Need Help With Low Pressure 455 Mk1 loads

jakester

jakester

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I have read many of the postings in other threads on using smokeless powders with a burn rate slower than 2400 for low pressure loads for antique revolver cartridges. Win 38-55 had supplied much information that peaked my interest, and I too would like to venture into experimenting with loads along these lines.

My Project:

I am loading for a Navy marked Webley Mk1 built in the first month of production. It had been Nitro Proofed at sometime during its life. It's been refinished, and the bore is pitted some, but it shoots quite well and has all of its original parts except for the grips (I have repro's coming).
I've measured the cylinder fronts, and they are within spec at .4495"
I slugged the barrel, and it too is within spec at .449". I was initially puzzled at the sizes for the cylinder fronts and the bore. After a bit of enquiry, a freind loaned me a copy of Bruce & Reinharts fine Webley book. A bit of searching turned up a copy of the sealed pattern for the mk1 revolver. It gave the specs for most parts of the revolver including screws. It was then I had found the answer. To make a long story short, the Webley Mk1 was initially adopted as "Revolver, 6 shot, .441 caliber". However, they were from inception chambered for the .455 Mk1 cartridge. This made finding a suitable bullet much easier.

I chose some .451" 250gr. lead roundnose flatbase "cowboy" bullets that are manufactured locally. I decided early on for this project that I would use the Mk1 case length. My thinking was, that I could use both smokeless and Black powder. It would be nice to have the versatility. I was able to obtain a fair bit of Starline 45 Schofield brass, and it was trimmed to .870" and the rims thinned to head space properly.

My only loads so far have been with Unique. While the loads are fairly accurate, I would like a higher load density. When I read the postings about low pressure loads using slower burning smokeless powder, I began to think this might be a viable solution.

I know "WIN 38-55" used 4198 in developing his 45 Schofield loads, but I'm thinking that it may be too slow for the Mk1 Webley case.

So that's where I'm at. I would appreciate any help with which of the slower burning smokeless powders would be a good starting point.

Jake
 
I would try SR 4759 by IMR/Hogdon, I used it with great success in .44-40 with a Colt SAA and M92 Winchester.

SR 4759 was designed as a bulky smokeless powderr for blackpowder cartridges way back in the day and is my favourite .45-70 target load powder.

It leaves some unburned grains in the bore but that is normal and does no harm.

You might also try Trailboss which will almost fill the case at low-pressure loads. I have some but haven't tried it yet.
 
In my later Webleys, the round nose colt bullets do not shoot at all well and I think it is because of the lack of a forcing cone at the beginning of the barrel. The long pointed Webley design bullets from OMAH here in Nanaimo, are far more accurate and I think the reason is that the gun design requires the long point to the slug to guide the slug into the bore.
I use them in a Webley model 5 (not mark V), a Webley Pryse, and a Webley mk VI

cheers mooncoon
 
The MkII ctg used the long pointed bullet. The Mk IV & V were full wadcutter bullets. DCCo and Kynoch loaded a wadcutter bullet similar to the MKIV/V for match use. They were produced for several years so they must have shot well enough for match shooters to use them.
 
Like Opcx6 said, IMR SR4759 is an excellent powder for your application. The pressure curve is very close to black powder, though not quite as high. You need to start a bit on the low side (way low if you have no idea what you will be getting) and fire each shot over the chronograph until you reach original black powder velocities. With 4759, at original black powder velocities, your pressure will be close to, but not quite as high, as BP pressures. If you run out of case capacity before you get there, you may have to go with a faster powder like 2400 or a less bulky powder like IMR 4227 or 5744, which still has a pressure curve a little lower than BP for the same velocity and bullet weight.
 
Is there any place where graphs of pressure curves are available for different powders?

I saw the ones win38-55 posted a while back but they seemed more applicable to rifles with higher pressure than pistols at 15000psi or less.
 
'My only loads so far have been with Unique. While the loads are fairly accurate, I would like a higher load density. When I read the postings about low pressure loads using slower burning smokeless powder, I began to think this might be a viable solution'

Just why are you looking for higher load density, as the powder capacity is quite limited to begin with? I have used Unique and achieved low pressure (and relatively low velocity of 625 fps) loads with some accuracy. I would suggest that you try the Hornady 250 grain swaged bullets as they are soft enough to slug up to fill the bore. I am not sure that you want to start exploring strange new powders to answer a problem that might not exist.
 
In the short MKII cases I use 5grs. of blue dot and magnum pistol primers for around 600fps. In the longer MKI case I use 5.8grs. of blue dot.
 
Blue Dot has pretty much exactly the same pressure curve as FFFg for the same original BP velocity, so you're working with a good powder.
 
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