ShotGunWorld Shotguns

It is currently Wed Dec 02, 2020 2:42 pm

All times are UTC - 6 hours [ DST ]


Image



Post new topic Reply to topic  [ 47 posts ]  Go to page 1, 2, 3  Next
Author Message
 Post subject: Back boring
PostPosted: Thu Jan 10, 2008 9:50 pm 
Utility Grade

Joined: Thu Mar 18, 2004 6:17 pm
Posts: 12
Location: Central NJ
In normal 12 ga the bore is about 0.730" and the plastic wads in shells are meant to flare out to seal at that diameter. Now with a back bored gun like the Mossberg 835, the bore diameter is larger.
Doesn't this cause a problem for the wads to seal the larger bore? I have heard of problems with certain wads made of recycled plastic.




Top
 Profile  
 
 Post subject: re: Back boring
PostPosted: Thu Jan 10, 2008 10:22 pm 
*Proud to be a*
*Proud to be a*

Joined: Sun Nov 09, 2003 6:01 pm
Posts: 6795
I don't think it causes any problems. Nothing obvious anyway. And I shoot a overbored (.735) gun and load with the recovered plastic wads. but I got no way to really tell. I do get a lot of plastic fouling in the bore, but don't think it is an issue. The gun goes bang and the clay breaks unless I miss it. I shoot the same shells in several guns, one with tight bores and one with the overbore. No problems that I can see.

My guess is you put 7000-10000 psi on the plastic base was and it will easily expand another .010 inch in diameter. I bet you could make it the size of a nickel in a press pretty easy.


Top
 Profile  
 
 Post subject: re: Back boring
PostPosted: Thu Jan 10, 2008 10:56 pm 
Crown Grade

Joined: Tue Jan 09, 2007 5:35 pm
Posts: 3396
Location: Las Vegas, Nevada
Yes it does cause problems, but not a lot of them. It causes
slightly lower pressure which with most loads does no more
than decrease muzzle velocity slightly. For very light loads
though, say something like 7/8 ounce loads at less than 1200
fps you might get inconsistent results, especially in cold
temperatures. In practice though the average shooter will
probably not notice anything as long as he is using factory
loads.


Top
 Profile  
 
 Post subject: re: Back boring
PostPosted: Thu Jan 10, 2008 11:14 pm 
*Proud to be a*
*Proud to be a*
User avatar

Joined: Sun Dec 23, 2007 2:57 am
Posts: 20896
Location: So Cal (Near Edwards AFB)
I don't think it is said any better than this article on Browning's website: click here -Back Bored
Back boring is a good thing.


Top
 Profile  
 
 Post subject: re: Back boring
PostPosted: Thu Jan 10, 2008 11:58 pm 
Moderator
Moderator
User avatar

Joined: Tue Nov 14, 2006 5:47 pm
Posts: 5494
Location: Salt Lake. Unless I'm off shooting....
I can't imagine .735 being problematic, considering that Kolar produces a substantial number of .750s. I've never heard anyone shooting one complain of insufficient wad seal.

_________________
Mike Power
NSSA 170504

Kill 'em all


Top
 Profile  
 
 Post subject: re: Back boring
PostPosted: Fri Jan 11, 2008 12:32 am 
*Proud to be a*
*Proud to be a*
User avatar

Joined: Sun Aug 21, 2005 8:42 pm
Posts: 28429
Location: Missouri
All of the world's militaries have spend untold millions of dollars and God knows how many man hours researching the ballistics of rifles and artillery rounds. For ballisticians, rifles and artillery are old, settled, absolute science.

On the other hand, shotguns haven't changed a great deal in a hundred years, and the only "scientific" testing I'm aware of was done by Bob Brister about thirty years ago, Overfell and Thompson about fifty years ago, and Milo Farms about thirty five years ago. None of those tests were truly exhaustive, although they were indeed useful. What I'm really trying to say is that I don't think anybody really knows, to a reasonable scientific certainty, whether back bore really improves patterns and reduces recoil to any appreciable degree.

