What's the real deal on bore axis?


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vanfunk
April 7, 2003, 08:20 PM
Hello fellow High Roaders!
For years I've contemplated the relevance of the much lamented "high bore axis" and, like many, found myself in search of the elusive "low rider". As my firearm affinity has waxed and waned and waxed again, I've wondered if anyone out there has ever had the time or inclination to measure the actual distance from the web of the hand to the bore centerline on the USA's most popular sidearms.

It is a commonly held belief that SIG Sauer handguns have a high bore axis and thus are more apt to exhibit muzzle flip than, say, Glocks of equal caliber. The Glock, as reflected in numerous postings, seemingly has the lowest bore axis of any modern handgun.

ANyone out there wanna run the numbers on these theories? For example, by sight, I can't see any difference in the bore axis of my SIG P220 as compared to my Colt Combat Commander with a high ride beavertail. Has anyone literally taken calipers to their pistols and measured the distance from web-of-hand to bore centerline?

I know I'm getting geeky here, but my theory (hardly original, I know) is that the weight of the weapon and grip shape have much more to do with recoil control than any supposed advantages offered to "high bore axis".

I'm looking for hard evidence here, with due process given to mass/vector/fulcrum dynamics. C'mon you engineers, you know who you are, have at it!:D

Thanks,
vanfunk

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Handy
April 7, 2003, 08:29 PM
Well, 1911s don't have any lower bore axis than a Sig, so there you go.

The Glock's is low, but not as low as a P7 or a Steyr M. Both of which have less muzzle flip.

A heavy framed gun with a higher axis may have about the same flip as a lower axis polymer gun. My steel Baby Eagle had less flip than my G19, for instance.

Ideally, light muzzle rise comes from a gun with a light slide, low bore (compared to the beavertail area that the gun rotates around) and a relatively heavy frame. The P7 is like that and has almost no muzzle flip.

blades67
April 7, 2003, 08:31 PM
The "high bore axis" excuse has been used to explain poor shooting so often, some folks have started to believe that it matters. :rolleyes:

bountyhunter
April 7, 2003, 08:33 PM
Don't forget: a plastic framed gun like a Glock is very top heavy, which tends to make it rotate more from recoil compared to a better balanced gun where the weight is more evenly distributed above and below the center of gravity. Bore axis is very important, but not the only factor in determining felt recoil. A good set of grips is probably the biggest thing to improve it.

Mylhouse
April 7, 2003, 08:39 PM
I'm actually with blades on this one.

vanfunk
April 7, 2003, 09:05 PM
Thank you for your posts, gentlemen.
Does anyone have any measurements available so that we might debunk this "high bore axis" phenomenon so bandied about in indictment of SIG's, et al?

What I'd really like to dispell is this insistence that the "high bore axis" of [insert offending pistol here] is responsible for horrendous controllability as compared to my [insert most recent pistol purchase here].

I guess I'm hoping that other, more wizened sages than myself can prove conclusively that bore axis has far less to do with recoil control than other factors such as weight, grip angle, and, er, um, ability:rolleyes:

Granted that we are dealing with the subjective when dealing with any aspect of perceived recoil assessment; I guess I'm always looking for a way to elevate the subjective to the sublime:p

Thanks,
vanfunk

blades67
April 7, 2003, 09:18 PM
I haven't tried measuring my P220 and Custom II with a micrometer, but I have compared them side by side.

My SIG Sauer P220 and my Kimber Custom II have the same bore centerline in relation to the bottom of the triggerguard where it meets the frontstrap of the gripframe. The P220 has the same grip profile as a 1911A1 (that means the round mainspring housing). In double action (trigger forward) the P220 has the longer trigger reach, but in single action (trigger back) the P220 has the shorter trigger reach as compared to the stock Kimber trigger.

Handy
April 7, 2003, 09:38 PM
Hey, I don't shoot lower bore pistols "better", but I have noticed being able to get their sights back on target and pull the trigger faster.

While some here might not believe it, I've owned seven different 9mms of every different kind of construction and the full range of bore heights. It does make a difference. It's obvious when you shoot them side by side.

I would still choose a pistol by several other factors first. And I do like my Sig.

vanfunk
April 7, 2003, 10:14 PM
Handy,
Thanks for your observations!
How's about a breakdown by weight of the pistols you've mentioned?

Too bad we have no legitimate way of measuring recoil, otherwise we could analyze the variance of pistol recoil according to bore axis, weight and grip angle.

Thanks,
vanfunk

blades67
April 7, 2003, 10:37 PM
The thing that's being missed when talking about Glock handguns having a lower bore axis is that they also have a larger grip angle which increases the shooter's leverage on the gun, reducing felt recoil.

garrettwc
April 7, 2003, 11:47 PM
Handy and Blades have made some very good points.

The high bore axis will affect follow up shots, so will shorter slide length, or lighter weight.

However, none of these is such a help or a hindrance that a shooter using good technique can't overcome them.

Too bad we have no legitimate way of measuring recoil, otherwise we could analyze the variance of pistol recoil according to bore axis, weight and grip angle.

vanfunk, I think I may have something you can use. It was given to me by Jim Higginbotham, a respected trainer, and also a member here I believe. Here's a quote from the test he developed:

As you likely know, defensive marksmanship consists of an equal balance of Accuracy, Speed and Power (no one is more important than the other). While not perfect, most people simply will not go to the range and perform complex drills. This simple test is offered as an easy to perform measure of marksmanship skill.....

.....This index is primarily meant for the user to compare different firearms/loads under identical circumstances.

I have it as a Microsoft Word doc. If you would like it email me and I can send you a copy.

agony
April 8, 2003, 12:58 AM
Something interesting I've discovered.....

When I shoot a SIG 220ST (heavier than the standard aluminum-framed 220) I have noticeably quicker recovery times than with the standard 220. I'm assuming therefore that weight at the muzzle has more to do with flip than other issues.

The bore axis is identical.

45auto
April 8, 2003, 02:21 PM
Perhaps one way to experiment on one gun is to try a 1911.
Shoot it with a low grip, thumbs down and then try it with a higher grip(if you have an extended beavertail) with your thumb on the safety.
I notice a big difference between the two, in so far as sight recovery and recoil sensation.

But, I have seen some pretty fast revolver shooters and they seem to have a much higher bore axis than autos, at least they appear that way.

Handy
April 8, 2003, 07:01 PM
Van,

Of the pistols I was thinking of, all in 9mm, their weights break down as follows. I couldn't find good numbers that I trust for weight, but this should be correct, high to low:

Baby Eagle (CZ clone) (2nd lowest total recoil)
P7 (most recoil)
P9S (lowest total recoil)
Browning BDM
Sig 225
G19

By muzzle flip, I would go in this order (Low to high):
P7
Baby Eagle/P9S (tie)
BDM
G19
225

Weight and bore height are both obvious factors. The P7 wins because of where the bore is in comparison to the gun's center of gravity. The Glock edged out the also light Sig due to the lower bore axis, but was not better than heavier guns with higher barrels.

All were good guns, but I got rid of the Eagle and the BDM as the others had qualities I liked more, muzzle flip aside.

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