doublegunshop.com - home Forums General Discussion DIY Gunsmithing @ doublegunshop.com Cutting barrels and point of aim issues ???

I am sure I am just not getting it but if a set of barrels are properly regulated and the axis down the centers of each bore are straight, then how does cutting off an inch or two of barrel change the point of aim?

The cutting does not change the relative bore axis' (axises axees ???)

What am I missing?

Thanks

The original choke and remaining choke after the cut may affect the point of impact of one or both of the barrels, and there might be some change in how the gun is recoiling and the duration. Just thoughts.

In theory, the cut would need to be "square" to the axis of each barrel and they converge, so this is difficult. I suspect the "re regulation" would be done with files and "crowding" a reamer to one side or another.
Mike

On original barrels are the ends of each barrel cut to be square with the bore axis?

I have never noticed this before. Every barrel I have with factory ends appears flat and perpendicular to the center of the rib.

Make sense that a significantly out of square barrel end would throw pattern negatively but I can't imagine an amount unnoticeable to the naked eye would make much, if any, difference.

The barrels were "square" to the axis before being joined to each other.

Anything done to change the muzzles of a double gun has the potential to change POI, thus affecting regulation. However, when both barrels are shortened their relationship to each other is not changed. That relationship, and proper choke work, is what allows regulation. Regulation does not mean the gun will shoot to POA, it just means that both barrels shoot to the same POI. POI of both barrels, together, can be adjusted to where needed.

If the barrels are shortened a reasonable amount due to muzzle damage, and most of the choke remains, and the muzzles are faced properly, I would not expect a change to regulation. But, I've messed with double guns long enough to know to not make guarantees concerning regulation after drastic surgery.

SRH

Almost makes me wish the late Burt Becker was with us, to give his insight into this question. In re-reading Jack O'Connor's Shotgun Book- the chapter on chokes- he mentions that Winchester's WS-1 and WS-2 were based on a slightly different radius that the standard Imp. Cyl., Mod. and Full Winchester chokes. My 1939 M12 28 gauge has a solid rib and is marked WS-2, but it is a field grade, not a Pigeon Grade skeet model (like my friend has-- his has the WS-1 choke markings. Any Winchester M12 addicts on the forum care to elaborate on this a bit? RWTF

At what distance was regulation set? Is there a standard?

Many thanks

I can't say that I can remember ever reading of a "standard" distance at which barrels were supposed to be regulated, on a shotgun. When I test double guns for regulation I like to do it at 16 to 20 yards. I want a small pattern on the plate because it is easier to determine the center of the pattern if it is small. I have found that if the gun in question is regulated at that distance I don't have to worry about it at any distance I will be shooting game or targets.

Just my findings only, SRH

Thanks Stan

I cut the 30" barrels in the mismatched Lefever Nitro 12 gauge down to 27". Barrels gauged .729 all the way down from end of forcing cone to the start of chokes. I imagine I cut most if not all choke out but a a cyl/cyl 12 ga is great for what I am wanting this for.

I am using this for close in wood duck shooting. I am close to having all fitted and ready to test fire before final finishing and re-assembly.

I will start at 20Yds and see how she pattern/chokes out to 40.

Cheap gun and a leaning project for sure.

Thanks again.

I can relate to shooting woodies "up close and personal". Many times any choke at all is a handicap.. They're the only duck I know of that lights on the water at 50 mph, 10' from you.

Good luck, SRH

Yep sometimes I have thought a tennis request would be a better tool than a shotgun.

Sounds to me like you boys know a little about roost shooting?...Geo

...... that and flood oak hammocks

Great fun

Morning woody shoots can be just as bad. Little suckers will light right by you so early you can't see them coming in.

SRB

It should make no difference at all .Shotgun barrels are not "regulated " as would be a double rifle . They are put together and they shoot where they shoot . In shotguns regulation is the boring of chokes to give a set pattern with a set cartridge at a set distance . Thats all .

