Crazy Question

Can an m14 be used as a support weapon? With a high cap.

Technically no. The basis for an actual support weapon is that it must replicate a support weapon. Unofficially you can suppress with any weapon. Continuous fire on a target will limit their return of fire, regardless of weapon. Dont call yourself a support gunner, but as a group you can provide support fire. The idea of actually using an approved support weapon is that you have extended FPS limits. My new SAW utilizes these limits to their fullest extent making more effective than the average aeg. So in short... YES and NO.

from my experience, mid caps are more useful for supressing fire than hi caps, because every 15 or so rounds with a hi cap you have to crank it (unless you have an autowinder or something) whereas mid caps can empty the full clip and some of them can hold like 150 rds. that and there are no feeding problems like i've had with hi caps. so you'd need extra mags.
http://www.airsoftpost.com/product_info.php?cPath=23_56_437&products_id=30138
keep in mind if you're gonna be laying down supressing fire you're gonna need a very large battery, the one i bought dies after around 700-800 shots, which may sound like a lot but you go through it really quickly if you're laying down fire like that, so you're either gonna need a few batteries or one really big one, i'd say something like 3500-4000 mah, and you're also gonna want your ROF to be good so that means your battery needs to be even bigger to accomodate the higher voltage, so you're gonna want an 11.1v li-po which can run you $85 alone for an 11.1v 4000mah battery, and another $35 for a li-po charger with a drip.
http://www.airsoftpost.com/product_info.php?cPath=31_171&products_id=27374
http://www.airsoftpost.com/product_info.php?cPath=31_171&products_id=30777

i have that same charger and it works pretty well for me.

Dont spend more than $40 on a lipo.

Try ebaybanned.com. They have free shipping. Its coming from HK so it does take 2 weeks. For under $30 you can get

http://www.ebairsoft.com/firefox-111v-1200mah-lipolymer-battery-p-1770.html

That is small enough to fit in an M4 hand guard, Mp5 hand guard, folding stock AK, Scar, etc. Its a very versatile battery with a 20c discharge rate. It is MORE than adequate for any gun. 1200 mah on a lipo is also more than adequate for a support weapon (mah on a lipo doesnt work the same way as regular batteries). That battery will last you for days. I personally have never had a lipo or li-ion battery go dead on me. One more thing. Suppressing fire does not necessarily mean automatic fire. Continuous fire that limits return fire or movement by the enemy will suffice.

A Horsemen secret that we practice regularly. Indoors at events it is semi auto only. When we are in a engaged in a hallway in order to advance we will establish fire superiority and maintain it through continuous semi auto fire as our stack moves down the hall. This can be done through single stack or double stack train, crossover, serpentine, or a rolling T. Regardless, it is continuous semi auto fire maintained by fast reloads, coordination, and a gun with quick reaction timing (done by using a lipo).

A good charger is easy to get. After a bunch of different ones I prefer the Imax B6. It does Li-poly, li-ion, nimh, nicd, and just about any other battery you can think of. They run $50-$60. Worth every penny as they will increase the life of your battery, and ensure that they are fully charged when you enter the field.

Keep in mind when using such a high powered battery you will put more wear on your gun. However with your guns you should'nt need to spray and pray. So you shouldnt have to worry that much.

dosent a gun have to be "lipo ready"?

my 1000mah lipo dies after 700-800 rds every time i use it, and i usually stick to semi-auto... i charge it up the day before i use it and it's on a drip charger so i know when it's done and i pull it off so i know i'm not overcharging it, am i doing something wrong?

any AEG can use a lipo, lipo ready just means that the gearbox is reinforced to take the greater amount of wear that a lipo gives out with it's higher voltage, so you can use any gun but with the cheaper one you just need to be prepared to work on the gearbox more often than with a lower voltage battery.