think velocity will warn you before signs on the cartridge, you run huge risks with some powders. Single based powders are netorious for having an exponential graph when comparing pressure and velocity towards the max cartridge capacity. Stating the chrono is the best way to gauge pressure is just as bad as only looking at the primer. It's bad advise.

OP, you're powder charge is way too high. Time to go back to testing loads till you find the accuracy node. It should be somewhere in the 22.5-24 gr area. Use good brass and don't mix head stamps on the test loads. Build the loads for the long gun then test them in the sbr. Test for accuracy and then chrono the most accurate load to ID what velocity the gun likes with that bullet.

[spqrzilla]

I do not believe that chronographs are the "best" way to gauge pressure. Obviously an actual pressure gauge is best. Chronographs do not tell us what the actual peak pressure is, and indeed its not a direct correlation (because the velocity is more correlated to the area under the pressure curve than to peak pressure) but there are enough correlations to infer some information about the performance of a load.

However, I do believe that chronographs are a better source of information than examining primers. Relying upon examination of primers is pretty much discredited practice. And I think that loading up cartridges with more powder than found in published loads without using a chronograph to find out what is happening is very reckless.

[Not_A_Llama]

Velocity and pressure do NOT directly correlate as a straight line if graphed for almost all powders. If you think velocity will warn you before signs on the cartridge, you run huge risks with some powders. Single based powders are netorious for having an exponential graph when comparing pressure and velocity towards the max cartridge capacity. Stating the chrono is the best way to gauge pressure is just as bad as only looking at the primer. It's bad advise.

Keyword "proxy", and absent an actual pressure gauge, I'll maintain it's your best bet for insight into what's going on inside your gun. Cartridge case pressure signs are, of course, not to be neglected, but in my experience, they offer insufficient granularity/resolution, are almost binary in nature, and the ones of consequence are typically an indication that, frankly, you done fucked up and gone too far.

I've always been able to detect upwardly concave velocity vs. weight before ejector swipes and serious primer conditions. Doubly so with single base powders.

Again, you do have to pay attention to case pressure signs, but they offer no quantitative insight into what's going on. Velocity vs pressure may be nonlinear, but so is any relation worth a damn in bigboy (not undergrad) science/math. Nice having quantitative input, vs feelings and "gosh, that there primer's REAL cratered!"

Incidentally, are we expressing with certitude that the rapid increase in pressure is exponential, or is that intellectual shorthand for "goes up real fast"?

Note: above discussion predicated on the notion that someone who lacks a chronograph likely also lacks a pressure gauge. I think it's a reasonable assumption, but am open to arguments.

[smchop]

Ok, so here is a little more information to look at. So have at it!
http://i581.photobucket.com/albums/ss256/smchop/Image4.jpg
Few cases fired that day, once fired brass, last case on right has torn rim.
http://i581.photobucket.com/albums/ss256/smchop/Image3.jpg
http://i581.photobucket.com/albums/ss256/smchop/Image2.jpg
Randomly selected cases from load development. Started at 22.5 up to 27gr.
I know, to high, but I trust myself, and had no intentions of anyone else trying the load. Thing to note is that this was brand new LC brass, not once fired.
Load Data, LC brass, CCI 400 primer, WC844 powder, 62gr Goldenwest bullet
set to mag length.

22.5 gr/2539 fps
23 gr/2335 fps
23.5 gr/2376 fps
24 gr/2583 fps
24.5 gr/2772 fps
25 gr/2554 fps
25.5 gr/2650 fps
26 gr/2688 fps

Now some of that made no sense on the way the fps changed on the charges, could have just been bad chrono data.

Second test same components, same seating depth.

24.3 gr/2496 fps
24.6 gr/2578 fps
24.9 gr/2539 fps
25.3 gr/2619 fps
25.6 gr/2693 fps
25.9 gr/2743 fps
26.3 gr/2693 fps
26.6 gr/2754 fps
26.9 gr/2795 fps

The best grouping and ladders showed up at the last three higher velocity, so I went and loaded 10 rds at 26.9 gr and this is how it showed up on the chrono.

Shot #
1 2836 fps
2 2836 fps
3 2830 fps
4 2836 fps
5 2861 fps
6 2849 fps
7 2836 fps
8 2824 fps
9 2801 fps
10 2873 fps

Hi/2873 Lo/2801 AV/2838 ES/72 SD/19

After all those loads, never had a problem with extraction and was running 3.4 mils to 550yds. I liked it. Then went to the once fired brass to start a batch and was ok. Then put my suppressor on and within two rounds, case rim tore and case stuck.

Compared to the XM855LC I had chrono'd 10 round string I had the following
Hi/2886 Lo/2842 AV/2875 ES/44 SD/13

So I thought I was on to something and liked it, but now its a no go. Thoughts?
Also note, I went back and checked my Dillon and it was dropping 27-27.1 gr.

[Delfuego]

I have also heard that LC brass can have a little smaller volume than other brass. Primers are showing some cratering. I'm no expert, but i have loaded some hot rounds, specifically with 75gr projectiles. I was getting pressure signs with less powder than that and 55 grainers.

[spqrzilla]

Well, that's very interesting performance you are getting out of WC844 (whatever lot you have), and its behaving quite differently than I'd expect. The first series shows some odd behavior but its hard to say whether or not that is statistically significant given the low round count. But the latter two series are unbelievable for what I'd expect to see in a round that was going beyond pressure ranges.

Whatever you do, I think you are going to want to watch out when you run out of that lot of WC844, that's for sure.

