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I have started Blowback9.com to house all the information I have put together about 9mm blowbacks and the AR9. This article has been added and will be updated there.


TL;DR: I am not complaining about 9mm blowback recoil. This is a technical discussion about reducing perceived recoil in simple blowback systems. Read the entire post before commenting.


Since this has been a hot topic lately, I wanted to post this as a separate topic.

To many people who are familiar with the AR-15, 9mm blowback recoil feels "harsh", "sharp", "abrupt", "excessive", etc. Simple blowback pistol caliber firearms will tend to have greater perceived (felt) recoil than a gas operated 5.56 rifle. This is the nature of the operating system. 1/2 of the energy of the cartridge goes forward to propel the bullet, 1/2 of the energy goes backward into the bolt/buffer, and eventually, the shooter's shoulder. Most of this feeling comes from the bolt/buffer striking the end of travel fast and hard.

How we perceive recoil is the result of how much energy (force) is applied to the contact area of the shooter's body, and how fast that energy is transferred (velocity) to the shooter.  Decreasing either, relative to the current configuration of the firearm, will decrease perceived recoil.

It's been reported that the U.S. military has historically wanted to keep recoil forces from small arms below 15 ft/lbs and 15 ft/sec. So, total rearward force and rearward velocity are equally important.

Think of the "punch" of recoil like this: you want to either get hit with a lighter punch, or a push instead of a punch.

Here's how:

1) Decrease the overall volume of rearward energy that is applied to the shooter. Decrease the strength of the impact or spread it out over a larger area.

Lower-energy ammunition
Effective muzzle brake
Larger buttpad/wider pistol grip (increases the contact area)

2) Decrease "how fast" the rearward energy is applied to the shooter. Give the shooter's body more time to absorb the impact. Spread the force of the impact out over more time by decreasing velocity or increasing deceleration time.

Heavier gun (decreases velocity = more push than punch) (AK-V vs. AR-V)
Heavier bolt/buffer (decreases velocity = more push than punch)
Sliding internal weight/deadblow bolt or buffer (deceleration over more time)
Hydraulic buffer (deceleration over more time) (Blitzkrieg, B&T)
Reactive/elastomer buffer bumper or end-of-travel bumper (deceleration over more time) (Jones Arms EAB, Tacticool Sub2k buffer)
Hydraulic/spring dampened stock (deceleration over more time) (HiPoint carbine)
Spongy/gel buttplate (deceleration over more time)

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I have two essentially identical blowback AR platform 9mm. 4.5" and 5.5" barrels, same bolts, same springs. I put 22 oz. reciprocating mass in one, and 27 oz. in the other. I can confirm that INCREASING the reciprocating mass of the bolt and buffer 5 oz. noticeably DECREASES perceived recoil.

9mm simple blowback can easily operate with 32oz. of reciprocating mass, see here, so an 11-12 oz. AR buffer (heaviest available) should operate fine with factory loads, any commercially available bolt (14-16 oz.), and a standard carbine recoil spring. My 27 oz. mass setup works equally well with 115 weak range ammo, 124 NATO, and 147 subsonic.

I can also confirm that a Jones Arms EAB buffer bumper reduces the impulse by cushioning the AR9's buffer impact at the end of its rearward travel. It's a small improvement, but in side-by-side comparisons, it is noticable. The buffer impact at end-of-travel is more of a "thud" than a "smack", if that makes sense. I used a Tacticool Products Buffer Cylinder in my long-gone Sub-9 (Sub-2000 predecessor). It performed a similar function, and it made a big difference.

It's reported by people who have tried it (I have not) that hydraulic buffers provide the greatest perceived recoil reduction in simple blowback systems. This is the method used by current B&T simple blowback fireams used by the U.S. military.

The ultimate in perceived recoil reduction is achieved by using a delayed blowback operating system such as HK roller delayed, CMMG radial delayed, or a gas operated system such as the MPX. These systems spread out the recoil forces over time, and bleed off some of the energy to operate the delay systems. These are more complicated than simple blowback, more expensive, and require additional maintenance.

By now someone in the peanut gallery is shouting, "But what about using a stronger recoil spring???"

