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keeping spare parts on-hand

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I started off with a S&W MP15 Sport and like it so much I am planning to do a 20" build. I just saw the PSA 20" CHF chrome lined upper just came back in stock so I snagged one. My question has to do with spare parts. I am familiar with cleaning this firearm and have a general understanding of how it works but I am by no means an expert in the functionality of every little part and I plan on picking up a spare complete BCG once the 20" has been built. From what I have come to gather it may be worthwhile to have a an bolt extractor and spring but I am curious as to what parts (if any) you'd recommend keeping spares of?

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I'd say get a LPK without a grip, a bolt repair kit, and a gas tube and call it a day for about $85. If you shoot anything other than .556 cracking bolt lugs is also a concern.

 

This. I usually just keep a spare LPK in my bag.

 

ETA - I also keep a spare BCG... a spare bolt should suffice.

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There is no set in stone PM scheduled for an AR. Parts are not created equal and people use them in different ways. Shorter barrels are harder in components that longer barrels, same with shorter gas systems. Someone who trains a lot firing high round counts in short intervals will need to perform more maintenance sooner than someone who fires the same amount of round over a longer period.

 

My rule of thumb is -

Extractor w/spring, and Gas Rings ~ 3k rounds

Action Spring ~ 5k rounds

Gas Tube ~ 5k rounds

Bolt ~ 7k rounds

 

Barrels should be replaced as well, but they are expensive so I wait until I see accuracy or gas issues before. I am currently well over 10k rounds on one barrel with no issues.

 

Keep in mind I use all mil-spec parts from quality manufacturers with a good reputation. I also shoot and train often, with high round counts over a short period of time, interspersed by more reasonable round counts on a more mellow schedule for sustainment practice.

 

All LPKs are not created the same. Buy quality even if it costs a bit more.

 

I don't know about Chrome-silicon springs. I use what is In the mil-spec LPK I get.

 

FWIW I have never seen the small springs/small parts in a lower fail. I have seen trigger/hammer pins break as well as trigger parts (springs, hammer, disconnector) but never the bolt catch, takedown springs, Mag release, selector spring, buffer retaining pin, etc....

 

Other than the action spring, the upper takes the most beating and needs to be periodically inspected with parts replacements at intervals that work for you.

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Nickjc
that link is awesome! thanks for sharing

High Exposure
Just looking to keep some spare parts aside from a spare complete BCG at home. I supposed my main intention is to (hopefully) prevent any potential downtime if I did indeed need to order a small part and wait for shipping. I did the same when I was into paintball but more basic parts as orings, bolts, ball detents, barrels etc...

n4p226r
lol

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I've got a variety of spare/replacement parts for many of my gunz - as in rifles, pistols and machine guns - but in 30+ yrs have had to replace almost nothing!  I no longer shoot a lot, but up till about 10 yrs ago I shot everything a lot! 

I'm of the opinion that having a giant stock pile of parts is a total waste of $$$ that could be spent on ammo! 

Of course I collect and shoot Only Military surplus (or look alike) firearms, Maby they are better made than some of the civilian junque? 

Sarge 

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My rule of thumb is -

Extractor w/spring, and Gas Rings ~ 3k rounds

Action Spring ~ 5k rounds

Gas Tube ~ 5k rounds

Bolt ~ 7k rounds

 

Barrels should be replaced as well, but they are expensive so I wait until I see accuracy or gas issues before. I am currently well over 10k rounds on one barrel with no issues.

 

There are schedules and then there are real life numbers. HE's is maintaining guns that not only can't be allowed to fail, but have very high costs if they fail, in human and legal terms. For him it makes perfect sense to replace cheap parts even half way through their lifespan so if anyone wants to ever question it he has a overly cautious and well documented maintenance schedule.

 

That is good.

 

However it isn't necessarily the right thing for everyone. I've shot a few rounds through ARs although probably not as many as he has, I have to pay for my ammo :)

 

I have NEVER replaced an extractor or its springs. In my experience quality bolt groups don't seem to have these parts wear out. I replace them when I get a new bolt. I have used my spare to fix other people's extractors and springs but they tended to be the older spring design on bolts of unknown origin. I have never replaced a set of gas rings nor have I had one fail.

 

I have replaced the action spring ONCE not because I thought something was wrong but because one day I realized I never had on my primary game rifle and it was 10+ years old. It is probably still fine but a 3pack was like $12 at brownells so why not.

 

I replace the gas tubes when I replace the barrel or the gas block. Never had one fail in any way.

 

I had a bolt fail at around 15k so that one I now replace around 10k, but interestingly not because I schedule it that way but because that is roughly where I replace my barrels and I consider barrels and bolts matched for life.

 

None of this is to say you shouldn't replace parts earlier. Most of the wear items on HE's list are dirt cheap and you should certainly have them in your spares kit. My spare kit that goes to the range has a entire LPK and a complete BCG in it because I rather replace the entire bolt on the range then futz with the springs in it. I do think at a minimum everyone should have spare LPK worth of parts and at least a complete bolt if not a whole BCG as spares. The other components are far less likely to break.

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I have seen bolt lugs shear off a few times. Interestingly, in every case but one the rifle kept running and the damaged bolt was noticed at the end of the day of training during maintenance (wipe down and lube) for the next days shooting. In the other case, the sheared lug hummed up the trigger group. The bolt still functioned.

