doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Backboring a 20ga

If the intent is anything but tightening up fixed chokes, I'd take backboring off the options list.

A few 00 buckshot behind the buttplate of that BSS ought to rebalance it just fine!

I have a 20ga. 28" Miroku Daly Superior grade that ended up with a backbored set of bbls to remove the tool marks made by a previous owners attempt at 'something' which was never really all that clear to me. I guess he felt the bores were too tight and ran something like a drill bit on an extension down them toward the chokes to relieve them! The forcing cones are a bit longer now than they were originally. I simply had the bores cleaned up & polished. Chokes were fortunately not removed and I had them cleaned to up to be roughly .020 & .025 as I recall. I have not measured them for this reply. FWIW, that gun is still a bit muzzle heavy. The bores are not the same dia., each only got what was necessary to remove the tool marks & clean them up. The work was not done w/any intention of improving things, rather it was a salvage op on a very inexpensive acquisition.

As far as magic goes, there isn't any. You could expect a bit lower pressure [& velocity] from the bigger bores, all things being equal. Is it detectable? Probably, with gauges, but not by me shooting it. The gun throws good tight patterns with several dif loads using plastic wads. It did not/does not obturate consistently with card, felt, or Lujtic Mono-wads .. just got curious and I tried all three at the time.

Anymore, when asked a question as yours poses, I'm more inclined to say that the same effort/money spent on lessons with a well qualified coach, and shooting frequently, provides much better returns and results that are much more easily measurable.

The bbl. work mentioned above was either done by Kirk Merrington when he first came over & was working for Billy Hodge or by Scott Mayes who is currently the resident gunsmith for Beretta Gallery-Dallas, but it was in the 70's & to be honest, I just don't recall which of the two did it or if I had one do the bbls & the other the chokes. I would not hesitate to check w/Mike Orlen for that type of work today.

Hi Jim, Longtime no hear from.

Money? me? You have me confused with some rich guy. Weren't you the guy with the pricey 28g Super?

Deactivating the A-safety is a cinch with a BSS. My recollection was that you simply flip the rod that connects the toplever to the safety. There's a collar on the rod that catches the safety and pushes it back. If the rod is flipped, the collar is no longer in a position to catch the safety. You get to keep all the parts in the gun for future reactivation if someone wants to have it.

As for the double triggers, I'll probably leave this one as a single trigger. Most second shots where I hunt quail require the shot so quickly that I've found I'm not quite fast/smooth enough with a DT gun, but a ST allows me to get a well placed second shot. Don't get me wrong, I still love to hunt my DT guns there, but usually don't get a well placed second shot with them. In fact, that gussied up .410 Nitro is a DT gun and it's rapidly becoming one of my favorite guns for quail.

I'm kinda looking at the backboring as an alternative to re-striking the barrels to lighten them. I dunno, just tossing it around.

TW, I hate to verbally confront someone who has a similar opinion to mine about the worthless money pit that barrel work is, but how in heck do you determine that a certain wad does not "obturate" in a certain barrel?? Don't tell me that you chronographed loads with that load and another load with a different wad and they differed by thirty five feet per second at the muzzle. I would like a real answer.

Well dern fellows, I have spent a bunch of money on tooling for barrel work. Has it paid off? I think it has been barely worth while. My findings have been as follows

On cheap guns= Big difference!

On mid range priced guns= yes worth the cost, some times, maybe?

On high end guns= keep your money in your pocket, they know what makes the barrel work!

If the bores are chromed lined= not with my tools!

Ahh, I think I now see why Lowell stirs the pot. Controversy seems to raise many considerations to the surface.

As for velocity loss from overboring, I would think it'd be pretty much a moot point unless the wad doesn't seal as well. There seems to have been much written about the plastic wad bases doing pretty well at sealing in larger bores. If they do indeed seal as well in a slightly larger bore, the results could very well be an increase in velocity due to larger piston area. My calc says about a 2% increase in area for .010 in a 20g. Might increase the accel for the same pressure, but pressure may drop a bit. So, I'm betting on all of it being in the scatter and essentially no change in velocity.

Why not sell the gun, use the money to buy a similar one in 16ga and shoot 7/8oz loads in it. Of course you can't use a 16ga for 20ga registered skeet events(okay for 12ga events) but you said the gun was for quail anyway so you would be dollars ahead and shooting a proper quail gun to boot! My favorite quail gun is a 5lb 9oz 16ga 2 1/2" which loves RST 7/8oz shells. Apparently your gun is already flawed by shortage of triggers.

Jerry,
I couldn't afford both triggers, so I just got one. More evidence to the contrary of Jim's recollection of my financial well being. I'm on a 20g kick for the last few years. Apparently, so are a large percentage of the H&H customers, me not being one...a H&H customer that is. I watched the H&H dvd lastnite and they said something like 50% of their production is 20g now. One of the reasons I prefer the 20g to the 16g is the availability of inexpensive good ammo. Another is the lighter payloads of the 20g in typical factory loadings available at most discount sporting goods stores. Besides, 16g seems like overkill for a lil 'ol quail and some of my friends even accused me of using a "big bore" on them when I pulled out a 20g. Your 16 sounds like a great chukar gun though. Although, some of the places I've been chukar hunting I've wondered if it was wiser to take a gun that was more "disposable" than most of my guns.

I posted a link this test http://www.uplandjournal.com/cgi-bin/iko...ler+and+pattern in the past. It is a fairly elaborate pattern test experiment that he undertook. STS and Nitromag were used 2-3/4" 7/8, 1 oz, and 3" 1-1/4 oz. An Ithaca 37 barrel was used because it has lots of metal to accommodate being opened to 0.630" in 0.005" steps starting at 0.615". 2" forcing cone set at start and amount of constriction was kept to 0.025" (20 g full?). The patterns seem sub par at 0.615" barely IC, and seemed to arrive at full choke performance at 0.625" for the 7/8 and 1 oz loads. At 0.630" it patterned full with the 3" Nitro-Mags in #6 and #4 shot.

He said the wad was hard to push through 0.615" and the wad was damaged by the effort, which seems abnormal; those shells in that barrel might have given pressure spikes. Other shells and wads may have worked better at the 0.615" original diameter.

Says the patterns became more evenly spaced, denser, and less patchy as the bore was opened. Larger shot sizes patterned best at the largest overbore tested, 0.630". The results seem to change consistently as the bore was opened.

I only know what he posted. Some one may have an 0.610 20g that patterns great.

Many thanks. I'll give Brian a shout. He's somewhere around my area. Brian's work is certainly better than theoretical debate. If it's not a lot of money, and wallthickness permits, I might pursue it. I'm hoping Brian can steer me to the guy that did the work locally.