Choke Percentages

[Wasabi]

So yesterday I went to pattern test some Hull Pro Game cartridges. I worked out the shot percentage in a 30 inch circle. At 40 yards, measured, I was getting an average of 54% in the circle over 10 shots with 1/4 choke. The 1/2 choke averaged 75%. I can't find the percentages they are meant to throw but is 70% not more like full choke? Is the 54% a bit light for 1/4 choke?

[Stonepark]

1/2 Choke definitely appears to be significantly over tight (should be 60%), but being 1% out on 1/4 choke (55%) is nothing given you are using fibre cartridges like Hull Pro Game, but plastic wads will likely tighten up pattern by 5 percent or so.

 

I would suggest you choose another cartridge (fibre clay cartridge that you use) and retest to see if you get a similar result.

 

If so, it might be worth getting the half choke reamed out 10 thou.

 

Shows the importance of checking your pattern.

Edited March 19, 2017 by Stonepark

[Wasabi]

Thanks! They're teague thin walls so no problems changing choke. It's funny GB Black gold 30 gram no.6 produce 62% out of same choke!

[wymberley]

More often than not, I've found that - and particularly with fibre - the more open chokes throw a wider pattern than the nominal boring would indicate. As you have a fair few of these and dependent upon your needs, changing the 1/2 for 3/8 might be advantageous. What you're getting is more than likely down to the quality of the shot.

Thanks for posting, I'm looking forward to checking the 7s - whatever they turn out to be - when I get them.

Edited March 20, 2017 by wymberley

[Continental Shooter]

It's hard to standardise percentages as a lot depends on ballistic and components; surely a fibre one will disperse more than a plastic cup as well as Gualandi wads will concentrate more than B&Ps or SG Disperser.

 

A long range load will concentrate more than a standard load regardless of the choke so, the same choke might throw 50% with a light load and 60% with a long range....

 

However, this exercise will give you the measure of how your chokes fire which is always good

[neutron619]

Not mentioned so far is the importance of avoiding confusion between

- named nominal choke performances
- named nominal choke constrictions
- actual choke performance.

Unfortunately, either through ignorance, lack of understanding or disinterest, most shooters think that all three of the things I've listed above are the same thing. They aren't. Congratulations for being one of the few folk sensible enough to think about it, experiment and ask questions...

In order:

Named nominal choke performances are the numbers you started with and they are an average expectation of performance with any given cartridge. If I say "you're getting full choke performance with that gun and cartridge" it means that I've measured (or am estimating) that it's putting 70% of the pellets in the standard (30") circle at 40 yards. What it doesn't say is anything about the constriction of the choke.

Named nominal choke constrictions are the next different set of numbers. The nominal choke constriction for "full" choke is either 0.040" or 0.035" in a 12 gauge barrel, depending on who you ask. Again though, it's an average. Other gauges might have the same or different actual constrictions, again, depending on who you ask. What this does not mean, however, is that a 0.040" - i.e. full choke - constriction will give you full choke performance.

Finally, we have actual choke performance. This is what actually happens when your gun fires a given cartridge through a given choke and prints a pattern on paper. The point here is simple: the maker might print "full" on the choke tube and it may very well have a 0.040" constriction relative to the barrel, but if it's only putting 40% of the pellets in the standard circle at 40 yards, then it's a Cylinder choke because it's giving Cylinder performance (i.e. the name for a choke giving 40% performance, hence "nominal choke performance" above).

There's too much to delve into here for one post and you probably don't want that level of detail anyway. However, try to think of your chokes in terms of how they behave with a particular cartridge (as you're now doing) and not in terms of what they have printed on them, or the number of notches cut into them, etc. You'll do much better in the long run when you need to make an adjustment.

For the record, I've seen guns with "half" chokes that throw 90%+ patterns where the same gun's full choke will only push out 60% performance. I've also seen guns where the "quarter" choke (as the manufacturer calls it) ends up throwing 70%+ patterns and you have the slightly surreal experience of picking off 50-yard birds with tubes labelled "cylinder" / "quarter". It all depends on how the cartridge behaves through that choke with that particular constriction and geometry.

Edited March 20, 2017 by neutron619

[dipper]

Bottom line pattern your chosen cartridge with your chokes .Then You know what patterns you get.Dipper

[wymberley]

Bottom line pattern your chosen cartridge with your chokes .Then You know what patterns you get.Dipper

+1

Simple really and is what the OP has done.

[Wasabi]

I've always found large shot to pattern tightly. I've got a mossberg 500 which puts 100% or there abouts of 42 gram no.3 in the pattern at 50 yards!

[Guest cookoff013]

shame you're not local, i`d show you what subsonics can really do.

[Continental Shooter]

Bottom line pattern your chosen cartridge with your chokes .Then You know what patterns you get.Dipper

 

ultimately, that's what it is it alos help to see where your gun shoots