zdog Posted August 13, 2011 Share Posted August 13, 2011 I have been chasing this problem for awhile now and think I may have found the problem. I ordered and tried some push through barrel slugs from Lead Bullets Technology. Long story short it looks like my cylinder diameter is about 2 or 3 thousandths less than the grove diameter of the barrel. According to LBT the next step is fire lapping. I am not sure this would be the best way to open up the cylinder diameter. I feel that sending the cylinder out for a ream job might be the answer. I would appreciate other opinions including where to send the cylinder to get adjusted if that is the best answer. Thanks, zdog Link to comment Share on other sites More sharing options...
Norther Posted August 13, 2011 Share Posted August 13, 2011 I think you can buy the reamer from Brownells for about the price of getting it done. Then you have it for other guns. Haven't tried it myself, but it looks pretty simple. Item # 513-000-001. Link to comment Share on other sites More sharing options...
zdog Posted August 13, 2011 Author Share Posted August 13, 2011 I think you can buy the reamer from Brownells for about the price of getting it done. Then you have it for other guns. Haven't tried it myself, but it looks pretty simple. Item # 513-000-001. I took a look at that reamer at Brownells. $80 plus shipping. That may be the option of last resort. I guess I could sell it after I used it once. I only have one 45ACP revolver. I don't suppose there is anyone out there that has a reamer that they would loan or rent to me for a one time use. Thanks, zdog Link to comment Share on other sites More sharing options...
Gregg K Posted August 13, 2011 Share Posted August 13, 2011 I am pretty sure that Mike Carmoney has mentioned doing this for others as it's a pretty common problem with S&W. Just get in touch with Mike and send the cylinder to him. Link to comment Share on other sites More sharing options...
zdog Posted August 13, 2011 Author Share Posted August 13, 2011 I have learned a few things today. I talked to Veral at LBT about the undersized cylinder on my 625. I was mistaken when I thought that fire lapping would open up the cylinder. Veral said if I want a reamer to check with a machine tool maker which would be cheaper. After a little conversation he suggested chucking up a 3/8 in or so slotted rod in an electric drill and wrapping some medium grit emery cloth around it to polish the cylinder with. He said that is what some gun smiths do. I had some 3/8 in wooden dowel stock so I cut off a piece and used a hack saw to cut a slot in it for the emery cloth. Long story short I now have all the cylinders evened up where a .4525 cast bullet will pass through with equal and very little resistance. I had to hammer the .4525 bullets through before I polished the cylinders. After slugging the front of my barrel the grove diameter measured 454 so I have a little more to go. I understand that slugging just the front of the barrel and then pulling the slug back out will keep the slug from being undersized by whatever restrictions may be in the barrel. Veral says to shoot for 1 thousandth over the barrel grove diameter. My plan is to keep polishing the cylinders until I can push the barrel slug through the cylinder with little resistance. If I were shooting jacketed bullets then I would stop here as they are not so persnickety about diameter. Hopefully this is going to resolve my forcing cone leading problems and the not so good accuracy I was getting with cast bullets. Best to all, zdog Link to comment Share on other sites More sharing options...
zdog Posted August 13, 2011 Author Share Posted August 13, 2011 I am pretty sure that Mike Carmoney has mentioned doing this for others as it's a pretty common problem with S&W. Just get in touch with Mike and send the cylinder to him. I emailed Mike and he would polish the front of the cylinder, which allows the rounds to drop into the cylinder easier, not the forcing cone or exit of the cylinder which is under sizing the cast bullets and causing the leading problem. zdog Link to comment Share on other sites More sharing options...
mwx40x40 Posted August 13, 2011 Share Posted August 13, 2011 Maybe this guy can help http://www.cylindersmith.com/ Link to comment Share on other sites More sharing options...
