Opening Chokes
 

Here is a question for the experienced. Am not a gunsmith or machinist, do have a lathe and have been a hobby gunsmith for a long time. Looking at many SxS shotguns have seen mostly very poor opened choke jobs, you can spot them right away.

Way I have always done deep hole drilling is drill the hole first then turn down the outside to make the finished job concentric. Never filed a shot gun barrel but my guess is the inside bore work choking and polishing was done before the barrels were filled outside. If not to finished at least the majority of inside work was done before the outside was filed.

When the outside was filed the gunsmith finished muzzles up to have a minimum thickness. No doubt if he needed to take more weight out of the barrel he did it away from the muzzle. Mark of a factory choke is plenty of metal at the muzzle everything concentric no thin or thick sides.

100 years later open up a choke result is a very thin wall thickness at the muzzle. And if opening up it takes a very good workman to keep the finished job concentric. Working by hand with a reamer I doubt if there is a 10 % chance of the finished job coming out looking like a factory muzzle. Chucked up in a lathe everything carefully set up perhaps the chances are better, still it takes a very good man to keep things centered when right or wrong is couple of thousandths you can spot with your eye.

Am I missing something or is my theory that open jobs go wrong more that right correct. Are there gunsmith that can alter chokes that can’t be spotted from factory? Might be I never spotted good open jobs because they were good.

I get open patterns with Spreader loads, just thinking about how open jobs are done, don't plan to have it done to any of my guns.

William

1. Yes

2. Yes

Th chokes were cut from the rear using the bore to center the cutter. Parker Bros. chokes are sometimes 5" to 6" long but generally around 3". There is often a parallel section at the muzzles that measure as much as 3/8" long.
There are a few smiths who can properly cut chokes. Mike Orlen in Amherst, MA, Abe Chaber in CT, and Kirk Merrington in TX come to mind.

Even if good work much opening at all the gun is still going to end up with thin metal at the muzzles. Clear flag it's been altered.

William

There is no one that knows so much about what they are doing in the "opening chokes" business that I would trust a medium high condition 12 gauge Trojan to their skills. This has worked for me in fifty years of shotgun gunsmithing experience. There are too many horror stories out there. I just don't do it.

bill if it worked for you for 50 years it should work for another 50 easy..good advice for sure....charlie

There are many smiths who can open chokes correctly - Brad Bachelder comes to mind. I open my own, but then I don't have to satisfy anyone but myself. And I am satisfied.

William, first one has to check barrel thickness at the muzzles before opening the chokes. I've found the American made doubles I've checked all have thick walls. English doubles are a different story. If you're going to open a gun with .035 constriction [ full choke ] to say .015 [ I/C ] you're removing .020, or .010 on a side. The guns I've done for myself all had at least .040 to .060 wall thickness, so removing .010 isn't going to hurt a thing. The Americans seem to like heavier guns, where as the English like light guns, meaning thinner barrels. But then we also like heavier loads of shot. I guess it's just our nature, bigger is better, too much is just right.

I have to side with Bill on this one from my experience. I can certainly tell you of a very well know smith who apparently CAN'T do it properly and left me with a set of non-concentric chokes with as little as .017" on one muzzle and a +.004" blunderbuss choke on the right barrel... this on a very very nice transition era 26" SG VH12. Makes me embarrassed and sick every time I look at it and degraded the gun's value dramatically.

Some years back I was asked to look at a Parker 16 ga that was missing many targets that seemed to be centered. The first thing we did was get out a patterning board, and found both barrels shooting laterally elongated patterns without much high or low. The muzzles bore that out, thin and oblong. The chokes had been opened by an unknown gunsmith to .006 or so, and there was not enough barrel wall thickness left at the muzzle to bore them again to round.

So the lesson is I suppose to be very careful, have enough wall thickness, ream them out gently, or better yet, leave them alone, use spreader loads, or just shoot for the head.

A reloader can get a greater spread by not using a shot cup, just an over powder wad. Or an even greater spread by a true spreader post and wad combination.

Keep in mind that the difference in a killing circle on a pattern board (30" at 40 yards) between full and cylinder is a 6" radius. So chokes give you inches in killing effectiveness whereas misses are usually much greater than that. Doing shotgun instruction, you look over the shoulder at the shot pattern by the clay and see misses by three feet or more. That is for an effective killing circle on game, generally six or more pellets on a game bird silhouette in the 30 inch circle. If you are shooting clays, one or two pellets is all it takes to break it. So, when you are considering chokes, keep in mind there is a difference between a clays effective choke and the tighter choke necessary for an effective and humane kill on a game bird.

Very well stated Bruce.