It is a type of mold and is common on the older rifles, take a soft brush and clean it in warm soapy water or WD 40. Then just coat it with oil and reinstall. IMO it will not effect the value of the rifle, it is considered maintenance.

 

Congrats on your new acquisition! Bone is correct. For a bit more information here is a response I posted to the same question a few years ago -

"Winchester buttplates manufactured after WWII can and will shrink. One of the by-products of the war were advances in plastic research, diversity and usage. Post WWII Winchester updated their buttplates with a cellulosic plastic in lieu of the "hard rubber" buttplates formerly used. Cellulosics basically describes a group of plastics that are made from cellulose which generally fall in to five main subcategories: cellulose acetate, cellulose propionate, cellulose nitrate, ethyl cellulose and cellulose acetate butyrate (the Model 69A buttplate material). While cellulosic plastics are not normally biotic in nature, the mixed esters like cellulose acetate butyrate react when exposed to high moisture levels, heat, and acids. This exposure will initiate hydrolysis and cause breakdown of the polymer chains which results in some weakness and shrinkage of the buttplate. Note; this breakdown of the polymer chains can also be triggered auto-catalytically.

As a byproduct of the hydrolysis, the degradated polymer chains on the buttplate surface react with other stimulants to create the "white residue". The white residue is most frequently found on the latter composition buttplates and some common misconceptions are that it is a surfactant (such as a mold release) or an organic growth such as a mold/fungus. In reality it is likely caused by the polymer chain breakdown coupled with a combination of organic oils and the aforementioned heat and humidity. It requires a combination of those elements to create the surface residue. When I lived in Ohio, the white would reappear on the buttplates every 6-12 months. Now that I live in the desert with low humidity (but higher temperature) the white does not develop at all but the buttplates seem to shrink at a faster rate.

It is actually very easy to clean and control. WD40 and a stiff tooth brush are all you need to clean off the residue. Good 'ole Hoppes #9 also works but is slightly less effective. "

Best Regards,

 

Congrats on your new acquisition! Bone is correct. For a bit more information here is a response I posted to the same question a few years ago -

"Winchester buttplates manufactured after WWII can and will shrink. One of the by-products of the war were advances in plastic research, diversity and usage. Post WWII Winchester updated their buttplates with a cellulosic plastic in lieu of the "hard rubber" buttplates formerly used. Cellulosics basically describes a group of plastics that are made from cellulose which generally fall in to five main subcategories: cellulose acetate, cellulose propionate, cellulose nitrate, ethyl cellulose and cellulose acetate butyrate (the Model 69A buttplate material). While cellulosic plastics are not normally biotic in nature, the mixed esters like cellulose acetate butyrate react when exposed to high moisture levels, heat, and acids. This exposure will initiate hydrolysis and cause breakdown of the polymer chains which results in some weakness and shrinkage of the buttplate. Note; this breakdown of the polymer chains can also be triggered auto-catalytically.

As a byproduct of the hydrolysis, the degradated polymer chains on the buttplate surface react with other stimulants to create the "white residue". The white residue is most frequently found on the latter composition buttplates and some common misconceptions are that it is a surfactant (such as a mold release) or an organic growth such as a mold/fungus. In reality it is likely caused by the polymer chain breakdown coupled with a combination of organic oils and the aforementioned heat and humidity. It requires a combination of those elements to create the surface residue. When I lived in Ohio, the white would reappear on the buttplates every 6-12 months. Now that I live in the desert with low humidity (but higher temperature) the white does not develop at all but the buttplates seem to shrink at a faster rate.

It is actually very easy to clean and control. WD40 and a stiff tooth brush are all you need to clean off the residue. Good 'ole Hoppes #9 also works but is slightly less effective. "

Best Regards,

Great info, my son recently picked up a Winchester 94 with a buttplate thats undersized. I said that cant be the original but now I have to re-think that. By the way I like your avatar, just picked up a Winchester 67 this week and has the same mark.

