Perform a Trigger Job On the Beretta A391 Xtrema

Beretta’s Xtrema semi-automatic shotgun is now well known to hunters and target shooters. It was introduced by Beretta in 2002, and quickly became recognized by many waterfowl hunters. This 3.5-inch-chambered shotgun has a number of attractive features including an overbored barrel, long forcing cones and chokes, a self-cleaning gas piston, and an adjustable stock.

Although designed for 3.5-inch extreme loads in waterfowl conditions, the Xtrema will also function with mild shells, making it quite desirable for target shooters. I believe, however, that there is one serious problem with this gun—its trigger. On many occasions, I’ve heard complaints from shooters about the Xtrema’s trigger, and most of the gunsmiths I’ve talked to have been unable or unwilling to deal with this problem.

Some discussion of this matter can be found in the product-review located at http:// waterfowlreview. com/review/ber etta_xtrema.htm. The problem itself sounds very simple—the gun comes from the factory with a trigger pull of around 6 to 8 pounds. In addition, the pull is long and rough. So it’s not surprising that owners want the pull made lighter, smoother, and shorter.

Routine polishing of the sear and hammer, which might suffice with other guns, doesn’t work on the Xtrema, since even small changes of the sear-hammer engagement can make the hammer slip from the sear at every reloading. In other words, every time the bolt is closed, the hammer, instead of holding in the cocked position, jerks off the sear and makes a shot impossible.

After doing several trigger jobs with results between 4 and 5 pounds and never knowing for sure whether the hammer is reliably cocked or is Figure 1. going to slip down at some future time in the field, I decided to take a serious look at the problem and find an effective remedy. In this article, I’ll analyze the mechanical reasons for the problems with the Xtrema’s trigger, and suggest away of fixing them. At the time of this writing, the new Xtrema 2 is on the market.

I hear that it does not suffer from these trigger problems, but there are many guns of the previous issue that can benefit from the adjustments outlined here. A Close Look at the Problem The shooters’ major complaint is that the trigger pull is heavy, long, and rough. For the gunsmith, this complaint presents a challenge, since trigger-pull adjustment almost invariably leads to an unstable hammer-sear engagement; i.e., the hammer does not stay cocked, but slips from the sear. I call this the "hammer-jerk" problem.

So, my goal was to first find away to reliably engage the hammer and sear. Only then would it be possible to adjust the quality and tension of the trigger pull. Let us look closely at the ham Figure 2.

mer-jerk problem and the related mechanical elements of the action. In so doing, it may become clear what changes in mechanics are necessary to eliminate this problem. Figure 1 shows the action with the original hammer and sear engaged, and all other elements removed.

The trigger-pull qualities such as length and smoothness are defined by the shape of the sear tooth and the sear notch of the hammer, which I call the "hammer notch." To a large extent, the tension of the pull is also a function of this engagement, but has the resistance of the trigger spring as an additional component. Figure 2 shows the trigger with trigger spring. I found that the factory spring alone creates a resistance of more than 2 pounds. This can be measured when the hammer is not cocked.

The spring can be easily replaced, which is the first thing I did. Note that this trigger spring still needs a resistance of about 1 pound for reliable working of the trigger and disconnector. Since my goal was to reduce the trigger pull to 3 pounds, the remaining 2-1/2 to 3 pounds had to be removed by polishing the sear-hammer engagement. At the factory, the sear and hammer are adjusted so that they "catch" each other. This is shown with certain exaggeration in Figure 3-A.

Such adjustment creates a lot of resistance during the trigger pull. In fact, the trigger pull in this situation drags the hammer back against the mainspring tension until it is released by the sear. This very drag is the source of the excessive trigger pull. Usually, trigger pull can be reduced by polishing the hammer notch.

This is easy to do and to check with a trigger-pull gauge, since the Xtrema’s trigger group can be dealt with separately from the receiver, meaning that there’s no need for assembly and disassembly after each session of polishing. When the trigger pull is adjusted to 3 pounds and tested outside the action, everything still looks good. The problem, however, shows up immediately after replacing the Figure 3. trigger group in the receiver.

Pulling the bolt back and releasing it, which is a normal way of loading the gun, causes hammer-jerk from the sear. If I didn’t do this polishing myself, I would suspect that the sear and hammer notch were bitten or worn out. But it must be something else. One difference between manually cocking the hammer (when the trigger group is taken from the receiver) and doing so by cocking the hammer with the bolt, is in the speed with which the hammer lowers on the sear.

The bolt drops the hammer on the sear with significant speed—especially during live shooting. Doing this manually puts the hammer on cock much slower; first, because cocking the hammer manually stops right after hearing the click of the hammer-sear engagement, and second, because the hand cannot release the hammer momentarily. The bolt, in turn, moves the hammer much farther than is needed for engagement, and then quickly releases it at a distance from the engagement point.

This consideration made me assume that a hammer cocked by the bolt slams on the sear and opens it enough for disengagement. This is somewhat similar to what I’ve seen on pistols and other semi-automatic guns. Such a possibility on the Xtrema is even more feasible, since its sear opens in the same direction when the hammer pushes it. This is easily visible in Figure 1. To prove this assumption, I checked the real travel of the hammer when it is cocked by the bolt.

