BC gap too tight; gunsmith

FLgun · Aug 2, 2022

The Stainless Security six I'm looking at getting; the seller measured the BC gap and said the thickess he could get a feeler gauge between the barrel and cylinder was 0.0015
Pushing the cylinder back and pushing it forward it Did not change. I have been told this is a pretty tight BC gap. Do any of you know a Gubsmith near central Florida who could correct this before it would become an issue and the possible cost to do so? I would already be into the gun for around $650.00 or so. As it is now, with the cost of the the gun plus the shipping and repair cost should I pass on it with that BC gap?

- Austin

9x19 · Aug 2, 2022

Did the seller measure that gap at more than one chamber?
How much faith do you have in:
1. The cleanliness of the cylinder face/forcing cone
2. The seller's ability to accurately measure the gap?
Taking a few thousandths of an inch off the forcing cone is not a high-cost task, in my past experience.

Dan in MI · Aug 2, 2022

Agree with the above.

FLgun · Aug 2, 2022

9x19.
Didn't mention where on what chambers he measured. Good point regarding accuracy.
Would Uncleaned cylinder face carbon build up be the # 1 for such a tight BC gap on a security six? Could it be the gun has been fired so little, reason for the tight BC, firing it more would increase the BC to in spec normal dimensions?

beentheredone · Aug 2, 2022

Being tight is no problem -- it will gradually get looser over time. Being TOO tight is a problem only if it gets dirty enough, or hot enough, to close that gap and foul rotation of the cylinder. I have an SP101 with a gap far tighter than "normal" spec, but I am delighted as it is extremely accurate and never gets fouled enough to matter.

Rockrat75 · Aug 2, 2022

Dan Wesson Big Bore revolvers had a .002" feeler gauge supplied to re-set the gap when you removed the barrel for some reason. I would much rather buy a revolver with a .0015 gap vs a gun with a .006" gap

Hondo44 · Aug 2, 2022

I agree with the two posts above. Worst case scenario if it's a bit too tight and you get binding after a lot of shooting w/o cleaning, a couple of strokes with a fine file on the end of the barrel will easily fix it. Not even worth the gas money to take it to a gunsmith.

Biggfoot44 · Aug 2, 2022

IF the seller is accurately measuring , and IF it actually is causing problems , it's way easier to open the b/c gap than to tighten .

Undoubtedly it is frequently addressed with a freehand file , best practices to to use the proper tool to assure being perectly square . I'm too lazy to look up at Brownell's , but should be same or less than a typical minimum shop charge .

Dave P. · Aug 2, 2022

As already posted above, I would not worry about it, not even a little!
If it stays equal as the cylinder is rotated...even better.
How did they measure it ? Give 3 sorta trained people some feeler gauges and they will all likely tell you something different.
While you can buy gauges at .0005 sizing, they're not all that common.

Johnnu2 · Aug 2, 2022

Hondo44 knows his stuff.... Get yourself a "fine" file and give it a stroke or two (after you've cleaned everything and get get your own feeler gauge and measure it. P. S. If you cannot visually inspect the gun yourself before you buy it..... I would pass on it.

IMHO,
J.

Rum River · Aug 3, 2022

As others have stated, IF it becomes a problem it can be taken care of. While it's easy to remove metal it's very complicated to put it back on.

If you buy it my suggestion would be to shoot it until it's good and dirty to see if that tight gap is even a problem.

mikeAZ · Aug 3, 2022

IF you decide to cut/square the forcing cone face? and are leary of a file?... Get the Brownells kit. It will cut square AND can cut/clean the forcing cone angle with the included adaptor.. I wouldn't worry about it for now, just if it is a problem later. ( I have the Brownells kit).

wheelerdan · Aug 3, 2022

FLgun said:
The Stainless Security six I'm looking at getting; the seller measured the BC gap and said the thickess he could get a feeler gauge between the barrel and cylinder was 0.0015
Pushing the cylinder back and pushing it forward it Did not change. I have been told this is a pretty tight BC gap. Do any of you know a Gubsmith near central Florida who could correct this before it would become an issue and the possible cost to do so? I would already be into the gun for around $650.00 or so. As it is now, with the cost of the the gun plus the shipping and repair cost should I pass on it with that BC gap?

- Austin

4D reamer rental rents kits for just this purpose. Eaay to use. <$50 done.

KurtC · Aug 3, 2022

Measure each chamber, with a clean forcing cone and cylinder face. The hammer should be cocked.

If the pistol can get through a 100 round course of fire without binding up, it's fine.

You can easily use the Brownells tool to cut back the forcing cone, if needed.

magpouch · Aug 3, 2022

Buy it.

Clean it.

Shoot it.

Do nothing else unless you must. I'd be on that in seconds...

Tight cylinder gaps are very hard to find and very much preferred. Besides, I kind of doubt its actually that tight.

Durango Dave · Aug 3, 2022

You found a revolver with a really tight cylinder gap! Great! No problem there.

jdavis · Aug 3, 2022

.0015 ten thousandths is not much different than the thickness of a fine hair which is mighty tight for a B/C gap. It would cause binding of the cylinder with the slightest amount of fouling. Perhaps the seller put one too many zeros behind the decimal. In either case, It seems that he measured it incorrectly. The ideal B/C gap is .004 to 006 (4 to 6 thousandths) which gives reliable operation with minimal velocity loss according to most authorities on the subject.

needsmostuff · Aug 3, 2022

Since it is already a 30 year old , used gun I might be more suspicious that it has been shimmed to that degree.
And that removing the shims would reveal plenty of gap.

Chief 101 · Aug 3, 2022

I have 4 revolvers with a similar gap. 1. SBH 2, 686 3. GP100 4. Redhawk. All of them get shot all of them have had no issues. just my experience. I also have revolvers with twice that gap that also perform flawlessly. I say shoot it and find out especially since it's 30 yrs old.

BC gap too tight; gunsmith

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