Need assistance with a H&K P7M8
- Thread starter wildchef
- Start date
I only use the CCI 124grn on this but generally on all my hand guns I only use federal/AE or CCI/Blazer brass ammunition. too lazy and busy to do hand loads
Ok.....
...but how is that a problem?
I mean... if you overgas say an AR-15, or a Vz, that could lead to problems... but on the P7, gas is not used to unlock or accelerate the action open... but rather gas keeps movement from occurring, preventing movement.
I'm guessing too much gas may make reliability lower... but not nesisarily make the operation truly unsafe. But maybe you could add to your statement for more clarification?
Hey Rick
Go to HKPRO forum in the states. The P7 has a cult following with some members that work in HK. As for the 147gr bullets you talk about, here is an explanation for one such expert.
No "catastrophic failure" has ever happened in a P7 firing +P ammo in Germany or anywhere else to my knowledge. I throw the BS flag on that one.
As for the 147 grain ammo question, here is a post that covers why not from years back.
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This is not an uncommon stoppage with 147 grain ammo in the P7M8 or P7 PSP. These stoppages are called "nosing up" and are in fact failures to feed. They are caused by "over function", too much recoil impulse to the slide. Let me guess. These stoppages occur on the last or 2nd last round? If so what is happening is that the heavy 147 grain bullet is imparting excessive recoil energy to the slide (the P7 was designed for 124 grain NATO ammo). When it does so it increases the slide velocity rearward. This causes the slide to strike the frame at its most rearward position harder than normal. When it does the top round slides slightly forward in the magazine (due to less upward pressure on the round under the feed lips towards the end of the magazine). When the slides comes forward again at higher than normal speeds and strikes that partially fed round the round “jumps” out of the magazine rather than being pushed forward by the slide under controlled feed as designed. It then often ends up sticking up and out of the ejection port or impacts on the top of the chamber when the slide comes to rest out of battery. This problem is increased when the piston is worn and there is thus less braking effect in the gas retardation system. It is also made worse by weak magazine springs. Likely the reason others here do not report the problems with 147 grain ammo is related to the state of their mag springs and piston, the specific ammo characteristics (not all 147’s are the same) or they shoot P7M13’s where this problem is less likely to occur.
So how do you fix this? Don't shoot 147 grain ammo. 115-124 is best and +P or +P+ is okay (US +P+ is @ NATO spec). It is the excessive bullet weight that causes the issue. This is why the .40 S&W P7M10 has such a massive slide, to slow down the slide velocity. Or try replacing your magazine springs and/or piston. HK makes a little go/no go gauge for the piston. Send it in and have HK check it out. This does not happen in the P7M13 because the magazine springs are stronger and the feed lips are longer. Newer P7M8 magazines (after @ 1990) have longer feed lips like those of the P7M13 to help reduce this. They are marked with a date code but I do not recall what that was. If you keep you P7M8 magazines fully loaded I would replace them every 5 years or less and leave the magazine down loaded by one round (7 versus 8) regardless of the ammunition used. That will extend the life of the springs considerably and thus insure the best reliability. Cheap life insurance.
Always remember to clean the gas cylinder with the brass bristle brush AND the metal tool provided after each firing. If you don’t have the tool, contact HK to get one. NEVER clean the piston with metal brushes (nylon brush and solvent only). Also never shoot lead bullets in a P7. Small particles of lead get shaved off and melted and build up in the back of the gas cylinder. In time that accumulation may cause the piston to stick to the lead build up in the cylinder and impair the free movement of the slide.
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Big thanks to johnl for posting the answer to Rick's question. From the general tone of the reply, I'd guess it was originally posted by a former HK-USA honcho who, among other corporate duties, authored the Owner's Manual for the P7 series. In later versions of said manual, the prohibition against using 147 gr loads was included therein. (I did use the term "over gas" in my previous post, but it has been awhile since I've read some of those posts pertaining to the use of 147 gr loads in the P7. The term "over-function" seems to be a much more accurate way to describe what sometimes happens with those loads.)
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Ah... thanks! Yea that makes sense!
So not really about gas or pistons, but recoil energy from heavier bullet... yep, I can imagine that.
Thanks for posting the source info!
Geeze this makes me want to get a better job so I can afford a P7 !!!
So not really about gas or pistons, but recoil energy from heavier bullet... yep, I can imagine that.
Thanks for posting the source info!
Geeze this makes me want to get a better job so I can afford a P7 !!!
