Bore Axis

M

marine6680

New member
Got to thinking, and a little bored... so I took some measurements.

I took two types of measurements, as there is no standardized way to measure these things. Both measurements are taken from the centerline of the bore.

For the first... I picked the highest part of the web of my hand that could be said to be perpendicular to the ground when holding the pistol. Basically, the highest point of my hand that could be considered "gripping" the pistol. I then measured from where this point of my hand was located on the grip when holding the pistol properly. This measurement was a little tricky, and required several double/triple checks to ensure consistency.

For the second... I picked the highest point that my hand touched the pistol's beavertail, which represented the highest point my hand was in relation to the pistol. This point was even with the top of my thumb, when it was extended out parallel with the slide. This gave me a reference point on the frame that I could measure to.

Backstrap and beavertail designed made a big difference... some designs caused a large difference between the two ways of measuring.



So now for the measurements, they will be listed by pistol, then first measurement method, then second. I rounded up to the next .05, so a measurement of 1.03 would be 1.05, and 1.07 would be 1.1, I did this as measurements smaller than that were meaningless, due to the errors the measurement methods introduced. Those induced errors meant that I could measure the same pistol several times and get different readings within .05...

1911:--------1.3"----.9"
Sig 226:-----1.3"----1" (elite model with extended beavertail)
Sig 320 :----1.25----.85"
Glock 19 :---.9"-----.5"
CZ 75:-------1"-----.8"
H&K VP9:----.9"-----.65"
S&W M&P:---.8------.5"


Some observations.

The 1911 has as much bore axis height as a Sig 226... People love to complain about the 226 bore height, but rave about the 1911's... And it fires a harder recoiling round. Funny that...

The M&P had the lowest measurements for both methods and low deviation between them. The Glock was very close. Also, the M&P has a very long beavertail for a striker pistol.

The beaver tail is very flat on M&P, Glock (though a bit truncated), H&K, and CZ (which actually has a slight downward angle at the end). The other pistols had an upward rake to their beavertail, and they had larger deviations between the measurements as a result.

The CZ had the lowest deviation between the two measurement methods... Knowing how the CZ feels and behaves in recoil, I think I have hit on the true nature of what makes a pistol flat shooting...


The difference between the two points of measurement is key to a flat shooting pistol, the lower the deviation the better. These two points basically represent the top of your actual grip, and the highest point the beavertail rests against the top of the web of your hand. The beavertail helps spread out recoil to the web of your hand and helps limit the rotation of the pistol.

The smaller the deviation between these points, the less leverage there is between your grip, and the added support of the beavertail. This aids in controlling the torque of the recoil pulse.

The pistols with the flatter beavertails tend to get praised for how well they shoot and feel in recoil. The resulting lower deviations between the measurements, due to the flatter beavertail design, is a common factor for those pistols.

Thats my take on this, what do you guys think? I welcome other's opinions on this subject.
 
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Bore axis tends to be an inflammatory subject, however...

I had a Sig 220 a few years. It was very tall with lots of muzzle flip and I never did well with it in our matches. I had high hopes for the G21sf with it's super low axis but the darn grip angle...

My best times were with my 75bd. Straight back push, quick follow up shots. Same goes for my P01. Now my 97b has a fairly low axis but the barrel isn't parallel with the slide, resulting in an unnaturally high rear sight.

I would like to try an M&P 45 at some point. Our best match shooter uses one in 9mm and 3" double taps at ten yards are the norm with him. Scary fast.

I think 1911's are interesting but you're right, it's like sighting down a SAO revolver.:cool:
 
Interestingly for me, the CZ often touted as a king of the low bore-axis is not one of the lowest, but almost middle of the road.

I'd have been curious to see how the Steyr M9-A1 would have faired. LBA was one of their major selling points.

What about the Chiappa Rhino?!
 
The hammer fired pistols tend to run higher bore axis than striker fired.

For a hammer fired pistol, the CZ is very low.


I tend not to worry too much about the bore axis of a pistol. While I can feel a difference, it's not so great that I can't shoot well or not enjoy the pistol.
 
The position of the fingers under the trigger guard has quite an effect, too.
But the only semi-auto that had a high enough bore axis that seemed to be detrimental was the old, all steel S&Ws.
The ones that were of the Browning designs, more or less.
At least in their stock configurations.
 
Always nice to see actual data, and especially nice when there's an explanation of how it was obtained. Interesting, the Sig vs M&P data agrees perfectly with what I recall after measuring my P220 and my M&P 45...about a 1/2" difference.

