doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Barrel Regulaton - Update

Hi all, well here I stand with egg on my face!! I over reacted on my Grulla's bbl regulation.

I took her out and patterned her at 30 yds. Nice even patterns (a bit low, but nothing to worry about).

I even shot a round of clays with her, broke 23 out of 25.

So...it was a classic case of the Indian and not the arrow!!

I guess the 16yd POI was to close. The bbls converged well at 30yds. So..............shame on me!!

Thanks however for all the kind words and advise, it was much appreciated. Plus you do learn a few new things.

Thanks again!!!

Greg

Greg:

That's what I thought all along Greg as I had posted....but didn't want to argue with the 'herd'.........who were convinced it could not be fixed.....and was a bad set of barrels....!.....

Most factories use a fixture and a torch to solder and regulate the barrels as they assemble them, then they pattern the new guns to double check their work, bluing is after patterning usually in case adjustments are needed.....then it is inspected and passed then boxed for shipment......

Glad you are a happy camper and have your fine gun tuned up...I'm sure you sleep better now too....

You can also bring those patterns up as much as you want with different loads, no bending of the wood required.........

Enjoy your new gun....

Thanks Doug!! I appreicate the kind words!!

Greg

Not to hi-jack this thread but Doug could you expand on:

"You can also bring those patterns up as much as you want with different loads, no bending of the wood required........."

Thanks,
Phil

I was hoping Jim'bo would expound on the virtues of having a bow-legged woman.

Phil:

By reloading shotshells and the use of different charges and wads, most scattergun POI's can be adjusted slightly....there is a limit to the adjustment as too much powder will just blow the patterns....but slight adjustments can be accomplished....on paper.....

Once you find the 'sweet load' for your gun, stick with it....

Most factories pattern average double guns with 7.5 shot....what powder charge is anyone's guess....some probably use a laser to regulate the barrels during assembly and don't even pattern the mass produced guns....the higher dollar guns are patterned after regulation for sure.....


As with other projectiles, the arc changes with charge, weight, velocity and resistance.....nothing high tech here, just common sense.....

Greg:

Glad it worked out. After doing this for 40 years your learn a thing or two. There can be good information on these bbs and are very helpful. But there is lots of bad information too thats just not right.

Best


John Boyd

And bad starting points. A gun that shoots the right barrel to the right, and the left barrel to the left at 16 yards will never 'converge'.

It will diverge, and the problem will be worse at greater yardages.

Argue with that.

I agree.

Best,

Mike

Take a modern Over and Under of your choice......pattern the gun at 15 yards while turning it on its side and shooting it as a side by side.........use a high power load and a low power load.....patterning both barrels of course on paper.....

Use the center rib as the sighting plane....a small ball of masking tape can be affixed as a bead if desired.....

Answer your own questions.........

What the hell are you talking about?

That's about the silliest experiment I've ever heard of.

All firearms are compensated for drop, just look at one. Over and under guns also use various tricks of the trade, including bending the lower barrel, to regulate to point of aim.

SxS barrels converge at the muzzle. This compensates for torque. The chosen load does indeed affect POI, no argument. That's the FIRST thing I mentioned to the man.

BUT, what he's describing now is a physical impossibility unless the gun is three feet wide across the breech.

Barrels are assembled to a design spec and that's it. I dont know of one maker who "regulates" shotgun barrels on a production gun . Why not work it out mathematically? that will tell you exactly wear the barrels converge, cross over and wear the theatrical pattern centers will be at any set distance.

When it comes down to it, its the shooter who hits the target .Nothing to do with some mythical barrel maker making magical barrels the do the work for you.

For the load to raise the POI, wouldn't shooting a slower fps loads shoot higher?, like the barrel will be a bit higher in recoil before the shot leaves the barrels?
Just a thought.
Franc

I shot nice gobbler this spring with my SBE 'gangster style' at 35 yards....

Doug I think the point is that if the left barrel shoots 6" to the left at 16 yards it will shoot 12" to the left at 32 yards and 18" to the left at 48 yards, everything else being equal.

Vice - versa on the right barrel.

I assume Greg has since concluded he didn't check the POI/POA correctly when he wrote his first post on the previous thread.

