New S&W B/C gap Spec.

[Fide686]

I was noticing a lot of cylinder endshake, and lower than expected FPS in my older ND K-Frame Smith. I took it to my gunsmith who confirmed excessive endshake. He stretched the crane barrel and set the B/C at the "new S&W B/C Spec. of .010" - .012".
Needless to say, that dropped the FPS about an additional 50FPS.
I thought the B/C gap was supposed to be ideal at .006. Has anyone else run to S&W changing the B/C gap Spec. ?
Thanks.

 

[stansdds]

Where you been? I think it was in the Bangor Punta era that acceptable B-C gap became 0.010" and it was definitely that way in the Tompkins PLC era of ownership. I want to say it was somewhere around 2000 that 0.012" became the limit and some revolvers have fallen out of the factory with even larger gaps.

 

[ms]

Did he fix the end shake and just end up with the big b-c gap, or did he actually trim the barrel extension to get it that large?

 

[GBertolet]

That size gap, shouldn't affect accuracy any, but it will spit a whole lot, with that big of a gap. And as you noticed already, the velocity will be lower. Sometimes fixing one problem creates another. Probably a barrel setback will be best to fix the gap issue. Go for about a .004 gap.

 

[Fide686]

yes

endshake is fixed. I think that he only stretched the crane barrel. There are 2 tool mark rings in the crane barrel. I don't plan on investing on more smithing. I will use it as is.

 

[Hapworth]

S&W has long (decades, possibly a century) held .010" to be within spec, with .006" near ideal.

There is ongoing debate on the forum as to whether or not "in spec" has opened up to .012"; no one seems to know for sure.

When I contacted S&W a few years back with two new purchases well past .010", the rep told me .010" was their max and they sent me a label and corrected both revolvers to well below on their dime.

 

[ms]

I'm pretty sure

endshake is fixed. I think that he only stretched the crane barrel. There are 2 tool mark rings in the crane barrel. I don't plan on investing on more smithing. I will use it as is.

If you correct end shake, the functional (when high pressure is driving the bullet) gap is not altered much. Since you lost 50fps I guessed that the gunsmith had trimmed the barrel extension.

 

[AJR337]

One of mine has a .009 - .01 gap and I haven't noticed any spitting or notable difference in velocity compared to one with a .006 gap when shooting .38s .... .357s might be a different story.

 

[chief38]

The main reason they changed what is “acceptable” is because they are no longer capable of consistently holding the proper B/C gap. Since they realize their revolvers are no longer used for self defense (for the most part) I suppose they don’t really care about velocity. If a gun actually comes out of the factory properly-it’s shear luck!

Not telling anyone here what to accept or do but I do not accept any B/C gap over .006”. When I buy a revolver I always have a feeler gauge with me. If it’s over .006 or exhibits end shake, I walk away and look for another. Gun smithing and parts for vintage revolvers has gotten way too expensive and the shipping process is out of control as well. Just better off starting out with a good one in the first place. Patience is a virtue!

 

[series guy]

I think too much emphasis is placed on barrel/cylinder gap. If you want to shoot D/A a gun with a .004 - .006 gap can bind up pretty quick. I have found .009 - .010 to be a good spec for reliable D/A function. No spitting issues either. I believe this is why S&W adopted these specs also.

 

[Green Frog]

I have had two custom K frame 32 cal. revolvers built in the last decade. The first has a BC gap of about .003”, which I thought was wonderful. The second runs about .006 or .007”, and I wondered whether this was excessive. I will occasionally get a little hitch or drag with the former. Not so the latter, but I’m still not convinced that .004-.005” wouldn’t be optimal. Note that the vast majority of my bullets are cast lead.

Froggie

 

[stanmerrell]

I once bought a revolver and after getting it home, noticed the gap was quite large. The gun shot very well and I liked it all the same. Still, the gap bothered me. I sent it to a smith and he closed it up nicely. Now I too check with feelers if I'm going to buy a new or used revolver. I've heard that big gaps do allow for dirty shooting, but I clean after a range trip, so it doesn't really matter to me. This is an area where quality can be measured by the consumer imho.

 

[.45mtngun]

I prefer .004 to .006 also. Never had any binding issues and I shoot cast bullets in .38 to .45 Cal.
Jim

 

[Nick B]

Last year I checked the gap on a brand new 629PC . I stopped measuring at .014 and it still had more room to measure. I told the sales counter guy to have management send it back . They never did.

