Richard Atkins tests the FOB Viper BG cartridge

The FOB Viper BG is a fibre wad cartridge with an important difference. Could it offer the best of two worlds, asks Richard Atkins

Clay Shooting magazine recently featured two FOB plastic wad cartridges, the Viper BJ and the World; now it is time to look at one of their fibre wad options, the Viper BG.

This cartridge is unusual because it is loaded with an obturator, a small plastic sealing disc under the fibre wad for improved gas sealing properties. This option of an additional obturating component has been available to cartridge loaders for some years, but has not been widely employed as yet.

Given the current trend for moving away from full cup plastic wad ammunition, it seems a good time to see what this wad combination offers. (Note that there is also a Viper BGC, which does not have the obturator disc.)

Like the other Viper load options, Viper BG come in strongly made dark grey and black boxes boxes, which have a highly recognisable Viper snake design complete with red forked tongue. Details of calibre, shot load weight and pellet size are clearly printed on the carton.

Understanding the test results

  • Velocity is measured at 2.5 metres from the muzzle.
  • Pressure is the mean breech figure in Bar (as per CIP).
  • SD is Standard Deviation (consistency).
  • CD is the Central Density rating. This records the percentage of pellets landing in the 30-inch circle that were also within the inner 20-inch circle.
  • Shot size is derived from actual pellet count per ounce and is listed to the nearest UK size, with < and > symbols used where the shot is slightly smaller than or larger than listed size. UK No. 7 = 340 pellets/oz; UK No. 7.5 = 400 pellets/oz; UK No. 8 = 450/oz; UK No. 9 = 580/oz.
  • Shot weight is the average actual shot load, measured in grains. 1 Grain = 0.065 Grams = 0.0023 Ounces.
  • CV is Crush Value. This is the amount by which the shot is reduced in size when subjected to the standard crush test. A smaller value means harder lead, so a CV of 20 per cent indicates harder shot than a CV of 30 per cent in pellets of similar size. Smaller shot crushes proportionately more than larger shot.

The type of wad is denoted by a suffix: the BJ tested previously is the full plastic wad Viper; the BG tested here contains the fibre wad combined with an obturator and the BGC has its own special fibre wad.

These suffixes can be a little confusing so I recommend double-checking when you buy to ensure you get the wad option you are seeking.

The FOB BGC uses fibre wads supplemented by the use of a plastic obturator

As part of the Nobel Sport Group FOB naturally use Vectan propellant powder and Martignoni cases and primers. The clean burning and efficient Vectan AS, a single-based, square-cut-flake nitrocellulose powder, is used; this is readily identified by its mix of light green and pink flakes. A consistent charge of just 22.4 grains provides the required energy.

The main driving wad is a 16mm long, one-piece fibre wad. This is used in conjunction with a plastic obturator disc that sits between the powder charge and the wad.

This disc is 8mm high; it has a full outer rim with a solid central disc, which has some short supporting ribs radiating from its centre. This allows the disc to be loaded into the case either way up and provide exactly the same sealing properties.

FOB Viper BG 28 gram 7.5 shot fibre wad with plastic obturator

  • Shot load – 433.5 grains
  • Pellet (count per oz) – 345
  • UK shot (size/CV) – 7/35%
  • Pellets in 30in dia (Av) – 207
  • Pellets in 20-30in – [90]
  • Pattern – 60.5%
  • CD – 56%
  • Velocity mps (fps) – 370 (1215)
  • SD – 6
  • Recoil (M) (unit= Ns) – 10.4
  • Pressure (unit = bar) – 590

Viper BG uses the same strong, bright orange, parallel plastic tube Reifenhauser made by Martignoni with 7mm brass plated steel head and plastic base wads as the other Viper loads. The cases are closed with a neatly formed six point star crimp.

Viper shot size is marked as 7.5 and gave an actual pellet count of 345 per oz, which indicates that it is is actually UK size 7; this is typical for continental shot where there is often a half size average difference from UK shot size in the clay shooting size range.

Recovered the obturator discs clearly show that they’ve done significant work controlling gas expansion

The shot pellets were reasonably graded for size although there was some variation. Pellets had been polished in graphite to obtain a smooth, regular coating.

This assists the smooth flow of pellets during metering and in the barrels; it also acts to prevent pellets sticking together under the compressive pressures created during acceleration.

The shot proved a little less hard than that loaded into the plastic wadded Viper BJ tested previously with a crush value result averaging 35%. This may show a slightly reduced antimony content, but it’s still a decent figure for a budget priced cartridge. 

