Just wondering if anyone here had any experience with this?
https://maximdefense.com/product/244978/
I saw a thread on AR15.com regarding it, and interested me enough to pick one up from Optics Planet (with coupon, just under $160).
I run a 6” Stern Defense SBR that has my Dead Air Odessa on in all the time. Use an 11 ounce buffer. Figured removing that and the bolt weight would be a nice way to lighten it up.
Please post up your impressions when you test it!Originally Posted by Screwball
Also following- my brother is interested for his wife's KP9/FM build.
I'm having trouble pictureing how it works from those pics.
I'm also not sure if my overy pedantic head can agree with calling this a roller delayed blowback if it's just the buffer.
The rollers are in the buffer, which require a decent amount of force to overcome. Similar idea, just putting the rollers behind the bolt instead of on it.
Once the delay is over, the pressure is lower, making the action opening “safe.” And after the delay is over, the spring takes over, so it is just slowing it even more… not the only thing (with the buffer) keeping it closed.
Standard blowback… the weight of the buffer/spring is what keeps the bolt closed until pressure drops to “safe” levels. When you suppress or run more powerful loads, it requires more weight to keep the gun “balanced.” Like my buffer is 11 ounces, which is pretty heavy… but I’m also trying to keep the sound from the breach/ejection port down by slowing the bolt from opening.
Here is a review of it… should give you a little better view of the working parts.
https://youtu.be/ChXOTy-v9h8
I’ll definitely post reviews of it. I got a DHL tracking number, but not in their possession. Come on, Optics Planet… who still uses DHL?!?
9mm AR pattern PCC's are straight blowback. In a blowback system the recoil spring and mass of the bolt (and buffer in the AR PCC's case) initially hold the bolt in place until the pressure generated by the expanding gases from firing drive the bolt to the rear. In straight blowback systems the weight of the bolt is critical. Too heavy and the the force of the cartridge firing won't be enough to reliably cycle. Too light and the bolt can come out of battery before the pressures have dropped to a safe level.
When they explained RDB versus straight blowback at the HK MP5 course they told us that if the HK G3 Rifle was made in a straight blowback system, the bolt would need to weight 37 pounds, obviously too heavy. Additionally, the mass of the lighter bolt in SMG's causes excessive muzzle jump in straight blowback SMG's as it reciprocates.
The roller delayed blowback system is smoother because it requires a much lighter bolt (reciprocating mass) and smoothes the recoil impulse by spreading the recoil forces over time and distance.
In the roller delayed blowback system (most common is HK) the bolt is locked into position by rollers which rest in curved 'female' cuts (figure A); as the weapon fires the bolt is driven to the rear and the curves force the rollers against the locking block (red part of figure B); the rest of the energy is used to force the bolt and the carrier (orange part in figure C) to the rear against the pressure of the operating spring.
So in this case the locking system is in the buffer and the weight in the tail of the standard PCC bolt carrier must be removed. In this case, I'd think of the roller delayed buffer as an extension of the bolt.
Adding nothing to the conversation since 2015....
In most delayed blow back firearms the bold carrier is heavier than the bolt so that the effect of the rollers acts on the heavier portion of the reciprocating mass. Seems like this product flips that relationship. I wonder how effective it would be because of it as most of the mass of the carrier is still essentially functions as a direct blowback.
My thought is that the difference is 1) smoothing of the initial firing impulse and 2) reduced muzzle dip because of the weight that is removed from the bolt:
The Roller Delayed Blowback System requires an open channel in your 9mm bolt assembly for the guide rod to pass during fire. For most bolts, this will require you to remove the pinned-in central mass. This central mass must be removable to allow the BCG to function correctly with the RDB; the bolt must remain at its full length without it the central mass removed
(Pretty sure the bolded underlined is an editing error - it should read WITH the central mass removed.)
My thought, from looking at the pictures on the site, is that the roller delayed spring assembly is in direct contact with the bolt and functions essentially the same as the HK system with exception that after the rollers unlock the locking piece moves backward in contact with the bolt (like the bolt carrier of the HK) while the rod moves through the channel which results from removing the weighted mass from the PCC bolt.
Not sure how much the reciprocating parts of the RDB assembly weigh, but I would venture less that the regular PCC buffer, so there is also that reduction in forward moving weight to smoothe the action and reduce muzzle dip.
Aside from that, all my PCC bolts are just that, bolts that are shaped like AR BCG's to fit the AR upper.
Last edited by DDTSGM; 07-29-2023 at 04:43 PM.
Adding nothing to the conversation since 2015....
This is the big unknown in the system for me. If they sold it with a different lighter weight bolt I could see it imrpoving felt recoil but with the standard weight BCG I'm a bit... maybe not skeptical but while I'm sure this will have some effect on the recoil but I'm unsure if it will be enough of an effect for me personally to bother with it.
It's going to be hard to take their word on it or even the word of someone on the internet because I had a dollar for every time someone over-sold the recoil lowering effects of a gun, gadget, or piece of gear I'd have hundreds of dollars.
I mean watch any youtube review of a PCC and take a shot anytime they mention how light the recoil is because it's 9mm and you'll be too drunk to drive for the rest of the day in short order.
Watching with interest… I have a 9mm AR pistol awaiting an amnesty stamp, and I think this would be an improvement.
Ken
BBI: ...”you better not forget the safe word because shit's about to get weird”...
revchuck38: ...”mo' ammo is mo' betta' unless you're swimming or on fire.”
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