 

[chief38]

I think too much emphasis is placed on barrel/cylinder gap. If you want to shoot D/A a gun with a .004 - .006 gap can bind up pretty quick. I have found .009 - .010 to be a good spec for reliable D/A function. No spitting issues either. I believe this is why S&W adopted these specs also.

I beg to differ with that statement/ Every S&W Revolver I own has a B/C Gap just around .004" - .006" and I have NEVER had one bind on me. Of course I always clean my guns after shooting them so that is never an issue. I suppose if one was to neglect his revolver and let the lead build up to unacceptable levels then eventually any B/C gap would be too small.

I have shot next to guys with excessive B/C gaps on their revolvers and I have gotten hit by spitting lead many a time. Lead spitting, erosion and velocity loss are typical signs of a B/C gap that is too large.

 

[Nick B]

If you like tight cylinder gaps you’ll love Freedom Arms . They usually run around .002 .

 

[Protocall_Design]

In my personal experience, a .006 is the most I want for shooting lead or combined lead and jacketed. For shooting only jacketed, a .003 to .004 is better. If you're running a tight cylinder gap, you have to stay on top of endshake, because it takes less endshake for the cylinder to rub on the barrel when they are close together.

 

[Piwo]

I bought a model 49 bodyguard new in 1990 to use as a backup on the job. I didn't know much about cylinder gap back then. The gun spit and sprayed all over the place. I measured the gap and it was .018! The service guy on the phone at S&W thought that no gun would leave the factory that bad and told me I was measuring it wrong! I sent it back in and they corrected it. It now measures .011. Still spits, but very accurate. I only use lead bullets to keep a bullet from sticking.

 

[chief38]

If you like tight cylinder gaps you’ll love Freedom Arms . They usually run around .002 .

Sir,
For about 100 + years S&W held their B/C gap to .006" and I truly can't remember ANYONE I have ever met having binding issues. That includes all the LEO's and Military men who carried them.

The ONLY reason the Company changed their standards is that they are (unfortunately) no longer able to hire enough qualified people with a good work ethic and train them properly to do it correctly. They don't really look upon revolvers as SD tools anymore - they look at them as shooters that some people like to bring to the range and B/C gap, velocity, etc doesn't really matter as long as the gun goes bang when the trigger is pulled. Therefore, instead of raising the bridge they lowered the water. It's not that the revolvers won't shoot with a large B/C gap - but they don't shoot properly and lead spitting, loss of velocity and erosion increase drastically.

FYI - up until the 1990's if your S&W revolver exceeded the .006" B/C the Factory was happy to repair it at no charge. What does that tell you? It tells me that most of what left the Factory back then was actually correct and very few had a gap out of spec and they acknowledged that greater than .006" was too much. All of a sudden someone in an executive office waived a magic wand and revised policy that double the standard spec for 100 years was now acceptable. NOPE! There's something rotten in Denmark!

 

[Mercury]

Sir,

The ONLY reason the Company changed their standards is that they are (unfortunately) no longer able to hire enough qualified people with a good work ethic and train them properly to do it correctly. They don't really look upon revolvers as SD tools anymore - they look at them as shooters that some people like to bring to the range and B/C gap, velocity, etc doesn't really matter as long as the gun goes bang when the trigger is pulled. Therefore, instead of raising the bridge they lowered the water.

FYI - up until the 1990's if your S&W revolver exceeded the .006" B/C the Factory was happy to repair it at no charge. All of a sudden someone in an executive office waived a magic wand and revised policy that double the standard spec for 100 years was now acceptable. NOPE! There's something rotten in Denmark!

I agree and IMHO S&W has lost some of its vision of building guns for enthusiasts and is no longer a gun manufacturer but has become a corporation that just happens to make guns.
As evidenced by the change in acceptable B/C gap, its QA/QC has been deemed less important than its production quotas.

I realize its talented gunsmiths may have retired and the qualified labor pool, being what it is, is now considered to be assemblers of MIM parts rather than gunsmiths that build hand-fitted guns.

I also realize that most customers today, would balk at the price tag of a hand-fitted revolver but let's see reasonable B/C gaps, barrels that aren't clocked, etc.

This is not meant to bash S&W but just my opinion based on today's industry and market. S&W is still my go-to brand, it's just sad to see the slide away from greatness.