|
Forum Rules | Firearms Safety | Firearms Photos | Links | Library | Lost Password | Email Changes |
Register | FAQ | Calendar | Search | Today's Posts | Mark Forums Read |
|
Thread Tools | Search this Thread |
June 9, 2012, 09:58 AM | #1 |
Member
Join Date: February 22, 2011
Location: Northern CO
Posts: 38
|
Choke to Bore Measurement Experiment
Greetings All,
I bought a Savage/Stevens 9478 Break Barrel 12 Gauge shotgun at a pawn shop recently and I am trying to figure out the choke in this shotgun. From what I have pieced together from various forums, all the 9478s were made with full choke barrels. What I am finding with my measurements is different. I measured the end of the barrel with my caliper found the diameter to be .729(typical 12 gauge). Next I fashion a "choke diameter tester" by taking a AA battery and wrapping electrical tape around it very tightly(to minimize any squish of the tape) and kept trying to slide it through the whole barrel until it felt snug, but still passed through. Once it was snug, I took it out and measured it with my calipers and found the diameter size to be about .720. Now, on all the "choke to bore diameter" charts I can find, a .009 reduction in the bore diameter for a 12 gauge results in an Improved Cylinder choke. This barrel definitely does not have the .035 reduction(.694 dia) that a full choke would be. So I figure that someone had the choke reamed out to Improved Cylinder at some point(or the gun came with an IC instead of a full choke to begin with). Would that be an accurate assumption based on the measurements I am seeing? I know that the "real" way to test the choke of a gun is to shoot it, but I haven't been able to get to the range yet and I was just curious. -Bryan |
June 9, 2012, 01:58 PM | #2 |
Senior Member
Join Date: August 23, 2008
Location: SoCal
Posts: 6,442
|
With a pawn shop gun, you never know what you're getting. Perhaps the previous owner had the choke bored out. Your best bet is to find out how your new gun actually patterns with some trigger time. That will tell you more than all the measurements in the world.
|
June 9, 2012, 03:41 PM | #3 |
Junior member
Join Date: June 23, 2009
Location: Orange County, CA
Posts: 2,149
|
I think your methodology is flawed. I don't care how tight you wind the electrical tape, isn't it going to expand after being compressed and throw your measurement well off?
|
June 9, 2012, 04:21 PM | #4 |
Member
Join Date: February 22, 2011
Location: Northern CO
Posts: 38
|
Thanks guys,
I checked my AA battery and electrical tape setup this morning again and it was still at .720 (I did the original test a couple of nights ago). I put the "gauge" down the barrel again and was able to see light around it the whole time I pushed it down the barrel. So it appears that, if anything, the diameter is even slightly bigger that the .720 I am measuring on my rig. Yes, it is not a perfect measurement, but I at least can verify that it is not tighter than a modified choke. Another strange thing is that according to all the documentation I can find, the shortest barrel that came on these shotguns is 26". Mine has a 20". I think someone did quite a bit of customization on this thing. I do plan on getting out to the range some time soon. -Bryan |
June 9, 2012, 04:27 PM | #5 |
Junior member
Join Date: April 18, 2008
Location: N. Central Florida
Posts: 8,518
|
What end measured .729"? And if it was cut back from 26 to 20 you would have the same bore diameter as the choke would be a Cylinder bore
Tale it any competent gunsmith and in 5 seconds, with the right tool, they can tell you what you want to know. It also matters not what any dimension says, it is what it does at the pattern board |
June 9, 2012, 04:48 PM | #6 |
Senior Member
Join Date: December 12, 2006
Posts: 1,512
|
Was always told a dime will not fit down a full choke, but will down any choke more open. Always worked when I tried it.
|
June 9, 2012, 05:02 PM | #7 |
Junior member
Join Date: April 18, 2008
Location: N. Central Florida
Posts: 8,518
|
The dime routine doesn't always work, simply because there is no longer a standard 12 bore dimension. Cylinder bore dimensions can run from as tight as .725 to as wide open as .750 - quite a difference
|
June 9, 2012, 05:13 PM | #8 |
Member
Join Date: February 4, 2012
Posts: 71
|
I herd about the dime thing, I was told if a dime goes through you can put a slug through. Just what Ive been told.
|
June 9, 2012, 05:23 PM | #9 |
Member
Join Date: February 22, 2011
Location: Northern CO
Posts: 38
|
It measures .729 at the muzzle.
It hadn't dawned on me that if they shortened the barrel, they probably would have cut the choke off. That makes more sense. Well, off to the range I go. |
June 9, 2012, 05:37 PM | #10 |
Senior Member
Join Date: August 23, 2008
Location: SoCal
Posts: 6,442
|
And, so ends Lesson #1 of Shotgun Detective 101.
|
June 9, 2012, 05:40 PM | #11 |
Junior member
Join Date: June 23, 2009
Location: Orange County, CA
Posts: 2,149
|
Okay Hardy Boys!
|
Thread Tools | Search this Thread |
|
|