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Old December 22, 2019, 05:08 AM   #126
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FWIW: also measure random case lengths to be 1.702 - 1.7025 very consistent.
The bag I have seems to generally be closer to 1.703 to1.704 +/-. Maybe the cartridge is going off partially out of battery. The one thing your bulge case and my blown one have in common is greater than .355 bullets.
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Old December 22, 2019, 08:23 AM   #127
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Glad you are uninjured... best of luck understanding The Incident.
Thanks! The search is on.
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Old December 22, 2019, 08:33 AM   #128
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My philosophy about firearms malfunctions is that "the brass tells the story." I've got some interesting photos to follow shortly.
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Old December 22, 2019, 08:36 AM   #129
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greater than .355 bullets
Can't argue that point, save that Winchester itself says 0.357"

See https://rugerforum.net/reloading/379...ml#post4399961
Also: https://winchester.com/350-legend/faq

On the OTHER hand .... Commercial/pulled bullets just now:
Winchester 150 0.355"
Winchester 180 0.355"
Federal 180 .... 0.356"

To be saf[est], I venture Lee sizing down to 356 for jacketed then, although I found no difference in velocity(thereby imputed pressure) between HotCores at 356 vs 357. (I did note that you are seating the HotCores out to 2.27" whereas I'm running a standard 2.26". So I wonder if a throat/final-closure condition is involved.)

My anomalous pressure/velocity spikes were with Lil'Gun/Cast and nowhere else. So I'm really scratching my head until the [other] PoohBahs weigh in....






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Old December 22, 2019, 09:15 AM   #130
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Very interesting photos to follow shortly, I'm not that good with iPhone photography.
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Old December 22, 2019, 09:44 AM   #131
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Here are some "post mortem" photos of various cases. Sorry about the poor quality, I had to cut the resolution down in order to be able to upload them.

The first is a comparison of hornady's brass to starline's, specifically the rim to web area in the head. Hornady's chamfer from the main case down to rim groove is noticeably longer/deeper. Is this significant? I don't know; I can't measure the degrees of the chamfer though I'm guessing hornady's is the lesser of two.



In the next photo I have of once-fired starline brass used in an early test of the 180 hot core .357--even when the cartridge fired successfully there was a noticeable compression of the distance between the rim face an top of the head/web. leaked gas was also evident in the area. The blue lines I added to exaggerate the compression effect. The area in both the intact case as well as the blown one that are compressed and have gas accumulation appear to be roughly the same size as the width of the extractor.



In the last photo of the blown case you can see the area of failure is also compressed and about the same size as the compression area in the fired case that did not fail. Notice also the concave slope of the over-expanded case head area where it meets the case main body--I believe that is analogous to the radius machined into the chamber face.

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Old December 22, 2019, 09:55 AM   #132
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If what I'm seeing is correct, the case head is actually tilting to stretch/meet the bolt face?
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Old December 22, 2019, 10:00 AM   #133
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Also, wouldn't the longer Hornady chamfer result in less material/weaker unsupported case head in that area?

Thoughts? as this one's getting real strange......
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Old December 22, 2019, 10:11 AM   #134
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If what I'm seeing is correct, the case head is actually tilting to stretch/meet the bolt face?
I don't think so, I don't think the cartridge would go into battery if that were the case. what I think might be happening--for whatever reason--is that at the moment of failure the rim face is not backed into the bolt breech rim face. EDIT: unless what you mean is after ignition, in which case yes, I think that is a possibility.
Quote:
Also, wouldn't the longer Hornady chamfer result in less material/weaker unsupported case head in that area?...
Can't say, though I don't think so--but I do know the fired hornady brass does not show any of the signs of rim compression or gas leakage (so far) and their load must be pretty stout--in my gun it exceeds their advertised velocity average by about 40 fps. I also can't tell where the top of the head/web actually is in the brass nor even what the specs call for--I see a measure of .2 but it's not clear to me if that's rim face to top of web or not. Guess what needs to happen is cut the brass in half to get to the bottom of that.
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Old December 22, 2019, 10:32 AM   #135
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The gas leakage/incipient failure mode in the Starline brass reeeeeeally bothers me.
I'm going to swing out today with the HotCor's at .356"/2.26" and see if anything bodes weird.



