Revolver throat diameters

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barnfrog

barnfrog

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I have read that the chamber throat diameters in the cylinder of a revolver, and the difference between the individual chambers' diameters, can affect the accuracy of the revolver when shooting cast lead bullets. Does it have much effect when shooting jacketed bullets? The throat of one chamber of my Blackhawk is slightly smaller than the others, although I don't have the tools to measure by how much. A jacketed bullet will go through with just the slightest coaxing, whereas it will drop right through the others. Wondering if it's worth trying to find a set of pin gauges to measure.
 
I can tell you from personal experience it can lead down a rabbit hole of measuring gauges, then costly reamers, when the return on investment may not be worth it unless the gun just won't group worth a darn and nothing else (load experimentation) seems to help. What I probably would do if in the same situation is shoot some carefully rested groups and note which chamber is the tight one in the group, at whatever your usual distance is, and evaluate where it lands in the group.

It may make little or no difference. I remember back in the day I would shoot groups using just one chamber, then using all of them, and compare the differences. If I recall it was never enough of a difference to matter, at least with me behind the trigger.
 
I could not shoot the difference using jacketed bullets with any of my revolvers. But if using lead it can be a major pain with both accuracy and leading. Dont for get to measure the barrel diameter and check for it choking at the area of the attaching threads. That also affects accuracy especially with lead bullets. It really all goes back to how much you are willing to spend to improve accuracy. Or not.
 
Smith & Wesson M28 6"
Learned- Using only one chamber had the tightest group. (got lucky?) All shots from the same chamber. The 50 yard groups had a difference in point of impact. About 2 1/2 inches higher then the other. Wish i had my old chrono to check velocity. When using the 5 good chambers, accuracy seem OK. full.jpg

Only a High Master could tell the difference. Not I.
barnfrog said:
I have read
Click to expand...

Best to do your own testing. :)
 
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The value of the pistol, who made it, and how much I liked it would all matter. If it's a big company like Smith, you may be able to send it to them and have a quality fix for a decent amount of money. If it's a cheap pistol with no company support a good gunsmith can fix it but may cost more than is worth it to you.
 
Use the advice above to measure. If you do buy pin gauges, know that there are two types, inside and outside. You need inside ( sometimes called minus gauges) to measure a cylinder hole. For best results with lead bullets you need the cylinder holes to be .001 to .002 inches wider than barrel groove diameter. Buy lead bullets with a diameter to match the cylinder. For FMJ, it may not matter. Again, use the advice above.
 
Jacketed bullets have a little "spring" to them. If a throat (or a barrel constriction) sizes them down a smidge, they can expand back up to fit the rifling. Cast bullets can't - and that's why they tend to be trickier.
 
I still ream my throats and forcing cones, even for jacketed bullets. No downside, only potential upside, and considering I have dozens of holes needing attention, the cost of the gear to treat them became insignificant.

There are services which also do cylinder throats, typically for $75-100. Pretty small cost in the scheme of things, if you only have a few needing attention.
 
Sounds like some target eval is in order, as LaneP, Bcwitt and 243winxb suggested. It's my only centerfire revolver, so buying the tools is not worth the expense to me unless I see a significant effect on POI. However, I would like to hunt with it so improving its effective range is desirable.

Thanks for the advice, as usual.
 
Not all that you read about cylinder throats applies to every gun.

My Blackhawk 44 special, with throats .4314-.4323 and .4292 bore seems to do better with bullets sized .430 rather than .431. Accuracy and leading decreased when I switched to .430 sized bullets.

You can get a usable measurement by slugging your bore and throats and measuring with calipers. Calipers, if you have a feel for them, can do well. When I got my mic, it confirmed my feel for calipers was correct, and they are correct. Mostly I got the mic so folks on gun forums couldn’t say my measurements were useless because I made them with calipers.
 
It's not just a difference between cylinders, ideally a lead bullet should obturate in the throat to a diameter slightly over bore diameter and be sized down to seal bore. If throats are small accuracy can suffer and it'll lead worse.
I've reamed two Ruger 45 Colts Blackhawks and cut 11 degree forcing cones and the went from 2 to 2.5" @ 25 yards guns to 1.5" @ 50 yards.
 
