doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Has anyone ever had a damascus barrel blow up

The calculated bore dia of a 4 gauge gun is 1.052" This is also the diameter I have seen listed in ever bore size chart from the various proof houses. A gun with a smaller bore diameter, (Common on breech loading guns) even if chambered for a 4 gauge shell is not proofed as a 4. 5 gauge diameter is .976" while 6 gauge is .919". My understanding is that most 4 gauge breech loaders will have their bores marked as a 6. I have a Birmingham proofed 12ga which has its bores marked as 14 (.693"), but if one asked the Birmingham proof personnel what size is a 12 gauge they would tell you .729" & that would be the correct answer.
the bore size of any individual gun is what the maker made it.

I recall reading some time ago that Buck Hamlin took a decrepit L C Smith 12 ga damascus & cut the chambers for a 3�" shell & then began loading it up. As I recall he used loads of Blue Dot powder & loaded both powder charges & shot loads well above anything found in the loading manuals. He ceased his experiment when the rotary bolt would no longer stay closed but was blowing open with every shot, but did not succeed in bursting the barrell. I don't recall if he had recorded the pressures of these loads or not.

Miller, all of his 4 bores that I measured were either 12" from breech or 4" from muzzle and ranged from .928 to .938. An H. Holland single barrel had a bore of .941.
I do believe in what you are saying in that each maker made them to their size.
The rim diameter of the 4 bore shells I measured were 1.180 and the base 1.065. These shells were 4 1/4" long.

Buck was looking for his ultimate turkey gun.

Howdy! My first post here!

Only shotgun barrel I've seen blown open was a Remington 1100 12 ga with some dirt in the muzzle. Rough quail country in So Texas. Friend hacksawed it to just behind the "petals" and proceeded to have a very good hunt with cylinder bore 12 ga.

I have been shooting smokeless in my damascus barrels a long time. Like so many, my loads are quite a bit lower pressure than black powder! 1 oz of shot over any good plastic wad, over 19 grns of IMR PB powder gives right at 1159 fps at right at 5K psi pressure.

So I wonder...to get that velocity, the pressure must stay up much longer. So the higher pressure is not at the breech, but somewhere forward, where pressure behind the remaining. If it were gonna burst at this pressure, it would do so where barrel steel gets pretty thin; up around feft-hand position.

David;
I do not know if it is true or not, but the story I have heard on the 4 gauge guns was that when breech loaders first began to be made the bore was kept true to size but the chamber was cut for a thin brass shell. As Paper hulls began to replace the brass ones the chamber remained un changed with the bore size being dropped to accomadate the smaller wads. If made in a country with proof laws the barrel should be marked with he actual gauge of the bore. No inbetween sizes were set up for these larger gauges. Therefore a bore which would accept a .919" gage but refused a .976" one would be stamped as a 6. I have not had opportunity to examine many 4 gauges, in fact have only even seen a very few, but have been told that most of the British built ones indeed carry the 6 mark in their proofs. "True" gauge is of course determined by the number of ball which weigh one pound. By the formula used for this calculation a 4 gauge ball would measure 1.052" in diameter.
It is also noted that in the past many makers of .410's as either 36 gauge or 12mm. Neither is correct & they are not the same. 36 gauge has a diameter of .506" & 12mm converts to .472". The "True" size of a .410 is of course just that .410". These guns though were not made those sizes, just marked that way.

I'm enjoying this thread as it seems to validate some of my own observations regarding those awful 'twisted bbls.'

Probably should have said, "Welcome, Jim Irwin!" first. You'll find Joe Wood a long time believer/user of PB as well for safe loads in those awful twisted bbls.

I'm thinking that 'Longshot' may/can serve as the modern equiv. once someone gets around to developing/testing sufficient loads to publish them and the results will prove similar. Meantime, keep that PB dear. It works just fine, thank you.

The highest pressure is always in the chamber. Pressure curves do vary, with some loads showing a more rapid decline than others. But even comparing smokeless to black--and with black, the old wives' tale was that the pressure curve was very different, remaining much higher farther down the barrel--tests conducted by DuPont and by Sherman Bell, reported in Double Gun Journal, show that the pressure curves aren't radically different.

Please check the pressure curves shown here. The powders tested all intersect at 2 1/2 - 3 1/2"
http://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=384719&page=2

This is a Red Dot vs. PB time rather than distance curve by Neil Winston



I've never seen a Blue Dot curve but pressure IS slightly higher further down the barrel

Sherman Bell�s pressure testing published in The Double Gun Journal Summer 2002 "Finding Out for Myself, Part VI, Smokeless vs Black", p.19, and summarized in Volume 17: Issue 4, Winter 2006, p. 39
1 1/4 oz. 3 3/4 dram GOEX FFFg Black Powder at 1240 fps and the equivalent load of Blue Dot

..........1 inch.. 6"... 12"
GOEX.... 5900 4100 2100
Blue Dot 6000 4300 2300

1 1/2 oz. at 1236 fps Blue Dot (weight not stated)
..........10,000 4,400 2000

One difference of major importance between Black & Smokeless is that black will retain a near constant burning rate regardless of other conditions. You could for instance load a 10 gauge down to a � oz shot load & get everything out the barrel with no problems. Smokeless on the other hand burns faster as pressures increase & of course slower under low or no pressure. Note that in the chart Drew posted that only "Oval" (a slow progressive powder) had a max pressure lower than did Black.

PB is a great powder, "BUT" personally I would be extremely leery of any load with it which gave a lower max chamber pressure than black with an equal shot load pushed to the same velocities. I have seen published data which showed Black in a 12 ga pushing 1 oz shot loads to mild velocities as being down in the 4k range for max pressures. As my loading has always been more for hunting loads to be used in cooler weather than on a range in sweltering heat I prefer loads up around the 7K range when using fast to medium powders & don't like to drop below 8K with slow powders, they just burn better at these pressures. "IF" a shotgun won't take those kind of pressures it stays on the wall at my house. One of my long time favorite powders ever since its introduction has been Green Dot for use in mild loads for my Damascus guns as it easily meets my pressure requirements & has been readily available at more economical prices than may others.

Drew;
Note that the 1� oz Blue Dot load you posted even though its max pressure is 4K higher than the 1� oz load has a slightly lower pressure at 12". This tells me that ligthter load of Blue Dot is not really burnimg effeciently. I would personally not want to carry a 6K load of Blue Dot into a duck blind/swamp in freezing weather. I made that mistake "Once" with a load of 7625 with published data @ 7K pressure & it totally let me down.

When evaluating things that happen in milliseconds, it's often a good idea to look at things in percentages. Time, pressure, stress, etc.. It puts more perspective on the situation that sometimes our minds trick us into thinking is an insignificant difference.