Bulging at base of 9x19 cases

[AWLAZS]

I am going to mail him some ammo. Matt email your address

[matt2ace]

OK....back from the range with a positive report. Using WOLF SPM primers with 7.4 and 7.6gr at 1.175 OAL definitely improved the apppearance of the cases. Out of 100+ rounds shot, I found 3 cases showing any signs of bulging and one of the was a GECO. 7.6gr made a 168PF on this pass. The last pass with this load using WSPM at 1.7 and 1.8 OAL were at 170/171 PF......only now there is very little sign of bulging/over-pressure with either gun. I am going to move the OAL up to 1.180 to give a little more volume in the case.

Just to be clear, I have done no modifications to the barrel or chamber on my own with the exception of a little polishing of the ramp on the KEAL gun. I do not believe that there is anything wrong with either gun. IF this problem was a headspace issue, it would imply that Shuemann has built 2 completely different AET barrrels over a year apart with exactly the same problem. Since I observe the same bulging problem from both guns, I really do not believe it is either gun. The load is the source of the problem. I have also received several PMs from others who have observed this same type of bulging with 9mm major shooting Silhouette and HS6 loads.

I did try to push back a chambered, empty case per suggestion from OLP73 and could not see any movement towards the breechface. The case is not setting back when the gun is in full battery.....either gun.

I took some more pix of a loaded round and spent cases from today. One case was slightly buldged, the other looked fine. I don't see much, if any difference in the depth of any case. See the attached pix.

The GANS gun still makes 8-9pt hight PF at the same load vs the KEAL. I am going to focus on the GANs gun at this point, the KEAL is my backup and will go up for sale as I posted earlier.

7.4gr / 1.175 OAL Wolf SPM primer

GANS Avg 1321, ES 40, SD 17 PF 164

KEAL Avg 1254, ES 40, SD 18 PF 155

7.6gr / 1.175 OAL Wolf SPM primer

GANS Avg 1354, ES 21, SD 9 PF 168

KEAL Avg 1294, ES 28, SD 13 PF 160

Pic 1 -3 = KEAL gun: loaded case, good used, slightly bulged used

Pic 306 = Gans gun: same order

Finally (for now), I do have differnt ammo on the way from a friend. I have a local friend who should have his 9 major SV open gun in a few weeks. SV has recommended 7.5gr Silhouette so we will be able to compare loads in both guns. If I only had some non-magnum primers, I could clear up the impact of magnum primers on these loads.

I will keep posting as I get more data..........thank you all for your help and advice. Keep it coming.

Edited March 28, 2009 by matt2ace

[Shay1911]

I guess it's a combo of:

Worn out brass

Magnum primers

Not a fully supported chamber

[G-ManBart]

Not a fully supported chamber

From the pics it's pretty clear that it's a fully supported chamber. People get this notion that because the chamber is larger than the cartridge diameter (at any given point) that it's unsupported....that's not true. The case will always expand to meet the walls of the chamber, and the only part of the cartridge in a quality barrel like the Schuemann AET's in the pic that isn't supported, is the very last little bit right before the extractor groove. Clearly, these cases are expanded well beyond that point so something really odd is going on. If it was a lack of chamber support, it would be just in the area of where the ramp meets the chamber. This is just freakin' crazy weird....nothing seems to make sense

[Tom E]

Would be interesting to see a chamber cast.

[twodownzero]

I've been following this post since it started, and, if nothing else, there exists a great deal of evidence right here that 9mm Major is just as scary as one who has never loaded it might suspect.

I know that Major 9 is quite popular in USPSA, but I would be quite surprised to see actual pressure numbers from the most common loads that people are using in major 9. I suspect that most all of them are running much higher pressures than we realize.

[chrisa006]

Matt,

I still wonder if the mag. primers are forcing the gun out of battery before all the powder is burned. Did you try a heavy recoil spring as a test to see if this is what is happening.

[larry cazes]

Whats the lot number on the silhouette powder? I have shot lots of it out of 3 different 38supercomp guns with zero indication of pressure problems.