Tom E Posted August 13, 2011 Share Posted August 13, 2011 (edited) MEASURE the throat diameters. Most people don't realize a zero clearance fit is a light press. Throat diameters on 625-8's are usually right on .452. The chambers run undersize and need reamed. The barrels are tapered, bigger at the forcing cone end than the muzzle. Edited August 13, 2011 by Tom E Link to comment Share on other sites More sharing options...
zdog Posted August 13, 2011 Author Share Posted August 13, 2011 Maybe this guy can help http://www.cylindersmith.com/ Thanks for the idea. I decided to hand ream the cylinders myself. I will let folks know how it turned out when I get a chance to shoot it more. The first 18 rounds showed no sign of leading in the forcing cone. zdog Link to comment Share on other sites More sharing options...
zdog Posted August 13, 2011 Author Share Posted August 13, 2011 MEASURE the throat diameters. Most people don't realize a zero clearance fit is a light press. Throat diameters on 625-8's are usually right on .452. The chambers run undersize and need reamed. The barrels are tapered, bigger at the forcing cone end than the muzzle. The cylinders are now reamed to where I can push the barrel slug through them with a little effort. I will try it out for a while and I may need to open them a little more. zdog Link to comment Share on other sites More sharing options...
zdog Posted August 14, 2011 Author Share Posted August 14, 2011 Maybe this guy can help http://www.cylindersmith.com/ After thinking about the website these folks have and the info it contains I was wondering if the .4525 that they advertise for a finished diameter for a 45acp cylinder ream job would be big enough. The grove diameter on my 625-8 barrel measures .4540. I understand that a desired cylinder throat for lead cast bullets would be 1 thousandth over this number in which case the cylindersmith number would be 1.6 thousands too small. Am I thinking along the right lines here? Thanks, zdog Link to comment Share on other sites More sharing options...
Shadowrider Posted August 14, 2011 Share Posted August 14, 2011 (edited) Yes you are. I always follow the rule that you want your bullet (lead) sized .001" over groove dia. Some guns like them even bigger. What I'm wondering is why is your barrel groove checking so big? Have you called S&W? I'd be curious as to what their tolerance is these days, as they should be holding them to within tenths of a thousandth with their ECM rifling. Edited August 14, 2011 by Shadowrider Link to comment Share on other sites More sharing options...
zdog Posted August 14, 2011 Author Share Posted August 14, 2011 Yes you are. I always follow the rule that you want your bullet (lead) sized .001" over groove dia. Some guns like them even bigger. What I'm wondering is why is your barrel groove checking so big? Have you called S&W? I'd be curious as to what their tolerance is these days, as they should be holding them to within tenths of a thousandth with their ECM rifling. I was wondering that myself. I do not have a high quality digital caliper. My good caliper is in Arizona. What I am really going on is adjusting the cylinder to match the slug I ran through the barrel. I may send a slug of the muzzle to Veral at LBT and have him measure it. I am not the original owner of the 625-8 so who knows what treatment it has had in the past. zdog Link to comment Share on other sites More sharing options...
Shadowrider Posted August 14, 2011 Share Posted August 14, 2011 Yes you are. I always follow the rule that you want your bullet (lead) sized .001" over groove dia. Some guns like them even bigger. What I'm wondering is why is your barrel groove checking so big? Have you called S&W? I'd be curious as to what their tolerance is these days, as they should be holding them to within tenths of a thousandth with their ECM rifling. I was wondering that myself. I do not have a high quality digital caliper. My good caliper is in Arizona. What I am really going on is adjusting the cylinder to match the slug I ran through the barrel. I may send a slug of the muzzle to Veral at LBT and have him measure it. I am not the original owner of the 625-8 so who knows what treatment it has had in the past. zdog You really need to measure the slug with a micrometer. Calipers aren't accurate enough to measure below about .001 and even that's iffy. The external jaws and internal jaws can be different from each other too due to wear, being dropped or slide adjustment. I'm fortunate to have been a machinist for about 20 years and still have all of my tools. But, you can probably find someone around you that has an 0-1" mic. Otherwise sending it to LBT is a good idea. Measure your cylinder throats with a telescoping gage and micrometer. They are kind of tricky to use as there is a certain "feel". Or a set of precision gage pins will work but those are even harder to find unless you know a machinist or something. I have a 625-8 too. And I get some leading in the cylinder and the forcing cone too. My cylinder throats are right on .4525 give or take .0001/.0002". I haven't gaged my barrel yet. Good luck and please post up what you find about you barrel. Link to comment Share on other sites More sharing options...