We at least think we know that if all other things are equal a 12 gauge will pattern one ounce of shot a little better than a 16, which will do a bit better than a 20 gauge. But, we are going from a .615 to a .665 to a .730 bore (give or take) when we go up from 20 to 16 to 12 gauge. That's about .050 "overbore" for each gauge we go up, not only .005 or even .020, in the case of the Koloar with a .750 bore. You can drown in a river, but not a mud puddle. I don't think anybody's ever really "proved" that an extra five or ten or twenty thousands "overbore" makes enough difference to matter.

For brand new guns, I suppose a reasonable "overbore" is the way to go. I don't think it hurts anything, and in theory it might help just a bit.

There's an outfit called "Chamber Mates" that makes sub gauge inserts to stick in 12 gauge guns. Evidently, you can shoot a 28 gauge shell in a 12 gauge bore and it works. That's a helluva "overbore", about 180 thousands. I understand that the .410 insert does require a short barrel section, but not very long. If ever overbore caused a problem with plastic wads expanding, it would be in such an application. Chamber Mates claims that a 12 gauge shotgun will shoot about the same size pattern circle with any gauge, so what seems to be happening is that the charge expands out to fill the bore, then the choke works on the charge about the same regardless of the gauge fired. A friend of mine, who's very knowledgable, claims they occasionally give "bloopers", presumably due to lack of proper gas seal. I don't know. Haven't tried them.

One thing I do have an opinion about. Whatever benifits a few thousands overbore may give aren't worth taking an existing shotgun and spending perfectly good money reaming it out. The makers leave a certain barrel wall thickness, and when you take off five or ten thousands, you do so at your peril. For what little, if any benifit that results, you've altered a perfectly good shotgun and removed good metal from barrel walls.

It's your money though, and your shotgun. Provided there's a good excess of metal, an overbore won't blow up your gun. Make sure whoever does the work knows their stuff, though.
You might just think it's a wonderful thing. As for me, I'll use the money to buy another old shotgun. :lol:


Top
 Profile  
 
 Post subject: Re: re: Back boring
PostPosted: Fri Jan 11, 2008 3:24 am 
Shotgun Expert
Shotgun Expert
User avatar

Joined: Sat Sep 09, 2006 11:02 am
Posts: 26786
Location: Plainfield, IL
Rastoff wrote:
I don't think it is said any better than this article on Browning's website:


Ahem. Do you REALLY believe that?

Better patterns and increased shot velocity help you hit what you're shooting at. A back-bored barrel is a shotgun barrel that has a bore diameter increased beyond minimum specifications. Increasing the bore diameter of a shotgun barrel greatly enhances its performance. A larger bore diameter reduces friction of the shot charge against the barrel wall. Instead of trying to overcome friction, powder gases expend more energy on the wad base, resulting in an increase in shot velocity. Because there is less constriction or pressure from the barrel walls on a shot charge, there are fewer deformed shot pellets. A greater number of ballistically superior round pellets in a shot charge gives you exceptionally uniform patterns -- delivering more shot pellets in the effective part of your pattern.


Less felt recoil makes your shooting more enjoyable. The effortless transition of a shot charge through a barrel with a larger bore diameter results in a reduction in perceived recoil. Every reduction in recoil results in an increase in shooting comfort.


Who benefits from back-boring? A first time hunter, seasoned wingshot or competitive target shooter all benefit from a back-bored shotgun. More uniform patterns result in better hits, cleaner kills and more smoked targets.


There are a lot of things wrong, really wrong with Browning's self-serving blurb. Of course there has been a great deal of science put into back-boring (over-boring), and the mythical benefits go to Stan Baker . . . and many years prior.

The notion that "A larger bore diameter reduces friction of the shot charge against the barrel wall." is more than a bit goofy. Surely Browning must know that scant little shot contacts the barrel wall at all, and has not since the advent of plastic 1-piece wads. Wads themselves have a very low coefficient of friction.