[G-ManBart]

After PMing about this with someone else I have a theory about what could be going on. For starters, we know 9mm is tapered. We know the AET has a fluted chamber that allows gas from burning poweder to center the case in the chamber (in theory anyway). We know there's no way those cases are completely in the chamber when the bulge happens. One, they won't go back into the chamber all the way. Two, if they were in the chamber 100$ when the bulge happened, the bulge would be a gradual taper starting farther foward and growing as it gets near the case head. The AET chamber has a very slight chamfer to it for feeding reliability. Put all those things together and think about it. When the round goes off, the bullet moves and the slide starts back immediately and while it's doing so, it's extracting the empty case. There still has to be quite a bit of residual pressure in the first instant or so....moreso with slow powders as it may still be burning. The fluted chamber has to help aid extraction...that's what they're used for in other guns. So, we get a chamber that eases extraction with a tapered case that wants to get squirted out of the chamber, with some reasonable measure of chamber pressure still extant. The case moves back a tiny bit and as soon as it's moved back enough to creat a gap, the case swells significantly....so we get the sharp corner in the case we see in the pics. As it moves a little farther back the pressure has lowered and what there is has plenty of room to get past the case so the mouth and upper part of the case don't swell.

If a change in ammo suddenly caused this problem it could simply be that it just caused the load to get to a pressure that the case wall can no longer withstand once the chamber is no longer supported. You used to see this same problem in machine guns (like 1919 aircooled Brownings in 30-06)....the brass looked "Glocked" because the bolt unlocked and started extracting the case before the pressure had dropped enough to keep from ballooning the brass.

That's my theory and I'm stickin' to it

[Shay1911]

After PMing about this with someone else I have a theory about what could be going on. For starters, we know 9mm is tapered. We know the AET has a fluted chamber that allows gas from burning poweder to center the case in the chamber (in theory anyway). We know there's no way those cases are completely in the chamber when the bulge happens. One, they won't go back into the chamber all the way. Two, if they were in the chamber 100$ when the bulge happened, the bulge would be a gradual taper starting farther foward and growing as it gets near the case head. The AET chamber has a very slight chamfer to it for feeding reliability. Put all those things together and think about it. When the round goes off, the bullet moves and the slide starts back immediately and while it's doing so, it's extracting the empty case. There still has to be quite a bit of residual pressure in the first instant or so....moreso with slow powders as it may still be burning. The fluted chamber has to help aid extraction...that's what they're used for in other guns. So, we get a chamber that eases extraction with a tapered case that wants to get squirted out of the chamber, with some reasonable measure of chamber pressure still extant. The case moves back a tiny bit and as soon as it's moved back enough to creat a gap, the case swells significantly....so we get the sharp corner in the case we see in the pics. As it moves a little farther back the pressure has lowered and what there is has plenty of room to get past the case so the mouth and upper part of the case don't swell.

If a change in ammo suddenly caused this problem it could simply be that it just caused the load to get to a pressure that the case wall can no longer withstand once the chamber is no longer supported. You used to see this same problem in machine guns (like 1919 aircooled Brownings in 30-06)....the brass looked "Glocked" because the bolt unlocked and started extracting the case before the pressure had dropped enough to keep from ballooning the brass.

That's my theory and I'm stickin' to it

You mean like a banana being stepped on? (Pressure gets released and makes it expand once it breaks the peel)

In other words, the unique design of the chamber is "squirting" out the cases while they are still under pressure.

[G-ManBart]

You mean like a banana being stepped on? (Pressure gets released and makes it expand once it breaks the peel)

In other words, the unique design of the chamber is "squirting" out the cases while they are still under pressure.

That could be it. I guess the acid test would be to shoot some of that ammo through another gun with a different brand of barrel and see what happens, but I'm not so sure someone is going to agree to that

[RiggerJJ]

Add to that theory that a case will "grip" a non-fluted non-chamfered chamber for a nano second when the pressures are peaked...

jj

Edited March 31, 2009 by RiggerJJ

[matt2ace]

Used a PACT chrono vs my Chrony F1 and found what I suspected....the Chrony is running on the low side for velocity readings. It was consistently 80-90FPS slower than the PACT. I am going to try a CED next to verify.

I am now down to 7.5gr Silhouette (from 7.8gr) at 1.185OAL using Wolf SPM primers making 169PF with the PACT chrono. Cases look good enough to use this lot for now, but I think there is still opportunity to lower the pressures. Next step is to try ammo from a friend who is using Wolf SR primers at the same 7.5gr charge of Silhouette. I also have a standard sizer die on order which will increase case volume slightly to help reduce pressure more.

[wide45]

.... When the round goes off, the bullet moves and the slide starts back immediately and while it's doing so, it's extracting the empty case....

That's my theory and I'm stickin' to it

That is not how a 1911, or any other locked breach gun works.

[North]

.... When the round goes off, the bullet moves and the slide starts back immediately and while it's doing so, it's extracting the empty case....

That's my theory and I'm stickin' to it

That is not how a 1911, or any other locked breach gun works.

