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I have no explanation for this????

3508 Views 20 Replies 15 Participants Last post by  Scott Johnson
Hello:
I recently purchased a Remington 870 28" choke tube field barrel from a neighbor. The barrel is like new and it came with three chokes Full, Mod, and cyl.

I have never owned a choke tube barrel of any kind before but the price was right so I decided I have some time on my hands and I would try it.

I placed a white middle bead on the gun along with a standard Bradley front bead. I patterned the barrel from a rest with the full choke tube inserted at 13 yards.

A friend of mine has a gauge and the full choke tube measured .041. The barrel patterned straight but 50% of the pattern was below the line and 50% above. I made an adjustable stock and added bushings of 1/32 thickness to the comb but the poi hardly rose up with each added bushing???

I had to place a total of six 1/32 washers in the stock before I noticed a poi diffrence where the pattern is now showing that it is now all above the line by only 2 inches????

With every washer that I added the poi should have gone up above the line but did not. I have no idea why not, but it finally took a total of 6 washers before it clearly moved above the line that I was shooting at.

Any one have any idea why the poi did not raise up with every bushing that was added as the poi finally raised up only 2 inches above the line after a total of six 1/32 washers were added?

I am extremely puzzeled as I have never seen anything like this before.
Steve Balistreri
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If you are still trying to stack the beads, you can override the comb being raised by getting into the gun harder. You should be able to start seeing a gap between the beads if you are mounting the gun the same way, and raising the comb. Keep adding washers, the pattern will come up. Mark
 

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Oregunner nailed it. You are trying to keep the same sight picture so you are bearing down harder to stack the beads. Just hold your cheek lightly on the comb and you will see a wider and wider gap between the beads as you raise the comb. Bill
 

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"With every washer that I added the poi should have gone up above the line but did not."

Steve, why do you believe this is true? Every gun and shooter combination is a law unto itself. While mathematically your assertion may be true,
(or not) mathematics doesn't account for the human element.
 

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<blockquote><I>"Why were you patterning the gun at 13yds?"</I></blockquote>Good question!

A 1/16" increase in comb height will raise the POI about 2" at 40 yards. You'll NEVER see the difference that 1/32" makes at 13 yards. Considering the variables in the mix, a 3/16" increase (6, 1/32" spacers) should raise your POI about 6 inches at 40 yards.

Keller
 

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Discussion Starter · #12 ·
You guys make some sense. I will try the barrel at 40 yards and see what happens. It actually took six spacers before I could not stack a figure 8 when mounting the gun. Subconsiously, I must of been bearing down hard on that stock to obtain my figure 8 without actually realizing it.

Now watch, once I pattern at 40 yards my poi will most likely be a pattern and a half high? I will try and go out to the club to pattern sometime this week at 40 yards.

As you can tell brains is not my strong suit. What ever, maybe I was blessed with good looks?
Steve
 

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Actually you should be adjusting the comb for Point of Impact (POI) at 13 yards. From a rest you are seeing were the gun shoots. Also try some shots free hand to see where you are shooting at 13 yards.

I think that you jumped the gun by putting a mid-bead on.

You should adjust the comb to get the POI that you want. Once that is established then you put a mid-bead to get the fig 8. This way when you see fig 8 you know you have the gun mounted correctly and don't have to guess if the amount of space between the beads is correct.

That said, after the above, you are at the point where you shoot at 40 yards free hand to confirm where the pattern is were you would be breaking the target. You can also see what your pattern looks like.

Step 3 lock the trap for straight aways and see if the gun still shoots where it is suppose to for you.

Jason
 

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If your eye is 36" from the front bead and you cheek the stock the same after each adjustment, a 1/32" rise in the comb should result in the pattern moving up about .4" at 13 yards or 1.28" at 40 yards.
 

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Discussion Starter · #17 ·
Dick:
Here in the Milwaukee area we have had rain storms the last couple days going through the weekend. Rougly 4" of rain causing some flooding. The Gun club will most likely be under water.

As soon as I can get out to the club I plan to pattern the barrel at 40 yards. My guns usually shoot 8" above line at 40 yards so I will have to see how many bushings I need. This appears to be one flat shooting barrel, or maybe it's this particular choke tube?

Dumbest question I can think of. Do they make choke tubes that will shoot high if you need them too?
Steve
 

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They do make chokes that change the POI, but really not worth the effort or the cost on an 870 barrel. There are thousands of old Wingmaster 30" fixed full choke barrels out there, that throw a great pattern. They were the standard on duck guns before steel shot. Mark
 

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Discussion Starter · #19 ·
I put on my hip boots and went out to the local club to pattern my gun at 40 yards. Keller was right, my new barrel patterned 6" above the line at 40 yards.

Years ago, I was told if you really want to know the true impact of a barrel shoot a slug through it. I still don't understand why the poi is not the same at 13 yards as it is from 40 yards. Someone please enlighten me.
Steve
 

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Steve, 40 yards is 3x farther than 13 yards. So you can figure that whatever you get at 13 yards will be 3 times greater at 40. You were 2" high @ 13 so multiply that by 3 and you get 6" @ 40. That's what you just measured. This rule of thumb is close enough for government work.
 
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