If the average 28" 12 bore side by side were to be regulated as many seem to think then the muzzle ends would be about 5/16" to 3/8" apart to give overlapping patterns at 30 yards

It can be calculated mathematically to give the muzzle centers compared with the rear centers that would be needed to achieve this and shotguns were never been made that way .

I think what you say is true, but if the barrel of a double is bore sighted, the rib point of aim and marking where both barrel look. The patterns fired off the shoulder don't necessarily end up where the bores pointed.

I disagree. That may be your opinion of regulation, but not most of the gun trade's. Regulation, as regarding a doublegun means that both barrels print their respective patterns dead atop each other at usable range. That is NOT accomplished by how the chokes are bored (though sometimes correction can be made by altering the choke bore on a non-regulated gun) but rather by how the barrels are joined with convergence. This is done to compensate for the lateral recoiling of the left and right barrels on a S x S. Sure, they aren't regulated in the same way that a double rifle is, by bench rest shooting and adjusting the relationship of the barrels by changing the amount of convergence, until perfect ............ then soldering them up. Shotguns are regulated by building the barrel sets to a certain spec. If done exactly right they will be regulated with a reasonable load. The word regulation, again, regarding shotguns, does not mean they're shot, adjusted, shot some more, adjusted, ad nauseam, until finally right, then permanently joined. "Regulation" re: shotguns simply means that the barrels have been built in such a way that the centers of the patterns print to the same place.

I have seen Miller post on here the exact angle of convergence that Hunter Arms used when building their doubles. Their guns are "notorious" for being very well regulated. Given how badly many over the counter doubles are out of regulation, some manufacturers should pay more attention to it. Beretta refuses to acknowledge a problem unless the two barrel's patterns are over 8" off, from each other, at 25 yards.

SRH

Stan after 50 years in the English gun trade that includes years in Birmingham building new guns and years involved with sleeving I think I have little more insight into the construction of double gun barrels than some .
We may differ on what you on your side of the pond call regulation but on this side it is as I previously stated .

A pair of barrels were built taking into consideration the centers of the action at the breech then were brought to together at the muzzle . A Gun maker would have the same centers on the action regardless of the barrel length , be it 25" or 30 "so that alone should tell you something .
Apart from being paralleled that was all the barrel maker considered .

You can believe what you like and I dont really care , all I try to do is to set the record straight and correct misinformation when I see it .

Let's back up a bit, for the sake of trying to reach a common understanding of what each other is saying, if you will.

Are you saying that, in the British gun trade, no care or forethought was ever put into having the proper amount of convergence so that the barrels will print the individual barrels' patterns perfectly atop each other? It seems you are by saying that they are positioned at the breech for the correct center to center distance, then all were brought together at the muzzle until they touch, and they "shoot where they shoot"? Asked another way ......... if the muzzles were always brought together until touching before soldering up, would no consideration have been given, to where each barrel shoots, when deciding the distance between centers at the breech?

Not trying to be argumentative here, gunman, just trying to understand your position. Most of my guns are touching at the muzzles, with uncut barrels. However I have a few that are decidedly apart, also with uncut barrels, nowhere near touching, but shoot patterns that are dead atop each other. This shows me that the makers knew that the gun would crossfire if the muzzles were touching and would not have shot regulated patterns, so they designed in the proper amount of convergence for the amount of recoil.

SRH

You are basically correct in your first statement , The vast majority of guns were made like this .
There may have been guns like live pigeon guns that were built as target guns but these in my experience have been few and far between .
You bought a gun and learnt to shoot it . No one bothered with all this point of aim / point of impact stuff and it seems generally confined to enthusiasts on forums as with talk of theoretical ballistic effects , that gunmakers of the late 19th and early 20th century did not concern themselves with ,if indeed they even thought about .

