View Full Version : Spring and bushing question

06-10-2005, 04:45 PM
I'm getting an upgraded spring and some metal bushings for my TM m4 soon and had a few questions that I've been unable to get clarification on.

1. I'm going to get a System M120 spring, but I've seen a few variations on this, I know the M120S is too strong, but for the regular M120 spring I've seen it advertised as 'irregular pitch'...is there a regular pitch version or is this what I'm looking for?

2. As far as metal bushings go, metal is metal, but I've seen oily and oiless bushings for sale, are there pros or cons of using one or the other? I think I've also seen some teflon coated metal bushings as well. Just wanted to know what the general concensus was as far as bushings are concerned.

Thanks in advance.

06-11-2005, 09:49 AM
The irregular pitch has to do with the coil configuration on the spring. When you get the M120, you'll notice that instead of looking like a "standard" spring, it'll have tighter coils in the middle of the spring than on the ends. This is one of the things that gives the spring more power.

The purpose of the bushings is to not only reinforce the holes for the gear pins, it also helps reduce friction on the gears. My CA M15 has oily bushings, but I grease them whenever I open the mechbox anyways. As long as the bushings are metal, you should be in good shape.

I've never messed with the teflon bushings before, but it sounds like a pretty good idea. Anything to reduce friction is a good thing!

06-11-2005, 10:08 AM
Yeah I didn't figure it really mattered as far as bushings go, again...metal is metal but I figured I'd have to grease em up anyway which is fine. So...sounds like the m120 and 'random brand' metal bushings outta do me good.

06-12-2005, 06:48 AM
shakman, reducing friction is good. However, the bushing (or bearing) has to be strong enough to take the radial stresses. That is the reason for going from plastic to metal bushings. The stock plastics ones are fairly smooth, i.e. low coefficient of friction. It is because of additional radial stresses that cause them to fail. Same reason that 6mm bearing bushings can't handle higher-powered springs even though they reduce friction compared to metal bushings. 7-8mm bearing bushings are awesome though. :)

06-12-2005, 08:33 PM
The M120 is the same spring as the M120S energywise. They are the same strength. They will both put you at 400 fps. The S is made of a different material.

Regular M120 is made from oil tempered wire, and was prone to breakage.
M120S is made from stainless wire, and I have not had one break yet.

Irregular pitch is just what the others have stated. The coils aren't evenly spaced all the way down the spring. No big deal.

I can't comment on the bushings as I have only used Area 1000 oilless bushings extensively with no failures. I have seen the stock ones shatter and destroy gears. I would be interested to see some info on the teflon coated ones.

06-13-2005, 12:38 PM
I saw a spring guide that posted the M120S as having 30 or so fps more than the M120, which is a negligible amount. I think the stainless quality and it being known for less breakage is more of a determining factor for me. More than likely that's the one I'll end up with.

06-13-2005, 02:53 PM
Hehe, I wouldn't use that guide anymore. :)

Do you have a link?

06-13-2005, 05:15 PM
Yeah, well I found the chart on a few airsoft sites. I just did a search for 'airsoft spring comparison' and that's what I got.

This site for example has the chart: http://www.arniesairsoft.co.uk/?filnavn=/articles/newbie_guide/faq/spring_guide.htm

06-13-2005, 08:34 PM
I recall seeing that chart elsewhere, and I think it originated from a Canadian site.

The problem with Systema springs is the tolerance range. In the same setup gun with constant variables, you'll get one M120 spring shooting 420fps/.2g, but with the next M120 spring you'll see 405fps/.2g. Then, there is the velocity dropoff as the spring settles in. For example, I've seen Systema M120 springs at 420fps/.2g settle in at 405-410fps after a few hi-caps. Similarly, initial 405fps/.2g M120 springs settled in down at 395fps/.2g.

Guarder and PDI springs are more consistent in my experience.

06-14-2005, 10:07 AM
I believe I heard somewhere that PDI springs are also easier to install. Any experience on the history of breakage with PDI?

06-14-2005, 10:26 AM
The only thing you need to be careful with PDIs is that the wire used is thicker, and you can run into problems if you have bearings on both your piston head and spring guide. PDIs are a little shorter than the equivalent Systema part, but are roughly the same stiffness, so they are a little easier to install.

06-14-2005, 11:41 AM
Well I was considering getting a spring guide with bearings, anything I can do to reduce wear and tear on the parts I'm willing to get. Does a stock piston TM M4a1 piston head have bearings on it? And also, while I'm being a noob here, why does having a bearing on the piston head and the spring guide cause a problem, mechanically speaking it seems that the more bearings there are the better, less resistance and less stress on the parts. But, I'm sure you can set my theory straight. :)

06-14-2005, 01:11 PM
Does a stock piston TM M4a1 piston head have bearings on it? No.

And also, while I'm being a noob here, why does having a bearing on the piston head and the spring guide cause a problem Can't say for myself, as I don't think I've encountered such a problem.

06-14-2005, 08:02 PM
I've dealt with 140%, 170%, 190% PDI/CA springs no problems thus far. Like Wolv said when I had a M120S spring, I did have a good drop off of about 9 FPs. But I've been running a 170% with a spring guide with bearings 4 months of use with no problems. You must also remember to shoot semi-fire after your done using it, so that your spring isn't compressed.

06-15-2005, 12:40 PM
The reason you don't need bearings at both ends of the spring are simple- you don't gain anything for the extra cost. I have had a problem in the past when I tried running a bearing spring guide and a bearing piston head where the extra room taken up by the bearings and friction plates at both ends of the (PDI) spring wouldn't allow the piston to cycle at maximum spring compression. Simply put, adding bearings subtracts from the existing space the spring has to compress. If you subtract too much space the mechbox will essentially lock up.

02-27-2007, 08:56 AM
...Same reason that 6mm bearing bushings can't handle higher-powered springs even though they reduce friction compared to metal bushings. 7-8mm bearing bushings are awesome though. :)

I've found sites advertising metal bushings and then metal bushings w/ bearing. Is there a difference in installtion? Also, will all bushings fit into a v3 mechbox regardless of being 6,7,or 8mm without modifications?

02-27-2007, 09:16 AM
Yes, there is a difference. A bushing is just solid with a hole for the axle. A bearing actually has an inner ring that the axle goes into, but that ring rotates on little ball bearings (little metal balls) inside the larger outer ring. There is less friction using bearings, so things run smoother. These pictures are not from airsoft, but do show the difference between a bushing and a bearing:

There is no difference installation other than you need to be careful when pressing bearings into place. You cannot push on the inner ring, as it can be damaged/deformed. They will not rotate correctly if that is the case.

No, not all bushings will fit into a Ver3 mechbox. Standard stock mechboxes use 6mm bushings (or bearings). The only way 7mm or 8mm bearings/bushings will fit into a 6mm mechbox is if you drilled out the holes.
7mm and 8mm bearings/bushings are intended for *typically* aftermarket mechboxes.
Example (http://www.wgcshop.com/pcart/shopper.php?itm=KA-GB-03_srch_7mm)

However, because of the increased radial load that larger bushings/bearings can take, some stock guns are now coming with 7mm mechboxes.
Example (http://www.wgcshop.com/pcart/shopper.php?itm=CA-AEG-M15A4SPC_srch_7mm)