Food for thought: The relationship between 'Skin' and 'Foam' on foam filled stocks

[brown dog]

Some food for thought on the interplay of filler and skin on foam filled stocks.

 

Deliberately haven’t mentioned the make of stock; intended for discussion / illumination only.

 

 

 

The comments and photos below are from a chap whose education & background is material science:

 

“No idea how many rounds went out of this stock or what kind of life it had, just know that it was undamaged and in very good nick on the outside and had the original gel-coat.

We got this stock in from a friend of a friend. Just for a re-spray as he didn’t like the gel-coat finish. At first didn’t notice anything but the stock sounded funny...something was wrong. Started sanding the stock when we had a closer look. The shell on the forend was separating from the core, almost all the way round. Stock was cracked in every corner of the inlet area. This is a very heavy stock. ~ 2 kg Took us ages to fix this stock. Turned out sturdy again. The positions of the cracks in the inlet area are all where you would expect them

for this lay up style. As far as I know the manufacturer injects the fill into the outer shell after the outer shell has cured. Two complete different materials. Outer layer polyester/inner fill Epoxy. Polyester doesn’t glue well if not sanded or keyed somehow.”

 

" I only took the pictures to show the customer as he had just recently bought that stock.This is the worst I have seen, maybe one that went really wrong in the production. Not intended as a go at the manufacturer as we also don't know what had happened to it. If nothing else, at least it shows typical weak points to look out for when buying second hand."

 

 

 

 

 

 

 

 

 

[baldie]

Thanks for the pics Edi.

I,ve never seen that before...you live and learn.

The inner simply hasn,t bonded to the outer has it ?

That also has to be the very worst bedding job i,ve ever seen, and probarbly hasn,t helped matters by not holding the action securely.

[Ronin]

Ive seen the pics before, however, I will say its the worse one Ive ever seen.

 

The crack in the "strengthening rib" bettween trigger inlet and mag inlet has been caused by a poorly (tight) fitting mag system forcing the sides apart.

 

Aside from the structural issues seen, whoever worked on the stoke PRIOR to getting in the hands of the chap whose education & background is material science (Edi),,, shouldn't bother trying rifle work again - wrong vocation, whoever you are.

 

I think that some of the cracks and fissures "could" be attributed to the "bedder" - not all though.......

[oaken]

Looks to me as though it has been run over by a truck.

Were there tyre marks and a bent barrel as well?

[jcampbellsmith]

Surely a stock in this kind of condition should have just been sawn up into three pieces and thrown in the bucket? Regards JCS

[ejg223]

Surely a stock in this kind of condition should have just been sawn up into three pieces and thrown in the bucket? Regards JCS

 

Actually yes, but the guy that bought it could not afford another and is a friend of a friend. We fixed the stock and it is

perfect again. To get structural strength in the inlet area we milled channels along the stress directions and

laid carbon bundles into the channels covered by thin glas cloth. Forend had to be milled out quite generously and filled

with reinforced resin that was covered by glas cloth again. Very time consuming.

 

Oaken, can only speculate what happened, the outside looked as if she was well kept, not abused at all.

edi