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HuntingNut: Gun Smithing

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  Reworking a Worn-out Remington Rolling Block, an Alternative Approach
Gun Smithing My scout master presented me with a .43 Egyptian Remington Rolling Block back in ’67. I had a 28-inch Numrich 45-70 barrel installed in 1979. It has no Remington markings on it and looks like it was made in Belgium under contract.

In its worn condition, the rollers had a slight amount of play when open but minimal play when the hammer was forward in the fired position. However, the gun did not function. I figure the gun had been shot until it wore so much that it wouldn’t shoot any more. I had to replace the firing pin because it had worn too short, then the hammer spring because it couldn’t hit the primer with enough force to set it off - it would barely leave a dent in the primer. With a new firing pin and main spring installed, I proceeded to the firing line a few months ago in my drawn out quest to bring this antique back to life. I used 40 grains of Varget, a smokeless powder I had on hand, with 405gr Laser Cast bullets to test it out. The Hodgdon loading data listed this recipe as less pressure than black powder which I didn’t have. At the range, I wore my safety glasses and wrapped the action in Kevlar cloth for the first two shots. On the fourth shot I split a case. Inspection of the primers showed the first shot had backed the primer out 0.004”, the 2nd shot 0.010”, and the 3rd shot was out 0.015”. The 4th shot had a flush primer but that was because the split case base was pushed against the breech block. I had used a light lubricant on the barrel and figured by the 4th shot the case had fully gripped the chamber exposing the wear in the action. I used a bullet to extract the forward part of the case that was stuck in the chamber. I tapped the bullet in just far enough to engage the rifling, then used a wooden rod to tap it back out from the breech. The broken case came with the bullet.

On closer inspection of the action, I could get an 0.018” feeler gauges between the breech block and barrel with a strong tugs backwards on the breech block. If I didn’t pull hard on the breech block, I could fool myself into thinking there was only about a 0.004” gap. The hard pulls took up all the slack in the action. This slack amounts to excess headspace. I decided to take the rifle apart and mic every part and see if I could figure out where the slop was. Most of the slack was between the receiver to the pins and the pins to the rollers. The pins were 0.453, the holes in the receiver were 0.458 and the hammer and breech blocks were 0.460. These are the stack-up.

0.008 to 0.010 pins to breech/trigger blocks
0.010 on the breech pin to receiver
0.005 on the trigger pin to receiver

After some Internet searching I found a gunsmith in Idaho that machined part for antique guns. Ryan Roberts, Muzzleloader Builder Supply, had oversized pins on the shelf so I purchased 0.4600 and 0.4615 pins for a very reasonable price. I used an adjustable reamer to match the hammer, breech, receiver holes to the new pins.

The blocks were significantly harder to ream. The sides of the receiver cut very easily. Even though the pins were snug and had to be tapped in the receiver, I could feel the pins rotate slightly every so often. I lightly staked the pins on the right side of the receiver with a punch and they stayed put after that. Ensuring the pins stay fixed in the receiver is key to longevity of the action. The breech pin only took one stack but I wanted to make sure the hammer pin stayed put so staked it several times.

With the new pins installed almost all the slop in the pin interfaces was gone. I still had 0.005 of slack between the back of the breech block and the hammer when it moved forward. I test fired a couple of rounds. The group was bout 3 MOA and the primers were still moving aft out of the case pocket a consistent 0.007 upon firing. This was something I wanted to fix. A weld bead had been added to the back of the breech block in a prior repair to compensate for wear so I thought I could add some more metal and file/fit it to take of this slack. I found a local argon welder at a custom motorcycle shop to do it.

After having the weld added, I started to fit the breech block back into the action. Two issues became evident with this “repair” technique. Taking up the slack by adding metal to the back of the breech block tilts the block forward causing it to no longer be square with the receiver. It had a slight tilt to begin with and this course of action was only making the tilt more exaggerated. The breech block was touching the top of the case but the center primer area was visibly off the block. Also, with the breech block tilted farther forward, there was an interface issue with the striking portion of the hammer. It would no longer fit into the firing pin pocket so it could freely strike the firing pin. I came to the conclusion this technique was a dead-end.

Next, I measured what it would take for the breech block to be square with the barrel. The barrel would have to move aft 0.028” or the breech block forward the same amount. I determined this by measuring the action with the new pin installed and the breech block held perpendicular to the barrel, and with the breech block pressed up against the barrel and measuring the offset in the receiver to breech block pin holes.

Most shooters I talked with recommended I have a gunsmith move the barrel aft and recut the camber. In my particular gun, this would cause the barrel to project aft of the receiver. It also would not solve the interference problem I had when the breech rolls under the hammer to extract the case or load the weapon. Based on the wear observations of my rifle, I came up with a theory that the breech block and its pin progressively wears aft in the receiver over time and use, thus the ultimate solution would be to leave the barrel alone and move the block forward to be square with the barrel. A shooting buddy suggested an way to accomplish this. A new larger hole could be machined in the breech block with a 0.028” offset, press a bushing/sleeve in, and refitting the roller pin. I had access to a machine shop so I started seriously considering this option. I wanted to remove as little metal from the breech block as possible. The thinnest area of metal in the breech block is located on the front side of the now oversize hole to accommodate the new 0.460” pin. By doubling the required offset of 0.028”, a new hole of 0.516” could be machine with its forward edge just touching the forward edge of the existing 0.460+ hole and minimizing the metal removed in the forward section of the breech block. This would allow a symmetrical 0.028” bushing to be inserted to get back to the hole for the roller pin. I made sure the new hole was offset horizontally as opposed to up or down the angle of the receiver because I didn’t want to have the firing pin rise in its relationship with the primer. I also checked to ensure there was enough clearance in the aft lower section of the barrel to still allow the breech block to roll open.