As to the better patterns, if you believe that-- then Brownings pattern better than Beretta's, Perazzi's, any Italian or non-overbored gun. No competitor in their right mind would bother with any shotgun other than a Browning.

As far as reduced recoil, that is pathetically easy to show-- if it existed. Holster up a shotgun to the recoil machine, firing through a "standard" barrel. Now, again with a series through an overbored barrel. There it is, or more correctly-- there it isn't.

Not only would Browning 12 gauges pattern better and have less recoil than most of the market, Browning 20 gauges would have scant competition-- they have the overbored "advantage" to themselves.

Backboring a barrel does not, and cannot decrease maximum average pressure-- as that happens inside the hull, the barrel does not see peak pressure in shotshells.

"Instead of trying to overcome friction, powder gases expend more energy on the wad base, resulting in an increase in shot velocity."

This is an amazing new branch of physics-- we have higher velocities, and LESS recoil. It doesn't happen on this planet.

While we are re-writing physics, let's just remember that now gas does not act in all directions with equal force, it now ignores that and just expends "more energy" on the wad base.

Recoil force and velocity is easily measured; so easy in fact that showing the merits of "before and after" overboring are simple to display-- if they existed. They do not.

Pattern percentages are also easy to display before and after overbore-- if there was a meaningful difference. There isn't, so you won't see a claim of pattern percentage improvement-- it cannot be shown.

So obvious and clear is the advantage, that the savvy consumer would be compelled to buy only overbored 16 ga. and 28 ga. shotguns as well, enjoying the better velocities, lower recoil, and improved patterns. Somehow, after all these years, gimped 16 ga. and 28 ga. guns still perform-- even the current production non-overbored Brownings. :roll:


Top
 Profile  
 
 Post subject: re: Back boring
PostPosted: Fri Jan 11, 2008 3:33 am 
Crown Grade

Joined: Tue Jul 03, 2007 7:16 pm
Posts: 4383
Chronographs and pattern boards don't lie.

Backboring isn't anything new. It was proven effective a long long time ago. Becker and the Super Fox comes to mind. The only reason it's not carried through with smaller guns is due to cost, their already lower recoil and their limited use as compared to the 12. Some targets guns, like the K32 & K80 have always had slightly larger bores and slightly longer forcing cones and have always been thought of a somewhat softer shooters than other gun of similar weights and dimensions.

News flash... the world is not flat either.


Top
 Profile  
 
 Post subject: re: Back boring
PostPosted: Fri Jan 11, 2008 8:46 am 
Tournament Grade

Joined: Sat Jan 05, 2008 1:14 pm
Posts: 172
increasing the bore wold increase the friction caws it wold have a greater surface area for the wad and shot to rub on

if the wad expands larger it wold receive more energy because pressure is measured in lbs per sq inch so enlarging the piston wold increase the pressure on the wad going in that direction but (like having a bigger piston in a car) but its such a small amount i doubt its noticeable

if you want a bigger bore get a 10 ga


Top
 Profile  
 
 Post subject: re: Back boring
PostPosted: Fri Jan 11, 2008 9:05 am 
Crown Grade
User avatar

Joined: Mon Mar 07, 2005 4:16 pm
Posts: 4643
Location: Long Island, NY
The 835 isn't just back bored (ore more corectly overbored), it's a bloody 10ga!

Randy's desemination of the Browning page is a good one. There is just no possible way that accepted science can account for any of the claims.

However, barrels are individuals. Some barrels with certain loads may see an improvement with back boring. Others may not. Whether is is the pattern, percieved recoil or whatever, altering any of the factors involved will most likely alter the results.

Like most things with shotguns, if you believe it works, it will definitely have some benefit.

