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Sigma Frame Bulging

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Old 11-20-2009, 12:41 AM   #1
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Default Sigma Frame Bulging

I spent much of the day at Ammo Brothers in Cerritos CA today, doing my part to support National Ammo Day.

While there I played with bunches of guns. In one of the display cases they had a new S&W Sigma, 9mm.

A few months back I was discussing the Sigmas in a post here on FTF and mentioned one of the issues with the Sigmas back when they were first introduced (1990's) was the fact that the frame bulged when the trigger was squeezed. Some members said they have Sigmas and the frames do not bulge. I figured they had fixed the problem at S&W when they came out with the "new and improved" Sigma.

But the one I played with at Ammo Brothers today bulged when I dry fired it.

The place that they bulge is on the right side of the frame near the slide, maybe an inch behind the ejection port.

If you own a Sigma and want to check this, just make sure it is unloaded and look straight down at the top of the slide while SLOWY dry firing. You will see that as the trigger is squeezed, the frame will bulge on the right side. It is only about 1mm, but it does bulge.

Anyone else notice this?
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Old 11-20-2009, 03:00 AM   #2
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Frame bulging? Oh my!
“If ye love wealth better than liberty, the tranquility of servitude better than the animating contest of freedom, go home from us in peace. We ask not your counsels or arms. Crouch down and lick the hands which feed you. May your chains set lightly upon you, and may posterity forget that ye were our countrymen.”Samuel Adams
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Old 11-27-2009, 12:48 PM   #3
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Glocks do the same thing.
When you pull the trigger, it bendsthe metal transfer bar outward, therefore making the plastic side of the frame bulge out.
Take the slide off the frame and pull the trigger, you will see the little metal bar bending.
Actually the Sigma doesn't bulge out as much as the glock.

Last edited by General_lee; 11-27-2009 at 01:01 PM.
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Old 11-27-2009, 03:37 PM   #4
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So? It has nothing to do with a problem. The frame is a little flexible. You probably have never seen how much an alloy famed pistol flexes iin firing. Have you never seen the slow-mo video of an AK barrel whipping as the bullet is fired. Absolute rigidity comes with a steep price in $ and Lbs.
In life, strive to take the high road....It offers a better field of fire.
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Old 11-28-2009, 09:04 AM   #5
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Strength through flexibility.

Otherwise it cracks.
Gunpowder Addict For 40 Years Now
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