doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Shooting nitro loads in BP proof Damascus?

BV....

Not my gun....old stock photo's...but this Baker did belong to a member here.......the shooter's hand was injured as I remember.....gun was shot about ten times then switched shooter's as I recall and burst with the first shot as the second shooter fired the gun.......

As memory serves, the chambers had been lengthened poorly with numerous tool marks left un-polished.....?.....

This Baker was discussed on several lengthy threads here, I do not think any conclusive reason for the burst was ever given....?....As you can see the forcing cone area wall thickness is very minimal.......

Good example of why metal "should never" be ground out of any gun barrel ........guns with butchered barrels should be wall hangers ......

Others will probably chime in here about this Baker....I think PeteM originally posted the photo's....?.......

Great example of "if it ain't broke, don't fix it."

BG,
Take a look at data for Hodgden Clays with 1 oz of shot. I found a combination that worked out well for me that is around 7000 psi using Federal papers and Fed wads. The pressures seem very consistant even in cold weather where some of the other really slow powders get really weak burning.

There are several things of interest in this thread. One thing I would like to make very Clear though is there is a lot more involved in getting the shot load from a standing position in the shell, out of the muzzle with useful velocity than just the max or peak pressure. In Fact Max pressure has Absolutely "NOTHING" at all to do with that thin spot 22" down the bbl (30"-8").
Look at those 4 pressure curves recorded by DuPont back in the early 1920s. Note that those curves all swap places at around 2�"-2 3/4" from the breech. Beyond there the lowest pressure curve becomes the highest one etc. Though these curves are only carried to 10" it is seen that by this point they are all close together. The biggest gap her is the "Higher" pressure at this point of the shell bearing an "Underload" of a Slow Burning Progressive Powder". Those of who tout your very low pressures using an underloaded slow powder might well bear to keep this in mind.
Another point of extreme interest is the vast difference in pressires recorded by DuPont at that time between those in the 2001 Lyman data reported. I do not currently have an explanation for those differences. It is noted that DuPont used 3F powder while Lyman reports with GOEX powder used 2F. For the nearest load comparsion though Lyman used 90 grains (3�+ drams) while Dupont used 82 grains (3 drams). DuPont did not stated their velocity but a 3-1� load shouls fall in the 1150-1175 fps range. Lyman reported 1100 fps vel. Max pressure listed by DuPont was 9,000 psi, that by Lyman was 5,100? (perhaps LUP). Could the difference in 3f vs 2f, PE vs LUP & perhaps a higher quality powder in the 20s result in a 3,900 difference in max pressure, I am just not sure.
While true, the bbl really doesn't know or care if the pressure upon it comes from BP or Smokeless there is one major difference between the two. That is their abilities to burn. Black powder will burn about as well unconfined as under pressure. You can thus load BP down to as light as you like withoput fear of a squib. One needs to keep in mind that the slow progressive powders were designed "NOT" for low pressures, but for pushing heavier loads of shot or acheiving higher velocities (Or Both). They acheive this ability by being made Harder to ignite, which when loaded to pressures below their design rate can (& often Does) result in inefficient burniong, even to the point of an ineffictive load or a wad left in the bore, something to keep in mind particularly if you try to use them in colder weather.

Miller,

Thank you for your comments and I do understand where you are coming from. There is a ton of information to wade through on this topic and I have been eagerly reading the data from Hodgedon trying to figure out what a decent recipe might look like. The variables are staggering and I'm trying to stick with what I have experience using. The faster burning powders will yield about 7000PSI while the slower burning powders can get lower than 5000PSI. I may try some loads with IMR PB which is number 25 in a list of 134 common powders available according to the Lyman 5th ed. reloading book (burn rate fastest to slowest).
My initial inclination was that the thin spot should be of no concern 22" down the bore with the exception of the susceptibility to dents.

Interesting discussion. Re the Dupont chart, although the loads in question do indeed swap positions in terms of highest pressure vs lowest, they're actually becoming closer rather than farther apart at the end of the chart. Of course that stops short of any weak point 20" or more down the barrel, but the difference is so small--looks to be only 2-300 psi between the BP load and the highest pressure smokeless load--that it seems to me, unless the curves start moving apart again, it would not be a matter for concern.

Bell did similar tests in one of his "Finding Out For Myself" series in Double Gun Journal. Once again, very little difference in the pressure curve between modern smokeless loads and black--although he also stopped short of showing what happens beyond the 12" mark. However, at that point on his charts, it does not appear that the difference between the loads was increasing; no indication that the modern loads were going to be more problematic farther down the barrel than the BP loads.

Larry & all;
I have never seen anything to indicate that any major changes would occur to the pressure curve beyond that 10"-12" point. A careful study of the DuPont chart shows the two places of greatest difference between the curves occur first within the chamber at the 1"-1.5" point, folllowed by a point around 4" down where the curves are well reversed, IE the Low pressure load is now the high pressure one & vice-versa. My thinking here is the curves will maintain there relative positions from the 10" point to the muzzzle with a continuing decline to a pressure somewhat below half of what they show there. I would not expect another reversal. It is also noted the curves are very close together by this point. That thin spot @ 22" down the bbl is not really going to know, or Care, which load was fired through it, though what slight difference there may be will at this point favor the faster powder which started with the highest pressure.
In accessing loads it "MUST" always be borne in mind it takes a given amount of work to get a given load of shot to a given velocity. If you push a given amount of shot out the bbl at the same velocity then the total pressure area beneath the curve is going to be essnetially the same.
The only way to reduce the total impact on the gun is to load a lighter shot charge, A slower velocity or both. For most of my use I need no more tan an ounce of shot & never load it in excess of 1200 fps, usually a bit less. I then prefer to use a powder which gives a peak pressure within the 7K-8K range. This puts that pressure peak Right under the thick chamber walls where the gun was designed to take it. I then don't have to worry much if I'm shooting on a hot sweltering day or shivering from the cold I can expect reasonable performance under either condition.

Stay in that 5,000 -7,000 zone and you will be OK, provided the gun is sound.

Check out Hodgdon reloading online
http://data.hodgdon.com/shotshell_load.asp

Pete

Hello, Blue Grouse. I have Sherman Bell's spreadsheets for 12 ga loads 1 1/8 and 1 oz with pressures starting at 4300 psi. I have supplied it various times over the years to members of this BBS, and I use loads in the 6000 psi range for my damascus Rem 1889 shotgun in local competition for older SxS shotguns. If you send me your email address, I will send both spreadsheets as attachments.

Jim Haynes
jhaynes@earthlink.net

If you want to load BP use paper wads from www.circlefly.com - plastic wads will melt in the barrel and be bad to clean. For 10 years or so I've used a Mec [ 600jr, 650, or Grabber ] to load BP. Don't understand how you get a spark with a aluminum charge bar - anyways, I've never had a problem. A 46A bushing will throw 75grs. Cut one in half and get 84grs, or no bushing and get 95 grains. I've been shooting 10 or so damascus guns for about 10 years with both smoke and smokeless. For nitro I've kept my loads around 5500 to 6500psi - there are many loads out there at 1150fps with 3/4oz to 1 oz. And I believe Sherman Bell proved there's not much pressure increase by useing 2 3/4" shells in a 2 1/2" gun. If you're only at say 6000psi the pressure wouldn't go above 7000psi, if that. Good luck - Paul