In semi-auto pistol (Browning short recoil operated) tuning, it's common knowledge that a lighter recoil spring improves the competitive shooting experience (yes I've tried it, and yes it works) by reducing the force of the slide slamming home. Although not technically "recoil", it is part of the operating cycle and is perceived as part of the "recoil experience" by the shooter.

A strong recoil spring may provide a slight decrease in the initial perceived recoil, but it will force the bolt forward equally as hard as it resists recoil, slamming the bolt into battery. This can cause the muzzle to lurch forward and dip when the bolt slams home, significantly slowing target transition. It can also damage parts and cause several types of malfunctions. This approach to recoil reduction should probably be avoided.



Edited to add tl;dr at top for the people who can't be bothered to read before commenting.

In playing with added weight to the bolt/carrier, heavy buffers, JP SCS, and Hydraulic buffers, nothing has come even close to the difference made by the hydraulic buffers.

I use a Blitzkrieg and it made the gun much more fun to shoot (blowback 9mm with 5" barrel).  

Shooting low power ammo made a big difference as well. I had a pretty big lot of Fiocchi 115gr 9mm that was way downloaded and super soft.  But other lots of this same ammo changed over time.

Ive always wondered if you could bottom out a AR15 bolt on the carrier

You pew, energy goes into the locked bolt, then moves into the carrier moving the locked bolt to unlocked

I guess thats kinda like CMMGs radial delay

Honestly I don't get it.  I skimmed the wall of text, but still don't get it.

Most of us shoot 9mm out of a handgun, many of us, pretty damn fast, at matches and things.

How could you then complain about recoil of 9mm through a...........RIFLE?

I changed my buffer to a Spikes St-T2 for reliability reasons, but after tens of thousands of 9mm rounds through two AR9 SBR platforms, recoil doesn't come into the picture anywhere but threads like these.

Am I just damaged from years of shooting .45-70 and 12 gauge trap?  



The thing on the end isn't for recoil or flash, it is a thread protector.

Its fine for what it is

Its a rifle converted to 9mm instead of a gun built around 9mm

It simply recoils more than it should for 9mm due to it being blowback as well as bolt and carrier weight.

I have a 9mm blowback gun thats a pussycat to shoot. Its bolt is much larger and heavier than a AR15s however.

I think it’s got more to do with the blowback, my 9mm AR pistol does have more overall felt recoil than my .300bo AR pistol shooting subs.

Not that it’s bad or unmanageable, but a blowback action with a heavy buffer will still feel different from a DI or a lock breech action.

In ARs I’ve found heavy buffers will smooth out or stretch out the recoil impulse, but bumping up to stronger springs like a Wolff +10% ran +p loads great but would occasionally choke on light range loads. I settled on an 8.5 oz buffer & std. spring.

If the carrier isn’t slamming the back end of the receiver or opening up early enough to allow cases to bulge, you’re good.

Edit to add: when I ran the Wolff spring & 8.5oz buffer, I could definitely feel the carrier slamming home much harder than towards the back

When I shoot a 12GA or 45-70, I expect recoil.  When I started shooting 9mm in the AR platform, I was shocked with the amount of recoil.  It isn't painful, its just annoying, and it absolutely slows down follow-up shots.  If we could make all rifles have zero recoil, we absolutely would.  And due to the blowback design of a 9mm AR, the amount of felt recoil is much higher than it needs to be.  There are systems to mitigate that recoil, and it is absolutely worth it to people who want to maintain a sight picture or compete where speed matters.

If it doesn't matter to you, great.  You are right - you don't get it.

I used to shoot trap and competitive pistol, so I hear you. Lots of folks new into shooting PCC looking at these pages and asking the same questions lately. PCCs do have a more abrupt and staccato recoil than most folks expect. I can't fault someone for trying to make their gun shoot smoother.

Hey OP....

Go shoot a CMMG radially delayed 9mm barrel/bolt set up and then get back to us about 9mm blow back recoil.

It's about as good as it gets for the 9mm AR BB platform.

Perhaps someday, but for now I'll stick with my MP5 when I feel the need to play with delayed blowback, thanks.

