44-40 Barrel and Cylinder Dimensions

[Johnm1]

I have a Hopkins & Allen XL no. 8 in 44-40. There is a thread on this particular revolver here:

https://www.thehighroad.org/index.php?threads/hopkins-allen-xl-no-8-army.880718/

The revolver is a black powder cartridge gun and I want to order the correct Big Lube bullets for loading so I slugged the bore and cylinder throats with the following results:

Throats 0.425"
Bore 0.439"

The options are for 0.427" through 0.429". With 0.425" throats it doesn't make sense to order anything larger than the 0.427" as anything over that will just get swaged down to the 0.425". Is that correct?

Does anyone see a possible blow by issue with those numbers? Or will a dead soft bullet obturate to fill the grooves?

I know @Driftwood Johnson shoots these older black powder cartridges a lot. So maybe he has an opinion. I have been shooting 0.428" bullet but they are not the big lube bullets that I want to shoot. Accuracy is still somewhat of an unknown even after shooting the 0.428's. The front sight is so mismatched to the load my hold point is very different from the point of impact. So I don't have a lot of feedback from the shooting I have done so far.

As I develop a load for this revolver I may well have to devise an alternate front sight that is much taller than what is currently on the gun. It 25 yards it shoots way high with a full case og 3FG black. As in off the target at 25 yards. Not sure if someone filed the front sight or not, but what I have been shooting should be close to the original black powder load.

 

[Driftwood Johnson]

Howdy

Are you sure about that .439 number?

How did you slug the bore?

When you say 'Bore Diameter', that is misleading.

The Bore of a rifled barrel is the diameter the hole has been drilled, but before the rifling has been cut.

This diameter represents the diameter of the lands after the rifling has been cut.

Rifling groove diameter is what you want.

Slugging the bore can be tricky to measure rifling diameter, depending on how many grooves there are to the rifling. It is easy if there are an even number of grooves. One simply measures across the widest parts of the slug, which will represent the depth of an opposing pair of rifling grooves. However all bets are off if there are an odd number of rifling grooves. Then one has to measure across the slug, which means measuring the depth of only one rifling groove. Then one has to take the depth measuring probe on your caliper and balance it as best you can and measure the height of one rifling groove. Tricky at best. I have never had a lot of luck measuring rifling groove diameter with an odd number of rifling grooves, I just do the best I can. Most modern Smith and Wesson revolvers have an odd number of rifling grooves.

Here is a 458 diameter 45-70 bullet that I ran through my Trapdoor rifle so I could measure the groove diameter. As stated, I measure across the high points on the bullet, which will represent the rifling groove diameter.






To measure chamber throats I NEVER use the inside measuring jaws of a caliper. The tiny flat on each jaw always introduces a slight amount of error.

Rather than invest in an expensive set of .250 -.500 gauge pins, I use a set of Small Hole Gauges. These can be quite accurate. I select the gauge I need, close it down enough to fit into the hole, then turn the handle to expand it just enough to contact the walls of the chamber throat. Then I remove it and measure ACROSS THE WIDEST SPOT on the gauge with my calipers. And I always repeat it the measurement a few times. This gives a very accurate measurement.






All of my 44-40 rifles have groove diameters of either .427 or .429. This is both antique and modern replica 44-40 rifles. Last count I think I had seven of them.

You may be aware that the 19th Century standard for rifling grooves in 44-40 was .427. However, this tended to vary all over the place, from as small as maybe .425, all the way up to .430 or even more.

I used to always load .427 diameter bullets in all my 44-40 Black Powder cartridges.

When I bought my Uberti replica 1860 Henry, with its 'modern' .429 rifling groove diameter, I started using .428 diameter bullets instead. I used to cast my Big Lube bullets myself, but I don't do that any more. I buy my Mav-Dutchman Big Lube bullets from Whyte Leatherworks these days. Yes, I know he lists .427 and .429 as the two diameters, but he always sizes them to .428 for me when I ask.

Do my .428 diameter bullets slug up in the bore to fill the .429 grooves? Who knows. I do know I get good accuracy out of my Henry.

I only have two revolvers that are chambered for 44-40, a Colt New Service.






And a Merwin Hulbert Pocket Army. I do shoot my Black Powder 44-40 cartridges with the .428 diameter bullets through the Merwin Hulbert. This revolver has chamber throats right at .428. Of course it has five groove rifling, so the best guess I can come up with about rifling groove diameter is .427. My .428 bullets seem to do fine through it.






I would be very leery of that Hopkins and Allen 44 of yours. Yes, I am aware it was made in the same factory as my Merwin Hulbert.

I am pretty experienced with old revolvers, and felt comfortable firing my Black Powder 44-40 ammo through it.

I have no idea how safe your revolver is.

Fist, I would double check your chamber throat and rifling groove diameters. If it has five groove rifling, good luck getting an accurate measurement.

If you decide to go ahead and shoot it, I suggest you do what I always do with an old firearm. I walk right up to the berm at my club, hold the gun as far away from my body as possible with one hand, then pull the trigger.