Time to cut metal. With the help and guidance of a buddy, we used the new roller pin to position the breech block on the machine’s turn table with the 0.028” offset and machined the new 0.516” hole. We made the bushing 0.0015” over-sized (0.5175”) so there was an interference fit with the breech block. The internal dimension of the bushing was also undersized so we could fit it precisely to the new 0.460” roller pin. We should have also made a matching centering pin for the undersize hole to reposition the breech block back on the turn table to fit the pin because we were off about 0.002” from center when we bored out the hole. This turned out not to be critical because the interface with the barrel is well above the center of the pin reducing the affect of the error. BTW, the bushing was 4041 steel, the same harness as the oversize pins. I will this will be adequate for the reduced loads I am planning to shoot.

Now the fitting began. With the tilt forward eliminated, the aft part of the breech block was now lowered in its relationship to the hammer block. Thus, I had a significant amount of fitting to do. It turned out that all the new metal from the added weld had to be taken off. I slowly and patiently removed metal until the hammer just started to roll underneath. I would then use a carpenter’s hammer to tap the rifle’s hammer spur forward a little than aft to become free again. This would leave a mark on the bottom of the breech block and showed precisely where more metal had to be taken off.

I used a file and sometime a battery powered grinder with a small abrasion drum to remove the interference mark. I repeated this process until I could lightly tap the hammer block all the way into the firing pin well of the breech block. I took me about an hour to work the action to the point. I then dry fired the action until the hammer could freely come forward and strike the firing pin while leaving the action tight. With the breech block now square and closer to the brass case, I checked the firing pin to ensure it was not too long. To reduce the risk of piercing a primer I shortened the firing pin to provide 0.040” protrusion. This is the original large diameter firing pin, much fatter than today’s firing pins, so make sure its tip is nice and round with no sharp edges or corners. I did a few firings with primers only just to make sure the firing pin work correctly. BTW, the firing pin was initially protruding 0.055” but, with the large diameter firing pin, it never crushed the primer more than about 0.030”. Still, I shortened the pin to be safe.

There was one additional modification that was required before the rifle was fully functional again. The extractor was binding with the breech block during opening. As the breech block rotates aft to open the chamber and with the new roller pin hole offset aft, the breech block now rises slightly at the point of extractor engagement. I had to remove metal from the lower side of the extractor just behind its interface tab to accommodate the breech block. Looking at the picture more closely, it looks like I should have taken just a bit off the lower tab that engages the groove in the breech block.

The action was now very tight with excellent lock-up. It was so tight that Winchester Brass with a 0.063 rim base would fit. Starline brass with its 0.065 rim base would not. I wanted to use the Starline brass because it has thicker walls. So, I laid a file flat on the work bench and removed 0.002” off the bottom of 10 cases. This task only took about 15 minutes to accomplish. The stamp marks still show on the bottom of the case and I will save the other cases for when the action has worn in a few thousandths. With the action a new, I loaded the cases and took the rifle to the range. Below is my target at 50 yard - 1 MOA, a dramatic improvement! The load was 41gr H4895 with 405 Oregon Trails Laser Cast Bullet resulting in 1435 fps muzzle velocity. I switched to H4895 powder because Varget left unburnt powder grains in the barrel. H4895 burns slightly faster and at a slightly lower pressure, e.g., approximately 15,000 psi chamber pressure compared to 17,000 with black powder. BTW, Reloading is a breeze. Press out the old primer, insert a new, fill with powder, and insert bullet. Don’t even need to neck-size.

You can see that I had *****d a scout scope. I needed to do this so I was sure of my point of aim. My eyes are too old to shoot open buckhorn sights well enough to evaluate a load's accuracy potential. There was also one other mod. I installed an aftermarket trigger spring kit from G. S. WOMACK. The wire spring reduced my trigger pull from well over 10 pounds down to approximately 4 pounds. This is well worth the $15 spent. I also got some rolling block specific screws from WOMACK to replace ones that were too worn. One final step I took with the action. I used Action-Magic (dry moly lube) from Brownell’s on every part of the action that touches another part, e.g., the pins, inside the breech and hammer blocks, firing pin, trigger pin, spring to roller interfaces, and the breech block to hammer lock-up surfaces.

Now that I know my rolling block is a worth shooter, I have motivation to fit and finish the Schnabble-style fore stock that I got from Dave Crossno Gun Stocks. I’m ready to work on maturing my loads and using this rolling block for another hundred years.

Ryan Roberts
Muzzleloader Builder Supply
PO Box 848
Aberdeen ID 83210
(208) 397-3008 or (877) 397-3008

5100 Garden Valley Rd
Garden Valley, CA 95633

Dave Crossno Gun Stocks
23380 N. Anderson Road
Arcadia, Oklahoma 73007
Tel: (405) 396-8786

Posted by slimjim on Wednesday, September 04, 2013 (15:24:21) (4967 reads)
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