In tests with lasers mounted centrally in bores and sighting down the rib at a target 25 yards away , it was found that on average the right barrel shot high and to the left of the center and vice versa . The actual cross over point some 12/15 feet from the muzzle .These tests did not take into any ballistic affect of the cartridge .
The tests were carried out using barrels form a variety of British and Continental guns of all grades and values .I can not speak for guns made in the USA .

With O/U's the general rule was that the top barrel shot flat and the bottom up to 12" high [ this was later prove using solid slugs at a target]
These tests were carried out with the idea that when sleeving a pair of barrels the alignments would be achieved more accurately to achieve the theoretical ideal configuration .

Like many others in the trade we had an excepted belief that the average 12 bore with 28" barrels would have over lapping patterns at 25/30 yards , so you can imagine the results came as quite a shock .

You can work out mathematically the theoretical dimensions that a pair of barrels would need to achieve the desired results .Take the convergence of centers ,from breech to muzzle , than project that convergence to a 25yard point .
Taking into consideration the centers at he the breech can be 1.1" to 1.1/4" work out the centers at the muzzle on a set of 30" barrels and see what muzzle centers they would need . Also work out with the same centers for differing barrel lengths as any maker using the same action would do and you will begin to see the points I have tried to get across .
I have never seen any gun that will meet the requirements and thats about all I can say on the matter .

Thanks very much for your added input. I appreciate it.



One more question, if I may. What requirements are you speaking of?

SRH

That would be perfectly overlapping patterns at say 25 yards.

Thanks, that is so interesting. Regulation of shotgun patterns has been a keenly interesting topic for me for many years. I guess that is why I find it so interesting that it was not even considered in England. I have patterned many, many doubles over the years to see if they, as we say, are regulated. I know that I am in the minority in my genuine concern for this.

I have somewhere on the order of 20 doubleguns that I use, from occasionally to regularly. All fit me, and all put their respective patterns atop each other almost perfectly (within an inch or two), with the loads I use in them. I will not own a gun that does not. If I buy one that shoots patterns 6-8" off from each other I get rid of it, or don't buy it. Trust me please, when I say that there are many doubleguns from inexpensive to high priced that are regulated perfectly. There are also many of all price ranges that are not.

My interest in this comes from a desire to have total confidence in my gun. If it crossfires, or one pattern is 8" too high, I cannot have that confidence. I am an avid student of wingshooting, and work constantly to improve. I've found over the years that one way is to begin with a solid gun that I have the utmost confidence in.

It's been an interesting discussion, gunman. Thanks.

SRH

Stan , the one thing we will fully agree on is confidence . I do know from years of gun fitting that if the man has confidence then all other things will eventually fall into line .How that is achieved is and can be an individual or personal thing .
It is a whole other subject for another thread .
Graham .

Interesting comments from Stan & Graham ( Gunman).
I have personal experience of a high end gunmaker that sold me a gun that didn't pattern anywhere near how I wished it to . So I had to make adjustments when taking shots at clays . This was no good at all and we ended up falling out big time about it .
I will have nothing to do with them or their products ever again , but they must have listened as their current products are not too bad , although I have had to help a friend out with dialling his in via the twiddly bits at the muzzle. Quality Control ? Bah.

Absolutely, salopian. High $$ is no guarantee of properly regulated patterns, though it certainly should be.

Speaking of gunfitting and confidence .......... it can come different ways. When I first began shooting sporting clays seriously, some 20+ years ago, I had but one gun that was suitable for it ............ the 1100 12 ga. autoloader my dad had given me on my 16th birthday. I had shot it well on birds for many years, I thought. In my search for ways to make it better I began to shoot a pattern plate with it. My patterns were not centered on point of aim, so I began tweaking the gun fit to make it do so. I put on an adjustable buttplate fixture and a recoil pad to get the length I needed. I began building up the comb with cardboard and duct tape (I did use brown duct tape ), and I would shoot the plate before and after each change. I got the gun to shooting consistent 60/40 high patterns, perfectly centered right and left. My scores improved as a result.