.

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Old December 22, 2019, 10:58 AM   #136
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In case I don't come back....

Baseline to establish effective NORMA-200 burn rate

50 LEGEND Ba=0.555(Std) Size 0.356 / Expander 356
SPEER 180FP(#2435) #2)/ NORMA-200/29.5/CCI #41/OAL:2.261(-)”
QL15”= 45,737psi/2,073fps( act)* 107/93.5 Fill/Burn/
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
50 LEGEND Ba=0.555(Std) Size 0.356 / Expander 356
SPEER 180FP(#2435) #2)/ NORMA-200/30.0/CCI #41/OAL:2.261(-)”
QL15”= 48,709psi/2,112fps( act)* 109/94 Fill/Burn/
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Old December 22, 2019, 11:21 AM   #137
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Again--I'm not jumping to any conclusions until I talk to some people who know this stuff a lot better than I do.
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Old December 22, 2019, 07:19 PM   #138
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Test this PM using the SPEER 180FP (HotCor)
LABRADAR Chrono

Small numbers to be sure, but nothing anomalous, everything inside commercial results (anecdotal/single-datapoint though they may be)
I'm "thinking" that the OAL/Bullet-Shank/Throat matchup is critical.
Note 2.26"


For Record Only -- Not for recommended use under any circumstances w/o workup --
Discussion Later. But w/ the Effective Pressure Burn outlined with safety limits, I'm going to kick the Norma-200 up a bit more.

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Old December 22, 2019, 08:42 PM   #139
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You are not the first. I have seen similar photos from Winchester factory 350 L ammo. Some have simply been where the brass takes on the look of a belted round, more extreme are the blow outs and case splits.

It is pretty obvious that a gross overcharge of AA1680 can not be be the cause. The powder fills the case with normal loads. I have loaded some compressed loads with WC 680 (milsurp equivalent) in my 357AR. Pressures were too high for my liking but nowhere near the pressure needed to flow the base.

Your AA 1680 load is also very unlikely to have partial ignition followed by a spike. To get your velocities, you have to be above 90% load density. High load density is not generally associated with a secondary pressure spike.

Larger than bore bullets (by 0.003 or so) are used all of the time. The resistance of the bullet being squeezed down can increase pressure some but this should be predictable and consistent. Having a bullet get cocked, jam or otherwise hang up is very dependent on bullet shape and "freespace" in a chamber. In no way do I see the profile of your Speer getting hung up in your chamber.

Just for the sake of argument, can you estimate either the free space above the powder or the amount of compression for your loads in your brass.

Now lets discuss those other failures. They were attributed to one or more of the following: Over-length cases, over crimped brass, bad chambers.

The 350L does headspace on the mouth. On the drawing, there is a distinct step at the front of the chamber. The dimension shown is 1.710 - 1.720 in front of the bolt face. The case mouth is supposed to be resting against this step when the round is fired.

If a round has too much crimp, is too long, or if the chamber does not have the correct step at the front of the chamber, a small amount of case can end up just forward of the step. In this configuration, you have a crimp that will not release. The bullet can squeeze out, but the pressure gets way over normal due to the extra resistance to initial bullet movement. The case mouth may look close to normal afterward as it expands after the case slides rearward in the chamber during the overpressure spike.

I do not know what caused your event. It is really hard to see it as a powder charge problem or an oversized bullet problem. A way out there possibility would be an ignition problem. As best I can tell, all other possibilities involve the end of the case getting in just past the headspace step in the chamber.

