Another B/C gap go-round with the feeler gauges

[Riomouse911]

The earlier posts where the good folks here broke out the feeler gauge and checked the barrel/cylinder gap on their revolvers got me to thinking how variable the gaps are on my stuff...so I picked up a set of feeler gauges from Sears and opened the safe to see what size gaps my revolvers sport:

S&W 686+ 4" .357 .0025
S&W 629-4 6.5" PwrPt .002
S&W M&P .38 4" .006
S&W 629-4 Mtn 4" .0025
S&W 642-2 .38 .002
S&W 19-4 2.5" .357 .0025
S&W 49 Nickel .38 .003
S&W 17-2 6" .22 LR .003
S&W 13-4 3" .357 .0025

Ruger Super Redhawk .454 7.5" .005
Ruger Redhawk .41 Mag 7.5" .006
Ruger Single Six 6.5" .22 Mag .004
w/convertible cylinder .22 LR .004
Ruger GP 100 .44 Spl 3" .002

Taurus 941 4" .22 Mag .0025
Taurus 94 4" .22 LR .004

Colt Cobra .38 .002

I didn't measure the Dan Wessons since they are adjustable. I set them at .003 to .004.

It seems to be pretty consistent across the S&W spectrum, with a .001" variation across all the calibers and models I own...with the exception of the old M&P .38 that was my great Uncle's duty gun that he carried as an officer with Las Vegas PD from 1945-1965. About all that hampers it is cosmetic; the 20 years of holster wear, a scratch that mars the S&W crest, and the initial "B" that is etched over the trigger on the left side of the frame, other than these the gun is pretty darn solid with a mirror bore.

I was surprised to see the largest B/C gaps in the Redhawks, especially the high-pressure .454. The single-six has the same gap with both cylinders, I guess they must fit them to the guns individually to be this consistent (I'm not sure about that, but these are both well-fitted and shake-free).

The Colt Cobra is one well-fitted and nice-handling handgun. From the smooth. non-stacking trigger pull to the tight and shake-free cylinder it is a real pleasure to carry and shoot.

The Tauruses are fun little guns as well; I like to start beginners with the 94 and then quickly move them up to the louder and slightly more "felt-recoiling" 941.

Again, these are merely things that I observed, following up on the previous thread...feel free to add what you observe when checking out the B/C gap on your specimens.

Stay safe.

 

[351 WINCHESTER]

Boy those S & W's are way too tight for me.

 

[Riomouse911]

I was surprised how tight they were as well, I was expecting them to be in the .004-.006 range. I will say that even eyeballing them by holding them up to the light before using the feelers the S&W cadre looked tighter than the Rugers in the B/C gap, so the numbers I wound up with seem to fit what I was seeing.

I must say none of the Smiths have ever bound up from crud building on the cylinder face or forcing cone, so (knock on wood) all has been working well to date.

 

[sequins]

I think a tight bc gap is best. .002 seems ideal as you'd need to spend hundreds of round to clog that. My Ruger have enormous bc gaps and it's maybe the one thing I don't like about the otherwise excellent revolvers.

My 6" GP100 once had a guy at the range exclaim at the size of the flash when I fired. No, not at the muzzle, at the cyclider to cone gap :-(

 

[Riomouse911]

My buddy has a Dan Wesson .44 that for whatever reason he keeps a wide B/C gap on, as he says, "For reliability in case crud builds up on the cylinder face." That evil thing spits fire and tiny bits of unburned powder and bullet lead on every trigger pull. It'll pepper your face if you aren't careful.

The numbskull doesn't have other barrels so he doesn't have a .44 cal barrel nut wrench (mine are in .357), so I don't want to risk damaging his gun if I were to fix it for him when he isn't looking.

 

[AZAndy]

Here's a re-post of what I found a while back, with a couple of items added:

Taurus 85 .006
Taurus 82 .003
Ruger SP101 .004
Kimber K6 .006
S&W 625-8 PC .010
S&W 64-3 .004
S&W 325 .005
S&W 36-3 .005
S&W 640-3 .002
S&W 19-3 .004
S&W Model 1905 .005

The big honkin' gap on my only Performance Center piece befuddles me. It can't be because of the chambering, because the 325 gap is half the size. Looks like I need to order an Acme Premium Cone Stretcher.

 

[warnerwh]

My buddy has a Dan Wesson .44 that for whatever reason he keeps a wide B/C gap on, as he says, "For reliability in case crud builds up on the cylinder face." That evil thing spits fire and tiny bits of unburned powder and bullet lead on every trigger pull. It'll pepper your face if you aren't careful.

The numbskull doesn't have other barrels so he doesn't have a .44 cal barrel nut wrench (mine are in .357), so I don't want to risk damaging his gun if I were to fix it for him when he isn't looking.