Frank


Top
 Profile  
 
 Post subject: Re: re: Back boring
PostPosted: Fri Jan 11, 2008 12:51 pm 
Shotgun Expert
Shotgun Expert
User avatar

Joined: Sat Sep 09, 2006 11:02 am
Posts: 26786
Location: Plainfield, IL
SS wrote:
Chronographs and pattern boards don't lie.

Backboring isn't anything new. It was proven effective a long long time ago. Becker and the Super Fox comes to mind. The only reason it's not carried through with smaller guns is due to cost, their already lower recoil and their limited use as compared to the 12.


Neither pattern boards nor chronographs are capable of conscious though. Chronographs, particularly consumer chronographs may not be accurate-- one of the reasons Doppler radar has obsoleted chronographs, lab radar being the standard.

20 gauges, due to their lighter weight, can offer more recoil than 12 gauges-- and would need physics-defying recoil reduction more than 12 gauges in some cases, not less.

The "cost basis" has no merit-- try to count the number of Beretta / Benelli choke tube styles and barrel styles out there. You'll run out of fingers and toes in one big hurry. It seems that manufacturers go out of their way to avoid standardization. It costs no more to make an overbored barrel than a standard barrel.

I've invested (wasted) many hours with true back-bored barrels, particularly Stan Baker "Money Maker" barrels. The reduced recoil / better velocities / better patterns didn't happen.

Likewise, I spend many hours patterning an A-5 Light 12 with a wide variety of barrels-- several fixed, Invector, and back-bored "Invector Plus" barrels. Less recoil happened nowhere, velicities were within 20 fps averages of each other, and the "better" patterns didn't happen. Fixed IC and fixed mod chokes threw obviously more consistent patterns than their "modified" factory-screw-choked counterparts.

You won't find "before" and "after" backboring patterns from Browning, you won't find data showing recoil reduction after using a back-bored (over-bored) barrel vs. a standard barrel, you won't find any data showing velocity increase in percentage or feet per second--- because it does not exist.

You won't find any reputable, independent company claiming better patterns, higher velocities, or reduced recoil with overbored barrels. Not Lyman, not HP White Ballistic Labs, not Olin, not Down Range Manufacturing, not Trulock chokes, not Alliant Powder. The best you'll get is a definite maybe, or a "try it and see." There is no data to support it.

There is a reason for backboring, true back-boring-- that being to pull weight out of heavy, sluggish barrel sets. That it does, as well as throwing off choke constrictions.


Top
 Profile  
 
 Post subject: Re: Back boring
PostPosted: Fri Jan 11, 2008 12:54 pm 
*Proud to be a*
*Proud to be a*
User avatar

Joined: Sun Dec 23, 2007 2:57 am
Posts: 20896
Location: So Cal (Near Edwards AFB)
Well, since the initial question was,

caseype wrote:
Doesn't this cause a problem for the wads to seal the larger bore?


yes, I do believe that the Browning site description of Back Boring answers his question.

Do I believe that all claims by manufacturers are true? No. I'm sure that every manufacturer tries to put whatever they do in the best light in order to sell more products.

Do I believe that a larger diameter bore will create less friction? Well it seems reasonable to me. Will less friction produce faster muzzle velocities? Yes.

Do I believe that it will make better patterning? I don't have the first clue.

Do I believe that a larger diameter bore will reduce recoil? Newton's third law says that isn't possible.

I'm not trying to turn this into a discussion about physics or weather or not a manufacturer is telling the truth; I just wanted to answer his question about potential problems. The answer is, no it shouldn't cause problems.

Folks keep saying that there hasn't been any real testing of the effects of back boring. Let's do the testing. We will need several guns both normal and back bored. There are enough people here that we should be able to get the necessary guns. Next we need to set up testing parameters. Then we need to take some shots at a patterning board. Then we need to compile the results.

I believe that we will find no significant difference in patterning between standard and back bored guns.