If the gun was currently shooting as Greg posted in the first thread it would still be my conclusion that he has a barrel regulation problem.

Best,


Mike

Normally yes, Franc. This is called 'barrel time'. But... a SxS is subject to a phenomenon called 'barrel flip' which is related to the flexibility of the barrel set. It's a different animal than, say, a Ruger Redhawk.

Barrel time WILL effect latteral POI, somewhat. There are variables here, consider the effect of cast for instance. That would change the lever problem wouldn't it?

Guess why the Ruger Gold Label failed to sell? They couldn't find an economical high volume production method for the barrel set so they gave up. As it turns out, when a man buys a SxS shotgun he sort of expects it to shoot where pointed from both barrels.

And JOe, I normaly just ignore you but if you fired your SBE 90 degrees out of plane you wouldn't hit crap at 35 yards unless you pointed right and high because guns shoot left and low when fired 'movie' style. I call BS on your turkey.

Greg, are you claiminmg that your gun will still have POI as first described and second described based only on patterning distance??? I'm having trouble with that. What phenomonen would cause the pattern center to follow a horizontally curved path (not to be confused with the ballistic arc)?

Hi all, very good points made by all. As I said, I think this was a classic case of the Indian and not the arrow.

I took her out again today. I shot 23 out of 25. Same as yesterday. I didn't re-check the POI. To be honest, I'm not going to worry about this gun anymore. She's shooting fine now.

I will add that I had shot Federal Game Loads and RST, both to either check the POI (I used RST's) and at clays (FGL). When I used the FGL I shot 12 out of 50. Today and yesterday I used Winchester Game Loads. It seems that this gun likes Mr. Winchester.

As someone said previous, it was perhaps MY technique and MY screw ups. I'll settle for that.

All I know are the results of today and yesterday. I'm happy and I'm not going to dwell on it.

Again, thanks for all the great responses, I did learn from you all as I always do. Thanks!

All the best!

Greg

After some years working on aerospace dynamics analyses and more years as a professor of mechanical engineering teaching dynamics, I can see no way that patterns with the described horizontal spread of 14 inches at 16 yards could be even close to converged at 30 yards.

Either something has dramatically changed and patterns are now close to convergence at 16 yards, or they are still badly out of convergence at 30 yards.

Since convergence seems not be have been actually measured at 30 yards, perhaps the patterns opened up enough to break targets there even with poor convergence. If the "Winchester Game Loads" are promo loads with soft shot, deformed pellets can cause breaks fairly far from the pattern center.

I suggest a follow-up series of actual convergece tests at both 16 and 30 yards under a fixed set of conditions. There may still be a convergence problem with the gun that should be fixed by the importer. Now is the time to have it done.

Try shooting the gun at 10 yards, from a bench, with the front hand supporting the forend on sandbags or a bench rest. Aim carefully down the center of the rib, put the front bead in the center of your aiming point, hold the gun very steady and squeeze the triggers like you would a rifle. Both shots should make one pattern, from the size of a coffee cup to a dinner plate, depending on the chokes. You should not have two separate patterns.

I shot a tree trunk trying that same thing last Spring. Sight picture looked good, but turning the sxs over just moved the barrels in closer to the tree...Geo

If, as Greg/gjw posted in the original thread, the left barrel is shooting 6" to the left of the POA and the right barrel is shooitng 6" to the right of POA then the barrels are diverging and the farther out the target the greater the lateral divergence.

Best,

Mike

Do me a favor and just "ignore" me from now on....

Call it what you want....two unknown gobblers came in behind me...one spotted me and started putting and walking off...I started calling hard on a diaphram another bird gobbled right behind the tree...I started calling and slid down the tree when I got the gun around it was at 90 degrees and he was about 35 yards...I was still calling as I looked "over the side of the barrel" and pulled the trigger. There might have been some luck involved but that's how it went down Jones.

No "BS"

jOe's storey sounds about right for a turkey hunt to to me. Strange stuff happens when they sneak up on you. All I can tell you is that gangsta style shooting will not curve a shot string around a tree trunk...Geo

I pull alot of things off in the turkey woods.

About 5 or 6 of the gobblers I killed this past spring I called up and killed standing up next to a small tree in open hardwoods. I guess he'll call me a liar on that too.

