Adjusting Ejector Timing on a Browning BPS with a Nylon Cam

The Browning BPS has earned a loyal following across Australia, particularly among pig hunters working the scrub in central Queensland, clay target shooters at clubs such as Melbourne Gun Club, and property owners clearing rabbits and foxes in the southern states. Its bottom-eject action keeps spent hulls out of the shooter's face, which makes it a top choice for left-handers and for anyone shooting from a vehicle or blind where a hot case down the collar would be a real nuisance. Ejector timing on these guns is controlled by a small nylon cam tucked inside the receiver, and when that cam wears or gets fitted slightly off, empty cases stop falling cleanly.

Before pulling the trigger group, it pays to understand what the nylon cam does, what tools you should have on hand, and how the local firearms transfer rules affect the way you source spare parts. Most owners will already own the basic kit, but a few specialised punches and a service manual specific to the BPS model year are worth chasing down through a registered dealer in your state.

How the Nylon Cam Controls Ejection

The BPS uses a simple stamped-steel and polymer linkage, but at its heart sits a nylon cam that rides on a pivot inside the trigger housing. As the bolt travels rearward, it nudges the cam, which in turn lifts the ejector claw at precisely the right moment to fling the spent hull downward through the ejection port. If the cam is rotated one tooth too far forward, the ejector fires too early and the case barely clears the port. If it is rotated too far back, the case hangs up and gets smacked by the closing bolt, which dents the rim and occasionally stovepipes.

Because the cam is made of polymer rather than hardened steel, it is designed to wear slightly over time. That wear is intentional, and Browning expects shooters to make minor indexing adjustments every few thousand rounds. The good news is that the part is cheap and widely available through licensed channels in Australia, and swapping it requires only a basic understanding of how the cam indexes to the hammer and bolt.

Tools You'll Need

Lay everything out before you crack the receiver open, and make sure the workbench is clean and well lit. An arvo spent chasing a lost spring across the shed floor is no fun, so set up the same way whether you are working in a suburban Brisbane garage or a back shed somewhere out Wodonga way. Keep small parts in labelled containers so the cam, spring, and roll pin can be returned to the correct position during reassembly.

• Roll-pin punches in 1/16, 3/32, and 1/8 inch sizes
• A small nylon or brass mallet to avoid marking the receiver
• A padded bench mat or old towel to stop small parts rolling away
• A headlamp or angle torch for inspecting wear marks on the cam
• A BPS service manual for the exact model year
• A magnetic parts tray to keep cam, springs, and pins in order

Common Signs the Timing Is Off

Before assuming the cam is at fault, run a few hundred rounds through the gun and watch how the empties behave. Some symptoms look like ejector problems but are actually caused by weak recoil springs or fouled chambers, so it pays to rule those out first by giving the bore a thorough scrub-out and swapping in a fresh spring. If the following signs appear consistently across different loads and weather conditions, the cam is the most likely culprit.

• Hulls piling up under the receiver rather than clearing the port
• Stovepipe jams that clear only after racking the action twice
• Dented case rims from the closing bolt striking before ejection
• A faint metallic click as the cam trips the ejector claw late
• Misfires on the second round of a fast follow-up shot
• Oil spray on the receiver tang from unburned powder in a stuck case

Step-by-Step Adjustment Procedure

Unload the gun completely, remove the magazine cap, and slide the barreled action out of the stock. Lay it on the padded mat with the trigger group facing up, then push out the two large receiver cross-pins with the appropriate roll-pin punch. Lift the trigger assembly clear of the receiver and set it on the bench. The cam sits at the rear of the trigger group, indexed on a small post that mates with a notch in the cam itself.

Rotate the cam one tooth at a time, reassembling and test cycling with snap caps after each adjustment. Most Aussie shooters find that rotating the cam one tooth clockwise advances the ejection timing, while counter-clockwise retards it. Once the case falls cleanly with a definite downward arc, reassemble the trigger group and reinstall the receiver pins. If the trigger group itself feels rough or gritty, the principles of indexing and pin alignment covered in how to remove and install the trigger group on a Browning Maxus carry across to the BPS even though the parts differ.

Field Testing and Refinement

Take the gun out to a local range or a safe patch of bush before trusting it on a hunt. Cycle twenty snap caps in quick succession, then load a dozen live rounds and work the pump with the action held partially open to watch the ejection arc. If any case hangs on the bolt face, retard the cam by one tooth and try again. Pig hunters in the brigalow belt often run reduced-recoil loads to keep follow-up shots fast, and these lighter shells are less forgiving of sloppy timing than heavy magnum loads.

Clay shooters at suburban Melbourne clubs, including those based around the Werribee range, will see a short-thrown hull as a distraction during a long squad run, so they tend to favour tight timing tolerances and full magnum loads. Spending a full box of cartridges refining the timing is the only real way to dial it in for your specific load and shooting style.

Ongoing Maintenance for Aussie Conditions

Dust, salt air, and the occasional tropical downpour take their toll on a working BPS, so a wipe down with a light oil after every range session is a habit worth keeping. The nylon cam tolerates dry conditions well, but it does attract fine red dust that can grind against the pivot post if left to build up. A quick spray of Inox or a similar light lubricant every few outings keeps the cam pivoting freely.

For shooters who use the BPS mainly during the dry season up north, the cam should be inspected at least once a year, ideally before the first big hunt of the year. Owners who store their gun in an air-conditioned safe room will see much longer cam life than those who leave it in a hot tin shed, so the location of your safe matters more than the hours of use. Tracking these intervals in a small logbook or on a phone calendar makes the next adjustment quicker and far less of a surprise.

Have a look at the parts catalogues and shotgun tips over at guns and magz for sourcing advice, or speak with your local dealer about pricing a fresh cam if the indexing adjustments no longer hold their setting through a long session.