For this purpose, I first measured the depth of the bolt from the lower edge of the receiver, which is close to 1.18 inches. Figure 1 shows where the bottom of the bolt moves during loading of the gun. Next, I projected this depth on the hammer travel during cocking. Figure 4 shows how much farther the hammer travels back than is required for the normal engagement when the bolt is backed up.

I call this "hammer over-travel." This over-travel (distance "D" in Figure 4) is about 0.3 inch, and allows the hammer to accelerate on its way forward to the extent that, instead of stopping on the sear tooth, it moves the sear forward against its spring, and unlocks itself. This is the major reason for the hammer jerk. The other reason for this problem is the position of the hammer notch relative to the sear.

As shown in Figures 1 and 3-A, originally the sear tooth is engaging the hammer notch (R) close to its edge. So, when the hook portion (F) of the hammer notch is polished away, the sear easily opens and releases the hammer. These were the two reasons for the trigger problem I found on this gun. Fixing the Trigger Problem As soon as these two reasons for the trigger problem on the Xtrema were identified, it became clear how to eliminate them. First, the hammer

Figure 4. Figure 5. over-travel (D) has to be reduced to a minimum. And second, the sear has to engage the hammer notch deeper, as shown in Figure 3-B. One way to achieve both goals at once is to braze a steel insert into the factory hammer and reshape it appropriately.

Figure 5-A shows the hammer after brazing the insert, reshaping, and adjusting the trigger pull to 3 pounds. (Figure 5-B shows the original factory hammer.) This photo shows how the original dimensions were changed to eliminate the hammer-jerk problem. One thing to keep in mind during the reshaping of the hammer is that the tail (T) serves as a secondary disconnector. On its way back, the hammer pushes the trigger link (#3 in Figure 6) down and disengages it from the sear by placing it into the sear recess (#1).

There is a primary disconnector on this gun shown in Figure 6 as #2. It disengages the trigger link and sear on every bolt opening and keeps them disengaged until the bolt is properly closed. So, the function of the disconnector on the Xtrema is duplicated by these two parts. This means that the disconnecting function of the hammer can be abandoned. Nevertheless, it is more reliable to have them both in place. The length of the hammer tail (T) is critical for the independent secondary disconnection.

At least, it should not be longer than required, since that would not allow the trigger link to engage the sear for the next shot. After brazing the steel insert into the factory hammer and shaping it as shown in Figure 3-B, I adjusted the trigger pull to a smooth 3 pounds. Testing with live ammo was successful. The trigger pull Figure 6. Figure 7. was light, smooth, and crisp, with no hammer-jerk problems. Thus, I believe my assumptions about hammer overrun and sear-hammer engagement were proved.

After approximately 100 shots, the insert brazed into the hammer broke off. Fortunately, it had already fulfilled the task of proving the concept. Instead of playing with another insert, I decided to make a completely new hammer from oil-hardened Starrett steel. This seemed to be more reliable; and besides, I wanted to properly heat-treat the new hammer since it’s important to have the hammer notch hardened enough to keep the shape and preserve the adjustment of the trigger pull.

After making anew hammer as a complete copy of the prototype with (continued on page 21)

insert, I spot-hardened the hammer notch and once again adjusted the pull to 3 pounds. Note that spot-hardening is the only possible way to harden the hammer notch, since the rest of the hammer should not be brittle. Figure 6 shows this new hammer engaged with the sear. The overrun of the new hammer was adjusted to the very minimum; Figure 7 shows this overrun during the bolt opening. As you can see, this overrun is minimal, since it is just enough to disconnect the trigger link from the sear.

Now it was time for testing again. I had to make sure that three things were holding up reliably; first, that the hammer didn’t jerk from the sear; second, that the new hammer didn’t crack or break even under hard stresses; and finally, that the trigger maintained smoothness and 3 pounds pull throughout. To create the most comprehensive test, I chose about 100 different shells—everything from 2-3/4-inch mild shells to 3-1/2-inch Magnums. The test went smoothly. There were no misfires or any other problems.

The hammer did not have any jerks, even when the gun became as hot as a stove. The trigger maintained a consistent pull. After this test, I disassembled the action and checked the condition of the sear and hammer notch. There were no signs of any damage. The gun has now been back in service for quite some time. After hundreds of rounds, it holds all my adjustments. Note that the change in the hammer shape now allows adjustment to a shorter and lighter pull.

It can be made even less than 3 pounds, which was not my goal in this case. Conclusions The problem of reducing and smoothing the trigger pull on the Beretta Xtrema shotgun can be solved with the two-step procedure outlined above. First, the hammer has to be reshaped so that it does not have an exceeding overrun beyond the sear-hammer engagement point. The sear has to engage the hammer notch on its entire depth. This step will ensure reliable sear-hammer engagement.

The second step is to do a quality trigger job in order to achieve the desired tension, length, and smoothness of the trigger. ■