Arrived this morning. Looks very good. Needs a through cleaning but rifling and everything looks very good. Anyone have a clue what the square block on the bottom rib is?

Base for a ground off sling eye, perhaps it gouged the owner’s hand on recoil.

Nice rifle, enjoy!

That's my first thought so I checked the butt. The stock has never had a sling eye in it.

Probably for the bipod, but that usually came with the collapsible stock;-) Seriously, that's going to be a blast. I am forever kicking myself for turning down one in England for $300. I just remembered I have a box of new Bertram brass for 500 3 1/4. Do you already have brass? If you want this brass I will send it to you for shipping.

Could the buttstock be a replacement, thus accounting for the lack of a sling eye?

Looks like it uses a short bullet. That rifling looks quite slow, so an express-like load may regulate best? What caliber and chambering is it?

Could the buttstock be a replacement, thus accounting for the lack of a sling eye?

Looks like it uses a short bullet. That rifling looks quite slow, so an express-like load may regulate best? What caliber and chambering is it?

The auction house only knew .50 cal. I'll make a chamber cast tonight. Butt has much finer checkering than the forearm so it's possible.

Straight wall case from just looking down the bore. 3" long. I'm hoping .500 BPE 3"

.500 BPE 3" would be the most likely cartridge of that period. Where was it proofed? Birmingham or London?

Proofed in London has 38 bore marked which from the chart I have is .497 caliber. Tight .500 I guess. Chamber cast measures 3.25" case. bore is .515. That's a 3" case next to the cast.

There's almost a hint of a line at the 3 inch mark. Could be the rest is freebore or the chamber was lengthened. Of course, the original 500 BPE was available in either length. Does that rim cast look like a thick rim? The 500 3 1/4 Bertram I have has a thick rim like that.

Mike could it have had a laced on sling attachment at the butt?

It's possible but I think that it's been restocked years ago. The checkering on the forearm is course and flat top the butt is very fine and sharp top.

The Lee 440 grain Flat point gas check for the .500 S&W drops out of the mould at about.501.

Paper patched to .515 (+?) makes a good choice for Nitro for Black loads.

Lots of choices for PP and GG here: http://www.accuratemolds.com/catalog.php?page=25#catalog-anchor and you can specify the actual diameter you would like on any design.

Even though it's still cold and snowing outside I couldn't wait any longer and I loaded up two rounds of the 500 3 1/4" BPE just to hear it go bang. Target was at 50 yds and I shot off of a stick. I put the bead to far down in the V notch. It seems it is suppose to be level with the top of the rear sight. But, I'm really happy with that group. 2 shots a left and a right.

What bullet did you use? At what diameter? Wads? How much powder? What kind? I know, questions, questions:-) That target looks like at least one bullet when through sideways?

naw the top flap of the box was leaning back at a pretty good angle. .504 450 grain bullet patched to .512. 57 grains of 4198 with 13 grains of dacron filler, standard rifle primer.

Question Mike, not sure I understand you comment. If you were to bury the front sight too low in the rear sight notch, that would make the barrels point low in relation to the target. Your rifle shot quite high as you know. Please help me understand.

I was confused. You are correct. Hope it's not going to keep shooting that high.

You might need to investigate if you think the sights have been modified over the years. At first blush it would say you front sight is to low, however that does not rule out load like bullet weight speed, etc. I personally would wait until you could try the rifle at 100 yards. I say this because the math to correct is easier if done on 100 yard results. (Just my way of mentally calculating solutions. ) Generally thinking load and speed are not the major contributor to the results. Physical sight heights being that major contributor.
Shoot the rifle a few more time as it is and get a better understanding of what is really happening here and then make corrections as needed.
As you may see I also am working with one of these great 2 barrel rifles. So much fun. Can't hardly wait till winter breaks and I and my good friend can shoot mine. Maybe if it shoots really well he will take it on his Elephant hunt he is going on this spring. LOL just for you Rick.

Or maybe your bullet is too heavy or it is spending too much time in the barrel and recoil is raising the muzzle before the bullet exits. If you want to check the sights use the original 136 grains of black powder as a test. You might also try the other standard bullet of 340 grains.

I'll try the other bullet but I'm not using black powder. I hate it.

A couple thoughts, does the rifle's front sight look original or may have been changed at some point in it's life?
And I suggest you do a little measuring of the height of both the front and rear blade sights above the bore centerline. Then the distance between the two sights. With a little math you can calculate whether the sights are reasonable or something is wrong. (If you want any help with this PM me and I can help)

top of front bead to best guess center of bore is .522, from top of rear blade to center bore is .590, top of blade to bottom of V is .045. Distance from rear of front bead to rear blade is 22 3/8" Front sight is original.

Basically, with the top of the front sight even with the top of the rear blade there is a difference of .068". With 50yds (1800") / 23.375" * .068 = ~5.2". That means when your sighted on the target the barrels are pointing 5.2" above the target center. That seems quite reasonable. But as you know your bullet impacts are quite a bit higher which would indicate the muzzles must be recoiling up due to recoil before the bullets leave the barrel muzzles.
I would try the lighter bullet and get the velocity up a bit higher. And experiment with the sight hold relationship between front and rear.

will do. I have a mold coming for the 340 grain bullets. And the 57 grains of 4198 is in the middle of the low to max range of load. When it's warmer I'll break out the chrono.

Mike you got me thinking so I decided to measure my sights on my 450 3 1/4" BPE. The sight difference front to rear is .064" and they are 21" apart. Which means at 50 yds the barrels are pointing ~5.5" above the aim point.
When the weather breaks here and warms up I will go shoot it. However, for reference, my first loads will be 120 grains of black pushing a 270 gr hollow point copper tubed paper patch bullet.

measured to top of rib there is .056 difference in height.

Typically I measure from the underside of the barrel to the top of the sight then subtract half the barrel diameter at that location. Then subtracting the front sight height from the rear establishes the angle of cant between the line of sight and line of bore. Just the way I do it.

the sight doesn't sit on top of a barrel on a double barrel. Sits on the rib between the barrels.

Ok but I want to know, as I said, the height of the sights over the center line of the bore. The C/L of the bore is the only reference that ties the relationship of the sight together. The rib it what just holds the barrel together and a convenient place to mount the sight to.
How does the way the sights are mounted play into the equation? Am I missing something here, if so I would like to know.

I have no idea how to guess and measure at or from the centerline of the bore.

Mike, put a straight edge under the muzzles resting on both the barrels. Measure the height of the front bead from the top of the straight edge. Measure the outside diameter of a barrel and subtract half that number from the "height" dimension.

The rib stands proud of the barrels by quite a bit. Luckily the caliper end will reach from the sights to the top of the barrel. Rear is .6745" from center line front is .537

This may help. Measure with a dial caliper is easiest

Using LRF's method I came up with these numbers. F .5545 Rear at top of blade + .7045 at bottom of V = .588.

Mike what is the actual measurement you got for the 4 dimensions: A, B, C, D Please

A using top of rear sight blade = 1.1395 A using bottom of v+ 1.034 B = .8705 C = .9105 D = .712

Just had a nice conversation with Mike on the phone. Measuring to the top of both sides gives us a difference in sight heights of ~.150" height over the bores. Extrapolating this difference out to 50 yds says the bores are pointing about 12" above the point of aim. So Mike in his shooting had the bullets impact about 14" above PoA. The rear blade is marked 100 yds.

Given this we agreed that working on the sight picture, trying a lighter bullet, and maybe some increased velocity will work to refine the position of the group on the target. We feel good with the results.