Currently running a geissele spring and buffer on a vented 10.4. It's pretty violent. It's ejecting a neat pile of brass at 5 o'clock with significant muzzle jump. Anyone know what the hk416 buffer weight is? And a suitable replacement?
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Currently running a geissele spring and buffer on a vented 10.4. It's pretty violent. It's ejecting a neat pile of brass at 5 o'clock with significant muzzle jump. Anyone know what the hk416 buffer weight is? And a suitable replacement?
I don’t know the weight off hand, but the general consensus it that you should just run an HK spring and buffer
Firstly, let's establish where you think "5 o'clock" actually is.
By accepted OPV standards, a 5 o'clock ejection (very far to the rear) means the gun isn't cycling properly with extremely weak ejection caused by slow bolt speeds. Pretty much anything past 4:30 means weak cycle or no cycle and eventually not locking back on the final round of the magazine (by USGI standards only).
Especially with the factory ejector spring installed. Considering that the HK factory ejector spring is slightly weaker than a USGI spring and allow ejection to be further forward with similar bolt speeds, ejecting that far to the rear means things aren't working correctly and the recoil/muzzle jump you feel is normal for a near bolt action gun.
Basics are as follows:
Slow bolt speed or stronger ejection spring = ejector pushes spent brass out of the ejection port quicker and the brass ejects further rearward as it can almost bypass the brass deflector entirely.
Fast bolt speed or weak ejector spring means the bolt travels further rearward before the spent brass exits the ejection port and impacts the brass deflector which causes the brass to eject further forward depending on the actual bolt speed.
Weak gas = slower bolt = rear ward ejection (3:30 to 4:30 and anything more then 4:30 needing maintenance)). Appropriate gas = proper bolt speed = side ejection (2:30 to 3:30). Excessive gas = fast bolt = forward ejection (2:30 or less with 2:00 to 1:00 being excessive and in need of maintenance).
All of that is assuming USGI ejection spring. Those numbers need to be modified by adding + :30-ish when running the HK ejector spring.
This is why it's not good for people to assume that the ejection pattern "chart" applies to all AR variants. It doesn't.
In short...
You need to run the HK buffer/spring the way HK intended. 416's are NOT AR-15's.
What did you expect to happen?
I don't know alot about the HK ar platform but a shooting friend has probably put around 500 rds down range with his
HK upper with a cut down10.5" barrel ( gas port on barrel opened up to .062 ) & adjustable gas block from HK Parts on my M16 lower (H2 buffer) (Semi/full auto/supressed/unsuspressed flawlessly ) Ejection between 2:00 and 3:00. I just asked him and he said his gas block is full open.
When HK released a vented gas block for the 10.4" barrels, the specification also called for the barrels gas port to be enlarged.
If the gas block was replaced and the barrel gas port not opened, then the gun is naturally undergassed and allows use of weaker action spring and lighter buffer.
Sure the gun will run and exhibit all the proper function indicators, but running the system like this without the heavier HK buffer and stronger HK spring also reduces some of the systems inherent reliability under harsh conditions. It will make the gun last longer though as bolt speeds are slower on the return /loading phase of the cycle of operation. Less wear on the internals, so there is a benefit to running it this way.
That being said, you might as well be running a DI gun unless this gun is kept for show-and-tell.
Maybe a silly question but when talking about the heavier HK buffer and HK spring is that the same as the MR556 buffer and spring? I've got an MR556 with a 10.4" barrel from HK parts and haven't shot it a lot but so far have not had any issues.
So if someone were to cut down an mr556 upper to 10.4, then whomever installs the 10.4 GB would need to change the barrel gas port as well? And if so does it matter if the GB is vented or not?Quote:
Originally Posted by InshallahTech
I had mine opened up a little at a time until it ran right.
http://i236.photobucket.com/albums/f...se4vx4p8n.jpeg
Yes and yes.Quote:
Originally Posted by jmes731
Some people don't know that the 10.4 barrels with vented blocks have larger gas ports so when they modify a 16 down to 10.4 and install a new 10.4 vented gas block, they don't do the port and wonder why things don't work with the factory HK buffer and spring.
Switching to a USGI buffer and spring seems to be a really good way to account for this without changing the gas port.