SPAS/LAW/SAS 12 Replacement Receiver Shock Absorber


Technical Details


New Style


Old Style

(For more help on deciding which you have, see Common Repairs)

The factory parts were likely molded of Cast Nylon 6.  This is about the best material if you are going to mass produce by molding parts.  It has an impact strength of around 0.4 ft.-lbs./in. and hardness of around Rockwell R115.  There are some white replacement parts being sold for $8 that will also break up over time, just like the factory parts.

Since we  are machining each part, we can use a much better material.  The new parts are made of Ultra High Molecular Weight (UHMW) Polyethylene.  This material has about the highest impact strength of any plastic at any price -- and what we want is Impact Strength.


Impact Strength -- The ability of a material to withstand shock loading. Determined by the notched Izod test, which measures the effect on a
material when it is suddenly impacted by a swinging pendulum. A larger number signifies greater impact resistance.

Note almost four times the impact strength of "unbreakable" Polycarbonate.  One Hundred times the impact strength of Cast Nylon.  I will offer a lifetime warranty against the part splitting or shattering.

I am using a special type called Oil-Filled UHMW Polyethylene.   This has oil impregnated within the Polyethylene.  This actually doubles its tensile strength and lets it survive down to -450° F.  The oil helps to make anything contacting slides and does not stick and dig in.

This does not need the metal load spreading steel disk on the factory part.  The "old style" had no disk, but often broke up.  They added the disk to the new part to try and get their Nylon to survive.  The superior material I am using will not break up under any circumstances and needs no disk.   Also, the new part is held in by a stainless steel screw from the other side rather that the "tit" that always broke off.  The "tit" helped with quick mass assembly -- the screw will last much longer.
 

The prototype is back from testing (90 high-powered loads, thanks Oscar!) and it worked perfectly.  Notice the slight mushrooming of the unsupported portion.  This shows plenty of shock absorbing was going on.
 
 


Installation

Please see bottom of page.



Old-Style vs. New Style

Be sure you determine which part you need -- the new-style or the old-style. Look here for details.


Purchase
 
 
New-Style
The cost is $49.95 plus S&H 
Old-Style
The cost is $44.95 plus S&H

Shipping and handling is a flat rate of  $8.00  per order to anywhere in the USA, sent via USPS First Class Mail (5-14 Days).


Yes, we use PayPal as our payment processor.  No, you don't have to join PayPal.  It's just like any other web-order or mail order.  You give your name, address, and card info, and they bill you.  While some sellers have beefs with PayPal -- no buyers have ever been upset with them.

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Installation

I suggest you have the part installed by a competent gunsmith.  I won't supply full instructions here, if you don't know how to install it -- don't!

The new part is held in place with a stainless steel sheet metal screw (supplied).
 
 

I’ve had a hard time making everyone happy with the mounting screw I supply.  So I supply an assortment of six different stainless steel screws to choose from.

With some screw selections it will be necessary to remove a small amount of material from the stock to clear the new screw head.
 
 

Note that the replacement part does not have to be bolted down like the whole force of the action will try to pull it loose.  The original parts were held in place by a tiny little knob – it is primarily there to keep the part from just falling out.

One difference between the two parts is the knob on the old style part (on the right) is at a bit of an angle.   The angled sides of the flat-head screws work better to allow the screw to not be perpendicular with the back of the receiver.  The truss-head (rounded head) screws tend to work better with the new style part.

No matter what – there isn’t going to be room for the new screw head.  Some material must be removed from either the stock or the receiver.

What did I do with my gun?  I used a 45° countersink and cut room in the receiver for a flat-head screw.  The tiny #6 I supply actually does a great job this way, less material to remove than for the #8.

 Don’t get too hung up on keeping the gun “stock” – the stock design doesn’t work.  (Anyone want the “stock” lever-style safety?)  And since the receiver is the actual problem, I’d rather fix it once than modify all the different stocks I have for it.  In my book, a cleanly installed replacement shock adds value to any gun.

Each shock ordered will come with at least one of each of these screws:
#6 X 3/8” Flat Head
#6 X 5/8” Flat Head
#8 X ½” Flat Head
#8 X 5/8” Flat head
#8 X ½” Truss Head



Comments? Questions? Additions?  Corrections?
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