Hey guys and gals I need your help. I have a s&w 340 m&p. I noticed the other day that after shooting a good 75 .357 rounds through it that there was some makings exposing metal on the cylinder. they are very small marks but have a circular mark as if the barrel in someway contacts the cylinder while rotating. I don't have any feeler guages yet but can see light between between the cylinder and barrel. I have ruled out leading on the cylinder because it is a fairly new gun and have shot maybe 10 lead rounds with it. The cylinder face has been cleaned so my question is this. Is it possible that the heat from the magnum rounds expand the barrel enough to touch the cylinder face during firing and later cool down to a normal gap???
cylinder rubbing somehow on barrel
- Thread starter dagerv
- Start date
- Status
buck460XVR
Member
- Joined
- Feb 6, 2007
- Messages
- 10,078
Are you talking about the drag line?
oldfool
Member
possible heat, forcing cone drag on cylinder face powder residue
but only 10 rounds fired sounds like not near enough heat potential,.. 75 yes, 357s
sounds mostly like gap is just too tight, in any case
but cone/face drag ought be real noticeable on DA trigger pull, much like a 'brake'
you didn't say if firing SA or DA; with more rounds fired it ought be real noticeable just cocking the hammer
(duh.. ok, strike that, 340 M&P ain't got no SA hammer)
but only 10 rounds fired sounds like not near enough heat potential,.. 75 yes, 357s
sounds mostly like gap is just too tight, in any case
but cone/face drag ought be real noticeable on DA trigger pull, much like a 'brake'
you didn't say if firing SA or DA; with more rounds fired it ought be real noticeable just cocking the hammer
(duh.. ok, strike that, 340 M&P ain't got no SA hammer)
Could it be that there is enough endshake as to allow the hand to push the cylinder forward when the trigger is pulled?
I'd clean it, check the cylinder to forcing cone gap with feeler gauges and recheck it while pulling the trigger.
Just a thought. It may be right. It may not. But it's a quick and worthwhile check to perform.
I'd clean it, check the cylinder to forcing cone gap with feeler gauges and recheck it while pulling the trigger.
Just a thought. It may be right. It may not. But it's a quick and worthwhile check to perform.
buck460XVR
Member
- Joined
- Feb 6, 2007
- Messages
- 10,078
How 'bout a picture?
The Lone Haranguer
Member
If the front of the cylinder rubs on the breech end (forcing cone) of the barrel, it might have a too-narrow barrel/cylinder gap in combination with carbon buildup, or excessive forward-backward movement (end shake) causing the cylinder to be pushed forward into the barrel when it rotates. Sounds like a trip back to S&W is in order.
Is this a new to you gun? Has it happened before? Didn't you notice the trigger pull got heavier? Shooting 75 times in a row may have expanded the metal enough to close the B/C gap. The circular marks are probably machining marks highlighted by carbon buildup.
If it's a used gun it could be endshake in which case you should be able to force the cylinder forward and not see a gap between the barrel and cylinder. Next time take a brash brush and some CLP and brush the end of the forcing cone clean plus a little on a rag to clean the cylinder face, load it up and see if it still drags....it shouldn't unless it's endshake.
I've got guns that drag after 5 or 6 cylinders full, brush em and there good to go again.
Or you could send it back but even endshake is repairable by the average shooter so it's up to you.
If it's a used gun it could be endshake in which case you should be able to force the cylinder forward and not see a gap between the barrel and cylinder. Next time take a brash brush and some CLP and brush the end of the forcing cone clean plus a little on a rag to clean the cylinder face, load it up and see if it still drags....it shouldn't unless it's endshake.
I've got guns that drag after 5 or 6 cylinders full, brush em and there good to go again.
Or you could send it back but even endshake is repairable by the average shooter so it's up to you.
GP100man
Member
Weellll
If ya shoot very low pressure lead loads & the bullet is undersized lead can build qwikly on the end of the cyl & barrel !!!
A revolver by design will allow this to happen ,no stoppin it !
But by all means clean & measure end shake & cyl gap to see if there in spec.
Rule of thumb is .003" on end shake & I like cyl gap to fall between .005"-.008" on ALL chamber holes !
If ya shoot very low pressure lead loads & the bullet is undersized lead can build qwikly on the end of the cyl & barrel !!!
A revolver by design will allow this to happen ,no stoppin it !
But by all means clean & measure end shake & cyl gap to see if there in spec.
Rule of thumb is .003" on end shake & I like cyl gap to fall between .005"-.008" on ALL chamber holes !
Some answers for you guys: It is a DAO and I don't notice any difference in trigger pull. I clean it religiously so no carbon build up.
Round count:
(all factory)
10 .357 hornady critical defense 125 gr
10 38spl lead round nose 158 gr
50 38spl jacketed 158 gr
220 357 jacketed 158 gr
I have sent it to s&w once before bc after cleaning it i noticed a dimple in the bore and the cylinder wobbled.
The circular marks after shooting are from the carbon build up but the marks I am worried about is the shiny exposed metal on the face of the cylinder that when the cylinder is spun can be seen on all the cylinders. I clean the forcing cone with hoppes 9 and a brush every other session.
I am not familiar with endshake. It moves back and forth when out of the frame but when locked in it barely moves and doesn't seem to move when locked in while holding the trigger back.