Top
 Profile  
 
 Post subject: Re: Back boring
PostPosted: Fri Jan 11, 2008 1:04 pm 
Shotgun Expert
Shotgun Expert
User avatar

Joined: Sat Sep 09, 2006 11:02 am
Posts: 26786
Location: Plainfield, IL
Rastoff wrote:

Do I believe that a larger diameter bore will create less friction? Well it seems reasonable to me. Will less friction produce faster muzzle velocities? Yes.


A larger diameter bore creates more friction, as there is now more contact area with the bore. The "more" friction is inconsequential, due to the very low coefficient of friction of wad polymers.

MAP happens inside the shell. Peak pressure does not change, it happens prior to entry into the barrel-- all in the hull.

Larger barrel volume means somewhat lower pressures in the barrel itself, meaning lower velocities. Neither matter enough to be tabulated; which is why they are not.


Top
 Profile  
 
 Post subject: re: Back boring
PostPosted: Fri Jan 11, 2008 1:16 pm 
Crown Grade
User avatar

Joined: Mon Mar 07, 2005 4:16 pm
Posts: 4643
Location: Long Island, NY
Quote:
...the Super Fox comes to mind.


The Super Fox was designed for a specific load, the Winchester Super X with Lubaloy pellets. That the gun failed to live up to its' guarantee with other loads caused Fox to revise their guarantee to 80% patterns WITH the Super X load only.

Frank


Top
 Profile  
 
 Post subject: re: Back boring
PostPosted: Fri Jan 11, 2008 2:41 pm 
Crown Grade
User avatar

Joined: Mon Jan 01, 2007 7:03 pm
Posts: 4065
Location: Southern Wisconsin
Compairing Browning on Browning. a pair of 26" lightning a former buddy and I bought at the same time. His being older with INV non back board barrels and mine being a tad newer with INV+ back bored barrel the diffferenve was obvious. Between the two the INV+ had more pellets in the pattern board useing the same ammo and it had a slightly less recoil feel in side by side compairison by not only us, but any that tried both guns shooting skeet that year with us. That is what I know there.

I have breifly shot a Kolar just once. It had a .750 over bore. All I can say is it shot wonderfully for me. I simple couldn't do any wrong shooting it. Was it the over boring? It probably was more like the superior fit, but I wouldn't have changed a thing that is for sure.

_________________
The deadliest weapon in the world is a Marine and his rifle.
Gen. John "Black Jack" Pershing, U.S. Army
Commander of American Forces in World War I


Top
 Profile  
 
 Post subject: re: Back boring
PostPosted: Fri Jan 11, 2008 5:57 pm 
Shotgun Expert
Shotgun Expert
User avatar

Joined: Sat Sep 09, 2006 11:02 am
Posts: 26786
Location: Plainfield, IL
Perhaps Frank's answer was the best; if you think it works . . . it likely does.

As to a subjective Citori test did you weigh both guns? Also, compare the constrictions of the chokes-- they are obviously not the same.

Oversized bores just don't do much. I'm certainly not trying to say Invector Plus barrels pattern badly as a matter of course, but of all the things that are involved in pattern quality (shot, wad, choke) and recoil (gun weight, action type, ejecta weight, gun fit, payload weight, payload velocity, barrel harmonics) making a hole .005 bigger, .010 bigger, or punching it out to "10 gauge" as in the Mossberg citation-- it ranks bottom of the list.

It just has no measurable effect either way, the main reason no manufacturer measures or guarantees any performance benefit.

I like Browning product, and always have. The Star Trek logic in their over-bore "explanation" is an embarassment.


Top
 Profile  
 
 Post subject: re: Back boring
PostPosted: Fri Jan 11, 2008 7:59 pm 
Crown Grade
User avatar

Joined: Mon Jan 01, 2007 7:03 pm
Posts: 4065
Location: Southern Wisconsin
You know Randy. Your some kind of sports writer. With any sports writer I think most people believe you guys get paid to write what ever it is they tell you to write. With that said I wonder whom is paying for the commentary now?

