Conundrum...Ruger SP101; 357 Mag.; Tighter cylinders than SAAMI spec

[Land_Owner]

While breaking in the gun, I noted that many of the reloaded rounds do not fully chamber in the cylinders so as to adversely affect the function of the revolver - it locks up the cylinder rotation!

I have boxes and boxes of 357 Magnum WC and SWC ammunition, reloaded for a similar handgun before I broke it (see that story here:  http://www.gboreloaded.com/forums/index.php/topic,265274.msg1099580721.html#msg1099580721 ) and I find that the chamber of the replacement revolver is tighter than the original by approximately 0.002" (0.356" fits but 0.357" and 0.358" diameter WC's do not). 

357 Magnum SAAMI rounds and Cylinder specs are here:  http://www.saami.org/PubResources/CC_Drawings/Pistol/357%20Magnum.pdf

What do I do now? 

[Bigeasy]

Could be a tight chamber.  If that is the case, a return to Ruger for inspection / repair would be in order.
 
But first, I would try a couple different factory loads, see how they function.
 
Some other issues come to mind -
 
Is maybe the resizing die a little on the loose / large size, and cases are catching at the base / web?
 
Are your bullets seated out a little to far, and catching on the end of the chambers?  If so, (and likely), just seating a little deeper may solve it.
 
Just because they worked in the other gun is no guarantee - It may have had loose / max chamber specs, while your new one has minimum chamber dimensions.  That, combined with slightly out of spec. reloads could be enough.  I had a similar problem with a S&W 29 once, where the chamber lead into the cylinder mouths was tight and abrupt.  My normal loads that worked fine in other guns sometimes failed to fully chamber.   It required using bullets that didn't have abrupt, full diameter shoulders, or if using such bullets (WC's come to mind), seating slightly shorter.
 
Larry

[mdi]

I'd use micrometers to measure the OD of the cartridges, in several places along the length of the body, to see where the cartridge is too big. Near the case mouth? Mebbe bullet too large. Near the middle or rim? Mebbe the cases are being bulged. You mentioned .357" and .358" don't fit. What are these measurements for?

[Land_Owner]

I'd use micrometers to measure the OD of the cartridges, in several places along the length of the body, to see where the cartridge is too big. Near the case mouth? Mebbe bullet too large. Near the middle or rim? Mebbe the cases are being bulged. You mentioned .357" and .358" don't fit. What are these measurements for?

All dimensions were caliper verified and are less than or equal to the SAAMI specifications.  Only the WC diameter of 0.358" is potentially larger than SAAMI.  If I read the spec correctly, they are "suggesting" a SWC in their diagram, which SWC nose diameter would be substantially smaller at the forcing cone of the cylinders. 

Using a full WC means the projecting 0.358" diameter bullet goes all the way to and through the cylinder forcing cone.  The "hang up" is the WC diameter of 0.358" and the cylinder forcing cone of 0.356" (with a tiny sliding friction at that dia.).

The previous SP 101 forcing cones were all 0.3575" and a whisker less than snug fits with 0.358" diameter WC's.

[dakotashooter2]

Just to clarify are the "chambers" too tight or do the rounds hang up when the bullet makes contact with the cylinder throats? Ruger is notorious for tight throats. If that is the case you may want to slug your barrel and have the throats reamed to that same dimension. If your throats are squeezing the bullets down to.356 shooting them through a larger bore will affect accuracy and cause leading if you are shooting cast.

[Land_Owner]

If your throats are squeezing the bullets down to.356 shooting them through a larger bore will affect accuracy and cause leading if you are shooting cast.

It leaded up with a vengence.

[shot1]

dakotashooter2 nailed it. Your cylinder throats are too tight. They need to match or be slightly larger than your bore. Gunsmith time for you.

[GH1]

My son-in-law had the same problem with his Blackhawk and I dealt with the same issue on my Taurus .38 snub. He had one of his machinist coworkers ream it out, I used a Dremel with a light sanding disc.
GH1