doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com .410 choke constriction

Miller, very interesting. Do you have the % for the other chokes, IC, MOD, IMP MOD.? Also how long ago did someone figure this percentage, was it patterned like we would do it now?

I understand the percentage thing for different bores, but where was this "Old 12 gauge standard" devised, or originally decided/deduced? It's interesting, and I don't dispute it, but I've never seen it written before, that I can recall.

SRH

I have never heard it expressed as a percentage of bore diameter but I certainly have heard of .040" being the old standard for full choke in a 12 bore. The Brits often expressed choke as 1/4, 1/2, 3/4 with each 1/4 being .010" of constriction.

I had a sxs Ugartechea that had .021 chokes. It was pretty tight patterning. One gun I have has been altered to cylinder bore on the right barrel, so I relieved the forcing cones to about 3" cones and polished them. The gun shoots more evenly dispersed patterns than any other 410 I own. This bore actually holds together for some decently long shots. It's my favorite quail gun. One gun I have with standard cones and full chokes has excessively hot cores in the patterns. My recollection is that Briley calls .020" a full choke in 410. I have one 410 gun that has a .035 choke. It patterns ok.

Thanks Chuck, the more you ask about choke constriction for .410's the more answers you get. Now with yours I have seen .022 to .035. The pattern board will tell. I think I will start at 30 yards at a 30" circle with a 25" circle and a 16" circle inside of that, and then go to 25 yards with the same configuration and see.

Sport with Gun and Rod in American Woods and Waters by Alfred Marshall Mayer, 1883
https://books.google.com/books?id=IJcCAAAAYAAJ&pg=PA781&vq
The choke-bore now almost universally adopted by gunmakers is as follows: Taking a twelve-gauge gun as an example, the construction of the bore from the front of the breech-chamber to within one and a half inch of the muzzle amounts to about 1/100 of an inch. At one and a half inch from the muzzle begins a sharp contraction which, in the length of one inch, equals 25/1000 of an inch. The last half inch of the bore is a true cylinder.

.010 + .025 = .035" constriction = 5% for "choke bore"

.410" X .05 = .0205"


The Gun and Its Development by W.W. Greener, 1907
http://books.google.com/books?id=3HMCAAAAYAAJ&pg=PA416
The various degrees of choking may be classified as:
Full-choke, which, with a 12-gauge gun, standard load, distance and conditions will make an average pattern of 215 pellets
The half-choke (same conditions) ... 185
The quarter-choke... 160
The improved cylinder... 140
The old cylinder�115
Any better average shooting than 215 may be termed an extra full-choke; the improved cylinder is a barrel very slightly choked.

Unfortunately, Greener doesn't define his "standard load". If it was 1 1/8 oz. No. 7 Tatham chilled shot (291 per oz.), then 1 1/8 oz. = 215/327 = 66% for Full-choke
On p. 354 he states 1 1/8 oz. No. 6 is 305 pellets. 215/305 = 70%
https://books.google.com/books?id=3HMCAAAAYAAJ&pg=PA354

Thanks Brother Drew.

I don't really know where I got the percentage thing, I think I just devised it working from stated as well as measured diameters of chokes in various gauges.

It could be a bit easier to say % of choke area in relation to bore area. Let B = bore diameter, C = choke diameter & R = % of reduction. The formula then is
C = √(B� x R) Thus for the 12 gauge √ of (.729� x 90%) = .692 or .37" of choke constriction.
For the .410 bore √ (.410� x 90%) = .389" or .21" of choke constriction.
These would be essentially full chokes.

David,
In my opinion, 30" is way too large a k8lling pattern to expect. An 18-20" killing pattern is realistic.

I fully agree. You have to keep remembering density. Density is what kills. Density is what gives multiple hits, contributing to the all important factor of pellets hitting vitals. Density with a .410 pattern means a smaller overall diameter.

SRH