Long cone test

To ensure the results of our tests would be comparable with previous cartridge reports in Clay Shooting, the Viper BG were tested for pattern results using the same standard size bore (0.729”) barrel as our regular test reports.

However, given the potential extra usefulness of the plastic obturator, I carried out some additional tests using a gun with larger than standard forcing cones.

We will not, at this time, name the particular gun, or the fibre wad cartridge we compared the Viper BG with. It would not be fair to do so when there could be similar guns and fibre wad cartridges that would produce better results.

A much wider, independent testing programme, involving a broad selection of fibre wad cartridges being fired through a selection of guns with lengthened forcing cones, over-bored or back-bored barrels, would be required to establish the combinations that work best together.

To check how the Viper BG coped with a gun with larger forcing cones I patterned some shots from a new gun with moderately lengthened cones cut at a fairly steep angle to yield a larger entry diameter to the forcing cones than was once considered standard.

I began by trying a fibre wad load with no plastic obturator and the results were more than somewhat worrying, with shot balls of various size appearing in a series of test shots.

A similar series with the Viper BG seemed to overcome the gas sealing problem and no shot ball impacts appeared in any test pattern from this gun.

The FOB BG from the same long cone gun with Imp Cyl choke at 30 yards

The results were noticeably different with the BG patterns, which compared well with a typical plastic wad load of a comparable grade. This test was only an isolated example of what might happen – the same gun produced improved results with some other types of fibre wads – however the BG, with its plastic obturator, produced hardly any pairs or triplets of joined shots, which have been shown in previous tests to be indicators of potential shot balling.

Currently there is a drive to remove all plastic from the cartridges we shoot, so it would appear to be worthwhile investigating the possibilities of making these obturator discs from one of the emerging starch based, biodegradable plastic substitutes.

That way we may have an acceptable solution for those who already own guns with larger forcing cones, not all of which perform at their best with ordinary fibre wad cartridges.

This could meaningfully reduce the risks posed by shot balling and re-instate the level playing field that sometimes gets mentioned in relation to fibre wads.

More testing is required but the signs are good. I have raised this possibility with cartridge makers, so let us see what becomes available in the near future.

In summary, the BG provides an effective and smooth shooting performance that will meet the demands to consistently break a great many targets found on a typical sporting round of clays and do so without breaking the bank.

I do also suggest that if you have a gun that might benefit from the plastic obturator (and the grounds you shoot allow them) that you try the FOB Viper BG.

Laboratory tests

The FOB Viper BG cartridges were submitted to the Birmingham CIP Proof Laboratory for pressure, velocity and momentum testing as per our usual procedure. Pattern tests were conducted at 40 yards from a 30” long, standard bore size barrel with 2¾” (70mm) chamber with standard length forcing cone and bored Imp Mod choke.

A fibre wad cartridge without an obturator from a long cone gun with an Imp Cyl choke at 30 yards

Additional patterns were also checked using a gun with lengthened forcing cones to check if the plastic obturator disc in the BG would help eliminate problems sometimes associated with longer cone shotguns.

The Proof Laboratory tests revealed velocity in that sensible range that is more than quick enough without being punishing, combined with good consistency.

Repeated patterning of the FOB BG shows good shot-to-shot consistency

With the shot size being a larger than UK 7.5, the actual speed into more distant clays will be very similar to that for higher velocity UK 7.5 shot due to the improved energy retention of larger shot sizes. 

I mainly used the Viper BG for Sporting clays, where they gave very good kills, on clays of all types, at moderate and longer distance. Again, the combination of moderately hard shot launched at fairly quick but not super high velocity proved both effective and comfortable to shoot; actually more comfortable than I anticipated.

The momentum result largely explains why but even that little extra sharpness that sometimes accompanies some fibre wad loads was not there. A few pals tried some too and found them equally comfortable.

FOB BG @ 40 yards, using a standard Imp Mod choke

The pattern plate showed that this combination gave a 60.5 per cent average pattern density. This is just above a Half Choke result from the Imp Mod barrel and a reasonable result from a cartridge of this type.

I tried some at DTL and they worked well for both first and second barrel use, with just 3/8 choke in the first barrel. Setting up my own trap, I found that the Viper BG responded to more choke well and got good kills out to past 40 yards from my Browning Citori Trap with Full Choke top barrel.

All in all, a very serviceable cartridge, and perhaps a glimpse of the future.

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