This slow motion video seems to disagree.

I thought the slide started back immediately, then the barrel link pulls the barrel down out of lock after a small amount of travel and the then the extraction starts.

[SLM]

The bullet is well on its way before the slide starts to move. The frame rate on that video is way too high. Check the top video here and you'll see that the bullet is way gone and the slide hasn't even started to move.

[G-ManBart]

The bullet is well on its way before the slide starts to move. The frame rate on that video is way too high. Check the top video here and you'll see that the bullet is way gone and the slide hasn't even started to move.

That's not exactly an Open gun with a light recoil spring and a lightened slide though is it? There's going to be some difference based upon that alone. Maybe not enough that the bullet isn't already gone, but without evidence it's impossible to know for sure.

Still, I'll amend what I wrote above....I should have said "the slide starts to move almost immediately".....because there has to be some delay.

In that video it does seem that maybe the slide and barrel are just starting to moving backwards together just before the bullet exits, but there's no way to know if it's that or some other cause (illusion, camera wiggle from pressure etc).

No matter what, those cases are not 100% in the chamber when the bulge happens.....however that happens to them. If they were, it wouldn't be a sudden bulge with a sharp angle almost perpendicular to the case wall (where the case must have left the chamber), it would be a gradual taper from front to back. However it's happening, there's too much pressure in the case while it's extracting. I think if we go back and look at the case that had a blowout, it's ahead of the extractor groove and that part is clearly supported when a normal case is shown in the chamber....only one way for that to happn. R,

[G-ManBart]

Cases look good enough to use this lot for now, but I think there is still opportunity to lower the pressures. Next step is to try ammo from a friend who is using Wolf SR primers at the same 7.5gr charge of Silhouette. I also have a standard sizer die on order which will increase case volume slightly to help reduce pressure more.

If you lower the pressure you'll lower the velocity....do you really want less fudge factor than 169PF? My load has gone between 171-174 (same exact batch actually) at a bunch of matches and it went 166.1 at Nationals.

Changing sizing dies isn't going to change the volume of the case any significant amount....what's .001" in volume? Even if it did make a measurable difference in volume you'd just be dropping the velocity with the pressure. In other words, you can't lower the pressure and still keep the current velocity....no free lunch

Edit to add: But hey, you're making progress, which is the important thing!!!

Edited April 1, 2009 by G-ManBart

[matt2ace]

My experience with adjusting this load implies that longer OAL does seem to help, though I believe that the primer change had a larger effect on pressure. 7.5gr seems to run 169-172PF very consistently, yet signs of over-pressure vary depending on the primer and OAL I use. Lower pressure does not imply lower impluse to the bullet. The dynamics here are much more complex including primer choice, OAL, and even case type (volume can vary by mfr). Many people are loading 7.5-7.6gr of Silhouette, but are they using magnum primers? I have pms implying that others do see similar problems that I have reported. I think this is more common than any of us believe.

I prefer to run 170-172PF consistently. For major matches I use only once-fired brass with the same head-stamp which provides for much greater consistency in PF (with the same load) than the mixed cases I use for local matches and practice. I plan to continue to experiment with this load until I get the PF to where I want it without concern for over-pressure. I may have to accept some signs of over-pressure until I can get standard primers.

I generally agree with the view that this bulging is happening as a dynamic part of the slide/barrel movement. Just look at the burst case, it could not occur until the round was alteast partially out of the chamber. It ruptured right at the base/rim interface and the bulge is much larger than the diameter of the chamber.

Keep the discussion alive gentlemen, its very educational.

Cases look good enough to use this lot for now, but I think there is still opportunity to lower the pressures. Next step is to try ammo from a friend who is using Wolf SR primers at the same 7.5gr charge of Silhouette. I also have a standard sizer die on order which will increase case volume slightly to help reduce pressure more.

If you lower the pressure you'll lower the velocity....do you really want less fudge factor than 169PF? My load has gone between 171-174 (same exact batch actually) at a bunch of matches and it went 166.1 at Nationals.

Changing sizing dies isn't going to change the volume of the case any significant amount....what's .001" in volume? Even if it did make a measurable difference in volume you'd just be dropping the velocity with the pressure. In other words, you can't lower the pressure and still keep the current velocity....no free lunch

Edit to add: But hey, you're making progress, which is the important thing!!!

Edited April 1, 2009 by matt2ace

[Tom E]

Used a PACT chrono vs my Chrony F1 and found what I suspected....the Chrony is running on the low side for velocity readings. It was consistently 80-90FPS slower than the PACT. I am going to try a CED next to verify.

