[Navigator]

QUESTION:

What is the difference between an "improved cylinder" bbl and
an "cylinder bore" bbl?

[Clemson]

An Improved Cylinder barrel is choked to shape the pattern a bit. Cylinder bore has no choke at all. IC is typically around 0.010 to 0.012" constriction on a 12 gauge gun.

[redneck2]

I believe Dave McCracken posted this sometime back. Anyway, I copied it to MS Word for future reference. Gives you most everything you need to know about chokes

Remington's Skeet choke is a negative choke, about -2 POC. Their sequence goes something like this.....

Skeet
Cylinder.
Improved Skeet,
Improved Cylinder,
Light Modifed,(Duplicates Skeet II)
Modified,
Full,
Extra Full.

IMO, having tubes of 4 or 5 POC difference is splitting hairs.

The tubes I use the most are 14 POC, 20 POC and 28 POC. The TB barrel is 25 POC and comes close to optimum for trap behind the 20 yard line.
My chokes Cyl=.724 Sk 1=.718 IC=.713 F=.688

Gauge 10 12 16 20 28 410
True Bore Dia. .779 .729 .667 .617 .550 .410
Cylinder Bore .000 - .779 .000 - .729 .000 - .667 .000 - .617 .000 - .550 .000 - .410
Skeet I .005 - .774 .005 - .724 .004 - .663 .004 - .613 .003 - .547 .002 - .408
Improved Cyl. .010 - .769 .009 - .720 .007 - .660 .006 - .611 .005 - .545 .004 - .406
Skeet II .015 - .764 0.12 - .717 .010 - .657 .009 - .608 .007 - .543 .006 - .404
Modified .020 - .759 0.19 - .710 .015 - .652 .014 - .603 .012 - .538 .008 - .402
Improved Mod. .025 - .754 .025 - .704 .020 - .647 .019 - .598 .016 - .534 .011 - .399
Full Choke .035 - .744 .035 - .694 .028 - .639 .025 - .592 .022 - .528 .015 - .395
Extra Full .040 - .739 .040 - .689 .035 - .632 .027 - .590 .024 - .526 .021 - .389

PERCENT
CYLINDER .000 40 at 40 yds- 70 at 25 yds
SKT 1 .005 45 at 40 yds- 75 at 25 yds
IMP CYL .010 50 at 40 yds
Skt 2 [light mod] .015 55 at 40 yds
MODIFIED .020 60 at 40 yds
IMP MOD .025 65 at 40 yds
FULL .030 70 at 40 yds
EXTRA FULL .040 73 at 40 yds
TURKEY .045 + 75+ at 40 yds

[Clemson]

spitrhyma,

The barrels in the photo are tapered on the outside. The bore inside is a straight cylinder.

Clemson

[sm]

http://www.colonialarms.com/

http://www.colonialarms.com/chokespecs.html

http://www.trulockchokes.com/chokeinfo.asp

[jnormanh]

<<Remington's Skeet choke is a negative choke>>

Huh? I've Measured skeet chokes on two Rem 1100 skeet guns. The first was a Skeet-B from the late 70s, fixed choke, about .007" constriction, and the other a new Tournament Skeet just bought, also about .007".

[kirbythegunsmith]

Here we have a Remington 870 12 ga. SKEET barrel
Bore starts minimal taper at 4" depth, about .001 per half inch, and would expect minimal choking effect from such slow taper effect, especially when the next .004 happens in .1" per .001", instead of .5" per .001"
Diameter of the choke holds within about .0005 from 2.1" in from muzzle
Starts to flare out to approx. bore diameter from 1.1" in from muzzle

Measurement from muzzle opening: 4" .735"
2.5" .732"
2.1" .728 - .7275"
1.1" flares (inverse taper) over about .4"
.7" about out to initial bore diameter of .734"

Conclusion: This choke I consider to be a "bump - relax" choke
Taper a small amount and then open that same amount before the muzzle

I have expected Rem. 12 ga. to be .003 of bump-relax nominal
I have made chokes that were more flared to give slightly more dispersion
I have measured 20 ga. Rem. barrels that were mainly just flared

The notion that some Remington SKEET chokes were of "negative" constriction would not necessarily be untrue, but not all of them could be considered "negative". If a measurement were only taken from the muzzle to about 2" in on the barrel described here, the conclusion would be that you had a "negative" choke in front of you.

I just lay out the facts the best that I see them, without the intent to make any hard feelings. I have not made a comprehensive study to ascertain dimensions of large numbers of barrels, but have enough exposure to decide what I would make for a special application for a specific shotgun barrel.

See the pictures and zooms to see the apparent taper and slightly rough frontal area that was relieved to the bore size

kirbythegunsmith@hotmail.com
Custom choke and tube specialist

Anybody interested in seeing choke disaster pictures? I have factory foibles and guntinker stinkers. Errors verily abound!