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Discussion Starter · #1 ·
After many hours of reading the Park Cities Tac P9s forum, I decided to Mod my 9mm P9s with the 16 lbs Wolff recoil spring to increase the buffer life and reduce wear and tear on the frame. This Mod has been suggested in many threads by many sources at PCT. No one seemed to have ever had a issue with this mod in the past. I got the 16 lbs spring from Wolff (stock is 13lbs.) and did the simple install. The slides resistance to racking was MUCH increased, seemingly out of proportion to the 3 lbs increase in spring rate. Before this mod. I shot 150 rounds on FMJ ball ammo (S&B, Blazzer, PMC) with perfect function. After the mod. I took it to the range again. First 18 rounds of FMJ S&B ammo worked fine. This ammo seems fairly hot for standard pressure loads. Next I shot Rem. golden sabre 124 HP (standard pressure) This load seemed softer then the S&B. The first 7 rounds went fine. When I pulled the trigger the 8th time, somthing went VERY wrong. Recoil was different and I felt fragments brush past my clothing. Thank god I had on a good set of saftey glasses. I looked at the gun, and found the 9th round had exploded in the open breach. Here are some photos to the gun, just as it was after the explosion. After I took the first photos I stripped the gun and took a few more pics.

















Note the slug from the 9th round lodged in the throat of the barrel. I had to pound it out with a dowel and hammer. So how did this happen? What went wrong? Of course, I have trashed the new spring and gone back to the used stock spring. Amazingly, nothing seems to be broken or bent.

One guy I asked thought the gun short stroked on the 8th round and set the 9th round off as it was trying to chamber it. I don't understand how the firing pin could hit the primer before the roller lockers here ingaged and the bolt was locked up.

H4
 

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From the pic of how far the slug went, it looks like a squib or underpowered load. I won't blame the spring as I've been using an extra power spring for years.
 

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Seems like an ammo and/or feeding problem. Failure to go into battery with a heavier spring would be unusual. The main thing is that you didn't get hurt /ubbthreads/images/graemlins/smile.gif
 

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I think the diagnosis over on PCT is accurate... If you look at the primer, it looks like the bottom of the bolt face struck the primer and caused an out-of-battery detonation. The casing sure looks like it was unsupported when if fired.
 

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If that's the 9th round casing exploded in the open breach and it's slug lodged in the throat, where's the 8th round?? I don't understand the sequence of events which could result in the situation you've described and shown if that's the 9th round. There's just no way the firing pin can reach the primer with the breach open like that in a P9S. What happened to the casing and slug of the 8th round?

What leads you to believe the exploded round is the 9th and not the 8th? If it's just the fact that the mag was empty when you removed it, perhaps you only loaded it with 8 to begin with. The main question remains -- if that's the 9th round, where's the 8th?

It appears to me that the exploded round is the 8th (you said the Kb occurred the 8th time you pulled the trigger). It looks like the 8th round was faulty (not the first Kb caused by S&B that I've heard of) with stuck slug causing the breach to open on firing. I've been using Wolff springs in my P9S's for many years and I can't see any way the spring could cause this problem. In fact, with the possible exception of CZ-75's comment above (which would also account for the missing 8th round), I can't see any way this could happen to a P9S at all except faulty ammo.

It's very fortunate you weren't hurt. You probably have Messieurs Heckler & Koch to thank for building such a strong pistol.
 

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The way I understand it....

The 8th round fired normally, but the 9th round fired out of battery via the lower part of the bolt face striking the primer as it was trying to seat the 9th round. The 9th bullet lodged into the barrel as a matter of luck.
 

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First off, simply removing the spring, and replacing it with the old is mut at this point. The firearm needs to be returned to HK for inspection. This episode can lead to damage that may not be detectable to the naked eye, and is well worth a thourough inspection. The round clearly appears to have discharged prior to completely entering the chamber. As someone that reloads, I may have 1 or 2 rounds out of five or six hundred that don't seet al the way in the tap, that I use for post inspection. That means you may have had a slight buldge in the casing of this single round. I don't know if that is even detectable at this point. However inspection is the real issue, and peace of mind after that is important as well I'm sure. I would include a CD with photos, as well as all the details, ( type of ammo, or even a single round sample from the same box) As you already noted, these springs are used with a long and positive track record, and I don't initially believe that's where the blame lies.
Please keep us posted and welcome to the forum
 

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Increasing recoil spring strength increases slide velocity. This looks like a slam fire that was contributed to by feeding difficulties from the slide moving quicker and/or short stroking. Having misfed, the extra spring pressure helped drive the raised parts of the boltface into the primer.