zdog Posted August 14, 2011 Author Share Posted August 14, 2011 Yes you are. I always follow the rule that you want your bullet (lead) sized .001" over groove dia. Some guns like them even bigger. What I'm wondering is why is your barrel groove checking so big? Have you called S&W? I'd be curious as to what their tolerance is these days, as they should be holding them to within tenths of a thousandth with their ECM rifling. I was wondering that myself. I do not have a high quality digital caliper. My good caliper is in Arizona. What I am really going on is adjusting the cylinder to match the slug I ran through the barrel. I may send a slug of the muzzle to Veral at LBT and have him measure it. I am not the original owner of the 625-8 so who knows what treatment it has had in the past. zdog You really need to measure the slug with a micrometer. Calipers aren't accurate enough to measure below about .001 and even that's iffy. The external jaws and internal jaws can be different from each other too due to wear, being dropped or slide adjustment. I'm fortunate to have been a machinist for about 20 years and still have all of my tools. But, you can probably find someone around you that has an 0-1" mic. Otherwise sending it to LBT is a good idea. Measure your cylinder throats with a telescoping gage and micrometer. They are kind of tricky to use as there is a certain "feel". Or a set of precision gage pins will work but those are even harder to find unless you know a machinist or something. I have a 625-8 too. And I get some leading in the cylinder and the forcing cone too. My cylinder throats are right on .4525 give or take .0001/.0002". I haven't gaged my barrel yet. Good luck and please post up what you find about you barrel. Is there a chance I could send you a barrel slug from my 625 and have you measure it? Zdog Link to comment Share on other sites More sharing options...
Shadowrider Posted September 14, 2011 Share Posted September 14, 2011 Yes you are. I always follow the rule that you want your bullet (lead) sized .001" over groove dia. Some guns like them even bigger. What I'm wondering is why is your barrel groove checking so big? Have you called S&W? I'd be curious as to what their tolerance is these days, as they should be holding them to within tenths of a thousandth with their ECM rifling. I was wondering that myself. I do not have a high quality digital caliper. My good caliper is in Arizona. What I am really going on is adjusting the cylinder to match the slug I ran through the barrel. I may send a slug of the muzzle to Veral at LBT and have him measure it. I am not the original owner of the 625-8 so who knows what treatment it has had in the past. zdog You really need to measure the slug with a micrometer. Calipers aren't accurate enough to measure below about .001 and even that's iffy. The external jaws and internal jaws can be different from each other too due to wear, being dropped or slide adjustment. I'm fortunate to have been a machinist for about 20 years and still have all of my tools. But, you can probably find someone around you that has an 0-1" mic. Otherwise sending it to LBT is a good idea. Measure your cylinder throats with a telescoping gage and micrometer. They are kind of tricky to use as there is a certain "feel". Or a set of precision gage pins will work but those are even harder to find unless you know a machinist or something. I have a 625-8 too. And I get some leading in the cylinder and the forcing cone too. My cylinder throats are right on .4525 give or take .0001/.0002". I haven't gaged my barrel yet. Good luck and please post up what you find about you barrel. Is there a chance I could send you a barrel slug from my 625 and have you measure it? Zdog Crap. I got busy and haven't been on in awhile. But yes, I'd be happy to measure it for you if you still need it done. PM sent. Link to comment Share on other sites More sharing options...
Toolguy Posted September 14, 2011 Share Posted September 14, 2011 Just for future reference, MSC at mscdirect.com has decimal reamers in the size range you're looking for in .001 increments. They are priced in the $35 to $45 range. They have hundreds of other sizes too. Link to comment Share on other sites More sharing options...
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