HKPRO Forums banner

1 - 7 of 7 Posts

·
Registered
Joined
·
12 Posts
Discussion Starter #1
Hey guys, what would be a good spares list for long term care? I know the rifle is very well built but things happen.
 

·
Banned
Joined
·
879 Posts
Most springs are expected to last between 3 and 7k rounds. Just to be sure things aren't used until they are entirely out of spec or break, I PMCS my springs generally around the 5k mark. I also keep the used springs (if still working within acceptable standards) in a "used" spare parts bag for future possible emergency replacement, or if I have a buddy who actually has a broken part, so as to hold them over until they can get a new part.

LPK's *should* last prety much the life of the gun, but having a spare LPK (trigger, hammer, disco, etc) just in case is a good idea. I generally replace my LPK springs (trigger and hammer) at around 10k rounds just for ****s and giggles and the used parts go in the same bag as the above springs.

Standard DI bolts are expected to last 10k rounds-ish, but checking headspace every 3 to 5k rounds is always a good thing. Having a spare complete bolt in your range bag is always a good thing along with a spare firing pin. HK bolts can be expected to last even longer, but it never hurts to have a spare bolt. Replace ejector and extractor springs every 5k rounds whether they need it or not as they are heavy use springs and are close to heat during the operation of the gun. The HK ejector spring is unique compared to standard DI springs, but they are still compatible in a pinch. Just expect different brass throw performance from a DI ejector spring as the HK spring is a dual coil spring and is longer and stronger then a DI spring.

I like to keep plenty of spares for my DI guns on hand, and since I found that DI bolts and parts are directly compatible, I realized that I have enough spares to keep my rifle going if need be until the barrel ****s the bed on me. That being said, I also have a real HK 416 complete bolt simply because it was meant to work in the gun and i'm thinking that the specs between the DI parts and the HK parts might be "off" just enough to make spare DI bolts last 5k rounds or less. This is something i'm going to test by installing a DI bolt and then inspecting major wear points (bolt lugs and cam pin hole primarily) to see if excessive wear is taking place.

On the other hand, that extra "slop" (and by "slop" I mean that a DI bolt with gas pistons slides freely in the MR556 carrier with no tension), may aleviate one of the recent issues being experienced with 416s being the forward carrier tilt and excess bolt lug wear/breakage that i've heard rumors of (no verifiable proof yet that I know of). Yet it also might induce a whole new set of stresses on the bolt causing even more wear, so I really don't know at this time how the system will be effected if DI parts are used.

About the only spring that I have not been able to find a replacement for on the 416/mr556 is the op-rod spring. I've been looking at several small pistol recoil springs (.22 cal) and am considering getting a few and testing spring weight comparison, outer diamter size, etc. to see if I can find a suitable replacement that can be cut to length so as to retain the performance and compressed spring length requirements for the system. Seeing as how this spring is subjected to a lot of heat from the barrel (the biggest spring tension killer besides the number of compressions the spring is subjected to), and it is also a spring that gets fully compressed as well as getting compressed a lot in high round count guns, I think that having suitable replacements is a good thing. But, seeing as how it's only job is to return the piston forward and apply constant tension to the op-rod/piston joint so that they don't disconnect and cause the system to stop working, as long as it is applying some tension, even if weak, it *should* still be ok. I just like having spares though.

The op-rod, op-rod sleeve and piston should probably last the life of the gun, but that being said, I have a spare piston. THe barrel and gas block are also major assemblies that shouldn't be worried about for several tens of thousands of rounds, but headspacing should still be performed every time the bolt is changed as this als gauges the chamber area of the barrel, not just the new bolt. But, when it comes to replacing barrels, you're on your own. In my discussions with the good folks at HK USA, it's become apparent that they are virtually impossible to obtain.

Also being that they are entirely proprietary in how the join the upper receiver, a simple replacement with a DI barrel is out of the question unless you have access to a full machine shop and the know how to mod the upper, create a shim for the barrel nut to still work correctly, and a barrel blank that you can drill out a properly placed gas port and notch for the gas block retaining pins.

Since I do have access to a machine shop, i've thought about doing all of the above, or at least getting a new barrel prepared and making a jig that would allow me to modify the upper receiver to accept standard AR barrel extensions. Still, it would be an extensive process and not suggested for most people.
 

·
Registered
Joined
·
12 Posts
If not the entire piston assembly, at least a set of rings. Besides wear item parts I try to keep small components that may be easily lost when servicing the rifle, such as detent pins or hardware. Not much cost to keep but a PITA if you lose one.
 

·
Banned
Joined
·
879 Posts
If not the entire piston assembly, at least a set of rings. Besides wear item parts I try to keep small components that may be easily lost when servicing the rifle, such as detent pins or hardware. Not much cost to keep but a PITA if you lose one.
Ah yes, I forgot those.

I have two sets of extra rings and will be getting more.

I will also remove them at some point and see how the gun works without them just to see how necessary they are and just how bad system performance degrades without them.

I would suspect that the piston, inside of the handguard, and barrel will be much dirtier, but i'm not convinced that the system will stop working entirely without them.
 

·
Banned
Joined
·
879 Posts
1 - 7 of 7 Posts
Top