I've never had a problem with them, as long as they're cut to length as you would with any aftermarket spring and have a correct fitting guide, I've never seen any internal damage.
The other aftermarket square section Spring is the Airforce.
I must admit though that I've not fitted any square springs since I acquired UKNeil's old Spring mountain.
All the best Mick
I would like to be able to say that it was that easy!
I thought that after thirty years technology would have moved on so I sprang for one of the kits that seemed well regarded on many forums.
I provided all of the information asked - calibre, rifle or karbine, 25 or 26mm internals etc but still had to strip and adjust the spring preload several times as the new seal bedded in and the power increased.
Eventually there were no more preload washers to remove and I had to collapse a coil of the new spring. I wondered why they didn't supply a spring that was a little softer having provided preload washers to adjust it up anyway but was told that having dead weight is very bad. Apparently, I should have returned the spring to the supplier who would have replaced it with a more suitable alternative. There was some suggestion that the subsequent failure of the supplied spring guide may have been related to my collapsing a coil even though it was not installed in that end of the spring!
I now have a cocktail of parts from various kits installed which work to my satisfaction but I would refit either the original Weihrauch or even the Ox if I have to replace the spring in the future. There seems little point in paying for a premium kit if you have to rework the parts yourself to get them to perform correctly or spend time and money sending bits back and forth to the supplier.
You are quite right, I was lucky to have a kit which come with a short spring and some spacers which after fitted was sub 12 , Saying that I still had to remove a spacer after a good few pellets had been put through it and even had to remove the last spacer as it had increased a bit to close to 12 ftlbs , Its now settled at 11.1 .
As you pointed out if the spring alone which was bought as a kit was over 12 ftlbs I would not be happy either , That's if the kit was made to fit and be sub 12 without cutting spring,
Their reputation is probably a throwback to the glorious () days where people would try to shove a massive spring into a cylinder half it's size in order to make their airgun 'powerful enough to shoot through two dustbin lids and the yellow pages', then wondered why their guns were shooting crap / low powered / making horrible grinding noises.
Many a brown trouser moment to be had opening up something like a BSA Mercury bought from the boot sale.
I’ve had both smooth shooting & fairly rough ones in equal measure. I’ve acquired numerous hw’s with an ox inside & I would never have guessed until I looked down the cocking slot.
I’ve also found iron filings & bell mouthed pistons in smaller rifles like the webleys. They do seem a good spring if correctly chopped & mated with nice guides. I wouldn’t go out of my way to buy an ox, but I certainly leave them as they are if they shoot nice & aren’t reaming the inside of the piston out 🙂
When I was about 17 years old I picked up a well used HW35E from a second hand shop. If I remember rightly I swapped my sega megadrive for it After having it for a couple of months I decided it wasn't powerful enough and picked up an OX power spring from my local army surplus store. After much grunt work finally managed to get the bugger screwed back together with said spring and proceeded to test the new beast. A huge kick and a hole through both sides of my dads shed told my it had worked. Christ knows what the power was but I knew nothing in them days. Eventually it did ruin the rifle although I feel it was more user error than spring being pants!!!
I think it was a combination of what Rich said about square section when it's wound into a coil ( it isn't truly square any more and some of the 'corners' point into guides etc ), and the posters who have mentioned correctly fitting guides.
I've opened up a few abused HW77/97 that were still using the old splayed ended ill fitting Weihrauch
rear guide. People had fitted an Ox spring in the search for mega power and the length of the spring and the poor fitting between the rear, soft metal guide and the inside of the Ox had meant that the corners of the square section had made a real mess of the guide.
People also put these in some of the earlier Webleys. Rifles designed for probably 9 or 10fp and then maybe the Vulcan could squeeze 12fp. Again way over sprung with Ox springs crammed in there and poor fitting. Results would be that the inside of the piston would be mauled and the very harsh firing cycle meant that the weakly designed main cylinder's holes would elongate ( where the hardened end block holding pin went through ).
I did come across an old 97 that had a square section spring. I have no idea if it was an Ox or one of the ones that HW fitted in the 97's for a while. It looked different than the Ox and Air Force springs. Even when coiled the coils were more square than the Ox. So the guides and inside of piston pretty much ran along the flats of the spring and not on turned over corners like on the Ox's I'd seen. When I Put some decent fitting guides in that spring and fitted it to a 97 it shot very well indeed.
I fitted an Ox to my old BSA 635 and my Dad's Mercury - along with a couple of other bits and pieces. The results were fine. Shot cycle was fine too.
However when I came to giving the 635 its first service in 15 years (having been stored in a cellar for that long) I noticed there were notches in the spring. Meaning that there were bits of metal in the cylinder. This I would say goes with the previous post about the edges on the square section.
Yes I managed to get a decent performance. No I wouldnt recommend them. My 635 now has a reduced length old Titan (not XS) spring in it and shoots incredibly sedately.