Edit: I wrote the above before seeing the post on the second "problem" round with starline brass. The 350L should have the transition from case wall to web occur inside the chamber. Too much rounding at the chamber entry, too much headspace, or "bad brass" could result in some unsupported case wall. The amount of extrusion of the blow out round does not seem to match with a failure due to unsupported case wall. Run a 5/16 rod, squared off pencil or other item into your brass an see how far down the wall goes. This will tell you where the case wall to web transition is.

For the failed round, the extrusion on the face into the hole for the extractor pin is typical for a pressure spike, this would not be there for a simple unsupported case wall failure.

Last edited by P Flados; December 22, 2019 at 09:41 PM.
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Old December 23, 2019, 12:01 AM   #140
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I was busy today too. I loaded up some 170 gr interlocks again using 1680; but gaining a bit more space in the case I ran my max charges 1 gr more than with the 180 hotcores. I saw no signs of any deformation or incipient over-pressure. However, just like the factory American whitetail, my groups while consistent were in the 1.75 to 2 MOA range @ 104 yds. The 180 hotcores sized to .357 I believe are engraving better to the grooves and lands than a .355 bullet and are inherently superior in accuracy potential IMO. It's interesting to see that mehavy's .356 sized bullet did not seem to differ much from the .355 in terms of accuracy potential.

My "gas leak" area in the former pictures I now think is nothing more than gas coming in from the cut-out in the bolt face wall for the extractor.

Another possibile issue that occurred to me is concentricity of the bullet to case, throat and bore. There isn't a whole lot of "stabilization room" between where the bullet exits the case and enters the bore. I wonder if it's possible that a .357 diameter bullet that starts out of concentricity might not get straightened in the throat and thus get forced into the bore out of concentricity--which in turn might ramp pressures up??

My modified case came in and the base of ogive on the interlock can be seated way beyond what will fit in magazine before it engages the grooves/lands.

P Flados--your wedging of the case mouth to the throat in front of the case step explanation is an interesting one and sounds like a way that pressures could ramp up. My failure cartridge was well within headspace tolerances and the diameter at the case mouth was maybe .001 more than a .355 cartridge, but it too was within tolerance for the diameter of case mouth.

The only other thing that strikes me as odd in my set-up is the carbine gas length system in a 20" barrel. I've never seen that before in a rifle length barrel and that amounts to 13" of dwell time in a cartridge generating 50,000 + psi

Quote:
You are not the first. I have seen similar photos from Winchester factory 350 L ammo.
That I did not know. That's kind of scary when you say it's using factory ammo! BTW--I found references to the "overcrimped" factory 145 gr ammo allowing the brass to enter the throat. I don't think that's happening in my case since I put only a very light taper crimp and my OD at the mouth actually slightly exceeds the hornady factory stuff I have as a baseline.--but it's still interesting to check and I will see if I can.
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Last edited by stagpanther; December 23, 2019 at 12:48 AM.
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Old December 23, 2019, 01:30 AM   #141
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I think I may have found a problem contributing to the over-pressure issue. I should have done this early, but didn't think of it until now. I just tried pulling a bullet from one of the cartridges remaining that are loaded with the .357 sized hotcores with an rcbs collet bullet puller --no can do, it's as if the shank is welded to the case! Bit of a mystery to me since I did not encounter notable resistance when seating the bullet--didn't seem much more than a standard .355.
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Old December 23, 2019, 02:41 AM   #142
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....factory American whitetail [0.355"?] , my groups while consistent were in the 1.75 to 2 MOA.... It's interesting to see that mehavey's .356 sized bullet did not seem to differ much from the .355 in terms of accuracy potential.
Stag,

Each of those Speer 180 (@0.356") Loads was under a minute

It just likes that bullet.
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Old December 23, 2019, 06:15 AM   #143
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Sorry--misinterpreted your print. Think it's more than "it likes the bullet." Of the available spire points, it has the shortest jump to lands while still being seated as long as the magazine allows, which in turn allows more powder capacity.

