45 GAP Boberg?
Since 10% of the State Police agencies in the US are now carrying sidearms chambered in 45 GAP - and I expect numerous other law enforcement agencies at the local and county level (since Glock is making a change to the cartridge/firearm model very attractive) -- how about a Boberg pocket pistol chambered in 45 GAP?
I know -- I was a staunch "who needs it, the 45 ACP is fine" guys...before I shot a Glock G39.
The OAL of the 45 GAP catridge is actually slightly shorter than the 9mm Para -- so the design and overall footprint of the pistol would involve few changes. The pressure of the cartridge is no issue.
Since I will be carrying a Glock G37 Gen 4 as a duty sidearm occasionaly in the near future, I would very much like to have a true pocket sized pistol in 45 GAP for a back-up. I like my G39s as CCWs for IWB carry -- but if Arne could do something in 45 GAP in comparison to the Glock G39 as he has been able to do with the XR9 in comparison to the Glock G26, I'll put a pre-order request in RIGHT NOW for one!
Arne -- seriously, give the 45 GAP some thought!
Thanks,
Bill
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Replies to This Discussion
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Permalink Reply by LASZLO DIGIOIA on -
Yeah; speaking of recoil springs, ovate springs (oval wired) offer more travel before reaching coil bind. I think they're also called "beehive" springs.
Springs can be made shorter in OAL, or narrower in diameter.
Is there a performance advantage for recoil springs having a linear rate vs progressive?
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Permalink Reply by Arne Boberg on -
What you have with .40 is a heavier bullet and very high pressure, which will lead to very high slide acceleration. I'm not as worried about .45 since the pressures are lower. i won't know for sure how well a .40 will work until I test it.
Ed said:Now I am confused. The SAAMI pressure caused by the .40 S&W should not exceed 35,000 psi, same as the 9mm Luger. The 9mm Luger +P maxes out at 38,500 psi, 10% more than a .40 S&W. The force exerted by the ,40 S&W in 135 gr. - 180 gr, loads, as quantified by the muzzle energy, is less than both a 200gr. .45 GAP and .45 ACP +P load at 23,000 psi pressure. With the increase in bore diameter from .357" to .40", with the barrel wall thickness kept the same, the mass of the barrel and correspondingly the slide should also increase, offsetting the increased force. Shortening the barrel and slide length would decrease the mass, but the shorter barrel would also impart less force in muzzle energy.
Arne Boberg said:As far as a .40 caliber model, I am a little bit concerned about the high pressure of the cartridge and slide acceleration. I will most likely need to do some development work to find a way to slow the slide acceleration down. Any improvements I discover will allow use of higher-powered cartridges, such as 10mm Auto, .41 Magnum and .44 Magnum. Inevitably, I would like to have a sub-compact pistol with the power of the Desert Eagle pistol. Right now, I kind of like the idea of this huge bullet (.45) coming out of such a small pistol, with roughly the footprint of some pocket-sized .380 pistols.
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Permalink Reply by Arne Boberg on
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Oval-wired springs probably wouldn't help if you are limited in both length and diameter - round wired springs are the optimal for that. As far as progressive (or non-linear) rates - I'm not sure how you would make a spring do that unless it is a conical spring with coils being "put to rest" or conventional springs operating through some type of mechanical linkage. If there were a simple way to have a spring be non-linear, I'm sure it would be very useful. One example of non-linear spring being desirable is the compound bow - pulleys and cams maximize the stored energy while providing a let-off at the end of the draw.
LASZLO DIGIOIA said:Yeah; speaking of recoil springs, ovate springs (oval wired) offer more travel before reaching coil bind. I think they're also called "beehive" springs.
Springs can be made shorter in OAL, or narrower in diameter.
Is there a performance advantage for recoil springs having a linear rate vs progressive?
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Permalink Reply by alienbogey on -
Unless I'm misunderstanding linear versus non-linear spring rates I just ordered some non-linear rate recoil springs from Brownells for my 1911. Quoting Brownells:
Variable rate springs function correctly with a wider range of loads than fixed rate springs can. Rate increases as spring is compressed; gives greater protection against frame battering, more consistent lockup and improved feeding, while allowing easier manual cycling of the action.
