high/low bore axis

[Mr_Monkeywrench]

Thanks for the breakdown. I get the physics involved so the general consensus is that the pistol with the lowest bore axis is the most ideal?

[zfields]

Thanks for the breakdown. I get the physics involved so the general consensus is that the pistol with the lowest bore axis is the most ideal?

No.

General consensus is shoot a bunch of guns, and get what is comfortable.

[tbc]

the general consensus is that the pistol with the lowest bore axis is the most ideal?

Well, there are other factors that contribute to the level of muzzle flip. Caliber, barrel length, weight, design...i.e. Comparing a G26 (low bore axis) to a Sig p226 9mm(high bore axis). The p226 would be more ideal. My two cents of course.

[NewbieDave]

When comparing bore-axis... 9mm may not be the best example since recoil is not that bad to start with. You can feel the difference more... let say in a 45. Go shoot a 1911 and a FNP45, you can actually feel and see the difference.

The FNP45 has one of the lowest bore-axis I've experienced and shoots pretty flat. While the recoil pulse is still heavy, the flat shooter allows for better follow-up.

[pipboy]

Fellow members have done a great job explaining the bore axis concept. I'm surprised this has not been referenced yet...



Essentially a lower bore axis allows the shooter to mitigate the recoil impulse in a more rearward direction as opposed to an upward motion (aka muzzle flip). Less upward flip=less time to get back on your sights for the next shot.

[MikeDre]

Lower bored guns should be less "snappy" and more of a solid push back because of where the force from the bullet accelerating (and in turn impulse) gets applied in relation to your hand. The higher bore axis creates a greater angular momentum and lower linear momentum than the lower bore axis which creates less angular momentum and more linear momentum due to the impulse acting closer to the hand. (This is assuming that the guns both have the same mass moment of inertia which is a function of the design of the gun)

Think about someone punching a board pinned at the center so it can't spin nor move backwards. The person who punches at the top of the board will cause the board to want to rotate more than the person who punches where the pin is at the center which will cause the bard to want to move backwards.

I was thinking about this more last night. I came to the conclusion that bore axis is actually not a huge deal because the impulse from the bullet accelerating is only acting on the slide which is sent mostly straight back and is independent of the receiver essentially until its all the way back and kicks the gun. As the slide is sent backwards, it is exerting a force which sent to the receiver through the recoil spring/guide rod to the receiver where they connect until the slide hits its rear end of motion and causes the most rotational momentum as it creates the kick and impulse where it finally connects with the receiver.

So my thought is that the bore axis does have an impact, but is a much lower impact on the snappyness than the slide C.O.M. height/slide to receiver connection height.

I could be wrong with this buts that's my analysis for now. Maybe someone wants to do some FBD's

[Turo]

I was thinking about this more last night. I came to the conclusion that bore axis is actually not a huge deal because the impulse from the bullet accelerating is only acting on the slide which is sent mostly straight back and is independent of the receiver essentially until its all the way back and kicks the gun. As the slide is sent backwards, it is exerting a force which sent to the receiver through the recoil spring/guide rod to the receiver where they connect until the slide hits its rear end of motion and causes the most rotational momentum as it creates the kick and impulse where it finally connects with the receiver.

So my thought is that the bore axis does have an impact, but is a much lower impact on the snappyness than the slide C.O.M. height/slide to receiver connection height.

I could be wrong with this buts that's my analysis for now. Maybe someone wants to do some FBD's

Except most of the recoil isn't caused by the slide moving back. It's caused by the expanding gasses pushing back against the breech face, along the axis of the bore.

What people call "snappy" recoil is caused almost exclusively by the bullet leaving and pushing along the bore axis. The movement of the slide is nearly non-existent.

[cfusionpm]

Glock= low
XD= high

Which is weird because the percieved recoil of the Glock feels a more than my XDM, and significantly more than my 2022; despite both having a higher bore axis. Overall weight and grip play a lot, and as far as I can tell, the difference in muzzle flip is negligible with a good firm grip.

[MikeDre]

Except most of the recoil isn't caused by the slide moving back. It's caused by the expanding gasses pushing back against the breech face, along the axis of the bore.

What people call "snappy" recoil is caused almost exclusively by the bullet leaving and pushing along the bore axis. The movement of the slide is nearly non-existent.

So your take is that most of the recoil is occurring before the slide is pushed fully backwards?

My thinking and watching of a couple low budget slow mo recoil's is that the muzzle flip mostly occurs when the slide is almost fully back. The slide has to translate its forces to the receiver for the receiver to feel anything and that force must go through the recoil spring/guide rod it seems.

