Cylinder Gap in Single Seven

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22short

Bearcat
Joined
Apr 27, 2014
Messages
11
I purchased a Single 7 a while back in the .327 magnum and have sent it back to Ruger a couple of times to look it over and fix some things. After my most recent return I wanted to check the cylinder gap. I was kind of curious what it would be as when firing it I notice a lot of stuff blowing back and hitting me in the face and on my arms. So I pulled out my feeler gauge and this is what I found. On the seven cylinders the gap is .009 minimum and .012 maximum with four of them being .011, the other one being .010.

I went to the safe and pulled out one of my Colt SAAs just to compare. The gap on the cylinder on the Colt was .003 on all but one which was a tight .004. The question I ask myself after seeing the difference in the two guns is whether or not the Ruger exceeds what is considered reasonable and whether or not I should send it back or if that is why I pay extra for a Colt.

What do the rest of you revolver guys think? Is that range acceptable and normal for Ruger revolvers?
 

Rainy Day Shooter

Single-Sixer
Joined
Apr 23, 2014
Messages
106
Most people have a "perfect" measurement in their head as to what a bc gap should be, but know that a larger gap doesn't effect accuracy only velocity. If it doesn't spray lead you technically should be fine - assuming now that you know the measurement you don't let it drive you crazy!
 

mindustrial

Single-Sixer
Joined
Jan 6, 2009
Messages
142
.012" is the numeric limit for Ruger. I know, I called, I sent back a single 7 that had .015"...It came back with .010" with .005" of end-shake that wasn't there before.....blah.

The Dan Wesson 445 Supermag, that has an operating pressure of 43K psi, came shipped with .002" shims to adjust bbl gap. I'm thinking that would be ideal.

To me, no more than .005 with a higher pressure round like the 327. With a .38; perhaps .006-.010 would be good.
 

WIL TERRY

Buckeye
Joined
Jun 8, 2003
Messages
1,973
I want at least .005" B/C gap MAX on any of my sixguns, SA or DA.
ALSO...let me note; your 327 pistol has ONE cylinder with SEVEN chambers.
And so it goes...
 

Ethang

Blackhawk
Joined
Jun 1, 2009
Messages
683
I posted up on mine, it was one of the first batches of 5.5 inch pistols. The gap was huge and got sent back to Ruger. They replaced the cylinder which improved the gap a great deal. If you have blowback I would agree it's way too large. Accuracy is not so much the issue, but lost FPS with a large gap. Not really what we are buying a 327 mag for is low muzzle velocity.
 

22short

Bearcat
Joined
Apr 27, 2014
Messages
11
While I'm not a reloading expert if you have a larger gap you're losing pressure and you are compromising accuracy because your not getting the same velocities you would otherwise so accuracy would be somewhat compromised by the different velocities you would be getting as a result of the different pressures.

I may send it back again and see what happens. I'm kind of getting tired of this game. And to be honest with you while accuracy is the ultimate goal having crap blow back in my face and those around me to the point they all comment on it is what really gets me. Just not as good as it should be.
 

David Bradshaw

Blackhawk
Joined
Sep 11, 2012
Messages
933
22short..... described here as "blowback," it is called SPITTING by the folk making revolvers. Gap----cylinder/barrel gap----degrades velocity while play no part, or next to no part, in accuracy. Spitting is heavily affected by chamber-to-bore offset (also called misalignment), rough chamber throats, rough or asymmetric forcing cone. Excessive gap aggravates spitting caused by roughness. A sharp leade between chamber and throat in cylinder will shave lead, always looking for a way out. Oversize chamber throats cause gas the blow past bullet until the bullet slugs up, sending gas to the side. Cylinder flutes to either side of the firing chamber, especially deep flutes, may direct combustion particles to the shooter's face.
David Bradshaw
 

REB

Bearcat
Joined
Mar 12, 2006
Messages
99
I did some experiments with a Dan Wesson years ago by increasing the cylinder gap and measuring velocity. I saw very little if any loss in velocity as the gap was opened. I went from almost no gap to .010.

As David pointed out spitting is most likely caused by some other issue. The most common issue I have seen that causes spitting is misalignment.

I would have a gun smith check the alignment with a good range rod.
 

Hondo44

Hawkeye
Joined
Apr 3, 2009
Messages
7,711
22short said:
While I'm not a reloading expert if you have a larger gap you're losing pressure and you are compromising accuracy because your not getting the same velocities you would otherwise so accuracy would be somewhat compromised by the different velocities you would be getting as a result of the different pressures.

I may send it back again and see what happens. I'm kind of getting tired of this game. And to be honest with you while accuracy is the ultimate goal having crap blow back in my face and those around me to the point they all comment on it is what really gets me. Just not as good as it should be.

I WOULD SUGGEST SENDING BACK AGAIN, but don't even mention the barrel/cyl gap, just complain about the blowback. That way you shouldn't get any pushback that the gap is within tolerance.
 

Prescut

Single-Sixer
Joined
Sep 2, 2015
Messages
253
my Colts and Smiths are all right at .006 ( a couple of .005 and .007). I measured about 25. Pythons, diamondbacks, models 14, 19, 27, 48, 686...
The dan wesson was .003.
So anything over .008 would be unacceptable to me.
 

Chief 101

Hunter
Joined
Feb 14, 2007
Messages
2,048
You might check the gap and end shake with a cylinder full of empty cases to see if it makes a difference. If the case rim takes up some of the slack in the cylinder(headspace) its not as bad as you think...I had a NM SBH a few years ago that had some extra .inches in the gap but loaded it was fine, and it shot exceptionally. On the other hand my Max revolver is really tight...just like my .30 Carbine revolver...
 
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