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Permalink Reply by Arne Boberg on
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OK - I see that they are varying the coil pitch. This spring has the coils on the left coming to rest before the ones on the right. Properly designed, the ones on the right never touch each other since that kind of pitch stacking up can lead to fatigue and shortened life. If I had the linear space, I'd probably consider such a design.
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Permalink Reply by Jose A. Montalvo on -
This is exciting...I like to think that were helping with the design by pointing things out to Mr. Boberg that he can consider for the design.
One thing though. I thought I read that the extractor or ejector spring was done away with. Was a workaround implemented, or is that in the back burner until more pressing design issues are addressed?
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Permalink Reply by Arne Boberg on
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Good catch - the ejector spring has been done away with in the .45 Micro. The way the ejector currently works is that a spring forces it in the way of the empty case, but a cam moves it out of the way. Years ago, I discovered that the ejector spring was not enough force in some cases, where the recoil caused the ejector to swing out of the way, missing the empty case, causing failure to eject. So I added an "outrigger" to the ejector so it is supported on the slide rail until the last instant, where the slide rail is milled away to allow room for the ejector to swing freely out of the way of a rising cartridge. Realizing that I might need extra slide stroke and/or recoil spring space in future guns that might be shorter, or a higher caliber, I ran an experiment that removed the ejector spring entirely. I knew that it wouldn't work well without it, so I turned the slide rail into an "outrigger cam" that "flings" the ejector into the path of the spent case at the last moment. It works just fine during firing. The only tradeoff is that if you are trying to manually eject live rounds, you either have to pull the slide back very fast (which you should do anyway), or tip the gun on its right side to make sure gravity gets the ejector into position.
I'm not removing the Extractor spring - it is essential not only for feeding, but also extracting from the chamber, so it will remain.
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Permalink Reply by Robert K. Stoddard on
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Quoting from Alienbogey's msg. yesterday:
"Quoting Brownells:
Variable rate springs function correctly with a wider range of loads than fixed rate springs can. Rate increases as spring is compressed; gives greater protection against frame battering, more consistent lockup and improved feeding, while allowing easier manual cycling of the action."
This sounds very good on paper-- more ability to accept wide ranges of loads while maintaining reliable cycling. Is it certain that the variable-rate spring requires more linear space than a fixed-rate spring, Arne? RKS
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Permalink Reply by Arne Boberg on
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I've been thinking about this type of spring for a few hours now. I can see two advantages: one, the longer-pitched coils on the muzzle end send the recoil impulse toward the back (closely-spaced coils) making the overall compression more even. Otherwise, for evenly spaced coils, the coils at the front would move first, then send a wave down to the other end, but not before the slide has reached the end, so the front coils would be more highly stressed. The variable rate spring would spread out this stress more, increasing spring life. And two, the force at the end of the stroke would be higher, when the closer coils are already stacked, the farther coils, being stiffer, compress at the end. This is not a true rear buffer, since a buffer is supposed to dissipate energy, but it probably reduces impact force of the slide by a slight amount. I disagree with Brownell's assertion about easier manual cycling - you have to pull a lot harder at the end of the stroke once the soft end of the spring has stacked up.
If I used this type of spring in the XR9-S pistol, it would probably have to be longer - but there is no room left. The equally-spaced coils on the current slide spring compress almost to solid height. Also, if I had a variable rate spring in there, the force at the end (battery position) of the slide stroke would be less, which is unacceptable since we need the extra force to make sure the tongs snap over the cartridge. The XR9-S already has a true buffer in the back (in all but the last shot) when the cartridge lifts and rubs against the breech face - a buffer that will never wear out due to the energy being dissipated in the cartridge.
As a side note - the mainspring (hammer spring) in the XR9-S pistol has a varied coil diameter to help distribute load to increase life. It technically isn't "variable rate" since it is one piece of wire and is an extension spring - all coils are hanging free at all times - no coils are put to rest at any time like the Brownell's spring.
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Permalink Reply by patrat84 on
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I think the supposed advantage of the progressive spring occurs in the over travel built into many actions. The spring exerts a force similar to original design when locked, and through a full normal cycle with minimum power loads. With higher power loads, the spring force progressively increases during the overtravel, taking up the excess energy before the slide is able to hit hard stop.
I could see it working very well in a long travel blowback action, like say the keltec sub2k.
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