_________________
The deadliest weapon in the world is a Marine and his rifle.
Gen. John "Black Jack" Pershing, U.S. Army
Commander of American Forces in World War I


Top
 Profile  
 
 Post subject: Re: Back boring
PostPosted: Fri Jan 11, 2008 8:30 pm 
*Proud to be a*
*Proud to be a*
User avatar

Joined: Sun Dec 23, 2007 2:57 am
Posts: 20896
Location: So Cal (Near Edwards AFB)
Again, based on the initial question, back bored guns won't cause any problems.

However, you seem determined to make some kind of statement.
RandyWakeman wrote:
A larger diameter bore creates more friction, as there is now more contact area with the bore. The "more" friction is inconsequential, due to the very low coefficient of friction of wad polymers.

This is an incorrect assumption. Yes, the surface area of the barrel increases. The surface area of the wad does not. Therefore, the area making contact does not change. This means that, at the worst, the friction remains the same and at best there is less compression on the wad which makes for less friction.

More to the point though, did some one with a back bored gun do you some kind of wrong? You seem very agitated with the fact that some guns are back bored. Why is that?


Top
 Profile  
 
 Post subject: re: Back boring
PostPosted: Fri Jan 11, 2008 9:37 pm 
*Proud to be a*
*Proud to be a*
User avatar

Joined: Sun Aug 21, 2005 8:42 pm
Posts: 28429
Location: Missouri
Rifle bores are standardized. Down to the thousandth of an inch. Shotgun bores vary up to five thousands either way, from their intended bore diameter. Now, add the complication that the Italians use .725, the American standard was .729, and now we've got .735, .742, even .750 for the overbored barrels. It's not going to end the world, but it would be nice if we had standard bore diameters. We could then measure the constriction of the choke and reasonably assume what choke we had in the gun. Even better would be to have one standard for interchangeable choke tubes. For that, we'd best have one standard bore diameter. .729 has worked for over a hundred years, and it's the likely candidate.

Reaming out a standard .729 bore does make the barrel lighter, at the expense of making the margin of safety less for barrel wall thickness. But, when Caesar Guerini came out last year with "overbored" (just barely, because the Italian proof house won't stamp 12 gauge on anything bigger than .735), they also made the barrel just a schooch heavier, to maintain the same barrel wall thickness.


Top
 Profile  
 
 Post subject: Re: re: Back boring
PostPosted: Fri Jan 11, 2008 10:35 pm 
Shotgun Expert
Shotgun Expert
User avatar

Joined: Sat Sep 09, 2006 11:02 am
Posts: 26786
Location: Plainfield, IL
01lariat wrote:
You know Randy. Your some kind of sports writer. With any sports writer I think most people believe you guys get paid to write what ever it is they tell you to write. With that said I wonder whom is paying for the commentary now?


You think the pen is for sale? :shock: Words, yes, articles, yes, but not the content of them. Soooner or later, people appreciate truth-- or, at the very least, sincere attempts to arrive at it.




Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 47 posts ]  Go to page 1, 2, 3  Next

All times are UTC - 6 hours [ DST ]


Who is online

Registered users: 47MolineRTU, ABLongbow, akadoug, albanygun, Batchelor, Bing [Bot], castnblast2, Cfelix10, chairman, Chris Ferres, Denver1911, dogchaser37, Fluke, geometric, Google [Bot], Google Adsense [Bot], Hal4son, Hognutz, icyclefar, ithaca49, Jaspo01, Jeepwm69, Keperkey, luckydogg, Maine Man, Majestic-12 [Bot], Malcolm7, noweil, ohio mike, Oldman1949, oyeme, painter*, Patently Obvious, Pine Creek/Dave, rabbitwhacker, RAT 3323, rkittine, Road Man, Roger Gascoigne, Rudolph31, Saltydog055, sera, StanofKansas, Steeler [Crawler], SWPAMike, Tex68W, Tidefanatic, Tom Shaffer, tschlemm, xsshooter, zxcvbnm


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group    - DMCA Notice