What Ultimately Determines Cylinder To Barrel Gap On 1st. Generation SSA?

[UtopiaTexasColt45]

I have finally been able to pull the stuck base pin from Great Grandpa's 1902 SSA after some soaking in PB Blaster. Upon polishing the base pin slightly to remove surface rust and finding it still would bind when inserting in the cylinder bushing, I inspected closer and found that the nose of the cylinder bushing was slightly deformed. I suppose this was from someone in the past hammering on the base pin while the cylinder was not centered in the frame to get it in all the way. Some light filing rounded out the cylinder bushing and the pin now slides in snugly by hand when oiled a bit. To familiarize my self with the pistol I have since found a schematic and totally dismantled the pistol, cleaned, lubed and re-assembled. I was measuring the cylinder to barrel gap and at first thought that the front lip on the cylinder bushing determined the air gap between the cylinder and barrel but noted that when 1/2 cocked there is slight fore and aft movement of the cylinder so the bushing must not be the determining factor in the air gap. After some more inspection I found that when the pistol was totally uncocked or totally cocked that the bolt rising up into the notch in the cylinder completely stabilized the cylinder where there was no fore or aft movement of the cylinder at all. Can I assume from this that the bolt actually determines the cylinder to barrel gap? Thanks...

[coltsixguns]

The bolt coming up might put some slight upward pressure on the cylinder, but you've also have the hand coming forward and pushing the cylinder forward as the revolver is fully cocked. If the cylinder bushing is a squeaky tight fit in the frame since you have a metal to metal fit the cylinder isn't going to be able to be pushed towards the throat of the barrel any further.

[UtopiaTexasColt45]

That makes perfect sense! I noted after partially assembling the pistol if I cocked the hammer all the way back without the cylinder in the frame the hand would travel too far up and forward and become stuck in the frame so it must put pressure on the rear side of the cylinder. By the way, do you know what the original cylinder to barrel gap range was supposed to be on the SSA?

[Blackjack33]

I believe I saw somewhere that factory tolerance was .006" but a gun mechanic would probably know for sure.

[swamprat]

Kuhnhausen states that for jacketed bullets bbl/cyl gap is .006, for lead bullets it is .008. The bushing is what will determine the gap if the bbl is screwed in the correct depth. The bushing should be as long as possible without binding on the front of the frame, to minimize fore & aft cylinder play.

[Jim Martin]

That makes perfect sense! I noted after partially assembling the pistol if I cocked the hammer all the way back without the cylinder in the frame the hand would travel too far up and forward and become stuck in the frame so it must put pressure on the rear side of the cylinder. By the way, do you know what the original cylinder to barrel gap range was supposed to be on the SSA?

The old colt spec.on the 1sts was .003 to .005 , .006 is excellent for an old gun that's seen some use.The base pin bushing DOES stabilize the bbl. cyl. gap which should always be measured w/the hammer @ full cock.The reason the hand gets stuck in the frame w/the cyl. out is because the left front of the hand below the secondary finger on the left front side of the hand should have a small bevel on it so that it doesn't catch on the milled hand slot in the frame.If you'll buy Jerry Kuhaussen's book The Colt SA Revolvers a Shop Manual Volumes 1 & 2 you'll find a more detailed description w/pictures of the modifications for the hand,I did them.When I set a SA up to be shot I always set the bbl. Cyl. gap @ .008 to allow for the fouling of the bbl. cyl gap when it builds up not to cause the cyl.to drag the bbl.

[Boge]

The old colt spec.on the 1sts was .003 to .005 , .006 is excellent for an old gun that's seen some use.The base pin bushing DOES stabilize the bbl. cyl. gap which should always be measured w/the hammer @ full cock.The reason the hand gets stuck in the frame w/the cyl. out is because the left front of the hand below the secondary finger on the left front side of the hand should have a small bevel on it so that it doesn't catch on the milled hand slot in the frame.If you'll buy Jerry Kuhaussen's book The Colt SA Revolvers a Shop Manual Volumes 1 & 2 you'll find a more detailed description w/pictures of the modifications for the hand,I did them.When I set a SA up to be shot I always set the bbl. Cyl. gap @ .008 to allow for the fouling of the bbl. cyl gap when it builds up not to cause the cyl.to drag the bbl.

Excellent point.


Colt first went to an integral bushing that regulated headspace AND prevented fouling from reaching the base pin on the '72 Open Top. The conversions did not have the integral gas "collar". As an historical side note, S&W had FOUR different lengths for their gas "collar" on their Model 3 as they lengthened it from the original length three different times to prevent cylinder binding from fouling.

On a personal note, I believe that the Colt '72 Open Top integral bushing was a better means to regulate headspace AND control fouling. So did the Mlitary as that model bested the Model "A" (SAA) in trial tests. However, the Military was dead set then on adopting a "strap" revolver and the rest is history.