I am now down to 7.5gr Silhouette (from 7.8gr) at 1.185OAL using Wolf SPM primers making 169PF with the PACT chrono. Cases look good enough to use this lot for now, but I think there is still opportunity to lower the pressures. Next step is to try ammo from a friend who is using Wolf SR primers at the same 7.5gr charge of Silhouette. I also have a standard sizer die on order which will increase case volume slightly to help reduce pressure more.

Move your chronograph back farther from the muzzle to make sure you're reading muzzle velocity without muzzle blast affecting your reads. Years ago I ran 2 Cronys on each side of an Oehler. Chrony-Oehler-Chrony. The difference between the 3 readouts was negligible. Less 15 fps on a 3,000 fps round.

[matt2ace]

I do place the Chrony atleast 8-9ft from the muzzle. I had gotton some ERR2 readings which can occur when the muzzle blast interferes with the reading at the first sensor. The comparison we did with the PACT place both chronos 8-10ft from the muzzle. I may just be my Chrony.

Used a PACT chrono vs my Chrony F1 and found what I suspected....the Chrony is running on the low side for velocity readings. It was consistently 80-90FPS slower than the PACT. I am going to try a CED next to verify.

I am now down to 7.5gr Silhouette (from 7.8gr) at 1.185OAL using Wolf SPM primers making 169PF with the PACT chrono. Cases look good enough to use this lot for now, but I think there is still opportunity to lower the pressures. Next step is to try ammo from a friend who is using Wolf SR primers at the same 7.5gr charge of Silhouette. I also have a standard sizer die on order which will increase case volume slightly to help reduce pressure more.

Move your chronograph back farther from the muzzle to make sure you're reading muzzle velocity without muzzle blast affecting your reads. Years ago I ran 2 Cronys on each side of an Oehler. Chrony-Oehler-Chrony. The difference between the 3 readouts was negligible. Less 15 fps on a 3,000 fps round.

[gunracer38]

I have shot Matt's Keal comp gun with my ammo. I use VV3n37 and VV3n38 powder. I have never had any brass bulging. When I used my Pact chrono it was correct with the 9mm and my 38 super. I also checked it with a 22 caliber pistol . I have used chrono for many years. When I shot Matt's gun with my ammo I used new brass and once fired brass. I have owned many comp guns and never had a brass broke apart. I shot 200 rds on Matt's comp gun with my ammo and it worked perfectly. All this talk about the Keal Gun is wrong. It works just fine. I have been reloading ammo since the 1980s. Matt just needs to check his brass and his powder. My Dillon 1060 and 650 make a lot of ammo. So Matt will find the right type of Brass ,powder etc.

[G-ManBart]

Lower pressure does not imply lower impluse to the bullet.

If you're talking the same brand of case, the same lot of powder, the same bullets and the same gun, anything that lowers the pressure has to lower the velocity in all but extremely unusual situations. Granted, what you've run into is pretty unusual, I'd be willing to bet that you ran into a spike in pressure and the velocity was higher as well....even if the chrono didn't show that. I say that after having some weird chrono readings lately that totally had me scratching my head.

I have a batch of ammo that I loaded last year for Nationals and a couple of other big matches. It went 173-174pf at two of them and then 166.1pf at Nationals....weird. I ran some of it over the same chrono just recently (different days with similar temps etc). On one day it went 179.75pf and the other was 175.5pf. WTF? That's almost a 120fps swing....crazy. If, by some strange chance you got a lower reading when you set that load and things seemed okay, and later changed primers it might have been just enough to push things over the edge. I'm planning on building a chrono box after I move because I think lighting is the biggest factor in weird readings like this. R,

Edit to add: PS, those pics just scare me!

Edited April 2, 2009 by G-ManBart

[matt2ace]

I agree with you about chrono variability......light conditions can have a big effect. A friend just build a chrono box that we will use for the next pass of testing loads. This should give us the most constant conditions for testing. In the end, I am looking to hit ~172PF to allow enough guard band. Based on all my testing to date, I do believe that I was using an over-powered load based on low velocity readings when I originally set the load up last year. Add to that the additional spike from Winchester magnum primers (WSPM) and you get way too much pressure. I never use anything other than my chrono up until recently. I have learned a lot over the past few weeks and believe I have a safe load making close the PF I want.

BTW - Yea, it was scary. I am lefty so I got a full face shot of powder blast, but no fragments........lucky to say the least!

[larry cazes]

Just out of curiosity, why does Schueman flute these chambers?