The increased performance of the 6.8mm combat rounds used by the NGSW series meant that surface danger zone requirements on many US Army training areas would no longer be sufficient for safe firing. (Photo: US Army)
Biting the bullet: how ammunition design can address training challenges
When expanding tactical capabilities, the introduction of a new weapon system can also create novel training issues. A case in point can be found in the US Army’s 6.8mm calibre XM7 and XM250 Next Generation Squad Weapons (NGSW).
According to Jason St John, senior director of strategic products at SIG Sauer, manufacturer of the NGSW series, the associated M1186 General Purpose Combat Round (GPCR) provides significant performance enhancements over many existing weapon systems. However, that performance also comes with new safety considerations... Continues below
This analysis article originally appeared in August's Decisive Edge Military Training Newsletter.
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The NGSW programme initially started with what was called ‘surrogate ammunition’, which was intended as a full metal jacket representation of what the army projectile was going to be.
The developmental weapons were tasked with desired performance levels initially using 135 grain projectiles. However, the initial ammunition design evolved for accuracy and performance reasons into a configuration using a 121-grain projectile with a reverse-drawn copper jacket and slug with a steel penetrator.
‘When you move to a round that has, let's just call it “magnum level of performance”, you also have a magnum level of SDZ [surface danger zone] requirements within your training area,’ St John explained. ‘And you could probably run into some facilities not having the necessary impact area to support that level.’
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One solution to the safety issue was development of an initial training round, designated M1188 Reduced Range Ammunition (RRA). With a 113-grain flat-base solid copper projectile, the intent behind the round is to mimic the holistic capabilities, trajectory and flight path of the M1186 GPCR in a way so that it could be used within existing SDZs and training areas.
Choosing his words carefully, St John described the training round as having the same general ballistic characteristics of the M1186 out to ranges of approximately 600-800m.
The solution was to create a bespoke training round, the M1188 Reduced Range Ammunition, avoiding the need to expand or otherwise modify firing ranges. (Photo: US Army)
‘And then one thing that the flat base on the M1188 RRA bullet provides is more drag,’ he said. ‘So the round destabilises more quickly than a normal “boat-tail” type projectile [like on the M1186]. As a result, it stays within the SDZ limitations of facilities that already exist.’
He added: ‘I do not want you to misconstrue that these two bullets – M1186 and M1188 – are ballistically matched or that the training round just falls out of the sky at 800 metres. Rather, around 800 metres the M1188 RRA is just rapidly decreasing in velocity due to the drag elements of the design, and it begins to fall away from the ballistic trajectory.
‘It falls further at 900 metres and even further at 1,000 metres. So, at ranges where that 6.8mm M1186 General Purpose Combat Round would continue in combat, the M1188 RRA is rapidly decelerating and destabilising.’
While declining to break down specific production numbers, St John noted that the RRA represents roughly 60% of the ammunition that SIG Sauer has delivered to date, with the remaining 40% of deliveries comprised of the M1186 GPCR, as well as M1192 Blank ammunition and M1194 Drill Dummy, Inert (DDI), with the latter used to facilitate gun handling and rifle manipulation drills outside of the range environment.
In addition, although specifics have not been confirmed, there have been some rumours and rumblings that indicate the ongoing development of an additional ‘training round’ that would be optimised for use in ‘shoot house’ applications. St John declined to comment on those rumours.
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Returning to the M1188 RRA, he observed: ‘Another point is that a lot of people think that the training ammo is going to have less recoil [than the GPCR] because they think that soldiers don’t want to handle it. You hear those kinds of rumours. But know that the training ammo is an exact training reference, meaning that it has the same high pressure, same high velocity and same two-piece hybrid case.
‘That ensures that the soldier gets the same one-to-one training comparison with the GP [combat] round. But it still fits within the existing US Army infrastructure and range facility surface danger zones. Some people say that the training round has less velocity and less pressure so that it’s easier to shoot and easier on the soldier. That's not the case.’
While optimised for its training benefits, the solid copper projectile in the M1188 RRA also offers a unique tactical capability as a so-called ‘blind to barrier’ or barrier-blind projectile.
‘When you look at blind-to-barrier projectiles, the majority of them are copper solids,’ St John said. ‘That’s because, when you shoot through auto glass or through other target mediums, a jacketed bullet, if it's not bonded, and even when it is bonded, can have jacket and core separation due to hidden target mediums.
‘Therefore, most of your blind-to-barrier or barrier-blind projectiles are copper solids. And now the US Army has got a combat training round that is blind to barrier and a ballistic match to their high-pressure [General Purpose Combat Round] to 800 metres. I don't know if that is purposeful or inadvertent, but it’s pretty cool.’
In terms of the solution selected, engineering a specialised round optimised for training is certainly a less complex enterprise than modifying and extending many of the army’s range facilities, and clearly has some side benefits as well.
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