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Cylinder center pin spring trimming


paul788

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Randy Lee

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Hi Guys,

Just a quick note- if you cut either the center pin or extractor springs, be sure to close the open end. The open end can cause excess drag and scoring/wear in the inside of the yoke or worse become unseated and tie up the cylinder when you least expect it.

After finding this I thought "if it's good enough for Randy to do".

 

Paul

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he might of been talking about a gun that locks up on the with the ejector rod. The 929 locks up at the front of the yoke onto the barrel lug with a large detent. From the factory it's a very stiff lockup, I'd carefully file away a small amount of material ( on the detent exit surface ) and polish it up to make opening the cylinder easier. 

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Thanks Alec.  This is advice that is useful.  I'll try that later today.  I had been storing the gun slightly open to keep pressure on the ball spring to see if that would decrease the spring tension.

 

Paul

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I still think you're crazy. We run our guns quickly. The hand on a Smith turns the cylinder counterclockwise, which tries to push the cylinder out of the frame. You want to lighten the ball detent so you can have a slightly faster table start? I think that's asking for trouble down the road.

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The original reason to trim the cylinder bolt spring is to minimize the forward push of the bolt against the cylinder, thus allowing it to turn easier. That is not the right answer to that problem. The real way to take that pressure off the cylinder is to take material off the back of the thumb latch where it stops in the slot in the frame at the rear. The forward pressure on the cylinder comes from the much stronger center pin spring pushing the center pin into the front of the cylinder bolt. By making it so that there is a little more rearward travel of the bolt, the center pin can go all the way rearward, and the only pressure on the center pin is the bolt spring and plunger, which is very light, and not an issue. If the thumb latch can be moved a little bit further back from where the center pin pushes it when you close the cylinder, the goal has been met.

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On 1/27/2018 at 5:27 AM, PatJones said:

I still think you're crazy. We run our guns quickly. The hand on a Smith turns the cylinder counterclockwise, which tries to push the cylinder out of the frame. You want to lighten the ball detent so you can have a slightly faster table start? I think that's asking for trouble down the road.

 

The 929s that won iron and open at the steel challenge, and the overall IRC had no lockup other than the center pin. No detent. The cylinder won't open up, at high or low speed. 

 

They have detents for this season, but only because of the notable accuracy increase. 

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17 hours ago, Toolguy said:

The original reason to trim the cylinder bolt spring is to minimize the forward push of the bolt against the cylinder, thus allowing it to turn easier. That is not the right answer to that problem. The real way to take that pressure off the cylinder is to take material off the back of the thumb latch where it stops in the slot in the frame at the rear. The forward pressure on the cylinder comes from the much stronger center pin spring pushing the center pin into the front of the cylinder bolt. By making it so that there is a little more rearward travel of the bolt, the center pin can go all the way rearward, and the only pressure on the center pin is the bolt spring and plunger, which is very light, and not an issue. If the thumb latch can be moved a little bit further back from where the center pin pushes it when you close the cylinder, the goal has been met.

I all ways cut the back of the cylinder release latch for this reason. When I do a action job on a IDPA gun I leave the tail on the hammer when bobbing it so it will pass safety check(checking to see if gun will cycle with cylinder open) and this requires the small spring that pushes the bolt forward to be functional to block the hammer. On a USPSA gun with the hammer tail removed I don't put the small bolt spring back in as it serves no purpose with the hammer tail removed.

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OP Alec was right about the ball detent probably being the problem. Another thing to check is the bolt face that pushes the centerpin. I have seen some lately from the factory that have been short, making the cylinder hard to open. With cylinder open and cylinder release pushed forward as far as you can the face of the bolt should be flush or very, very, very, slightly below the face of the recoil shield. I would guess(since I never measured it) that anything over .010-.015 will make the cylinder hard to open. I have had a couple that were bad enough that I just replaced the bolt and several I "adjusted" and it took care of the problem.

Something easy to check and make sure it isn't the problem.

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Bosshoss

I did remove a fair amount from the frame contact area of the bolt to get it to flush with the face.  This helped a lot with the opening.  I will try Alec's suggestion of changing the angle on the detent v-notch. 

Thanks

Paul

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9 hours ago, paul788 said:

Bosshoss

I did remove a fair amount from the frame contact area of the bolt to get it to flush with the face.  This helped a lot with the opening.  I will try Alec's suggestion of changing the angle on the detent v-notch. 

Thanks

Paul

Pain in the butt working that bolt face isn't it.:D

 

When working the detent notch, just to clarify, you need to remove the metal from the flat surface on the notch part of the barrel that is parallel to the front of the cylinder face. Not the angle part of the notch. Just take a file and keep that surface as flat as you can and take a little off of it, this is stainless and is fairly soft so check often and don't go to fast it won't take much to get it easier to open but you can't put it back if you take to much. This won't affect lock up at all as the ball will still snap out and engage the angled surface when closed. 

Edited by Bosshoss
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