High axis bore? Sigs and HKs.


Dr. Loomis
December 9, 2009, 09:53 PM
I have a question for my fellow gun enthusiasts: what does high axis bore mean? I usually here it in reference to Sigs and HKs. On another website one man said he hated the high axis bore on Sigs and HK USPs compared to Glocks which he loved. I've held all three weapons and fired all but the HK and find their feel similar. Please help a brother patriot with this question. Thanks. :confused:

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Larry Ashcraft
December 9, 2009, 10:15 PM
I usually here it in reference to Sigs and HKs.
:confused: What exactly are you trying to say, or ask?

December 9, 2009, 10:26 PM
They are talking about how high the bore sits on the frame of the gun. The higher it is, the more pistol whip you will feel, because of the way the recoil travels. A lower bore axis transfers the recoil closer to the hands, instead of above the hands.

Sorry probably not the best explanation.

chris in va
December 9, 2009, 10:46 PM
what does high axis bore mean?

Seems like a clear question to me.

Here's a comparison of high and low bore axis. Don't critique the picture too hard, it's the best I could do. The trigger faces are lined up exactly with one another from the side. Despite the Sig being a 45 and the CZ a 9, you can still see the difference in bore axis.

http://img46.imageshack.us/img46/1353/imgp4871.jpg (http://img46.imageshack.us/i/imgp4871.jpg/)

Dr. Loomis
December 9, 2009, 11:21 PM
Larry Ashcroft, you quoted a statement I made then asked "what exactly are you trying to say, or ask?" When in doubt look for the question mark. I clearly asked, "What does high axis bore mean?" At least chris in va and SsevenN understood my question.

December 9, 2009, 11:53 PM
an even simpler way to think of bore axis in terms of a handgun is to imagine a thin line entering the muzzle and staying centered in the barrel all the way through to the back of the slide. Now, when you hold the gun, where is your hand in relation to this line? The lower that our hand sits below this line, the more muzzle flip you will experience (given two identical firearms only differing in location of the bore axis. Yes, not ideal, but from a scientific standpoint it makes sense).

The cause of rotation of any object is called a "moment". The greater the moment, the more rotational force. How does this relate to handguns? If you mark the spot where the center of your hand is located on each grip, and measure the distance between that point and the bore axis (while maintaining a 90 degree angle between bore axis and the line leading to your reference point on the grip), and multiply that length by the force generated by the cartridge being fired, that is the rotational moment experienced about the center of your hand.

So if you REALLY wanted to get into "bore axis" and choose one that was low or high, you could draw a free body diagram of each gun, noting the location of its center of mass, drawing all the forces present when a cartridge is fired and the force due to gravity and calculate the moment about your reference point on the grip from all forces present.

Arguing solely about a high bore axis of a particular gun such as a Sig (aluminum frame, steel slide) and saying that a gun with a lower bore axis such as a Glock will have lower recoil because of the bore axis location is a flawed argument. They fail to take into account all forces on the gun. The Sig's heavier weight will cause a rotational moment opposite of the moment from the cartridge fired, which can be greater or lesser depending on the overall length of the gun. The Glock has a lower bore axis to counter the lower rotational moment due to it's weight by lowering the value of the rotational moment due to firing the gun. Since most people don't really think about all of this, unless they're designing a firearm themselves, you're probably best served shooting both and seeing which one is more manageable.

That's your engineering science lesson for the day, boys and girls.

Dr. Loomis
December 10, 2009, 12:21 AM
Wow. That was... very imformative. And deep. Just how I like things explained. Thank you. :)

David E
December 10, 2009, 12:48 AM
In general terms, the higher bore axis means it'll rotate more in the hand(s) and therefore take longer to come back on target. This translates to slower shot-to-shot speed.

The high bore axis may be more pleasant to shoot, however, if speed of multiple shots do not matter.

December 10, 2009, 02:00 AM
I don't think the bore axis height matters much. My Sig SP2022 .40 has less felt recoil than my Glock 19 did. Also, the other day at the range I noticed that my friend's XD40 seemed to have more felt recoil than both my SP2022 and my USP .40 Compact. It's almost as if these pistols with a low bore axis shock your whole arm in a bad way rather than allowing the gun to roll back smoothly and drop back down on target. But at the same time my Glock 19 was able to rip shots off pretty quickly. Same goes for my Walther P99 A/S, which also had a very low bore axis.

I think in the end it shouldn't be a deciding factor when choosing a handgun. There are many other factors that affect a pistol's recoil impulse and overall shooting characteristics besides the height of the bore. On that note, I like the bore height of my P2000sk. It's right in between the extremely low bore axis of a Glock and the rather tall bore axis of a Sig. Makes for a good balance of speed and smooth recoil. Just my 2 cents.

December 11, 2009, 10:55 AM
Bore axis DOES matter if there isn't more weight to compensate for a higher bore axis. It's force dynamics. Granted, there are definitely more important things to consider when buying a handgun, like reliability, durability, and capacity. But if you're looking at it from a controllability standpoint, bore axis and weight mean a lot. With .40 and 9mm guns though, the recoil should be plenty manageable regardless of bore axis unless you have a girly grip/arms. Not that I mean anything derogatory towards women-If I was rolling around in the sack with a woman who could crush golfballs with their fists and win a world champion arm wrestling competition, I'd be feel uneasy.

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