[SA Friday]

Keyword "proxy", and absent an actual pressure gauge, I'll maintain it's your best bet for insight into what's going on inside your gun. Cartridge case pressure signs are, of course, not to be neglected, but in my experience, they offer insufficient granularity/resolution, are almost binary in nature, and the ones of consequence are typically an indication that, frankly, you done fucked up and gone too far.

I've always been able to detect upwardly concave velocity vs. weight before ejector swipes and serious primer conditions. Doubly so with single base powders.

Again, you do have to pay attention to case pressure signs, but they offer no quantitative insight into what's going on. Velocity vs pressure may be nonlinear, but so is any relation worth a damn in bigboy (not undergrad) science/math. Nice having quantitative input, vs feelings and "gosh, that there primer's REAL cratered!"

Incidentally, are we expressing with certitude that the rapid increase in pressure is exponential, or is that intellectual shorthand for "goes up real fast"?

Note: above discussion predicated on the notion that someone who lacks a chronograph likely also lacks a pressure gauge. I think it's a reasonable assumption, but am open to arguments.

Although I do agree on some points, I completely disagree there is insufficient indication of potentially dangerous pressure on an expended cartridge case. The fact one may not be able to identify the signs of pressure before they damage or destroy a firearm is lack of experience and training. This is to be expected when conducting analysis dependent on qualitative attributes. Where as relying on velocity to indicate pressure without prior knowledge of the exponential growth of the powder for the exact specifications of the reload is assuming someone is actually going to graph it and look for the change in slope. So, how would one use velocity to preempt from firing an over-pressured round if they are not graphing results right there at the range? They guess. Reloading charts are based on one set of test parameters. You deviate from those parameters, you are making nothing more than an educated guess until you do your own testing.

Short of an actual class teaching what signs of pressure to look for on a cartridge, I don't know of any graduate class that would override actual experience. I know I in my just an undergrad education don't try to quantify pressure via velocity without a known conversion equation, and that's what you're recommending. It's bad advise, and I'll stand this until someone can show me how to derive a conversion formula for every potential variable involved in reloading ammunition without actual testing of that exact rifle and ammo combination.

[SA Friday]

Ok, so here is a little more information to look at. So have at it!

So I thought I was on to something and liked it, but now its a no go. Thoughts?
Also note, I went back and checked my Dillon and it was dropping 27-27.1 gr.

I cant see the 25.0 gr round in the pics, but the 24.5 gr cartridge looks OK. The 25.5 gr round is clearly showing indications of high pressure.

CCI primers are awesome for rifle rounds, but they have pretty stout primer cups. You just are not going to see rounding on the outer edge of the cup like you see with softer cups like Win and Fed. Hell, Fed's will even start to flow out beyond the primer hole when really over-pressured.

The two things I see that are showing high pressures are the sharpness around the primer strike on the primer and the line around the cartridge wall just outside the webbing. It's very distinct on the 25.5 gr round and the brass from the line towards the rim is all shiny in comparison to the lower charged rounds.

[smchop]

SA Friday, thanks for the input. I'll look at more of them, but I believe you are right. What do you think about the fact that I had no troubles with new brass, but once fired was giving me fits?

[jerrymrc]

SA Friday, thanks for the input. I'll look at more of them, but I believe you are right. What do you think about the fact that I had no troubles with new brass, but once fired was giving me fits?

In today's world much of the "Once Fired" military brass has been through MG's Besides the fact that MG's are hard on brass training guns have been known to have very loose chambers.

I have seen both over stretched and banana shaped brass. It may be "once fired" but is just about unusable. Just a thought. [Flower]

[Danimal]

This is something that I have run into recently. The other guys are right, but 27 grains is about the standard for production ammo. Pull a couple apart and see for yourself. I have found that they range from 26 to 27.5 grains of WC844 using the 62 grain ss109 projectiles depending on batch. This puts them up in the 3100 fps range that they are rated at on the box for M855. If you stop at 25 grains as the H335 data that is commonly used, you will be around 2700 - 2800 fps. As always work up the load watching for pressure signs, and it looks like you did that and the primers look fine.

Here is the thing though that was overlooked and I did the same thing when I bought my swage. The swage will add significant diameter to the very end base of the case if you swage too deep, and do not full length re-size afterwords. If you minimize the depth of your swage and just barely take the edge off you are better off than if you smash that thing in there.

I was so happy when I got my swage that I literally sat there for about 9 hours swaging about 2500 cases. Then when I was done I loaded up a couple hundred rounds of what has been super reliable LC brass and was horrified to find that about 1 in 10 cases did the exact same thing that yours did. I had to go back through and re-size everything again, and even then I still get an occasional stuck or cracked rim. Still am pissed about that because there really was not any relevant guidance with the swage and I think that some cases are worse than others.

This is just something that I came up with, and I measured a case before and after as best as I could and found small increases in diameter at the base. It did not seem like much, but in the end it was enough to be just a little too tight I guess. I needed a micrometer to see the difference. You might just want to deprime, then swage before you tumble and resize, and finally trim to length. That is what I do now and I ease that swage in there like a gentleman. [Beer]

[smchop]

Danimal, thanks for that, that was something I was looking at also (powder charge that is) I had not thought about the swage. I deprime and resize, tumble in stainless media, swage and then trim. I had not thought that the swage might do that but had noticed that some swage easy and some take some pressure, but you are correct, I do put a bit of pressure on them for sure. I had taken apart some of the XM855 I had also to check powder charge after I had ran that load and the ones I pulled down were 27-27.1. I ran into another member at the range the other day and mentioned maybe using an adjustable gas block and turn it down a notch when I run it suppressed, which I think is a good idea also. But since I am only 500 rounds in to a 5k batch, I think i'll readjust to a lower node and run on that.