Filing a choke to change POI

A discussion about Turkey guns, rifles, black powder, handguns, chokes, cleaning, and accessories.
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poorcountrypreacher
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Filing a choke to change POI

Post by poorcountrypreacher »

I have mentioned filing a choke to change POI on one of my sxs guns, and I've been asked to explain how to do it, so here goes. I started experimenting with sxs guns several years ago and found that its very hard to find one that shoots both barrels to the exact same poi with turkey loads, and especially tss loads. I've found that sxs guns are mostly designed for field loads. A gun with 2 barrels must have convergence built into it to account for the recoil, and recoil varies by load. Because of that, is essentially impossible to make a gun that will shoot ALL loads to the same poi for both barrels. It seems that the heavier the gun, the less the problem. If we are talking about dove loads being 2" different, it really doesn't matter, but on the tight turkey loads we are shooting today, it does matter.

I first tried to solve the problem by sending a gun to Briley's to make eccentric chokes. They have a formula to make any gun shoot to POI, but its based on lead. On the second try, I was able to get a choke that would make my Yildiz sxs usable, and it is my main gun today. But I have worked with 7 or 8 other guns, and had the same issue with all. In a sxs, the left barrel tends to shoot left and the right barrel shoots right when you use heavy tss loads. A guy on shotgunworld told me how to correct the problem.

Here is a Spanish gun that I bought that was totally different than any other gun I tried:

Image

With this gun with every load, the right barrel shot to the left and the left barrel shot to the right. This is exactly the opposite of most guns, and the problem is no doubt caused by too much barrel convergence. It does this with any load. If you shot at a can 40 yards away with both barrels, you would completely miss the can. The gun was made in the late 60s, but it was barely used. I'm sure the reason is that nobody could hit anything with the gun. I filed the barrels and made both of them center my #9 tss load. It did degrade the patterns a little, but the gun is at least usable and has killed a few turkeys.

Here is the way to file it: since the left barrel shot to the right, or inside, I needed to file the outside of the barrel to pull the pattern outward. Imagine that you are facing the gun and looking into the business end of it, and a clock is superimposed over it. The left barrel is shooting toward 9 o'clock, so I took a round file and started filing at 3 o'clock. I held the file at a 45 degree angle to the barrel and started filing the inside edge. Then I feathered it all the way out to 12 and 6, so that I was barely removing any metal at the extremes. So I was removing half as much metal at 1:30 and 4:30 as I was at 3, and virtually none at 12 and 6. After doing this, I tested the gun to see how much the pattern had moved. It doesn't take removing a lot of metal to move the pattern, so test often. Also, I started using dove loads and found that it didn't take removing as much metal to move tss loads. That made sense since the tss loads already tend to shoot left out of a left barrel. I was fortunate that I didn't go too far with it. After getting the left barrel to center, I did the same to the right and centered it.

HOWEVER, the gun is centered ONLY for my tss loads. For dove loads, it still shoots as it originally did, though the error is not as great. A sxs gun can be perfectly centered for only one load; everything else will be off somewhat.

This method will move the pattern of any gun. If your pump or auto is off, you can move it this way. In the age of screw in chokes, you aren't risking a lot by trying it. The only choke I've ever tried that I could not move was a SumToy turkey choke. That thing is built like a tank.

SXS guns have L-R issue, and it seems that O/U guns have up-down issues. If you are considering a double of either type, I would sight in the tight barrel and let it shoot wherever it wants. This will likely give you the densest pattern. Then on the open barrel, file it to make it shoot to the same POI. If you want an IC pattern from the open barrel, you might start by using a modified choke and it will shoot like an IC after filing. I am using cheap flush mount chokes with my Yildiz. A .585 choke is my tight barrel. With this stuff, a high dollar choke isn't really needed for hunting. My gun does about 300 in the tight barrel and 200 in the open, and fits my needs well. Good hunting to all!
Gar Commander
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Re: Filing a choke to change POI

Post by Gar Commander »

Thanks for explaining that where even I can understand it. Now I have to try it!
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hoobilly
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Re: Filing a choke to change POI

Post by hoobilly »

I understand what your saying. that is genius

how about a picture of the work you've done to the barrels?
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2Shooter
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Re: Filing a choke to change POI

Post by 2Shooter »

Thanks Preacher!!! :thumbup:
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hunterjoe37
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Re: Filing a choke to change POI

Post by hunterjoe37 »

Good stuff right there!
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RapscallionVermilion
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Re: Filing a choke to change POI

Post by RapscallionVermilion »

Excellent write up. Hope this gets captured in a sticky.
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Southern Sportsman
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Re: Filing a choke to change POI

Post by Southern Sportsman »

