I have been working on the new V4.x lower since March, I did a full redesign with many improvements and updates. One of these was a new buffer band to replace the worm drive hose clamp I have been using since the first Super Lower back in the spring of 2021. This new buffer band is something I started working on long before V4.x, and it is the subject of todays newsletter. Specifically, why I may be canceling development of the new buffer band.
The goal of the new buffer band was to eliminate the flaws of the hose clamp, these being the additional width of the buffer tower required to accommodate the wide band, and the worm drive mechanism, which is rather high profile. Unfortunately, the new buffer band has a number of issues of it's own.
Before continuing, you should understand the basic mechanism behind the new band. It uses what I call a screw-void system. The steel band has two holes, one on each end. These holes are tied together with a screw, and when the screw is tightened into a captured nut it pulls the ends of the band into a void, increasing the circumference and hence the tension of the band. Simple. Well, not really.
Space is very limited on the buffer tower, the only location where a void can be added without compromising strength is below the support rib on the left side, the depth of the pocket is limited by structural requirements as well as other features such as the rear-take-down-pin-detent-spring-hole. This means that the amount of tightening available is very limited, the band must be quite tight to start with. This makes installation difficult.
The screw must be used as a lever to pull the ends of the band together prior to threading it into the buffer tower and the captured nut. The high side loading on the threads of the screw make the process of sliding the screw into the buffer tower difficult, as the edges of the band bind on the threads. To reduce this issue, the holes must be radiused using a custom die set. This resolves most of the binding issues, but adds a significant amount of complexity.
The metal must also be ductile enough for the significant amount of stretch required. There are a couple ways that this could be improved, such as only radiusing the active side of the hole, but this adds additional complexity and stress risers.
Even with these measures, the bands tension level is still marginal, and this is made worse by failures. This is where things get a bit more complex, with material choice, thickness, and width playing a roll. I've used both 1075 steel and 304 stainless steel on prototypes, both with there own issues.
One of the advantages of the new band is lower buffer tower thickness. On my previous Super Lowers I have increased the buffer towers thickness from the mil-spec 0.500" to 0.650". This is to allow for the wider 0.500" hose clamp. The disadvantage here is that the lower is only compatible with buffer tubes that have enough extra threads to accommodate the thicker tower, specifically the mil-spec carbine buffer tubes. Civilian spec tubes and rifle tubes will not work. With the new band one of the goals was to make it narrower, and allow the use of any buffer tube, and maybe even folding stock adapters. However, due to the issues with cracking and creep, a wider band will be required anyway. So this advantage is not realised.
The final advantage of the new buffer band is that it is streamlined. And at this point, since the narrow buffer tower is not practical, this stands as the only true advantage of the new buffer band. To some the fact that it's not a hose clamp is also an advantage, but this is not a rational design decision.
Being streamlined improves ergonomics slightly, as you won't bump into the worm drive with the back of your hand when engaging the safety, or catch it when charging the rifle. But these are slight improvements that must be weighed against the disadvantages.
Comparing the worm drive hose clamp to the new buffer band, the advantages of the new band are:
The disadvantages are:
Difficult to manufacture at home.
Marginal tension results in a weaker buffer tower.
The more tension the harder it is to install.
Failure due to fatigue limits one band to only a few installations.
I have been working on the new band because it was an improvement to the existing hose clamp. I like improvements. However, considering the disadvantages, the two primary reasons I am not continuing development are:
The issues will require much more time to overcome, not allowing me to work on other more useful projects. It will also drive up the costs of the reinforcement kits.
A custom band that is hard to manufacture at home is practically a proprietary part, you would have to buy my kit to get it. Expensive proprietary solutions are not inline with the goal of 3D printed firearms.
I do add custom parts to the kits to make them nicer, such as the brass bushings, and soon the metal front take down plates. These parts are only minor improvements, and can be easily replaced by printed plastic and result in a still very solid weapon. The new band could be the same, I would simply have to provide a version of the lower that is still compatible with the hose clamps. However, the differences between the "basic" and "super" version would be getting even wider, and that's not a direction I want to go in. You should buy my kits because it's convenient or lower cost, and you want to support me work, not because you have to to get a good weapon.
The trusty hose clamp is here to stay. Let me know your thoughts on this. I know there was a bit of excitement around the new buffer band, and I'd like to know why. Was it just that it was "not a hose clamp"?
Oh, and I will make a note here that I have considered all if the other commercial off the shelf options, and non of them are as good as the worm drive clamp. This includes CV boot clamps, steel zip-ties, band and buckle clamps, T-bolt clamps, etc.. Now, if you have actually used one of these clamps on a lower, I'd be glad to hear about your results!
Using a epoxy and fiber composite wrapped around the buffer tower should also work quite well, but it's not a good option for many builders. If you like the process, you can always use it instead of the hose clamp. But I don't consider it a primary option.
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