Not to put things too blunt but there’s lots of guns in the country. If you get one that won’t shoot, and it can’t be corrected with hand loads or by a factory adjustment, sell it and find another.
 
I have a question on this topic since I'm thinking of loading some coated lead for 38spl soon.

I just went out to my shop after reading through the replies and did a bit of a poor man's test and took some .358 nominal sized bullets I have (they caliper to close to .359 actually) and tried to slid them backward down the throats on my K6S. The only make it about 1/8" of an inch in the throats, about the length of a case that's expanded for a lead bullet.

Is this a recipe for leading just based on that test or is that not enough to go on? Do coated bullets have any bearing in these situations? I took some XTPs and they slide all the way through each of my cylinders. I assume a bit of actual testing would be in order as a first step but any thoughts from those experienced are appreciated.

PS @barnfrog not trying to hijack your thread but seemed silly to start a new one. ;)
 
Bazoo said:
Coated bullets generally don’t lead if the coating is done right. It’s much more forgiving.
Click to expand...

That's good to hear. I'd be using my SNS 158gr. I had no leading with 357 mag at ~1600 FPS in my Henry so I'd say they're pretty good on the coating front.

My #1 concern up front is the leading. I know the throat to groove sizing/ratio is important for accuracy but I'm going to be honest here: I'm not the best shot with handguns. Maybe not even second best (ha!), but really, last time I had this revolver out with my XTP jacketed, shooting from rest at 25yrds I was happy to keep most shots inside of the black on an NRA 100yrd small bore rifle target which I believe is about 8". If accuracy was terrible I'd address it but I'd like to not gunk up my barrel bad just trying it out.
 
Don’t be afraid of leading. It’s easy as pie to remove. Choreboy copper pot scrubber section wrapped around a bore brush, larger than diameter of the bore, pulled into the bore from the forcing cone end. That will scrub a wicked leaded bore clean in 2 minutes. Before you pull it in the bore, spin it in the forcing cone some and it’ll get that.

The easiest way is to shoot a gas checked bullet load a cylinder full. Gas checks make cast bullets more expensive. But they are a godsend for an ornery gun.
 
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Bearded Phil said:
PS @barnfrog not trying to hijack your thread but seemed silly to start a new one. ;)
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No worries, mate. I got some good info about my topic (jacketed bullets) and the thread had taken a turn into cast lead territory, so why not let it keep rolling that way. No objection from me. I may have started the thread, but it belongs to the collective.
 
Bazoo said:
Don’t be afraid of leading. It’s easy as pie to remove. Choreboy copper pot scrubber section wrapped around a bore brush, larger than diameter of the bore, pulled into the bore from the forcing cone end. That will scrub a wicked leaded bore clean in 2 minutes. Before you pull it on the bore, spin it in the forcing cone some and it’ll get that.

The easiest way is to shoot a gas checked bullet load a cylinder full. Gas checks make cast billets more expensive. But they are a godsend for an ornery gun.
Click to expand...
Yup! 100% agree. Me personally I don’t even resort to abrasive scrubbing. I use Shooter’s Choice lead remover solvent and just follow the directions. Follow up with a normal cleaning using Hoppes No.9 and Ballistol for lubricant/protection and done. The Hoppes is just to clean out the Shooter’s Choice and I only ever bother with Ballistol if I’m putting the gun up for a while. Otherwise, it’s just a normal clean and wipe.
 
GeoDudeFlorida said:
Not to put things too blunt but there’s lots of guns in the country. If you get one that won’t shoot, and it can’t be corrected with hand loads or by a factory adjustment, sell it and find another.
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True enough. So far, this gun has shot some of my first loads tolerably well. Just wondering if some light smithing might tighten things up.
 
barnfrog said:
True enough. So far, this gun has shot some of my first loads tolerably well. Just wondering if some light smithing might tighten things up.
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Well, sure, a good pistol smith can work wonders - for a price.
I’ve still got a couple of custom worked revolvers. Some I even actually paid the full freight to get done. Mostly weren’t worth it. Mostly
And then there’s that one shot, at stupid long range and you feel like maybe it was worth it.
I get where you’re going. Been there. Enjoy the ride. :)
 
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