Y'all seem to think I'm the one complaining about 9mm recoil. The post was intended to help out new people with simple blowback, or folks who want to tweak their build to smooth it out without buying a whole new system.

If you had read the post, you'd have seen I mentioned that delayed BB, including the CMMG, have superior perceived recoil.

Almost all 9mm handguns are NOT straight blowback either.  
The exception would be something like a Stallard Arms straight blowback 9mm....
Shoot that next to something that uses a modified Browning lockup like a Glock, CZ, Sig or gas operated like an Walter CCP, HK P7 etc.  

There is a night and day difference.  
The same thing applies to a rifle but with a rifle you are talking about a bigger heavier setup than a 9mm handgun so most people may not notice it.  Most people are probably not shooting full auto or concerned about split times either.  Once they do get into competition or full auto, people start to notice especially compared to the recoil of the MP5.
So then you try to make it smoother and find there is not much you can do about it other than mess with various buffers and springs.  

The best solution is come up with some kind of delayed mechanism then also use a nice buffer / spring setup like the Kynshot hydraulic + a delayed action.
Is all of this necessary?  Of course not, I'm sure there are plenty of Stallard Arms and Hipoints that function fine but just not what I want to shoot.

As explained in detail in the post above, almost all 9mm handguns fire from a locked breech, which attenuates recoil significantly.

If you want to try something interesting, fire a few rounds from a Makarov pistol. The Makarov 9x18mm round is notably less powerful than NATO standard 9x19mm, but the blowback-operated Makarov has an abrupt “kick”, which isn’t present in a Glock, SIG, or any other locked breech 9mm pistol.

Most blowback firearms fire cartridges of relativity low power, such as .22LR and .32 ACP. Once you get to the .380 ACP power level and above, blowback firearms start to have “snappy recoil”.

This is a cave-man level post. I'm guessing you've either never shot or at least never done well in any serious competitive type PCC shooting with the above mentioned 9mm rifles you have tens of thousands of rounds through. This reminds me of every other fudd posting "why do you need a muzzle brake on your AR-15? Mine works perfect with a thread protector or an A2" in threads asking about the best muzzle brakes for whatever type of shooting they are doing. Doesn't mean those people run a muzzle brake on every gun believe it or not, most of us have a variety of rifles and configurations. People have different performance requirements/desires for different firearms they own for different purposes. We get it though, your gun shoots bullets when you pull the trigger and for you that checks all the boxes, which is great, but more sophisticated shooters tend to want more than that out of their firearms.

It's pretty simple and it seems like you either didn't read the OP, didn't understand the OP, or some combination of both. No one is saying 9mm blowback in an AR platform is harsh or hurts their shoulder or anything like that. That's not the point of OP's post. Like OP and others have said, the blowback in 9mm AR setups is surprisingly harsh, relative to the round. IMO, direct blowback 9mm's have more felt recoil than any AR-15 I have ever shot unless they are tuned correctly and even then the felt recoil is still more significant than AR-15s in most (if not all) configurations. It seems like it's mostly a combination of the nature of a direct blowback system and the weight of a 9mm bcg but there are effective ways to tame it to an extent.

Only in America with our thousands of options could so many panty waists cry about recoil of a 9mm in a 6 or 7 lb AR rifle or pistol.  We have threads here with people bragging about shooting elephant guns, and then threads crying about light recoil.   We are one seriously conflicted group here in GD.  

Otherwise, it was a lovely write up that I enjoyed reading.  

I modified my 9mm AR so that my light weight wife enjoyed shooting it more.   She still prefers shooting the Ruger PC more due to lower recoil.

This is NOT GD. I think that’s the point you and others are missing, some more so than others.

To break it down into bit sized baby pieces and spoon feed it to our less sophisticated members more simply, it is like myself and at least one other member above mentioned: It’s not that the recoil is violent, it’s that it is a lot relative to the round, especially compared to a rifle round like 5.56 which shoots softer and allows faster split times pretty much across the board in the exact same platform. If you can’t understand the concept at this point I’m not sure that it can be explained to you.

