Why do SXS barrel bore diamiters vary?

[Kenny Graft]

I have been looking at several American SXS guns and notice that bore diameter can very by 10K from each other? If gun is factory original why would that happen? or is this not normal practice and avoid guns with wide variations. Say a 16ga....left is .655 and right is .668 Would this be indication of hone job? Should it be a deal braker if all else is in spec? I would think that a proper bore job would be the same for both tubes or are the barrels bored prior to jointing them together and luck of the draw? thanks all SXS ohio My question is...did the barrels leave the factory bored the same in each tube? Like .662 and .662 ???/ Thanks all SXS ohio....(-:

[Larry Frey]

Kenny,
When I see a gun with one barrel more than a couple of thou larger than the other I assume the larger barrel was back bored to increase the choke in that tube. This may not always be the case but I have seen barrels that lettered Cylinder or IC that are now bored .010 over nominal and have .010 or more of choke.

[John Campbell]

SxS:
Much depends on the type and age of the gun in question. But, in general, yes. Both tubes should be within a couple of thousandths of the same spec. But remember... you a talking about a shotgun. It is intended to throw a cloud of pellets. and the charge expands to fill the bore on its way out - which is the principle of back boring. A little "tolerance" is not going to matter.

In the final analysis, the more metal you have in a SxS shotgun tube, the better. General rule. So... if one tube is thicker than the other, be grateful. And yes, it could well be the result of responsible honing that took out only as much metal as needed.

Bottom line: Don't let any of this worry you.

[Dean Romig]

But always be certain of the barrel wall thickness before you buy a gun with questionable bore diameters.

[Frank Srebro]

I agree that generally each bore should be within say .003" diameter of the other. But keep in mind that most shotgun makers bought rough tubes to their individual specs from suppliers, and an overrun for one maker could be a bargain buy for another maker. And thus, tubes with different bore diameters could find their way to the storage racks of some of the makers. Generally the barrel assembler would choose two tubes of like bore diameter for a barrel set but that may not have happened all the time. For example: an Ithaca 16 gauge on my bench now that has right tube at .685" bore diameter and choke .671 = .014" constriction. Left tube .674 bore diameter and choke .646 = .028" constriction. Gun is stamped 2 & 4 indicating Mod & Full and the choke diameters are spot on. This gun is absolutely "factory".

For those not familiar with barrel honing (not backboring) it can only be done UNIFORMLY using a Sunnen barrel hone or equivalent machine tool, and they are very expensive and not usually found in the shops of gunsmiths. Most gunsmiths used/use simplistic tools to "hone barrels" - such as emery cloth on the end of a mandrel spun by a drill motor or maybe a lathe. This does not produce UNIFORM bores. Therefore if you're reading larger-smaller-larger (variable bore) with your barrel mike, it's probably been "honed" by some gunsmith using emery cloth or similar. But if your mike is showing one bore is larger than the other, but it's UNIFORM to within .001" diameter along its entire run, that barrel is likely factory. The other possibility is it's been backbored using a lathe and reamer(s) but in that case a close visual inspection will show a difference in surface finish/appearance from one bore to the other.

Just my take on it fwiw.

[Dave Suponski]

I have always believed that Parker Bros. would rebore a barrel to achieve the desired choke/pattern/pellet count. And that would account at least partially for the varience we often see in Parker bore diameters.

[Linn Matthews]

I wonder if bore variation on a SXS is normal and we don't see it because we don't look or is it something that we should be concerned about?
When does a variation get "out of limits"....001, 002, 003" in or whatever?
Thanks for your consideration

Linn

[Paul Harm]

I'm not sure of what you mean by " out of limits ". As stated previously, there are reasons for a difference and as long as the barrels are thick enough there's really not a reason to worry about it.

[Linn Matthews]

What I meant by "out of limits" comes from my belief that when newly made a shotgun barrel has specifications--- like .650 plus or minus .002. This means it could be .648 to .650 and still could be within specification. This is not so??

[Bill Murphy]

Parker bores from side to side, in my experience, vary little, a thousandth or two at the most. If I see a .003 variance, I suspect that the bores have been cleaned up.

[Kenny Graft]

Wow...great info her. The reason I ask this question has more to do with originality than function. I have been wanting a hi condition graded small gauge....they are expensive! I wanted to know and be informed about this issue for value perspective. One of the guns that I looked close at has .010 over normal bore only in one barrel the other is correct. Most all the guns I buy are shipped to me after buying, no in hand inspections. As stated above when bores are not the same the flag goes up!??? I would prefer them to be the same, normal spec and still be choked properly. When old guns are priced 10-20K a feller has to know! Im still on a steep learning curve...(-: Buying is easy...selling with-out a big loss can be very tricky. Like John Wayne said...Life is hard and its harder if your stupid!!! Thanks all SXS ohio.............................

[Bill Murphy]

Kenny, .010 variance from left to right bore diameter on a small bore is excessive and should result in a very steep change in value and price for a graded gun. Let's put this in perspective. I have two nice DHE 20 gauge bird guns that I bought for about $2500 each. They would be $6000 guns except that the stocks are short. If the barrels had bore variances of .010, and original length stocks, the guns would be worth even less than they are with the short stocks, in my opinion.

