Miroku’s 1885 Browning/Winchester Failure Mode

By Wayne McLerran

11/2022

Although the rifles are very well made and enjoy a strong following there is one failure mode that can rear its ugly head, typically after the rifles have been fired a few thousand times.  As I have pointed out in my book on the black powder cartridge rifle (BPCR) version of the rifles and in separate articles, the entire modern Browning and Winchester single-shot line is called the Model 1885, an obvious reference to the late 19th century Winchester Model 1885 single-shot rifles.  But the action is not a copy of the original Winchester, and is much more complicated to disassemble and reassemble.  It’s an “improved” version of Browning’s prior Model 78 (B-78) single shot rifles.  The book is focused on the High Wall BPCR models but all the High Wall and Low Wall receiver action designs are essentially identical with some minor differences.  Disassembly and reassembly is not a good idea for someone unfamiliar with the process, which is the reason the book has been popular since it contains detailed instructions and plenty of supporting photos.

The Browning design incorporates a very effective safety feature.  One of the main differences between the original Winchester and Miroku/Browning design is the addition of a component called the hammer sear.  In actual operation it’s an inertial sear, making it just about impossible for the hammer to be in a fired position (pressed against the firing pin) without intentionally firing the rifle.  E.g., if your thumb slips off the hammer in the process of either “thumb cocking” or lowering it to the half-cock position, the inertial sear catches the hammer before it strikes the firing pin and ensures the rifle will not fire.  During normal firing operation the trigger sear releases the hammer sear which subsequently releases the hammer to strike the firing pin.

For the hammer sear to function properly a small spring is required.  Browning refers to it in their parts list as the sear spring.  Since there are two sears (trigger sear and hammer sear) in the rifles, to reduce confusion I call it the hammer sear spring.  It’s the most likely part to break.  To replace it essentially requires full disassembly of the action and removal of the trigger housing assembly.

Recently a good shooting friend started having problems with his Browning BPCR during a silhouette match.  The hammer would not go to full cock.  He managed to get it working by opening the action, jiggling the trigger back and forth and closing the action.  By doing so he was fortunate to make it through the match.  Later, after disassembling the action, I found the hammer sear spring was cracked.  It completely broke as I removed it (see the photo below).  He was lucky since the typical failure mode is the spring completely snaps resulting in a nonfunctional rifle – hammer will not cock and rests on the breechblock and firing pin.

The problem with the hammer sear spring is its design.  It’s a little too hard and stiff and will eventually fail, typically after being flexed a few thousand times.  It’s likely not a problem for non-match shooters that will only fire their rifle a few hundred times during its life time.  But some BPCR silhouette competitors will easily put 1000 or more rounds through a rifle in a year.

So what are the options if you experience a hammer sear spring failure, i.e. the hammer will not cock and rests on the breechblock.  Assuming you’re prepared to disassemble the action, one option is to order a replacement spring from Browning (part # B3474875).  But the replacement may result in another related problem, especially if the trigger sear has been modified.  In that case, once the new hammer spring is installed, the hammer may catch in the half-cock notch due to the spring being too strong, resulting in the hammer sear rotating too quickly and catching the hammer in the half-cock notch position.  Fortunately, the solution is usually pretty simple.  Turn the rifle upside-down and fully open the lever.  Locate the hammer sear just forward of the trigger.  It’s the shiny chrome looking part that’s about an inch long and inside the action just forward of the trigger.  Using a small punch or similar item, push on the forward end of the hammer sear.  Push it down into the action as far as possible while holding the trigger to the rear.  See Figure 1.  In most cases doing this will compress the spring to the point where it will work properly.

Another better option is to purchase Lee Shaver’s replacement hammer sear spring.  Lee’s spring is made from finer wire and has one more coil so it flexes easier and will last much longer than the original spring.  Looking closely at Figure 2 you should be able to see the double wrap coil in Lee’s spring.  But if the original or Lee’s spring does not fix the problem you’ll need your rifle checked out by Lee or a gunsmith that’s familiar with the Browning design and how it functions.

By the way, if you have a Miroku 1885 Browning or Winchester and would like to reduce the factory trigger pull, I highly recommend Lee’s trigger sear modification.  It’s very reasonably priced and I prefer it to other approaches that limit sear engagement.  The trigger/sear assembly, with the original factory sear is sent to Lee.  In a couple of weeks or so, the trigger with modified sear is returned along with a lighter trigger spring.  The trigger/sear is simple to remove by removing the buttstock and pushing out a small pin.

If you’re interested in purchasing a 3rd edition copy of my book titled Browning Model 1885 Black Powder Cartridge Rifle, the details are listed in the Books & Magazines For Sale and Wanted section of this magazine

Wishing you great shooting,

Wayne