Hammer BlowBack


June 24, 2006, 01:44 PM
we have considerable experience with colt-type replicas that try to function in a semi-auto fashion. The back pressure coming through the nipple knocks the hammer partially back and begins to rotate the cylinder. this frequently interfers with smooth functioning. A couple of fixes sometimes eliminate the problem. A heavier mainspring or replacement nipples from Treso may fix it very well. Other times the problem persists no matter what.

Bates has a uberti 51 navy that resisted the first two fixes. He then observed that the cylinder begins to move with the slightest backward motion of the hammer. He relived the radius on the "ear" of the locking bolt to delay contact with the hammer cam. Now the hammer will move back a little bit before engaging the cam and unlocking the cylinder for rotation. This is something that does not require much metal removal and can undoubtedly get screwed up if you go to far.

the hammer is still coming back a bit at each shot but the cylinder remains locked until he manually cocks the hammer. Very smooth functioning revolver now.

the area marked cam release

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June 25, 2006, 12:20 AM
Tha BOSS jus posted sometin on MAKIN a colt army into a full auto gun. Wasnt intended, worn tubes an big loads, he opened tha tubes up ta point tha thing would BURP out tha whole cylinder.

Parts breakage was high an he said at face level shootin it ya wanted real serious a face shield!

June 25, 2006, 07:18 PM
I've heard of them going to full cock -particularly antique with shot out nipples and I believe I remember a old 1960s brass frame going to half cock. Full auto would be nice though.

June 25, 2006, 07:31 PM
Remind tha BOSS next time ya talk, he'll tell ya how.

Old Fuff
June 25, 2006, 11:42 PM
Some of the first reproductions came with nipples (sometime called "cones") with the holed drilled straight through. On one such 1851 Navy I substituted a modern (read that to mean lightened) Colt S.A.A. mainspring and got an unexpected surprise. :eek:

As mec noted, bolt timing and the bolt's ball engagement in the cylinder notches can be very important. Some folks cut down the step at the front of the bolt to increase ball engagement in the cylinder notch, and this in turn lowers the tail end and causes the bolt to start dropping early. If you work on one end of the bolt you'll probably have to work on the other end too.

Jim K
July 4, 2006, 01:21 PM
Anyone think to check cylinder end shake? On a modern cartridge gun pressure drives the cartridge case back against the recoil shield. But on a percussion revolver with some cylinder end shake, the whole cylinder is pushed back. That movement can act like a short stroke piston (ala M1 carbine) and drive the hammer back.

The answer is to reduce end shake and also to make sure the hammer will not contact the nipples when there is no cap in place.


July 5, 2006, 08:27 AM
Time to replace the nipples when ya get enough blow back to cock the hammer .. your flash holes have done gotten to large in the old nipples .. not good on the gun to keep fireing it that way .. had a side lock doing that during a match shoot and i kept shooting and finally the hammer blowing back had enough force to break the sear in the lock .

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