M4 Maintenance

Beaver

Beaver

CGN Regular
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Location
Oshawa, Ontario
Well it is that time of year again.

Chestnuts roasting in an open fire... and the summer's used brass vibrating in cleaning media.

I have a few questions that I am hoping somebody will know the answers to, with regard to our annual maintenance of our black and green rifles.

1. The following warning appears many times in various manuals -- "WARNING... do not interchange bolt assemblies from one rifle to another. Doing so may result in injury to, or death of, personnel." Why? I would like to have a spare bolt or complete bolt assembly in my kit. How do I acquire one that is assured to work properly with my (Dlask) M4?

2. Occasionally I had feeding and ejection problems. On advice, I purchased a few replacement action springs (extra power) -- these springs are 13-1/4" long and are ideal for a Rifle buffer assembly. However, I am using it with a Carbine buffer assembly, and the manual says that the spring must have a minimum length of 10-1/16" to a maximum length of 11-1/4" (with a warning not to adjust the length). Should I cut this brand new spring down to 11 1/4" (cut off 1-3/4")? Note: the spring I replaced was 11 inches long and had been used for over 2,000 rounds.

3. I changed the extractor spring with an extra power one that included the following note: "Use with extractor spring insert from factory spring. Grinding is NOT recommended." Well I could not put the bolt assembly back together with the insert and just barely got the assembly back together without it. Is the insert really necessary and is there a trick to putting the extractor spring assembly back into the bolt assembly?

4. Aside from a good cleaning, is there any other annual maintenance that is recommend to prep the rifle for next year's shooting season?

-= Beaver =-
 
Regarding question 1) Bolt lugs will wear in simbios with the barrel extension lugs, it is good practice to keep the same parts together, if not the differences in wear geometry between parts will cause increased stress points and I guess this is where the "danger" warning comes from. If you run a new bolt as a spare it may not be as problematic but I am not an expert on this.
2) buffer springs are cheap, just get a correctly sized one, I would not recommend cutting one down.
3) can't say
4) Cleaning and lubing is an ongoing process, I would say just give it a good cleaning and lub, if it is being stored, apply oil to all surfaces (barrel, receiver, inside barrel..etc) to protect from rusting. When time comes to go shooting remove excess oil and run a dry patch through barrel.
 
Scarecrow said:
http://www.subguns.com/biggerhammer/manuals/pdfs/tm9-1005-319-10.pdf

Login: Manuals
Pass: chipin
Click to expand...

That login did not appear to work for me -- Perhaps it could be located on the Internet again by search for tm9-1005-319-10.pdf

My source was tm9-1005-319-23.pdf, however, that manual basically says: bad bolt assembly, "...evacuate to support maintenance for repair.". My question is, can I acquire and keep a replacement bold assembly in my kit?

As for the buffer / recoil spring... I have a proper length rifle spring -- would it be the same as a carbine spring if I cut 1-3/4" off it. In other words, I am not trying to adjust the length of a carbine spring, but make use of a rifle spring in a carbine. With the 1911 pistol, I have had very good success with adjusting full-length 1911 pistol recoil springs for a shorter reverse recoil system by cutting off a few links. Perhaps a 1-3/4" long spring is not to specification but works fine (it would not be allowed in the military because you would not be able to determine that it is no longer useful by its length since it was too long to being with -- keep it simple and standard [kiss]).

Regardless, I thought I would learn on the experience of others since I cannot be the first to consider these compromises in light of the materials immediately available to me.

Thank you for your thougts and ideas...

-= Beaver =-
 
1) I have a replacement bolt a a spare. It's carried in the pistol grip compartment. I had the headspace checked of my spare bolt when I got it.

2) I would get the correct spring. The spring has closed ends as delivered. cutting the spring will leave you with an open end that could cause problems like: tangling up with the buffer or the spring itself, accelerated wear on the buffer tube, buffer, or buffer tube end cap. A carbine spring is cheaper than damage to your rifle, or your time cutting the spring back coil by coil and test shooting.

3) Shoot the rifle without the insert. If you get malfunctions from the extractor, then you do need the insert. Another trick is to use an o-ring that just fits over the extractor spring. I get them from the local hardware store.

4) Do the maintence as per the TM. Replace broken or worn items as per the TM. You (and your local gunsmith) are "...support maintenance for repair." BSW
 
1) I have a replacement bolt a a spare. It's carried in the pistol grip compartment. I had the headspace checked of my spare bolt when I got it.
Click to expand...

I always wondered about this. Are you guys that have the spare bolts regularly rotating the spare with the one in your rifle/carbine? Only curious as I'm thinking you'd want both (your primary bolt and the spare) to wear evenly with use in the firearm in question - so as to keep the headspace consistent???

hsld.
 
Nope, spare is spare. It's also the spare for my wife's AR, so it wouldn't work for me to swap it with the normal use bolt.

I mostly have it so that a broken bolt (or small bolt part) doesn't ruin a day at the range. BSW
 
FYI regarding Rifle & Carbine recoil springs... for those that are interested...

Wire Sizes and Lengths are different for these two types of springs, so simply cutting off the extra length would not work and this explains why the manual says not to adjust the length of a AR recoil spring. Luckily, Wolff was willing to exchange the incorrect springs for the correct springs (I offered to pay for shipping both ways since it was my mistake).

Beaver
 
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