 

What I have seen the most is bolts failing at the cam pin hole. Cracks on one and both side of the hole. In every case it was an instant showstopper. Shooters typically states the gun felt fine, like a normal shot, they just had no trigger for the second shot. Inspection showed the BCG being out of battery.

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Also, you can fit an entire LPK in an Altoids tin. Add a few gas rings, an extractor, and a punch and you are all set. Throw a complete bolt - a full BCG is better, and a charging handle* in a ziplock with the altoids tin and you are good to go.

 

*Charging handle is good to have. I have seen a few of those fail at the latch and more then one get bent when shooters forget to slide them back in after locking the bolt back when clearing malfunctions.

 

Bending or crimping an aluminum charging handle is not difficult and is the fasted way I know to turn a rifle into a club.

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What I have seen the most is bolts failing at the cam pin hole. Cracks on one and both side of the hole. In every case it was an instant showstopper. Shooters typically states the gun felt fine, like a normal shot, they just had no trigger for the second shot. Inspection showed the BCG being out of battery.

 

My experience as well. The bolt I broke was at the cam pin hole, and so has every bolt I've ever seen fail.  Interestingly, some newer bolt design (like the current JP bolts) re-enforce the area so I guess I'll let you know if I break the current one before I wear out the barrel :)

 

*Charging handle is good to have. I have seen a few of those fail at the latch and more then one get bent when shooters forget to slide them back in after locking the bolt back when clearing malfunctions.

 

And I once forgot to assemble it at all and left it at home when I went to the range. :resent:

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Ok question for the forum. Has anyone seen has rings fail? Any idea of a round count? Cause I have not only never reached eol on a set, I've never seen anyone else's fail either. Just curious since they are in like every spares kit.

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Define fail?

 

I have seen guns run fine with 1 new gas ring. I have seen guns runs intermittently (a malfunction every few rounds) with no gas rings at all. It isn't ideal, but well built guns with quality parts shooting quality ammo will still run.

 

That being said, I define fail as when the tension between the gas rings and the inside wall of the bolt carrier won't hold the weight of the carrier. If the bolt is extended and rested straight down on the bolt face and the bolt collapses into the carrier, that's a failure and indicative of the rings needing to be replaced.

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I'll have to differ, in the days of ultra slick finishes.

 

I used to follow the guidance as well because that was what I read, but now I have two pretty high end BCG's which have "failed" that test from the factory yet have worked flawlessly for lots of rounds so far. Neither my VDI coated Voodoo carrier with a nickle boron bolt nor my JP BCG (qpq finish with a Chromium Nitride bolt)  pass this test, not even a little bit, they will barely pass this test holding the BOLT up, nevermind the carrier.  The milspec BCGs I have pass it. 

 

I think with the increasing use of ultra slick finishes that particular test is not going to be useful for anything other the more standard components. There is just less friction in some of the newer systems and even with the reduced mass components gravity takes it toll, but that doesn't mean there is not a good gas ring to bolt carrier fit .

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I'll have to differ, in the days of ultra slick finishes.

 

I used to follow the guidance as well because that was what I read, but now I have two pretty high end BCG's which have "failed" that test from the factory yet have worked flawlessly for lots of rounds so far. Neither my VDI coated Voodoo carrier with a nickle boron bolt nor my JP BCG (qpq finish with a Chromium Nitride bolt) pass this test, not even a little bit, they will barely pass this test holding the BOLT up, nevermind the carrier. The milspec BCGs I have pass it.

 

I think with the increasing use of ultra slick finishes that particular test is not going to be useful for anything other the more standard components. There is just less friction in some of the newer systems and even with the reduced mass components gravity takes it toll, but that doesn't mean there is not a good gas ring to bolt carrier fit .

Good point. I use standard spec BCGs so I have little to no experience with the fancy coatings.

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My definition if fail would be gun ran fine, gun gets used, gun starts malfunctioning, replacing gas rings makes it run again.

In that case, yes. I have seen gas rings be the primary cause of malfunctions in an AR - meaning that a previously reliable AR that was experiencing repeated malfunctions was made a reliable carbine again by installing new gas rings. I have seen it more than once on high round count guns whose owners did not believe in preventative maintenance.

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In that case, yes. I have seen gas rings be the primary cause of malfunctions in an AR - meaning that a previously reliable AR that was experiencing repeated malfunctions was made a reliable carbine again by installing new gas rings. I have seen it more than once on high round count guns whose owners did not believe in preventative maintenance.

Any idea on round count?

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No, I don't remember. The ones I saw were during EAG classes. They weren't my guns and I don't know the quality of the BCGs they were running.

 

I swap in new rings ~3k rounds, or if my mil-spec bolt fails the test I described above (I haven't had one fail early yet). For my needs it is cheap insurance.

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No, I don't remember. The ones I saw were during EAG classes. They weren't my guns and I don't know the quality of the BCGs they were running.

 

I swap in new rings ~3k rounds, or if my mil-spec bolt fails the test I described above (I haven't had one fail early yet). For my needs it is cheap insurance.

I go a little longer...5K rounds, but agree, it's cheap insurance.

Having a couple of spare lpk's handy isn't a bad idea either.

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