8 replies to this topic

[Pretty green flames]

I've got some professional chinese fiberglass mortars (3 inch) and after shooting about 14 shells from one, it developed cracks (small ones, they seem superficial). Are there any restrictions in using fiberglass mortars in cold weather (it was bloody cold for NYE), does cold weather compromise structural integrity of these mortars?

Thanks, PGF

[cooperman435]

I myself have noticed stress marks on many GRP tubes after their initial firing which show as lighter coloured streaks running along the wrapping direction of the glass fibre.

I don't believe it is detrimental to the life of the tube and they have never failed as a result, in fact they all have it so wouldn't see it as a problem.

[Pretty green flames]

Thanks cooperman, was a bit worried when I saw those stress marks, I guess it's nothing critical then.

[T-sec]

The company I work for uses fiber mortars only, and even after they are used for a long time and frequently, they still look ok.
Now and then one breaks, or shows to much stress marks, but that is due to the rough transport and not due to shooting shells.

One thing what is not advised to use fiber mortars for, is shooting the bigger cylindrical shells.
Those shells contain more lift powder and create more lift pressure due to the cylidrical form.
These factors will damage the mortars in short terms of use for sure.
Mutlibreak cylinder shells must never been shot out of fiber. those are even more destructing.

Edited by T-sec, 07 January 2009 - 10:16 PM.

[Vic]

Ok then, so Fibreglass Mortar Tubes are all right for spherical and cylindrical shells with a single break. However, just out of interest, what would you use for a 4” triple break cylindrical shell? Length would also be consideration I assume…

[Pretty green flames]

For big multi breaks, steel mortars are used, just ask the maltese pyros for their big beraq shells. I'd go with a heavy walled HDPE tube, I got some 4" ID and with 15mm walls and they are pretty much indestructible, short of a 4" salute shell going off I can't imagine a normal working shell destroying it.

[pyrotrev]

Special heavy duty fibreglass mortars for cylindrical shells are also available.

[Arthur Brown]

In the UK, HDPE, Paper and GRP mortars are insurable for professional use, steel mortars are NOT.

[Mumbles]

I'd feel safer firing a big multibreak shell from fiberglass over HDPE. They'd be burried anyway. The fiberglass has a solid plug, whereas the HDPE has a second piece of wood as the plug. This is especially bad with shitty guns with stapled plugs. I've seen multiple wooden plugs torn from the HDPE, whereas fiberglass has held up to 5" quad breaks. Just the run of the mill fiberglass mortars available in the US.