Or you could try strapping it down to something heavy like an old tire, point it at the berm, and pull the trigger remotely with a string.

Other than that, its a crap shoot as to just which diameter Big Lube bullet to order. If your chamber throats truly are only .425, I would go with .427 Big Lube bullets and hope the bullets don't skid down the barrel without engaging the rifling.

 

[Johnm1]

When you say 'Bore Diameter', that is misleading.

The Bore of a rifled barrel is the diameter the hole has been drilled, but before the rifling has been cut.

This diameter represents the diameter of the lands after the rifling has been cut.

Rifling groove diameter is what you want.

You are of course correct. Poor terminology on my part. The 0.439" is the groove diameter. It does have 6 grooves, so the measurement appeared simple enough.

I don't have a set of pin gauges or a set of small hole gauges so I removed the cylinder and drove a 58 caiber round ball through the cylinders and measured the slug. It too appeared a simple measurement.

I'll check the slugs again in the morning, but these numbers sound familiar from when I bought the gun.

 

[Driftwood Johnson]

Howdy Again

Yup, you used a good technique to get the chamber throat diameter.

Six grooves on the rifling makes it easy to measure the rifling groove diameter.

I must say though, that is quite a disparity,

Throats 0.425"
Bore 0.439"

.014.

I took a look at your previous post. Interesting to hear what Ian has to say about your revolver.

Also interesting to note the similarity of it to the Merwin Hulberts.

Notice the shape of this pair of Merwin Hulbert Army revolvers. Very similar to the shape of your Hopkins and Allen revolver. Note the shapes of the hammers, and the loading gate.






The hammers and loading gates are very similar in shape to the ones on my Merwin Hulbert Pocket Army. I would not be surprised if some of these parts all came out of the same parts bin.






Because of the location of the loading gate, rather than the old load one, skip one, then load four more, with a Merwin one loads two, skips one, and loads three more. I suspect the procedure will be the same with your revolver.






I was mistaken when I told you I only have two revolvers chambered for 44-40.

I also have a Remington Model 1875.






Mike Venturino has written how most of this model chambered for 44-40 were poor shooters. because the chamber throats are too large for 44-40. The chamber throats on this one are .448. I don't recall the rifling groove diameter, and I don't feel like slugging it right now, but .448 chamber throats with a 44-40 barrel are way oversized. There is a logical explanation for this, but I am not going to go into that right now. Venturino writes that the two original 44-40 1875 Remingtons he fired would not put a bullet pointy end first through a target, the bullets were tumbling. So I was pleased when my 1875 managed to put all the bullets pointy end first through my targets. There was no key holing. Yes, at 15 feet the accuracy was terrible, but at least the bullets were not tumbling.






But this is the opposite of the problem you are facing, with rifling grooves much too big for the chamber throats.


Interestingly enough, years ago I fired some of my 44-40 loads through a Colt chambered for 45 Colt. I did this at the end of a CAS match. Interestingly enough, even though the bullets were way undersized for a 45 Colt, I managed to hit the target with all five round. No idea if the bullets were tumbling or not, it was a very unsophisticated test. But I did manage to hit the target with five 44-40 rounds fired out of the revolver at close range.




So, bottom line. If your chamber throats are really .425, I suggest you use .427 diameter Big Lube bullets. No matter which size you use, .427 or .429, the bullets are going to squeeze down to .425 as they exit the chamber throats. No point stressing the old steel squeezing .429 bullets down to .425. I doubt your bullets will expand enough in the bore to engage the .439 rifling. You never know, they might, but even with the soft lead Big Lube bullets I doubt if they will be able to bump up in the bore enough for the rifling to get a good grip on them.

Your first shots at a paper target will tell the tale of whether or not your bullets are key holing, or are going through the paper pointy end first. Be sure to fire your first groups close up, as I did with my Remington 1875 so you can hopefully see the bullet impacts on the paper. Don't worry about point of aim with the less than perfect sights, just hold on the same spot on the target for all five shots so you can get an idea of the size of the group. Later you can worry about getting the point of aim to the point of impact.

I would not expect great accuracy from that revolver, but you may be surprised.

Let us know how you make out.

 

[Johnm1]

I'll check the slugs again in the morning, but these numbers sound familiar from when I bought the gun

I must say though, that is quite a disparity,

Throats 0.425"
Bore 0.439"

.014.

Thanks again Driftwood. As always you are a great source of information. The numbers are what I posted. This mornings measurements were a couple of thousandths smaller, but I think that was me and how I measured it. I have fired it and at least they don't tumble even at 50 yards. I'll go with the 0.427" Big Lube Bullets and see what it will do. I've been shooting 0.428" made for smokeless bullets with the smokeless grease replaced with proper black powder grease. Because the grease grooves were so small I would brush/grease the barrel after every shot. At 50 yards I had to aim below the target to hit the paper. This one doesn't have to be super accurate. I don't compete, I just like the gun and would love to carry it in the field along with my 1898 Krag Carbine and have a chance to hit something at 25 yards.