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

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.