The last session I shot 75 357's in about an hour. all of the 158 grain variety. From what i am reading the session may have expanded the cylinder causing the cylinder gap to shrink causing the barrel to rub against the cylinder??
Round count:
(all factory)
10 .357 hornady critical defense 125 gr
10 38spl lead round nose 158 gr
50 38spl jacketed 158 gr
220 357 jacketed 158 gr
I have sent it to s&w once before bc after cleaning it i noticed a dimple in the bore and the cylinder wobbled.
The circular marks after shooting are from the carbon build up but the marks I am worried about is the shiny exposed metal on the face of the cylinder that when the cylinder is spun can be seen on all the cylinders. I clean the forcing cone with hoppes 9 and a brush every other session.
I am not familiar with endshake. It moves back and forth when out of the frame but when locked in it barely moves and doesn't seem to move when locked in while holding the trigger back.
The last session I shot 75 357's in about an hour. all of the 158 grain variety. From what i am reading the session may have expanded the cylinder causing the cylinder gap to shrink causing the barrel to rub against the cylinder??
Last edited:
That is the normal carbon,powder burn and even vaporized lead that you will see on every revolver. It comes from the necessary gap between cylinder and barrel.
It is more visible on a stainless cylinder but easier to clean.
Solvent soak and a good brushing will remove most of it.A swipe with an abrasive cloth like the "lewis lead remover" will take it right off. Do not use this on a blued gun.
I just ignore it as it will be back the next time you shoot.
It is more visible on a stainless cylinder but easier to clean.
Solvent soak and a good brushing will remove most of it.A swipe with an abrasive cloth like the "lewis lead remover" will take it right off. Do not use this on a blued gun.
I just ignore it as it will be back the next time you shoot.
blakec3686
Member
yup... keep shootin man its a good gun!
Let's help you figure this out, get a feeler gauge and check the barrel cylinder gap on each and every charge hole. I can't tell from your pictures what it is exactly you are trying to describe. It does sound like a tight gap but the feeler gauge will tell the story.
A gap of .004-.009 is within serviceable limits.
A gap of .004-.009 is within serviceable limits.
243winxb
Member
Lead buildup if using lead bullets, think solder. Very good advice >
The face of the cylinder can have a high spot, this needs to be removed by a gunsmith using a lathe. Normal gap range is .004" to .009" for S&W firearms.
Missionary
Member
Greetings
I sure hope I never have a revolver with a cylinder gap of more than .006... that would be a mean side spitting varmet. That is another reason I very much enjoy the Dan Wessons. I run my DW´s as close as .001 and am happy to do so.
Mike in Peru
I sure hope I never have a revolver with a cylinder gap of more than .006... that would be a mean side spitting varmet. That is another reason I very much enjoy the Dan Wessons. I run my DW´s as close as .001 and am happy to do so.
Mike in Peru
Hmmm Missionary,
.006 is what Dan Wesson recommends running their guns at, in fact I've had a few Dans in my day and I've never owned one that didn't have at least 1 chamber that was .001 longer than the rest. I've never been able to run any of mine closer than .003 or I had interference before I even pulled the trigger.
Most revolvers @.006 to .009 will run lead slugs all day without cleaning, a plus in my book, a fair trade off for a little "spitting."
.006 is what Dan Wesson recommends running their guns at, in fact I've had a few Dans in my day and I've never owned one that didn't have at least 1 chamber that was .001 longer than the rest. I've never been able to run any of mine closer than .003 or I had interference before I even pulled the trigger.
Most revolvers @.006 to .009 will run lead slugs all day without cleaning, a plus in my book, a fair trade off for a little "spitting."
Thanks for the advice. I'm going to get some feeler guages this weekend and post the results. I didn't realize there could be high spot on the cylinder face. The shiny metal looks more like scratches so maybe the cylinder face is high. Do you guys know of a decent gunsmith in the st. louis area?
Missionary
Member
Good morning Remllez
I still have 7 of them and turn the barrel right down to just a squeek of light will pass through. Rotate the cylinder and if it hangs up on a cylinder mouth make sure it is clean and if need back the barrel out till it does not drag. Tighten up the lock nut and check it again. Yea DW said .006 and the gap guage is .006. But that is the joy of the system.. My caliber.41 is set at .001. My 414 SM is at .0015. All my .357´s are less than .002. You might want to visit the DW forum and investigate a bit more why the DW is still noted as the revolver that won more silly wet matches than all the rest.
Minimum gap with the barrel under the proper tension makes for a winning combination.
Mike in Peru
I still have 7 of them and turn the barrel right down to just a squeek of light will pass through. Rotate the cylinder and if it hangs up on a cylinder mouth make sure it is clean and if need back the barrel out till it does not drag. Tighten up the lock nut and check it again. Yea DW said .006 and the gap guage is .006. But that is the joy of the system.. My caliber.41 is set at .001. My 414 SM is at .0015. All my .357´s are less than .002. You might want to visit the DW forum and investigate a bit more why the DW is still noted as the revolver that won more silly wet matches than all the rest.
Minimum gap with the barrel under the proper tension makes for a winning combination.
Mike in Peru
Waywatcher
Member
Good call. That looks like endshake upon firing to me.
Waywatcher
Member
Cheers! 
Post back with range results!
Post back with range results!
- Status