Then I was asked to join three friends on an overnight road trip to a professional gunfitter, for a proper fitting. I went along expectantly. After my session at the plate with him and the try gun we went inside for him to take the measurements and write them down for me. He had instilled some confidence in me about my mount, and I was anxious to get home to measure my gun and see how much off his recommendations it was. When I did so I found that some of the measurements were spot on what I had determined was right for me beforehand. One measurement was 1/8" off, and that was the most of any of them.

Now, that builds confidence, I can assure you.

SRH

Stan,
100% agree .
I have shot Miroku guns for more than forty years, and shot them very well.
Went to Perazzi to buy a new gun (treat), they fixed me up with a suitable ? gun left handed for me , it was useless, shot very high, back to the gunfitter and another lower comb stock , back out , still useless , but better . "OH , we don't have another left hand stock that is lower ." I said okay give me RH one which they did , took it out , bingo I could shoot that brilliantly , back to the gunfitter to check gunfit and he announced " No , no, no, no, no good , is no good ." Okay but could you give me the measurements please I asked .
Duly done and armed with measurements I returned home , (without buying a Perazzi ) the measurements were very close to my Miroku.

With interest I have followed this thread. I purchased these laser bore sights for 12ga off Amazon. The laser sights cam with batteries and a carrying case. They only sell them individually so naturally I had to get two.





All I have are American guns to test, no British. How to do this test so the results are the same with each different shotgun? With a sharpie marker I made arrows on the base and the arrows were at 12 o�clock. I used a shooting stick to hold the gun steady while my son marked the laser dots on the poster board.



I have a long hallway in my house. I can stand in my living room, and it is 25yards to the wall of my master bedroom. So I tested at 15yds and 25yds.
Here are the results.


Rem 1894 CEO 32�bbls � at 15yds the right bbl printed 2�hi and 4 �� left of center dot. And the left bbl printed 3�hi and 1� right of center dot.
-at25yds right bbl was 5�hi and 8� left of center dot and left bbl was 6 ��hi and 1 �� right of center.


Rem 1894 CEO 27�bbls � 15yds right bbl was 4�hi and 5� left of center and left bbl was 4�hi and 2 �� right of center
-25yds right bbl 7�hi and 5� left; left bbl 7�hi and 6� right


Parker GH 28�bbls � 15yds right bbl was 3�hi and 8�left; left bbl was 3�hi and 3� right
-25yds right bbl 4 ��hi and 9�left; left bbl 4 ��hi and 7�right


LC Smith 00 grade 30�bbls � 15yds right bbl 2�hi and 2 ��left; left bbl 2�hi and 2 ��right
-25yds right bbl 5 ��hi and 5�left; left bbl 5 ��hi and 5�right


Ithaca live bird gun 30�bbls-15yds right bbl 2 ��hi and 2�left; right bbl 2 ��hi and 2�right
-25yds right bbl 3�hi and 4�left; left bbl 3�hi and 4�right

I don't know how to use the quote function, but Stan, you mention above about the "barrels patterning 6-8" off from each other"

would that be 6-8" from where the laser dots are from each other or 6-8" from the center dot?


All the shotguns I tested pattern above point of aim and the LC Smith and the Ithaca were the most consistent. I did this b/c I�m not sure if the Rem. CEO 27� bbls are original length. Doubtful. Although they are #2 stamped on the bottom.



thanks for the discussion,
Robert.

Robert, I would be referring to distance from the aiming point, for each barrel. If each barrel of a S X S puts it's pattern centered on the aiming point, horizontally, I consider it to be perfectly regulated for the load in use. The vertical can be dealt with fairly easily, to a reasonable degree.

While the lasers are interesting, and provide good and solid information, the results ignore the effects of recoil, which is why there is convergence built into S X S barrels. And the amount that things like loads, and how tightly you hold the gun, affect where the patterns print, too. The lighter weight the gun, the more the effect, in my experience.

SRH