Testing the Slavia 631 with non-lead pellets: Part 1

by B.B. Pelletier

Announcement: Here’s this week’s winner of Pyramyd Air’s Big Shot of the Week on their facebook page. He’ll receive a $50 gift card.


Choon Weng Chua submitted this photo from an airsoft skirmish. He’s this week’s Big Shot winner.


It’s a little crude but also elegant. The Slavia 631 is the testbed for this report.

I reviewed the Slavia 631 breakbarrel air rifle one time back in March 2006. At that time, I wasn’t reviewing airguns in the format you see today, so it got a quickie once-over and we moved on. Perhaps, if the rifle had been available here in the U.S., I might have done more with it, but since it wasn’t being sold here, and still isn’t, I didn’t think there would be that much interest among the readers.

I also used the rifle for a testbed back in 2003 when I wrote an article about the performance of pellets versus round balls. That’s an interesting article you may wish to review, and I find it a little interesting that here I go again, using the 631 to test the performance of non-lead pellets against lead pellets. Apparently, there’s something about this rifle that makes me think of it as a standard airgun.

This test isn’t really about the air rifle as much as it is about the pellets. We’re just using the 631 because of its accuracy and mild manners.

The Slavia or CZ 631 and 630 are breakbarrel spring-piston rifles made in the Czech Republic. The 631 Lux model I have was purchased new about 12 years ago when they were still being imported into the U.S. It has a rather plain stock that’s too blocky and square for my taste, but the barreled action is where the performance lives so I can put the looks aside. The 630 and 631 are the same rifle in different stocks, just like the Diana 48 and 52 sidelevers. The 631 is the dressier one.

The stock is a medium brown beech with a thin, non-reflective finish that’s very topical. Mine has several scratches that cut through the thin top layer of wood. Because it’s blocky, it doesn’t fit me very well. I do like the slender forearm, but the pistol grip just doesn’t fit right. There’s impressed reverse checkering on the forearm but not the pistol grip, and the overall appearance is one of cheapness. The metal parts are not polished beyond tumbling and are finished with a thin black color that comes through as matte.

This is a low-to-moderate air rifle power-wise. I expect to see the lighter-weight pellets shooting in the low- to mid-600s somewhere. We’re going to find that out in today’s report.

One of the reasons I’m using this rifle is because a number of our readers own them. Canadians can still buy them, as can Europeans and almost anyone else except Americans. But I’m also writing about it because one of our readers suggested that I test the accuracy of non-lead pellets in this rifle. He felt the power was not so high that it would scatter the pellets, and also because the 631 is a very accurate air rifle in its own right. I agreed and here we are.

As I describe the rifle, bear in mind I’m describing the one I own. It’s at least 12 years old and possibly more, and there may have been some changes to the design since mine was made. Generally, cosmetics change faster than fundamental design items, so my rifle is probably still a good representative of the type.

A couple features before I test velocity for you. First, is the barrel lock. Before you can open the barrel to cock the gun, you must push forward on the spring-loaded barrel lock that’s located under the barrel just forward of the baseblock. It retracts the chisel detent and allows the barrel to flop open a little. From there, you can cock the rifle with 35 lbs. of effort. My rifle is in need of a tuneup, and I can feel some metal rubbing when I cock it. I think it would drop back to a 28-lb. cocking effort with proper lubrication. I did oil the piston seal for this test but not the rest of the powerplant.


The barrel-lock latch (left) is pulled forward, retracting the chisel detent (right) and allowing the barrel to open.

Another feature is the automatic safety. It’s a knurled knob located at the rear of the spring tube; and when the rifle’s cocked, it pops out. You must press it back in before the rifle can be fired.

Although the safety is automatic, there’s no anti-beartrap device and the rifle can be uncocked by taking the safety off and pulling the trigger while restraining the barrel.

The two-stage adjustable trigger is very light. I don’t think too many owners will complain about the crisp l-lb. trigger-pull. Oh, and it has a metal blade! A screw in the plastic triggerguard adjusts the length of the stage-one pull, and it can be eliminated entirely.


Trigger adjustment screw (second from left) controls the length of the first stage, only.

The sights are things of beauty! The all-metal front sight is a hooded post that appears as a sharply defined rectangle through the rear sight. The rear sight is a study in elegant design. It’s all-metal, fully adjustable and yet simple and probably inexpensive to build. It ought to be a required study for any engineer wanting to design airguns.


The front sight is hooded and looks a lot like the front sight of an SKS.


The rear sight is all metal and an elegant design. It shows what some thought can do.

The firing behavior of my rifle is very buzzy. It takes me back to the 1970s, when all spring rifles buzzed, and I guess it’s the one thing I like least about the gun. But I’ve left it as it is all these years so I’d have something unaltered to reference.

The rifle does have dovetail cuts for a scope mount, but this is the very rifle that caused B-Square owner Dan Bechtel to enlist my aid in the 1990s to measure the width of as many airgun scope rails as possible. We found that 11mm airgun scope rails range from about 9.5mm separation to over 14mm! And, the Slavia 631 is the biggest one of them all. So, those “11mm” scope mounts you buy will probably not fit this rifle unless the package specifically names this model or the 14mm width. To my knowledge, only BKL now makes scope mounts specifically designed for this air rifle.


There they are. The widest set of “11mm” air rifle dovetails in existence. They measure just over 14mm, so they require purpose-built mounts. To keep the scope mount from moving, a half-round transverse pin in the bottom of the mount has to fit one of the grooves or you’ll need BKL mounts. That knurled knob on the bottom is the automatic safety.

Pellets selected
Because this report is really about the accuracy and performance of lead versus non-lead pellets, I’m not going to spend a lot of time on the performance of the gun other than to document the accuracy with lead pellets of known quality. Today, I’ll show the pellets that will be tested and chronograph each of them for you. In the next test, we’ll finish with accuracy at 10 meters.

The pellets I’ve selected to test are the following:

Lead

Crosman Premier 7.9-grain
JSB Exact RS
Air Arms Falcon

Non-lead

Gamo Raptor
Skenco Hyper-Velocity Type 1
RWS HyperMAX
Crosman SSP

The lead pellets should show the relative accuracy of this rifle under the best conditions. What the non-lead pellets will do is what we’re going to learn.

Velocity
Premier lites averaged 589 f.p.s. The range was 586 to 593 f.p.s. They generated an average 6.09 foot-pounds.

JSB Exact RS pellets averaged 593 f.p.s. with a range from 586 to 596 f.p.s. The average energy was 5.7 foot-pounds. These pellets fit the bore very loosely.

Air Arms Falcon pellets averaged 592 f.p.s. They ranged from 591 to 594 f.p.s. The muzzle energy was 5.68 foot-pounds. They fit the bore tighter than the JSB pellets, but not as snug as the Premier lites.

Gamo Raptor pellets fit the bore variably — from snug to so loose they fell out. They averaged 741 f.p.s., ranging from 727 to 754 f.p.s. The average energy was 6.59 foot-pounds.

Skenco Hyper Velocity Type 1 pellets averaged 719 f.p.s. The range went from 689 to 749 f.p.s. Their average energy was 6.2 foot-pounds.

RWS HyperMAX pellets averaged 743 f.p.s. They ranged from 639 to 750 f.p.s. The average muzzle energy was 6.38 foot-pounds.

Crosman SSP pellets averaged 738 f.p.s.. The range went from 658 to 750 f.p.s. The average muzzle energy was 4.84 foot-pounds.

So these are the pellets I’ll be testing for accuracy, and we now know how well they perform in this rifle. I’ll save my conclusions of the test for the finish, at the end of Part 2.