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Old 04-10-2010, 05:06 PM
rhmc24 rhmc24 is offline
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.44 DA Top Break - Fix for BC Gap .44 DA Top Break - Fix for BC Gap .44 DA Top Break - Fix for BC Gap .44 DA Top Break - Fix for BC Gap .44 DA Top Break - Fix for BC Gap  
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Default .44 DA Top Break - Fix for BC Gap

People who claim long time experience say that enlarged BC gap (bbl-cyl gap) is caused mostly by erosion from black powder acting on the barrel entry and cylinder. Frame stretch is claimed by some to be the cause. I doubt it from measurements I have taken. Also frame stretch would load the top break latch area which does not exist in my experience. Wear in the contact area of the ejector star button to the receiver can cause increased BC gap. Fore and aft play in the cylinder is seen in either/both BC gap and headspace.

Here is factual info from experience using my .44-40 DA Top Break. It fixes BC gap and maintains correct headspace. Tools used were micrometer, feelerguage and dial indicator.

To begin with the BC gap was max at .018" when the fore & aft slop of the cylinder was taken up and headspace was zero with a cartridge loaded. I put in a spacer of .014 between the lower side of the ejector star and the cylinder. That gave a BC gap of .007 and headspace of .003" with the cartridge loaded - pretty much ideal.

The abovementioned spacer reduced the cylinder end play to .003" without cartridge loaded. Take note that movement of the cylinder rearward is controlled by the button in the center of the star interfacing the frame (recoil shield). Further, the action of the spacer vis-a-vis CB gap can also be obtained by lengthening the aforemenationed ejector button by the desired amount. Chicoine in his book "Gunsmithing Old West Guns" reccos drilling-threading and inserting a screw. He mentions that it leaves the headspace increased and in max cases the firing pin may some attention.

With above success I made a washer .015" thick from sheet metal and installed it around the hex rod that pushes the ejector star. It works perfectly mechanically with ammo I have available. I will do a firing test as soon as I can find some 44-40 cowboy. To be continued -----
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Old 04-10-2010, 05:54 PM
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cgt4570 cgt4570 is offline
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.44 DA Top Break - Fix for BC Gap .44 DA Top Break - Fix for BC Gap .44 DA Top Break - Fix for BC Gap .44 DA Top Break - Fix for BC Gap .44 DA Top Break - Fix for BC Gap  
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I had Dave work his magic on two of mine. Not sure about his methods, but it worked great.
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Old 04-11-2010, 09:23 AM
dangt dangt is offline
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.44 DA Top Break - Fix for BC Gap .44 DA Top Break - Fix for BC Gap  
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Default Also same repair

I performed a similar repair to my No. 3 New Model about 35 years ago when I was doing quite a bit of shooting with it. I did not make the shim star shaped to conform to the extractor arms/ends but simply used a round washer of appropriate shim stock. I worried a little about the unsupported end points of the extractor but nothing ever seemed to stress them. It tightened up end play and barrel-cylinder gap just fine.

Dan T.
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Old 04-14-2010, 10:21 AM
rhmc24 rhmc24 is offline
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.44 DA Top Break - Fix for BC Gap .44 DA Top Break - Fix for BC Gap .44 DA Top Break - Fix for BC Gap .44 DA Top Break - Fix for BC Gap .44 DA Top Break - Fix for BC Gap  
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BC Gap Fix

I just made a simple washer out of .015" stock, hole to accept star shaft with OD to give clearance at cyl bores. I reasoned that the unsupported ejector ends don't matter. Firing gas expansion pushes the cartridge head against the frame, against the bullet and against the walls of the case - rather than against the ejector.
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