 

Ballastol works great also

 

JWA, were you able to run tests on the amount of shrinking of butt plates? Colt also used a bad plastic on the Government .45 Models from the 1950's. That plastic shrank down so much that the screw holes elongated.
But back to Winchester butt plates. I am of the opinion that Winchester sometimes left the wood proud to the butt plates when new. Because I have and have seen numerous original steel butt plated guns with the proud wood and we know the metal didn't shrink.

 

On the rifles with steel butt plates the wood is usually proud. The plastic butt plates were installed on the stock and then sanded together with the wood so that they were even/flush when brand new but then the plastic shrinks over time. I have not run any tests but it appears from observation that after the initial shrinkage the process slows and/or stops completely as all of the butt plates appear to have shrunk a similar amount whether they are from 1939 or 1959. Again, that is just from observation, I have not taken any actual measurements.

Best Regards,

 

My model 72-A had the same issue when I got it last year.A good scrubbing in the wash tub with a stiff brush and Dawn dish soap and some white vinegar did the job.Good advice from the above posts.

 

Good information here , I thought mine was growing fungus

 

Thanks JWA for your views on this, I do agree that some butt plates were sanded to be even with the wood and remain a perfect fit even after 70 or more years. So those butt plates did shrink. But some or even most stocks were left proud with both plastic and metal butt plates. So I do not believe the shrinking plastic butt plate theory. Just my opinion based on observation of 1000's of rifles. Why would Winchester make metal butt plates with proud wood and plastic not proud? The grain lines from the sanding should line up from wood to plastic if sanded together. Most have grain lines that do not line up. Seems to me Winchester gave a lot of latitude to the stock makers. So we see lots of variation. This is backed up by Pauline Muerlle's book on how it was at the factory. A very interesting subject to me and of course everyone has a right to their opinions. At this point it is hard to prove anything.

 

Here is some clearly shrinking plastic on Colt grips. This shrinking is well documented. Note the screw holes are elongated from the shrinking. Elongated screw holes are never seen on Winchester plastic butt plates.

 

Winchester proud wood on a 1890 rifle with metal butt and original wood finish.

 

Model 1873 with proud wood.

 

Winchester 67 smoothbore pre-WWII with perfect matching wood and plastic after 80 years. Some of the sanding grain lines appear to line up on this one.

 

Hi CJS57,

Thanks for the great photos!

All of the pre-WWII .22 rim fire hard rubber composition and post-war cellulose acetate butyrate were sanded with the stocks to achieve a flush finish, those fitting instructions are given on the Winchester stock blueprints and in the assembly notes. On the the 67, 68, 69, 69A, 72, 72A, 75 Sporting (late) and the 47 the drawings state "Match plate to stock all around". The difference in the present-day fit is that the pre-war material did not shrink much, if any, whereas the new post-war cellulose acetate butyrate did shrink. My photo skills are not as good as yours but I have dozens of post-war rifles with the sanding marks aligned but the butt plate is sub-surface of the wood, the only way that could occur is through shrinkage.

The metal butt plates were fitted differently, the stock was sanded to a standard jig which worked just fine since the metal butt plates were ground to standard dimensions so they were the same size for each model. The slightly proud wood was likely a little extra fitting tolerance "just in case". Again, the use of the jigs (called butt plate gages) are mentioned on the specific Winchester assembly notes for each model. On some of the drawings (such as the Model 57) the drawing specifies the "wood to extend .005" to .010" all around the outside of the (metal) butt plate".

Hope that brings some additional clarity to the subject.

Best Regards,

 

Thanks JWA! Well with that I can come over to your side. Odd however to me that Winchester specified proud wood with metal butt plates and flush fitting with plastic? But that is Like so many other oddities at Winchester. Here is one more picture of a late prewar (1940?) 69A Target that I presented in another thread. Has some matching sanding lines but with slight shrinkage only.

 

Well , this thread was interesting I have several old Winchester 69’s and have wondered about the white powdery looking stuff that that appears on a couple of them from time to time. I had thought it was mildew, but wonder why they didn’t all have it.