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Old August 12, 2011, 11:25 PM   #1
TheKlawMan
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Checking choke tube

Just on the off chance that my modified remchoke may be more open than that I was thinking of measuring it. Does that need a special smith's tool or can I do it with standard calipers? I believe the tightest point of constriction is what needs to be measured and I can only measure the the point at one end or the other of a tube.
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Old August 13, 2011, 12:21 AM   #2
zippy13
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My friend, you have to compare the diameter of the tube's constriction with that of the barrel's bore. The second measurement, due to its being deeply recessed, is frequently beyond the capability of typical calipers.
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Old August 13, 2011, 12:41 AM   #3
T. O'Heir
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"...may be more open..." Hi. Highly unlikely. Pattern your shotgun with the choke. How it patterns is more important. A Modified Remchoke puts 55-60% of pellets in 30" circle at 40 yards.
However, the ideal tool would be an inside micrometer. Don't buy one to check a choke though. They're not exactly inexpensive.
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Old August 13, 2011, 12:51 AM   #4
TheKlawMan
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Thanks Zippy. I was trying to compare the muzzle end of the choke threaded into my 28 inch barrel with the muzzle end of a cyllinder bore 18 1/2" barrel. Probably the easiest thing for me to do is to go to the patterning board. I read it at a restriction of .012", which would be more like a skeet choke if not for the fact that I likely am not measuring deep enough into the bore.
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Old August 13, 2011, 01:05 AM   #5
TheKlawMan
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I think you are correct T O'Heir about the patterning board being what counts. Re-reading what I wrote it is confusing. I didn't mean to suggest that the choke was more open than the cyllinder bore, but that it may be more open than a modified should measure.

Last edited by TheKlawMan; August 13, 2011 at 02:12 AM.
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Old August 13, 2011, 09:53 AM   #6
oneounceload
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Your gunsmith should have barrel calipers - as mentioned, you need to know bore diameter, and the correct tools will tell you that in 5 seconds. What it says matters not when compared to what it actually does - as also mentioned above, get ye to thy pattern board

IF your constriction is .012, that is nominal IC designation
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Old August 13, 2011, 04:45 PM   #7
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I was trying to compare the muzzle end of the choke threaded into my 28 inch barrel with the muzzle end of a cylinder bore 18 1/2" barrel.
YIKES It's a tremendous leap of faith to assume the two barrels have the same bore!
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Old August 13, 2011, 07:17 PM   #8
TheKlawMan
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How to pattern a choke

To borrow from our friend Zippy; not to reinvent the wheel is this how I should pattern my 870 with a modified choke? Also, should I shoot the reloads I am using or for this purpose buy some factory gun clubs. I beleive my reloads are pretty uniform now and I use good components. While at it I will also pattern with my skeet choke if time permits. (You can only use the patterning board where I shoot if no one is on the adjacent trap field.).

I am thinking that I shoot 7/8 ounce loads of #8 shot or 9 and if I have to count all those little holes I might want to shoot some 7.5 so there will be less holes to count.

The Chuck Hawks article didn't mention it but I was thinking of breaking the circle into wedges like pieces of pie and tabulating how many hits were within each piece. If the pie is cut on the horizontal I can also measue how flat it shoots.

If I also aim at a point marked in the middle and on a separate piece of paper shoot where I look without aiming, shouldn't that also give me an idea of where I am hitting compared to where I am looking?
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Old August 13, 2011, 07:20 PM   #9
TheKlawMan
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Quote:
YIKES It's a tremendous leap of faith to assume the two barrels have the same bore!
The more I think of it, the more this rings true and perhaps moreso for a bottom dollar 870 Express.
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Old August 13, 2011, 10:24 PM   #10
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Pattern the loads you'll be shooting: factory and/or reloads.