Hi all, I e-mailed Grulla abot barrel Regulation. Here is the response I received from them:

Dear Mr Westberg

Replying your email I suppose you have a new model 209H. We have regulated the barrels of all our
shotguns from the last 8 years produced a diatance of 20 yards approx. Because our shooting room
is limited in distance. However according our experience the pattern of the shots are giving us the good
idea that must be shooting to more yards in the same way.

best regards

Jose Luis Usobiaga
Grulla Armas
Eibar - Spain
Tel: +34 943 208


My gun was made in 2004, so it falls after the year they started to regulate bbls.

As I said, it must have ben me!!

Thanks again and all the best!

Greg

Greg:

Good Job Greg......thanks for posting......."a person who never made a mistake, never did anything".........

Enjoy your new gun.....and years of great shooting....

Best Regards,

Put a bore sighter down each barrel and see. A lot of chat no action.

Not much to do here except chat as Greg is happy with his revised opinion and none of the "train drivers" can shoot it without going over to his house. Just because the breeches are thick and the muzzles thin doesn't mean to me that there's angular convergence in the bores. If the plan view axes of the two bores were actually straight lines tending to convergence at the bitter end, this gun would shoot crosseyed (balance of pattern from right barrel left of POA, pattern from left to right of POA) at any range and so would any other so constructed. Most don't so most must have their bore axes brought into a condition of parallelism by bending prior to shimming, wiring and soldering. The analogy would be rifle barrels (same caliber, load, set up with bore axes parallel and muzzle exits in as close proximity as possible laterally. Yes, there are variables and machining imponderables but you ought to punch two little holes in paper separated by a distance equal to the separation of bore centerlines. Shot from a smoothbore with parallel bores should have the same separation of centers but with spread of pattern creating overlap and producing two practically concentric circles. The devout desire that all else "be equal" (for instance the lateral displacement or "autolead" created by cast) is always disappointed. JL's last post certainly makes the distinction between "where it shoots" and "where we shoot it."

jack

rabbit for me cast off gets my eye over the centerline of the rib. I need it more on high combed guns than I do the standard the modern American standard of 1-1/2 x 2-1/2. If a gun doesn't have enough cast off I can roll my head to the right so the left eye is higher.

Best,

Mike

The words of Mr. Usibiago at Grulla support the idea that patterns that are coincident at the yardage of regulation are coincident at all ranges. To say that "patterns converge" at a certain ydage is a geometric fallacy.

jack

Does the same for fat-faced, beady-eyed me, Mike. But the "lever" created by doglegging the stock hither or yon does give the shot from the offside barrel a bit of "law" as Thomas called it. Simple matter of the kick stick displacing laterally off a fulcrum. Least that's what Garwood says, even a goofy train driver like old Guffy couldn't have got THAT wrong, could he?

jack

I had a simular experience once, but found three factors that I feel certain contributed. First I hate to shoot a shotgun from a benchrest(it hurts), two- I can't see the rear sight on a rifle very well nor the top of the fences on a shotgun and third- my shotgun doesn't fit me when I shoot off a bench and I believe the arguement used against most SxSs for pro trap is that fit is more critical and the mount needs to be more precise. I admit my guns don't fit me as they should but one and two probably had more to do with my misplaced patterns than fit and in the end it wasn't the gun.

"...the barrels must be so set that the axes of the bores are not parallel but slightly converging, being closer together at the muzzle than at the breech. ...if the barrels were set with their axes parallel there would be considerable difference between their shooting. ... "

"When the right barrel is fired, the recoil tends to throw the muzzle out to the right since the axis of the barrel is situated to the right of the center of gravity of the gun. {states the same for left barrel to the left. ed} ... this effect is eliminated by setting the barrels with their axes slightly converging..."

Burrard - THE MODERN SHOTGUN - Barnes 1961 reprint pp 31, 32.

Anybody? No dispute with Sir Gerald? There usually isn't.

As it turns out, the 'train driving' was done a couple hundred years ago when gunmakers affixed two barrels side by side on the same stock.

The value of this board in connecting the fans of the double barreled shotgun with the actual, true, facts of their design, manufacture and use is obvious.

But, as the good Mr. Boyd points out, there is much information here that just isn't so.