Your friend can get a large frame barrel wrench here: http://www.ewkarms.com/zen8/index.php?main_page=index&cPath=5 They are only 25 dollars and he should have one anyway. The barrel nut can get loose so he needs to check that occasionally. Dan Wesson included a .006 feeler guage for the gap which is excessive imo but may be where his gap is set. Just getting the gap to .003 or .004 makes a big difference in spitting.

 

[Riomouse911]

Ya, I went to EWK for one of their 3" VH barrel/shroud sets for one of my model 15's. Perfect fit and finish, and with the exception of the writing font on the side it looks like a DW factory piece. Now all I see on their site is the PPC-looking slab-sided barrel shrouds for the .357 guns.

I think his is set at .008+, it really spits. He's a bit of a know-it-all, been-there-done-that type...I'll suggest it to him and let him deal with it himself. But thanks for reminding me about EWK, I totally forgot about them.

 

[Jim NE]

Boy those S & W's are way too tight for me.

I have to agree. As a casual non-competitive shooter, and a concealed carry guy, I'd have cylinder binding problems all day long with those gaps. The one way I can alleviate those kind of problems with those types of gaps is to wipe off the powder residue from the front of the cylinder and the back of the forcing cone after each cylinder of ammo fired. There are a couple of guns I do that with because I'd rather not alter the guns/gaps, but those guns won't be defensive guns I have to count on for protection. Mostly, those guns are older Rossi's, not S&W's. My ideal all around cylinder gap is about .006" for S&W and S&W style guns.

I believe that spitting lead is more of a timing issue in most cases rather than a wrong gap, at least with my (somewhat extensive) S&W collection. I'm talking about older guns here, just to be clear. I've never had a well-timed gun spit at .008. I should also mention that some of my minty (as in not shot much) older S&Ws can vary in gap a bit from gun to gun, and I presume from their high level of condition that they came from the factory that way. If I had to guess, I'd say they average maybe .007 or 006 or something, but some mint S&W's have been as high as .009. Again, I'm talking with older S&W's and newer guns may be a bit different.

I had a beat up well worn model 10 that had sixteen thousandth's gap in places. That's too much, of course, but it was the most accurate model 10 I'd ever owned.

 

[351 WINCHESTER]

Back when U.S. Customs armed their inspectors with revolvers in the 1980's, the assistant to the Comissioner gave S & W the specs. for their new revolver, the CS-1. The tolerances were way too tight & S & W told them the guns would not work. They wanted the b/c gap to be set at .002 & S & W did & the guns chocked & had to be sent back. There were other problems too, but the b/c gap was the biggest offender as I recall.

 

[45 Dragoon]

Hmmmm . . . . . wonder how Freedom Arms gets away with it . . . .
There's not a lot of difference from .004"+ but it's getting that really tight (.003 and less) that makes a difference. I know open top revolvers (of the Colt blk powder kind) stay much cleaner and shoot much longer with a .002"- .003" barrel/cyl clearance.
Both of my open top Dragoons (45C cartridge guns) work with a .0015" clearance. They are both the most accurate revolvers I've ever owned/shot. That goes for others that shoot them as well.

Mike

 

[FN in MT]

The CS-1 686's are an interesting story. The Justice Dept hired a "Firearms Expert" that had previously worked at one of the Proving Grounds , IIRC Aberdeen. He had worked on most everything OTHER than handguns. And had ZERO Law Enforcement experience.

He wrote the spec's for the Custom's Service revolvers , requiring tight tolerances and an accuracy requirement. The Factory treid to talk him out of the tight tolerances, but finally took the contract.

THE issue out in the field was unbunt powder getting under the extractor star , thereby jamming up the cylinder. This could possibly been fixed by simply changing ammo, but instead the guns were returned to S&W. Eventually many were sold to the Agents they were issued to...Where I got my pair of CS-1's. The rest were disposed of between out of Country LE sales and some IIRC were destroyed.

I'd like to know the amount of taxpayer money wasted on this boondogle.

 

[351 WINCHESTER]

The CS-1 686's are an interesting story. The Justice Dept hired a "Firearms Expert" that had previously worked at one of the Proving Grounds , IIRC Aberdeen. He had worked on most everything OTHER than handguns. And had ZERO Law Enforcement experience.

He wrote the spec's for the Custom's Service revolvers , requiring tight tolerances and an accuracy requirement. The Factory treid to talk him out of the tight tolerances, but finally took the contract.

THE issue out in the field was unbunt powder getting under the extractor star , thereby jamming up the cylinder. This could possibly been fixed by simply changing ammo, but instead the guns were returned to S&W. Eventually many were sold to the Agents they were issued to...Where I got my pair of CS-1's. The rest were disposed of between out of Country LE sales and some IIRC were destroyed.

I'd like to know the amount of taxpayer money wasted on this boondogle.

The inspectors and agents hated these guns. They were too heavy for most. The inspectors were required to carry these guns (4"), but most of the agents carried smaller/lighter guns. Some of the inspectors never could qualify so they missed out on a lot of o/t assignments.