A Tweaked Trap Barrel....

[Dave McCracken]

The 30" vent rib trap barrel that came on the 870TB here is a good one, and contemporary to the TB(1978) if not its original barrel. It is slightly off spec, being .733" instead of the standard .729", but I can live with a slight overbore.

For modern ammo, it was overchoked. Even with my fast loads of 8.5s, the pattern ran too darn tight, with a core of about 18" and quite a few flyers. The choke ran .695", or 38 POC. At 16 yard singles trap, a center hit meant smoke. Smoke is excess density and other than the confidence factor, has no benefit. I prefer the target just vanishing while microscopic fragments dribble down over 1/4 acre, and I often see it when I'm doing my part correctly.

So,Bill Gillette,the traveling gunsmith, came through the area recently. I left the barrel with him with instructions to lengthen the forcing cone and open the choke to 25 POC, or .0013" more open than of old.This runs around Improved Modified if one really has to name every degree of contriction.

For those coming in late, a longer cone, say 1 5/8", deforms fewer pellets so they stay in the pattern. It mimics a tighter choke thus. It also shortens the pressure spike, which spreads the recoil out over a slightly longer time, but I doubt I can notice the difference in a 9 lb trap gun shooting 7/8 oz and 1 oz loads.

Anyway, a dozen rounds of Trap, Wobble and Skobble went well, and a session at the patterning board showed I had picked up a few inches of core spread and a few less flyers. That's with my summer load of 8.5s, haven't patterned my winter loads of 7.5s yet. I expect results to be similar.

The mods cost about $130. Was it worth it?

Probably, since what I wanted was a more usable barrel. I wanted it set up for targets from 35 to 40 yards with a near perfect pattern spread, very good for 5 yards either way, and adaptable to dove shooting and open country upland hunting as well as the longer clay games.

With the long cone, overbore and realistic choke constriction, it's now a soft shooting, small shot precision instrument.

I'll let you know if my scores improve.

Questions, comments, donations?

 

[TrapperReady]

Modified barrel? Dave, are you gonna be a gamer?

Actually, your mods sound well-reasoned and effective. The cost seems comensurate with similar work I've had done in the past.

As far as questions... Are you able to quantify (even in a WAG fashion) how much softer it now shoots? I had forcing cone work done on my 425, and think it helped, but there were a couple other things done at the same time, so I wasn't able to appreciate each mod in isolation.

As far as donations... Have I mentioned that I'm filling the jelly jar in an effort to get a Model 42?

 

[Fred Fuller]

At least you asked for donations, not tips. 8^)

And if your scores don't improve, you have even less reason to blame the gun. Killed off one of your best excuses too, unless you start saying something like "Darn thing won't shoot for sour apples since I had the bore worked on, shoulda left it alone." No doubt all your listeners would stroke their chins and nod sagely at that one.

"My" gunsmith while I was growing up was Ralph Walker in Selma, AL, and he popularized backboring and long forcing cones in the region. I didn't have much of a clue what all the old guys were talking about then. I have since determined via my own experiments that about the most consistent improvement one can get in patterning for a given barrel comes from having the forcing cone lengthened. And taking a few points of choke out of that particular tube definitely cannot hurt. Modern shotshells are so much better at protecting pellets during their launch down the bore that many older fixed- choke guns shoot more tightly than their choke markings would indicate.

Worth it? I'd say so. It's a specialized instrument and the mods made it more suitable for its intended purpose. Not a fuzzy- dice sort of thing either.

Enjoy!

lpl/nc

 

[sm]

Well kinda goes along with what I posted in this thread . ( boy am I gonna get fussed at)
http://www.thehighroad.org/showthread.php?s=&threadid=98626

I agree the most useful money spent is the forcing cone being lengthened. Yes Trapper doing that modification alone - one can tell a difference in recoil and patterns.

Next up - I too agree having the fixed bbl "checked and tweaked" is good money spent. Just because a bbl is marked something - don't mean it is. Just like Dave had his measured and it was a bit overbored. The next batch off the assembly could have been different as well. Also - making sure it is "true" ( concentric ) makes a difference.

I tend to feel , most folks shoot too tight a choke . Oh there is a place for Full and Extra Full ....might surprise folks they are "not really" and if opened up some and using better loads the pattern and maybe even shorter shot strings will result.

Same deal for screw in chokes ...it might be marked something, don't mean it will pattern that way tho.

Dave - makes sense to me, I see no problem with what you did.

I will say again - I think there is a place for screw in chokes ....I think many folks would be better off with a fixed choke IC or Mod bbl and learning to pattern for 95% of hunting applications.

Skeet -cyl plus about 2- 4 POC.
Trap - Imp Mod ( what Dave came up with.)

by the time folks buy a bunch of screw chokes....single stage mec and learning could be paid for.

 

[Dave McCracken]

Thanks for the responses.

TR, no gaming in the works. I just wanted to make a good barrel better and more usable. As far as Wild Guesses go, 3-5%. This was a soft shooter anyway.

Lee, Mr Walker's name is not unknown to me. Up there with Stan Baker.

For anyone determined to modify their shotguns, I'd recommend fitting, trigger and cone work first.

I can take the choke down to IC,(8 POC) before scores drop and hits get too chippy with the LC barrel. I wanted this one for longer range work but not out past 45 yards, about my personal limit.

sm, a fixed choke with load selection makes more sense than a pocketful of choke tubes for more than new shotgunners. More choices means more mistakes, and keeping it simple has merit.

 

[Fred Fuller]

Dave,

Short trip down memory lane here...

Picture a simple white one- story cinderblock building off a side road, a building that got bigger as the years went by, with the sign painted in red by the door. The customer entrance led into a small office furnished with a full length carpet- topped counter and nothing else. The walls were decorated with a few firearms related curiosities and signs, including the inevitable single shot shotgun with an eight foot barrel. On the wall behind the counter above the door leading to the shop was a sturdy shelf. It held glass pickle jars, the gallon size. They were full of assorted ammo. There was a prominent sign below the shelf that said REMOVED FROM "UNLOADED" GUNS. Last time I remember being there there were six or seven of them.

IIRC Ralph was an armorer in WW2, who went on to the gunsmithing business a good bit later after attending the school at Trinidad State. I remember a couple of my 'old men' talked about buying guns and other personally owned gear from him when he was scraping up money to start the business.

Obviously he did well. He left quite a legacy.

http://www.walkerarms.net/

lpl/nc

 

[Dave McCracken]

IIRC, Lee, RW was one of the pioneers in choking to a particular load, working with lots of old Model 12s and patterning them, then honing the choke to an optimum spread at whatever distance. Also, Charles Askins had him do some choke work on the Super 10 of yesteryear.

Those jars remind me of the once common sight in gun shops of barrels, burst and bent, from overloads and bore obstructions. Usually mounted in a prominent place near the reloading components.

Burt Becker and Dan LeFever were the first generation of overbore, long cone proponents. The concept really took fire after the invention of the plastic one piece wad.

Newer shotgunners cannot conceive of the quantam leap in performance brought by that invention.