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Guide: What's a Good Bucking?

Posted: Thu Feb 05, 2009 9:16 pm
by Moondog
Guide: What's a Good Bucking?
by Moondog


Buckings are the condom-like sleeves that cap the inside end of your inner barrel. The hop-up unit pushes a spacer down, pushing part of the bucking through the hole in the base of your inner barrel. This creates the friction surface that makes your BB spin backward as it shoots past it: the hop-up effect.

Buckings serve a secondary function of holding a single BB in place in your in front of your nozzle. Otherwise your entire magazine would empty out into your barrel. Double feeding can be caused by worn out or damaged buckings.

The Long Story
Buckings are made of rubber or silicone or a mixture of both and come in various hardness/stiffness ratings. Clear or blue buckings are silicone. Black are usually rubber but can be silicone made to rubber-like specs. Silicone is softer than rubber. But rubber is more durable and lasts longer than silicone.

Softer is generally better for consistency which means better accuracy.

But AEG's that shoot above 375fps may require harder buckings. If you have to dial your hop-up all the way, that's a sign that you need a harder bucking or that your bucking is wearing out. If your BB's are very inconsistent or their trajectory changes wildly between semi and full auto, that's a sign you need to change your bucking (but first check the quality of your BB's and if your barrel is dirty.)

Some guys change their buckings every few months. Me, I've had the same Guarder 70% bucking in my AEG for over 2 years. Anybody who's been hit by me obviously knows I've had no problems with accuracy.

Don't forget new buckings do need a little breaking in. New ones are covered in a thin coating of silicone lube to protect from from oxidation and cracking. That coating needs to be worn away by BB's (or cleaned off with detergent and warm water and a dry Q-tip before installation).

Lubing/cleaning your barrel or hop-up with silicone oil will also adversely change your bucking's performance until this lube is worn away.

Systema, Guarder, Madbull etc. What do you use and why?

I have yet to find a comprehensive and objective comparison of buckings online. I've discussed this with the team's air-techs and we've all come to the conclusion that buckings are one of the most subjective and biased upgrade parts.

I'll cut through the brand bull and offer this simple bit of advice. Keep your bucking until you need to change it (like if your BB's are going all over the place.) Brand doesn't matter as much as hardness and newness.

50%, 70%, 80%? What's the Difference?
Many buckings are labeled with a percentage or degree number. The percentage is the value of stiffness compared to 100% rubber bucking (most buckings are actually made of silicone but the number simulates a mix of both materials.) So a 70% bucking has the equivalent stiffness of 70% rubber. The softer the bucking and the stronger the hop-up effect (except in high velocity guns.) But this also means that the bucking needs to be changed more often as it wears out.

50%-60% is fine for most AEG's. But with higher velocity BB's, the properties of silicone are too soft to impart enough hop-up friction. For AEG's above 380fps, try a 70%-80% bucking.


Fishbone/H-type Spacers
Madbull and some Asian suppliers have invented Hour-glass or H-shaped hop-up spacers. These are intended to impart more even hop-up spin. But in actual use, they perform no better than traditional flat spacers. This is probably because the bucking, not the spacer determines the evenness of the hop-up spin.

Lost Spacers
Spacers are tiny and easy to lose when opening up the hop-up unit. Your hop-up will not work without them. But they usually come with all replacement bucking sets. Or you can make your own by breaking open a disposable ball-point pen. Snip off a tiny bit of the ink-tube to use as a replacement spacer. Or snip off a bit of 18 gauge wire.

Again, your results will vary. I suggest you buy few different buckings (they're some of the cheapest and easiest parts to install) and try what works better for you.

Here's some guides on how to open up your hop-up unit to replace your bucking.

M4 Hop-up

G36 Hop-up

AK Hop-Up

Re: Guide: What's a Good Bucking?

Posted: Sun Aug 14, 2011 3:58 pm
by Russian
Link to AK page is not working.

Re: Guide: What's a Good Bucking?

Posted: Sun Aug 14, 2011 6:47 pm
by Moondog
Well 858 airsoft looks like they closed. Russian, maybe you would like to post a step-by-step guide on how to take down your AK?