Bump - so I can find this easier. Tinkering with an O/U now. Anyone know the most you can hope to move a pattern like this? Bottom barrel was shooting way low. I’ll probably send it back under warranty after season, but trying to get it in shape for this season. I filed quite a bit off the choke. It moved it some, but still have a ways to go. I feel like I’m going to run out of choke wall on that side before I get the pattern where I want it.
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hoobilly
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Re: Filing a choke to change POI

Post by hoobilly »

Southern Sportsman wrote: March 18th, 2020, 10:22 pm Bump - so I can find this easier. Tinkering with an O/U now. Anyone know the most you can hope to move a pattern like this? Bottom barrel was shooting way low. I’ll probably send it back under warranty after season, but trying to get it in shape for this season. I filed quite a bit off the choke. It moved it some, but still have a ways to go. I feel like I’m going to run out of choke wall on that side before I get the pattern where I want it.
Made it a sticky for you. Be easier to find that way
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Spuriosity
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Re: Filing a choke to change POI

Post by Spuriosity »

Great info, Preacher. Thanks for sharing.
quavodus
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Re: Filing a choke to change POI

Post by quavodus »

Pretty neat. Thanks.
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Giovanni20
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Re: Filing a choke to change POI

Post by Giovanni20 »

poorcountrypreacher wrote: April 17th, 2017, 6:29 pm I have mentioned filing a choke to change POI on one of my sxs guns, and I've been asked to explain how to do it, so here goes. I started experimenting with sxs guns several years ago and found that its very hard to find one that shoots both barrels to the exact same poi with turkey loads, and especially tss loads. I've found that sxs guns are mostly designed for field loads. A gun with 2 barrels must have convergence built into it to account for the recoil, and recoil varies by load. Because of that, is essentially impossible to make a gun that will shoot ALL loads to the same poi for both barrels. It seems that the heavier the gun, the less the problem. If we are talking about dove loads being 2" different, it really doesn't matter, but on the tight turkey loads we are shooting today, it does matter.

I first tried to solve the problem by sending a gun to Briley's to make eccentric chokes. They have a formula to make any gun shoot to POI, but its based on lead. On the second try, I was able to get a choke that would make my Yildiz sxs usable, and it is my main gun today. But I have worked with 7 or 8 other guns, and had the same issue with all. In a sxs, the left barrel tends to shoot left and the right barrel shoots right when you use heavy tss loads. A guy on shotgunworld told me how to correct the problem.

Here is a Spanish gun that I bought that was totally different than any other gun I tried:

Image

With this gun with every load, the right barrel shot to the left and the left barrel shot to the right. This is exactly the opposite of most guns, and the problem is no doubt caused by too much barrel convergence. It does this with any load. If you shot at a can 40 yards away with both barrels, you would completely miss the can. The gun was made in the late 60s, but it was barely used. I'm sure the reason is that nobody could hit anything with the gun. I filed the barrels and made both of them center my #9 tss load. It did degrade the patterns a little, but the gun is at least usable and has killed a few turkeys.

Here is the way to file it: since the left barrel shot to the right, or inside, I needed to file the outside of the barrel to pull the pattern outward. Imagine that you are facing the gun and looking into the business end of it, and a clock is superimposed over it. The left barrel is shooting toward 9 o'clock, so I took a round file and started filing at 3 o'clock. I held the file at a 45 degree angle to the barrel and started filing the inside edge. Then I feathered it all the way out to 12 and 6, so that I was barely removing any metal at the extremes. So I was removing half as much metal at 1:30 and 4:30 as I was at 3, and virtually none at 12 and 6. After doing this, I tested the gun to see how much the pattern had moved. It doesn't take removing a lot of metal to move the pattern, so test often. Also, I started using dove loads and found that it didn't take removing as much metal to move tss loads. That made sense since the tss loads already tend to shoot left out of a left barrel. I was fortunate that I didn't go too far with it. After getting the left barrel to center, I did the same to the right and centered it.

HOWEVER, the gun is centered ONLY for my tss loads. For dove loads, it still shoots as it originally did, though the error is not as great. A sxs gun can be perfectly centered for only one load; everything else will be off somewhat.

This method will move the pattern of any gun. If your pump or auto is off, you can move it this way. In the age of screw in chokes, you aren't risking a lot by trying it. The only choke I've ever tried that I could not move was a SumToy turkey choke. That thing is built like a tank.

SXS guns have L-R issue, and it seems that O/U guns have up-down issues. If you are considering a double of either type, I would sight in the tight barrel and let it shoot wherever it wants. This will likely give you the densest pattern. Then on the open barrel, file it to make it shoot to the same POI. If you want an IC pattern from the open barrel, you might start by using a modified choke and it will shoot like an IC after filing. I am using cheap flush mount chokes with my Yildiz. A .585 choke is my tight barrel. With this stuff, a high dollar choke isn't really needed for hunting. My gun does about 300 in the tight barrel and 200 in the open, and fits my needs well. Good hunting to all!
Good read.You made it look easy.
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