Yes, counting the holes (quite time consuming with #9s) in each quadrant will tell you how the center of the pattern relates to the point of aim. You may have seen shotgun reviews where they will publish the deviation for each barrel along with pics of the patterns.
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Old August 14, 2011, 01:00 AM   #11
T. O'Heir
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"...a bottom dollar 870 Express..." Uses the same barrels as a top dollar Wingmaster.
"...have to count all those little holes..." Don't bother. The density, with no holes in the pattern and where the centre of the pattern hits in relation to the sights at a given distance, is what matters. The size of the shot doesn't make much difference. Mind you, 7.5's to 9's are usually skeet/trap and upland bird loads.
Have a look at these. http://www.opticsplanet.net/picture-...g-targets.html
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Old August 14, 2011, 09:01 PM   #12
TheKlawMan
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Thank you T. O'Heir. I will be using the 870 90% for trap and 9% for skeet, which is why I am shooting the 7.5, 8 and 9 shot, for at least the immediate future. Perhaps someday I will give hunting a try when we move out of cosmopolitan Southern Calfornia.
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Old August 15, 2011, 09:03 AM   #13
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To do the job yourself,...

you will need to have a telescopic gage for the interior of the choke, the reading is taken using a Mic or caliper.

This will allow you to take individual measurements from the muzzle downward.

You may also use an inside measuring spring caliper, as you withdrawl fro tube the legs will collapse but return to measurement which you take using a Mic or caliper.

Most choke mandfactureres will have a table of measurement for reference.
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Old August 15, 2011, 11:27 AM   #14
TheKlawMan
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Thanks jrothWA, but I am convinced that the cost of special guages is prohibitive. Should I continue shooting the 870 I have a list of minor alterations that are best done by a smith and will add to it measuring the bore and chokes. For now, I will simply pattern what I have and see if it shoots like a modified, if it is tigher or more open. Most likely it will shoot like a modified.
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Old August 15, 2011, 11:41 AM   #15
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Many gun clubs have a "bore gague" ....that they will let you use at a table in the clubhouse - to check the diameter of the bore against the diameter of the various chokes --- and calculate that difference ...which is what you want to know. Most of us don't own bore gagues...

Ideally you should check every screw in choke you have - regardless of what they're marked / they could differ more than you would think.

Most every 12ga barrel will be a little different --- even within the same mfg's ...
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Old August 15, 2011, 01:47 PM   #16
Dave McC
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There's another way to tell the effective choke, not the actual by the numbers choke.

You mention trap. If a solid hit produces smoke a large percentage of the time, you need less choke. If your hits are chippers, you need more.

Smoke indicates excess density, which costs spread. Most folks take their trap singles at 33-36 yards from the muzzle, so gauge accordingly.

Depending on the load, a by the book Mod choke(20POC) can give patterns from Light Mod or even IC to well nigh Full.

Before we all had gizmos to screw in to our muzzles, shotgunners adjusted their patterns by shell choice. Cheap field loads gave open patterns, trap loads were tighter.

Oft I would hunt with my first 870 and Full choke with a cheap load of 8s in the chamber, followed by a long range load of 6s. I might even stick a trap load of 7 1/2s in between. It worked for me.

You should pattern and/or as sbove. Then, if the results are not to your liking, adjust your load or choke. Only one at a time,of course....
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Old August 15, 2011, 02:00 PM   #17
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Quote:
If a solid hit produces smoke a large percentage of the time, you need less choke. If your hits are chippers, you need more.
That's assuming you are "on the bird" - on some hard angles, you may be just off somewhat, while on a straight-away you smack it hard.

Bore gauge and pattern board, absent high-speed cameras, still give the best indication
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Old August 22, 2011, 01:16 PM   #18
TheKlawMan
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OK. I am not sure that I did a good job of patterning. To begin with I needed more paper and much was wasted on what I call "snap firing". I also screwed around with taking some shots with 7/8 loads and others were 1 oz. I think it best that I rule out differences between loads and will do one or the other.

I may have done things wrong, but I think my choke shoots too tight for a modified.
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Old August 22, 2011, 01:57 PM   #19
Dave McC
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You can change patterns by up to one full increment by switching loads.

There's also some variance in what we can call Modified.

In theory, it's 20 POC. But, if it's designed for a.729" barrel and is in one that's .726" and made a little tight, you may end up with 25 POC instead.

That's why we pattern and test.

I had some tubes measured a while back. Three Remchoke mod tubes here varied by 4 POC or so. All shoot well, given proper ammo.

If I'm shooting clays with an 870, it's Light Mod (15 POC) unless I'm doing skeet or Olympic trap.

Chances are if I'm shooting with the Beretta, one of the chokes will be LM again.
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