Back stop height

[ronboy]

I was working at the naval range on a island near Portsmouth with a range officer many years ago and can confirrm the backstop was very high.
Bullets were whistling over the top of the backstop and the oficer said Indians over there and cowboys over that way. On another island a group of
naval sqaddies had a massive bonfire.

[majordisorder]

Aye by the time we've piled up that amount of earth there would be no room left for the range.

Which is why I looked at using Hesco barriers as the backstop. They let you build higher with a narrower base and also mean you'll need less sand/soil.

[IainWR]

The basics of this are that you have to keep the projected cone of fire (which is a tabulated quantity, not what you think you might actually do) off the range floor as far as possible to minimise the extent to which the ricochet risk impinges on your design. Now if the CofF is 40 mils, thats 40:1000 or 4:100 so you need 4 metres above and below the target at 100 metres, plus a bit for the size of the target itself, plus some other allowances. It adds up to quite a lot, but 26 metres sounds wrong unless you are having to allow for a ricochet from about halfway down the range. If you are an NRA or NSRA affiliated club, email your parent organisation and ask for help - you are going to need their help anyway if you are building a range in order to get it certified.

Iain
iain.robertson@nra.org.uk

[Mike357]

I'll read through the JSP documents for now. Iain, can you PM a contact number and I'll maybe give you a call in the coming few weeks?

[kennyc]

thinking about it, I'm sure the Naval range at Portsmouth had/has at least that high a backstop, it proved not high enough to stop one sea cadet sending the back end of a Bren mag over the top towards Gosport when I was there on a marksmans course in the mid seventies sign01

And just how did he do that, pray tell, big chicken ?

recoil+lack of operator weight/coefficient of grip from highly polished parade boots on damp grass and a death grip on the trigger tongueout I saw the strikes on the mantlet,then the sand berm, then the red flag go down, followed by the field telephone ringing and a very peeved CPO tearing a strip off of the GI Killick acting as RCO

[mr smith]

thinking about it, I'm sure the Naval range at Portsmouth had/has at least that high a backstop, it proved not high enough to stop one sea cadet sending the back end of a Bren mag over the top towards Gosport when I was there on a marksmans course in the mid seventies sign01

And just how did he do that, pray tell, big chicken ?

recoil+lack of operator weight/coefficient of grip from highly polished parade boots on damp grass and a death grip on the trigger tongueout I saw the strikes on the mantlet,then the sand berm, then the red flag go down, followed by the field telephone ringing and a very peeved CPO tearing a strip off of the GI Killick acting as RCO

What sort of distance did this occur?

[kennyc]

What sort of distance did this occur?

now you are asking! from memory between 200 and 300 yards it was 1976 so a while ago !

[majordisorder]

Digging out my calcs I've got 100m range needs a 12.4m butt.

That's based on a 77mil CoF + 4.7m and this gives a NDA range according to the design guidelines