[will evans]

I would think the balance of a Parker would move behind the hinge if a barrel has been back bored. Let's not forget that the balance of a Parker is a large part of the brand mystique. What's wrong with just weighing the barrels? Does actual barrel weight match what is struck on the water table?

Opinions will vary, but I'm not sure I agree that a back bored barrel is more of a detriment to a cut stock. Both would upset the balance, but only an experienced buyer is going to measure bore diameter. If I were concerned, then barrel thickness would be my determining factor.

[Dean Romig]

Opinions will vary, but I'm not sure I agree that a back bored barrel is more of a detriment to a cut stock. Both would upset the balance, but only an experienced buyer is going to measure bore diameter. If I were concerned, then barrel thickness would be my determining factor.


Balance isn't the critical factor in how back-boring might affect the gun's value - but barrel wall thickness most certainly is.

Unfortunately not every buyer of these old guns is an "experienced buyer" and those who are not are more likely to get burned by their own ignorance. I do not use the term 'ignorance' disparagingly but we all started at that state and I have made some 'ignorant' gun purchases in the past and I very quickly became an "experienced buyer".

[will evans]

I was thinking balance might be used as an indicator. The VH 1-frame 12ga I have beside me right now balances perfectly with one finger directly under the hinge. I am below a neophyte in terms of Parker experience, but I would think the balance point would be moved back toward the stock if one or more barrels had been back bored. A variance in bore diameter AND a rearward balance point might lend itself to further suspicion. ???

[Mark Ouellette]

I would think the balance point would be moved back toward the stock if one or more barrels had been back bored.

Will,
Removal of a few thousands from the bores will lighten a gun by a surprizing small amount. Chances are that the balance would not noticably change.
Mark

[Dean Romig]

Chances are that the balance would not noticably change.
Mark

And if Parker Bros bored a barrel oversize or back bored it and the gun no longer balanced and felt as it should, I'm pretty sure they would have invisibly remedied the situation. Of course we can't say as much for an aftermarket back boring job by someone other than the factory.

[Bill Murphy]

When gun shopping, I would rather be equipped with a bore micrometer than a scale. A smallbore Parker with .010 variation in bore diameter from left to right has been screwed with, end of story.

[Paul Harm]

I don't believe back in the day 5 or even .010 difference in bore diameter made a big difference. It's just now, many years latter, that many of us want to believe everything was kept perfectly the same. Cut stocks or barrels - barrels too thin - yea, that makes a difference. A couple of thousands difference in bore diameter - not.

[Daryl Corona]

Bill is right, .010 difference in barrel ID probably means the barrel has been reamed. I say probably in that I understand Parker factory would clean up barrels at customers request. That would'nt be a deal breaker for me. I agree with Paul; cut stocks and barrels along with thin, less than MBWT, is a concern.

[David Noble]

The VH 1-frame 12ga I have beside me right now balances perfectly with one finger directly under the hinge. I am below a neophyte in terms of Parker experience, but I would think the balance point would be moved back toward the stock if one or more barrels had been back bored. ???

Will, not all Parkers balance perfectly at the hinge.
Of the Parkers I keep in my office, here is what I found.

All are original configuration.

Trojan 16ga 28" "1" frame ............ 1/4" behind hinge (towards trigger guard)

VHE 20ga 2 barrel "0" frame, 26" bbls ..... 3/4" behind hinge
-------------------------- 30" bbls .... at hinge pin

VH 410 26" "000" frame .................. 1 1/8" behind hinge

GH 16ga 26" "0" frame ................. 3/4" behind hinge

GHE 16ga 28" "1" frame ................. 1/2" behind hinge

DHE 20ga 28" "0" frame .................. 5/8" behind hinge

Five of my hammer guns are barrel heavy and balance ahead
of the hinge. (towards muzzle) One has 1" shortened barrels and one has a recoil pad.

[will evans]

Will, not all Parkers balance perfectly at the hinge.
Of the Parkers I keep in my office, here is what I found.

All are original configuration.

Trojan 16ga 28" "1" frame ............ 1/4" behind hinge (towards trigger guard)

VHE 20ga 2 barrel "0" frame, 26" bbls ..... 3/4" behind hinge
-------------------------- 30" bbls .... at hinge pin

VH 410 26" "000" frame .................. 1 1/8" behind hinge

GH 16ga 26" "0" frame ................. 3/4" behind hinge

GHE 16ga 28" "1" frame ................. 1/2" behind hinge

DHE 20ga 28" "0" frame .................. 5/8" behind hinge

Five of my hammer guns are barrel heavy and balance ahead
of the hinge. (towards muzzle) One has 1" shortened barrels and one has a recoil pad.

Hmmm...Sounds like you must have a bunch of back bored barrels, David. :rotf::rotf::rotf:
Where did I read that most are balanced on the hinge? Wherever, it was obviously wrong. Thanks for correcting me, as I might have thought being well off from the hinge would indicate an increased likelihood of something amiss. Sounds like a pretty nice assortment you've got there, too.