Now, I can't recall any shooting I did in IDPA where I specifically said to myself, "Oh man, I can't get this thing back on target fast enough." The comparison for me would have been between an MP45 Compact and a Sig P220 Elite Stainless...mass difference alone would level out any differences in bore axis height, given I was shooting loads that would just cycle the gun with a very light after-market recoil spring.

But, what I did notice was some mysterious heaven-sent feel to the M&P, and there's no mistaking it when you find it. The Sig looked and felt tall in the saddle, and while the Glocks feel like they sit low, it's the M&P that feels right...for me.

Nice work--I am surprised a bit by the equivalence of the 1911 and the Sig. I don't recall that I ever measured the 1911, probably because I never shoot it (it's a ratty 1920's era Argentine Colt with crappy sights).

I haven't seen measurements, but some of the polymer pistols I see appear to sit very high--I think it's the XD/Ms I've been seeing that at least look to be very tall. I certainly wouldn't take a firearm out of the running because of this--it depends so much on what you want out of it. It's not much of a factor for me for any gun anymore, but definitely not a factor for 'range toys' in magnum calibers. These are shoot, relax, shoot scenarios--if the gun climbs 5 inches or 10 inches, it makes little difference--that water jug is still goin' down.
 
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I think we need a new term instead of "flat shooting". Ever since forever, the term has meant a gun or cartridge that has a low ("flat") trajectory at a given range. For example, "the .30-'06 is flat shooting, compared with the high arc of a .45-70 trajectory."

That is obviously not what the term means in this thread, so maybe a new term for a different concept?

Jim
 
True... But that is outside the purview of this thread.


I personally don't care much about bore axis. I can feel the differences in the pistols, but it does not bother me or cause issue.
 
Good write up marine6680 and thanks for taking the time to list some measurements. Bore axis is often misunderstood in several ways.

The first many tend think that a thin slide automatically makes the gun have a low bore height axis. A perfect example was given with the CZ vs the M&P. Funny how a model like the Walther PPQ is considered to have a high bore axis and the CZ 75 has a low one, even though the PPQ has a lower bore axis height. It's true that hammer guns tend to have higher bore axis compared to striker models. The height of the bore axis is the height of the bore axis regardless of firing mechanism though.

The second is that a low bore axis height gun automatically translates into a low muzzle flip/recoiling model. The height of the bore axis is only but one of the many aspects that influence the amount of muzzle flip/recoil a particular model will produce for each individual. So, you can have a model with a low bore axis that has more muzzle flip/recoil than one with a higher one because of the other factors are in favor of the higher one.

The current Steyr line has a very low bore axis. Lower than the Glock and M&P. The Steyr M and L series has very muzzle flip/recoil. It not just the very low bore axis that contributes to this. It's also the balance of the gun, position of the grip to the muzzle, and it great ergonomics.

I think in the latest Sphinx SDP post here I had a few models with their +/- dimensions compared to the Sphinx SDP as the baseline.
 
I personally don't care much about bore axis. I can feel the differences in the pistols, but it does not bother me or cause issue.
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I don't either. I think it's one of those things that folks on internet gunboards obsess about, that in the real world when you actually get out and shoot it, just don't matter. In my experience, and YMMV.

(I shoot and occasionally carry a gun regularly described as "topheavy", and in a chambering half the internet gunworld derides as "too snappy". I don't notice either.)
 
While I would like a low bore line/axes it doesn’t actually affect my choice of firearm much. I would imagine if the bore were in-line with the center of the palm many of us would be complaining of wrist joint pain eventually, straight backward impact.

Lets look at tactical rifles for a moment without the butt used or extended. The AR rifle would have a very high bore line compared to the AK. For many the AR has nicer ergonomics and esthetics than the AK yet the AK is highly functional.
 
Get a manly wrist and bore axis doesn't matter?
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One thing I always like to point out whenever bore axis is brought up is the physics involved. you know for every action and such. So while a higher bore axis gives the barrel more leverage to cause the muzzle to climb, the shorter lever on your part requires less movement of your hand to bring it back down.
So very much yes if you have enough hand/wrist strength bore axis wont matter.
 
So while a higher bore axis gives the barrel more leverage to cause the muzzle to climb, the shorter lever on your part requires less movement of your hand to bring it back down.
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:confused: Can you explain this shorter lever?
 
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