I could also be confusing the term "snappy"

[Turo]

So your take is that most of the recoil is occurring before the slide is pushed fully backwards?

My thinking and watching of a couple low budget slow mo recoil's is that the muzzle flip mostly occurs when the slide is almost fully back. The slide has to translate its forces to the receiver for the receiver to feel anything and that force must go through the recoil spring/guide rod it seems.

I could also be confusing the term "snappy"

Yep. The bullet leaves the gun before the slide unlocks and the recoil impulse can only be caused by the opposite reaction of the bullet leaving. The slide does absorb some of that, which lets it cycle and come back, but most of the felt recoil is transferred directly from the barrel to the frame, and ultimately to the hand.

Next time you take apart your M&P, check out the locking lugs on the bottom of the barrel, and where they contact the locking block on the frame. That's where most of the force from the bullet is being transferred, not from the end of the slide's travel.

[elSquid]

Except most of the recoil isn't caused by the slide moving back. It's caused by the expanding gasses pushing back against the breech face, along the axis of the bore.

What people call "snappy" recoil is caused almost exclusively by the bullet leaving and pushing along the bore axis. The movement of the slide is nearly non-existent.

Take a gun where the slide is free to recoil completely off the frame: no locking logs on the barrel, no recoil spring assembly, front of the slide machined appropriately. When the gun is fired, you won't feel any recoil - the slide will experience an impulse, and will travel rearward and off the frame. Bore axis no affect.

And that's MikeDre's point - with a normal pistol, the force to the frame is applied along the recoil/spring guide rod.

-- Michael

[bohoki]

this is a good example of extremely low bore axis it should feel like straight back shove

the bore is another name for the barrel the axis is its angle and distance compared to its handle

when the slide reaches its rearward position the mass transfer to the handle causes the front of the gun to rise which can be used as an advantage if you want to strafe some bangers with a tec-9 you hold it sideways and knuckles up you strafe to the left

low bore axis is not a new concept

[Turo]

Take a gun where the slide is free to recoil completely off the frame: no locking logs on the barrel, no recoil spring assembly, front of the slide machined appropriately. When the gun is fired, you won't feel any recoil - the slide will experience an impulse, and will travel rearward and off the frame. Bore axis no affect.

And that's MikeDre's point - with a normal pistol, the force to the frame is applied along the recoil/spring guide rod.

-- Michael

The bolded part would be why there's no transfer of momentum from bullet to frame. The recoil in a semi-automatic occurs for the same reason it happens in a revolver. The only difference is that in a semi-automatic, a small amount of the recoil impulse is bled off to move the slide. The expanding gas imparts an impulse onto the barrel, the barrel lugs transfer it to the locking block, and the locking block transfers it to the frame.

Bore axis absolutely has an effect, and most of the recoil in a semi-automatic is caused by the barrel pushing on the frame, not the slide hitting the frame.

[elSquid]

The bolded part would be why there's no transfer of momentum from bullet to frame. The recoil in a semi-automatic occurs for the same reason it happens in a revolver. The only difference is that in a semi-automatic, a small amount of the recoil impulse is bled off to move the slide. The expanding gas imparts an impulse onto the barrel, the barrel lugs transfer it to the locking block, and the locking block transfers it to the frame.

How does expanding gas impart an impulse to the barrel? Does a fixed barrel gun - like a H&K P7 - therefore not have any recoil?

At combustion, pressure is uniform. If you draw force vectors, you have balanced vectors radiating outwards on the barrel, and vectors against the base of the bullet and the base of the case/breechface. This pressure exists only as long as the bullet is in the barrel - once it leaves the pressure, and the associated forces, drop to zero.

What this means is that the breechface receives an impulse. Because the mass of the slide/barrel/etc is much greater than that of the bullet, it accelerates at a lower rate. But it does accelerate, and when the pressure drops, it has inertia.

The barrel and slide are locked together at ignition. As the slide recoils, it drags the barrel along with it. What the locking block does is unlock the barrel. At a certain point in the rearward travel, the block and the lugs come into contact, and the rear of the barrel is pulled down, unlocking the action.

Now the barrel does impart an impulse to the locking block when it is forced to stop, but keep in mind that the mass of the slide is much greater than that of the barrel...

Bore axis absolutely has an effect, and most of the recoil in a semi-automatic is caused by the barrel pushing on the frame, not the slide hitting the frame.

So fixed barrel guns don't recoil? H&K P7, HiPoint, Walther PPKs, etc...

-- Michael

[RT13]

Some high bore axis guns ate HK USP's, Sig Sauers, and SA XD.

Some low bore axis guns are GlockStore, S&W M&P, and CZ.