Believe it or not there is a reason all these big manufacturers are spending large amounts of money on platforms like the MPX, radially-delayed blowback and other similar concepts in order to smooth out 9mm PCC operating systems by reducing recoil and reciprocating mass. Direct blowback operating systems are not the ideal recoil system for rounds above a certain caliber/weight/charge.

Only in America with our thousands of educators do people still not read the original post, then post absolutely stupid shit.

also, this isn't GD

You may as well save your breath. The neanderthals clearly didn't read OP's post and they won't read or understand yours.

The concept of wanting to reduce felt recoil and muzzle flip in order to return to target faster is totally lost on them. Any attempts to explain will only be met with more bravado on how they used to hunt elephants with .458 WinMag and if you are tossed around by the puny 9mm, then you're drinking too many soy latte's.  LOL!!!!

The SUB-2000 is only 4 & 1/4 lbs.  Gave one to my step-daughter when she turned 18 so she'd have something she could carry in a purse, and even FW_wife's ex-husband mentioned the recoil to me.

Straight blowback is a safe operating system, however.  It handles squibs very well.

@backbencher

Check out tacticool products.  They have a buffer that does work to dampen recoil in the sub2k.  I had one in my sub9 and it made a big difference.

I'm no expert on 9mm brakes, but I know some people who are...  watch for a new thread...

@Eric802

I think I can go to Kel-Tec & just get the .40 S&W weight, which will slow things down, but it adds weight, and I bought the SUB as a carry rifle.

Holy cow, how big is her purse?!?  Even folded, those are pretty sizeable.

That's the only gun I ever owned that I never liked. Nothing wrong with it. It just didn't work for me, at all. Length of pull was too short. Never could get a cheek weld that allowed me to look through sights comfortably, can't mount red dot (unless canted) and still fold it.  It's also only one of two guns I ever sold.

Glad to hear that others like them. I loved the concept and ingenuity, and performance was great. It ate anything.

I shot a Makarov at a military range in commie China.  Gun shot 12" left.  Recoil was insignificant.  It was funny that nobody was hitting the target and I took the gun to find where it was hitting.  Damn thing was bent.

Significant recoil:

I shoot some PCC matches and have been reading a little on another competition forum and I think it was explained best there.  You want the least dot movement so 2 shots on paper will neutralize the target.  Hydraulic buffers, certain compensators, and 2 and 3 stage recoil systems like the taccom will reduce rearward felt recoil but now your muzzle is climbing up and your splits will be longer for the dot to return, so many competitors will short stroke the bolt and not run the heaviest solid buffers to achieve the least amount of dot movement and have fast split times by making sharp straight to the rear recoil and not slow and soft recoil that lifts the muzzle more.  And maybe I suck at explaining this

Multiple ways to mount red dots on a SUB - canted, folded, rotating forend, rotating mount, offset.  LOP is adjustable on the Gen 2s.  My flashlight mount is on the top rail, so I can't fold it all the way - but it still fits in my sling pack.

Wemin have those teeny tiny purses, I think they call em clutches, but they also have great big ones that look like shopping bags.  A SUB will fit in one of the bigger ones and no one will know it's there.

...and they use powder puff loads, too.

What you described makes sense.

Yeah...totally get that....Kynshot released another new hydraulic that also short strokes the action: https://www.kynshot.com/products/our-products/kynshot-rb5020ss-short-stroke-24/
This would meet the goals for most PCC shooters....
I know I'm in the minority here but I want a slow cyclic rate for full auto use which is not a concern of the PCC crowd.
Short stroking will increase the cyclic rate which I'm NOT trying to do.

yes, that would increase cyclic rate but i want 2 shots as close together as possible, most pcc shots are 10-20 yards and yes we shoot powder puff loads too!

Sigh - more Cowboy Action shooting...

This

^^^Needs bigger gap between “roller delayed blowback” MP5 and “blowback” Scorpion.

I was surprised to learn this was the case. Very counter-intuitive.

I've never shot a hydraulic buffer. I was pretty happy to see USPSA add a PCC division because that will lead to all kinds of cool stuff for everyone.


Probably a lot of the same people that get mad when actual experts call us out not realizing they are the cause.

Agree... no way MP5 and Scorpion are at the same level

Bad info graphic.