Conversion troubles

I am getting rounds not wanting to fully chamber.  They are getting stuck at various points shy of fully chambered.  I push on the back of the slide and feel resistance.  Thinking this was crud based on folks here stressing the importance of a clean chamber, I started carrying a brush to matches.  It seemed to help but the issue I am now certain is not because of fouling because cleaning was not correlating to improved function; it was only randomly helpful.  I confirmed this by not cleaning after a failure and it cycled fine.  Look at the MAIN image of the bullet.  There is a dent swaged in the exposed bullet a bit forward of the rim of the case; perhaps .060" or so forward.  I did not pay attention whn clearing whether this was at 12:00 or 6:00 (or somewhere else).  Notice the bullet is also bent out of concentric.  It seems the bullet got jammed against the edge of the chamber but whatever caused this, was not severe enough to prevent partial chambering. So it corrected itself but then the swaged lead and bent bullet nose created the failure to go completely in to battery (I think).  I saved two samples and the one shown is the worst.  There are a variety of other, similar cartridge failures which also stopped short of fully chambering; some that only needed an additional .06-.12 of "help it home."  I've included some extra photos in case someone sees anything.  Notice that when the cartridge snaps out of the magazine and is partially chambered (I held the slide in this spot to take the photo) that it is not exactly concentric with the bore.  It is higher.  BUT....the failures do not happen with a Rock River lower and with that lower the bullet is in the exact same place; that being slightly above concentric, when it is picked up by the breech face.  I bought EGW's mag release that raises the mags .020 and with it, my mags do not lock in place.  So right now it is back out.  I am hesitant right now to take a bit of material off of the mag catch holes to "fit" them (I have a match tonight) with this new mag catch button but I may do it on only one of the four mags tomorrow and shoot this mag to see what i see.  Mags are original to the Unit 1 which was bought many years ago NIB with all four Colt steel mags from the era when these were original equipment with the unit.  I haven't tried to identify if it is only with specific mags.  I will note which one/ones if it happens. tonight.  The one thing I just noticed which is different between this SA lower and the RR lower is that when the conversion slide is going rearward and receives the upward reaction force from the hammer, with the SA I now see that the rails are not tight enough to keep the top of the slide from rubbing on the underside of the rib very slightly.  With the RR, the rails are so precisely machined that the conversion slide doesn't have clearance to make the same contact.  I guess if folks think this rubbing could be the cause, I can cut off the rear extension to the rail and just remount the dot forward a bit.  I have the iron sight rib as well and can put that on and if there is no obstruction, shoot irons to see what occurs.  For tonight I will try to get by with some lube between these surfaces.  With the R lower I recall using 7-9 pound springs and all worked fine.  With the SA lower I don't think I've had anything but 9 pound in.  So in the spirit of changing only one thing at a time, I just put a 6# in which worked fine today for thirty rounds.  I'm leaving it in.  If the problem is still there, (and the spring change is [b]not[/b] the solution) I will not make it through the 120 rounds tonight.  I don't oil the top round (and I will not tonight).  I shoot eley orange box fyi.  Thanks for any advice.  Ed

Which conversion and which magazines are you using?

Marvel Unit 1 and Colt steel magazines.

1. When the slide is coming forward and the hammer is pressing upwards, is the slide actually tilted on an angle downward from the rear to the breech face? I’m trying to visualize what’s happening there.

2A. Where on the clock are you seeing the indentation on the nose of the bullet?  If you chamber a round in the RR, and eject it, do you see the same indentation?

2B. With the 6# spring, you’re NOT having the problem? Only with the 9#?  Same indent with both springs?

3. What do you mean by not concentric to the bore? Laterally displaced? At an angle? Vertically displaced?

4. Can you reproduce the “jam” racking a round slowly? If so, can you hold the slide downward so that it is not contacting the rib?  Same problem?

5. Before cutting off the rib, can you glue a thin shim to the underside of the rib so that it may rub, but won’t allow the slide to move upward?

If it’s the rails being too loose a fit, maybe a smith can set them down ever so slightly.

Ok. So I have read the initial post a few times please correct the following if incorrect. Trying to get a full understanding of what is going on.
-Marvel and all colt mags work with the rock river lower
-Failures with one or more mags on the Springfield lower.

Somethings to look into:
-guide rod appropriately tight (do not over tighten, you can break the breach block)
-Mainspring and recoil spring combination. Both the mainspring and recoil spring work together for proper function. 
-Magazine lips on the metal mags may need to be adjusted for optimum function. Bob Marvel wrote a trouble shooting guide with details on that subject.
-Magazine position is critical. It is possible that it could be too high or too low. Not all mag catches are created to the same specification and tolerance.

[quote="chiz1180"]Ok. So I have read the initial post a few times please correct the following if incorrect. Trying to get a full understanding of what is going on.
-Marvel and all colt mags work with the rock river lower
-Failures with one or more mags on the Springfield lower.

(Ed) Correct


Somethings to look into:
-guide rod appropriately tight (do not over tighten, you can break the breach block)

(Ed) Good point. I have caught myself shooting a loose rod.  Who knows how long. I can’t remember whether there is a correlation with the problem we’re discussing but this would be great if it were in fact the cause. I will pay more attention. 


-Mainspring and recoil spring combination. Both the mainspring and recoil spring work together for proper function. 

(Ed) They are identical in both lowers. 

-Magazine lips on the metal mags may need to be adjusted for optimum function. Bob Marvel wrote a trouble shooting guide with details on that subject.

(Ed) Same mags are being used for both lowers so if they need to be tuned for each specific lower, then I’d need a person skilled in determining this, to look the gun over. I may have to resort to shipping it off but am still hoping not to.

-Magazine position is critical. It is possible that it could be too high or too low. Not all mag catches are created to the same specification and tolerance.

(Ed) I was hoping the included photo which shows the position of the top round in an inserted mag, might show you guys what you need to see to help determine this- too high, too low?  But a visual check of position with each of the two lowers shows they are very close to identical with both RR and SA.[/quote]

You should be running a 19 lb or slightly less main spring with conversions. I run an 8lb recoil with that in my old Marvel with colt mags

[quote="jglenn21"]You should be running a 19 lb or slightly less main spring with conversions. I run an 8lb recoil with that in my old Marvel with colt mags[/quote]


Main spring is a 19 in both lowers.  Thanks.