I've never heard of a rapidly worn buffer on a 9mm P9S. Why should this mod be necessary?
 

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Looking at the pics of the boltface and the punctured primer, I concur with Handy explanation.
 

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I think Handy cracked it. If you put the raised part of the bolt into the hole in the primer, I bet it would fit like a glove. Very observant Handy, well done /ubbthreads/images/graemlins/grin.gif
 
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Discussion Starter · #12 ·
[ QUOTE ]
I think the diagnosis over on PCT is accurate... If you look at the primer, it looks like the bottom of the bolt face struck the primer and caused an out-of-battery detonation. The casing sure looks like it was unsupported when if fired.

[/ QUOTE ]

This is indeed the case. The large rectangular indent on the primer matches right up with the projection at the 6 o'clock position on the bolt face. I think the 8th round fired normally, but as the slide was moving forward to strip the 9th round from the mag, the projection off the bolt face struck the primer squarely and set it off while the gun was still way out of battery. The case then totally gave way, into the shape you see. Also a lot of unburned powder was blown all around inside the frame and slide. The heavy spring likly brought on this event, maybe by short stroking the slide, or returning too fast and catching the last round before the mag spring had it in correct position.

I did this spring switch in the first place as I saw it recomended over at Park Cities Tactical, and there were no problem reports from anyone who had done it. Man have I learned my lesson about beliving everything you read on a gun board. I posted the photos as a warning to others who may be tempted to try the same mod.
 
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Discussion Starter · #13 ·
And just to be clear, the S&B ammo worked fine. It was a good 'ol made in america Remington golden saber 124 HP that went off out of battery. The Rem. ammo seemed rather soft in recoil compaired to the early 90s vintage S&B ammo. I think it did not have the "pop" needed to fully operate the slide against the 16 lbs spring.
 
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Discussion Starter · #14 ·
I think Henry is correct. I used to have a Springfield TZ in 9x21 and 9x19. All you had to do is switch the barrel and the recoil spring. I had to paint the ends so I didn't get them confused. If you used the 9x21 spring with the 9x19 barrel you would get a short stroke most if the time. Luckly it did not have the bolt face like the P9. Why would you change something that HK spent so much time designing. Well maybe I would for +P loads, but not for regular loads. Glad you are ok.
 

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I agree with Handy. I would have left the 13 lb spring in. Everytime I see someone start messing with their guns and after market parts (especially 1911's) they start to have problems. The most important thing is that your ok, and the gun appeared to be ok too.
 

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People balk at wearing safety glasses, but this is just another example. Pains me to see a kaboom like that but I'm glad you're OK and the gun isn't severely damaged beyond all repair.
 

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Talk about resurrection :D
 

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+2 on Handys theory, Be thankful to the strength of HK and ensure to have it inspected for stress cracks/fatigue.
 

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The questions are:

Did this happen because the primer was sensitive?

Did this happen because there was debris in the chamber? (like part of the brass from the previous round).

Did this happen because the magazine malfunctioned? ( released a round while the slide was moving rearward and then the slide slammed full force into a poorly aligned round)

Did this happen because the slide spring was slightly stronger than it should have been? (the round fed normally but the extra bit of slide force caused the breech to ignite the primer)

Have you had any feeding problems with the mag?
Did you find the brass for the previous round?

The whole thing does draw the safety of the pistol design into question. These kinds of things do happen with rifles (usually combloc ones), but for it to happen in a pistol is a bit more troubling.

One thing is for sure with this gun, it would be very wise not to manually drop a round into the chamber and slam the slide shut on it.
 

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Haha, kinda old topic....


I would say the extra strength spring gave the slide enough force to hit the primer and detonate it... look at the protruding piece opposite of the extractor, and then at the shape indented into the primer.



The way i see it, HK designed the guns in a certain way for a reason... Changing out recoil springs and hammer strut springs etc... to make the gun "feel" better ALWAYS compromises safety and function...

USP magazine springs are kind of the odd one out tho, many are quite weak...

This could have been a complete fluke, but i would stay stock with important parts like that...
 
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