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Discussion Starter · #1 ·
I recently picked up an older K80. I checked the bore with a bore gauge and it measured .728 bore. Why so tight? Is this a disadvantage? It just makes me wonder after seeing all of these big bore guns that are now available from the factory.
 

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You will be told by many that the barrel will pattern just fine. I'm a believer in a larger bore, somewhere around .740 and lenghthened forcing cones. Both micropolished.
 

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The British standard for a 12-ga bore is .729".
The British standard for an 11-ga bore is .751".
So, with .728", you are very close to a true 12-ga., while a .740" is technically an 11-1/2 ga. and a .750" bore is within .001" of being an 11 ga.
A lot of Beretta barrels are .726". Some other brands have been as small as .724".
About every K-32 and early K-80 Ive seen came equipped from the factory with rather long forcing cones.
Personally, I wouldn't worry about that bore size unless there is some issue with how the gun performs on targets. Keep your bore diameter in mind if you have/get choke tubes. For example, a modern day Krieghoff choke tube (.732") would not be a good idea in a .728" bore.
M.D.
 

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Discussion Starter · #7 ·
I use a bore Gage that was purchased from Brownells. It's not a cheap one! I guess I'm not to worried about any real disadvantage, the gun smokes the targets pretty good.
 

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For what its' worth, every newer (1989 production and newer) Krieghoff barrel I've measured with my Stan Baker gauge has come in between 0.728" and 0.730" and all six of my Beretta Optima bores (2006 and 2008-vintage) measure 0.730" to 0.732."

Perhaps 10 years ago, intrigued by all the beliefs that larger bores yield less recoil and better patterns, I obtained a used KX-5 barrel with a 0.730" bore that had been dropped on concrete and suffered a bent rib and deeply scratched finish but was otherwise okay. I patterned it and my own 0.730" KX-5 barrel and then shot 100 targets, shooting half the targets with each barrel. The target breaks and felt recoil seemed the same. I then sent the damaged barrel to Stu Wright and asked him to backbore it to 0.745" (more on that number later) and make some chokes for it. Stu said the idea interested him as he had never used recoil reduction as a selling tool for his barrel work and was as curious as I was, so he did the work for free.

Upon its return a few weeks later, I performed the same 100-target experiment with nearly the same results. Some of the patterns looked a hair tighter while others looked the same and I might have imagined the recoil to be a little less (damned little) with the altered barrel but I sure wouldn't spend what such barrel work costs just to maybe get that little bit of improvement. Let's face it, Krieghoff has been building some of the world's best shotgun barrels for a long time - I give them credit for knowing what they're doing.

Now, blowing a huge hole in all I've said so far is one of my 870TCs. That 1984-vintage gun has a Target barrel with a factory bore of 0.745" and it shoots noticeably softer than other 870 trap barrels with tighter bores. More than one 870 owner has shot his gun and shells with my barrel and couldn't believe the difference. One friend's gun went from bloodying his cheek in 100 targets to actually being fun to shoot!

So I guess the old adage that every barrel is a law unto itself remains true.

Ed
 

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Krieghoff may well have changed their nominal bore specification since I last checked one - it's been no less than five years that I last did that and I didn't take note of any of the ages of those guns.

Ed
 
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