I'm not sure if you answered the question--but did you do identical loads with the 180 hot core--the only variable being sized to .357 and .356--and then measure all the performance parameters and see if there was a drop of any kind between a .357 and .356 bullet?
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Old December 23, 2019, 06:52 AM   #144
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I just ordered a .356 bullet sizing die.

I still would like to know definitively why there is a malfunction--I get obsessed about getting to the root cause of these things--among other things if I don't there will always be that "might be skating on thin ice" doubt even when things are working fine (I suspect you already know that feeling having moved down to the .356 die ). So far, P Flados observation of the case mouth making it past the step-down in the chamber and locking the crimp seems the best explanation, even though the OD in my .357 loaded cases appear to exceed slightly that for .355 loaded bullets.

At first I thought that asymmetric compression of the case rim was due to the case head being slammed back into the bolt face. Now I'm confident it's more likely that it is simply a pathway of least resistance as pressure in the case ramps up--just like the ejector--and thus expanded outward with less resistance initially (the extractor readily shows the outward bending of the claw) while the rest of the case is contained within the bolt fcae wall.
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Old December 23, 2019, 08:53 AM   #145
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Did a little more "sleuthing" this morning.

Since it may be a very long time before I get my headspace gauges made, I decided to go to my "fall back" and make my own improvised no-go gauge. It ain't pretty, by works.



True to specs, I got the bolt to close up to just under 1.720; and at or above it would not. Nonetheless, .01 slack in headspace in an AR is "enormous" compared to what I've worked with before in any other AR cartridge--most of the trim-to case lengths I've seen for the 350L are around 1.701

Notice the odd scoring on the brass on removal from chamber. This was virgin starline brass on a freshly cleaned chamber.

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Old December 23, 2019, 09:34 AM   #146
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30 Carbine is exactly the same ... 10 thou clearance.
As long as the firing pin protrusion can handle combined extractor-hold/headspace, things work as designed.

And you want that clearance for bolt closure assurance.
You need that clearance for bolt closure assurance.
(I'm channeling my inner Nicholson)
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Old December 23, 2019, 10:36 AM   #147
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Last I heard--the go/ no-go gauge set-ups are designed to function at 1.701 and 1.714 respectively. That's a problem right there if the tolerance is .01 over-all and goes to 1.72.
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Old December 23, 2019, 11:31 AM   #148
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The only reasonable conclusion I can come at this point is that using anything other than the .355 bullets is wildcatting.
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Old December 23, 2019, 03:45 PM   #149
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Good thinking to check your headspace with the tape method.

If you flatten out a cast bullet just enough and then pound it into the chamber just enough, you can get an impression of the step at the end of the chamber. It is supposed to be real close to a squared off step. Make sure it is not more of a bevel and is not a "double step". Having the wrong step profile could lead to an infrequent and random problem.

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Old December 23, 2019, 04:54 PM   #150
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Quote:
Good thinking
It's rare--but it does happen very now and then.

Today I loaded up some .355 bullets in starline cases all of which were trimmed to 1.703. I was able to get a COL of almost 2.27 with 125 gr extreme penatrators. These bullets do very well in my past experience even when driven to rifle velocities. I used H110 this time and brought charge weights up to what QL predicted to be around 50,000 psi.

The first three charge weights functioned exactly like factory ammo I've shot--accuracy OK, but the brass was coming out nice and clean with no signs of pressure. Then, by the 4th charge weight, I still was getting no pressure signs, but now gas/crud was obviously leaking down the side of the case whereas the case was coming out entirely clean except at the mouth previously. I have no idea whether this had something to do with the charge or if it was more related to timing. I'm losing confidence in being able to really have a good idea of what's going on

Quote:
Having the wrong step profile could lead to an infrequent and random problem.
Makes sense, I don't recall seeing an issue with the step when I did the chamber cast, I tossed it somewhere in my black hole drawer and will see if I can find it again.
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