Why Were Carbines Factory Parkerized When ALL USGI Thompsons' Were Factory Blued?

All military Thompsons left the factory with BLUED (DuLite) finish over bead blasted steel. This gave a "flat black" appearance on the upper and lower receiver. Small parts and the barrel weren't bead blasted, so they turned out to be "semi-gloss" black. Parkerized finished TSMG's occurred only during an arsenal rebuild.

They weren't all parked.

Yes, some USGI M1 Carbines were not parked. Which leads to the question why it was policy for Savage/AO not to park any government contract TSMG's at the factory, while manufacturers of Carbines under government contract used their own discretion in the type of finish.

The vast majority of carbines were parkerized during the rebuilding programs in the late 40's and 50's. Almost all carbines were blued when first made as were most of the small parts on them including bolts. All carbine bolts were blued and later parkerized during rebuilding.

Only the very early carbines initially had a DuLite finish applied. The vast majority of carbines were parkerized when built. The small parts, bolts, triggers, hammers, etc. were blued.

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Originally Posted by Bruce McAskill

The vast majority of carbines were parkerized during the rebuilding programs in the late 40's and 50's. Almost all carbines were blued when first made as were most of the small parts on them including bolts. All carbine bolts were blued and later parkerized during rebuilding.

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Originally Posted by BrianQ

Only the very early carbines initially had a DuLite finish applied. The vast majority of carbines were parkerized when built. The small parts, bolts, triggers, hammers, etc. were blued.

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Is there more of a consensus on one or the other opinion? Is there no document information confirming one or the other?

I think the first carbines (early) but it would have been more the Inland and Winchester that were the DuLite than the others.

You can see that the majority of carbines were parked just by looking at original examples throughout carbine production. The early carbines were blued but since the finish didn't hold up well to the salt spray test a phosphate finish was adopted. The phosphate finishes didn't fare much better to the salt spray but it was an easier process. And yes there is documentation confirming the type finish applied.

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Originally Posted by BrianQ

You can see that the majority of carbines were parked just by looking at original examples throughout carbine production. The early carbines were blued but since the finish didn't hold up well to the salt spray test a phosphate finish was adopted. The phosphate finishes didn't fare much better to the salt spray but it was an easier process. And yes there is documentation confirming the type finish applied.

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BrianQ,
Could you refer me to the M1 Carbine reference where this is explained?

While there were only two entities manufacturing TSMG's during WWII, Savage and Auto Ordnance, and 10? entities manufacturing Carbines, it is odd that there wasn't a standardized finish that would be utilized for all factories for USGI small arms. Many USGI TSMG owners still believe their Parkerized Thompsons' sport the factory finish.

Phosphating is the same as Parkerizing (which was a proprietary process of the Parker Rust Proof Company just as " Du-Lite" is the name of a refinishing product) and would require that the parts be sandblasted first or the finish won't adhere. This would be a time consuming process and the parts would require protection from rust while awaiting the phosphating. There is no prep required for bluing other than the parts being clean. To machine a part, and then blue it is much faster than Parkerizing. The time savings in the middle of a war would surely tend to favor bluing, especially when the factories are already set up for bluing. The TSMG was subjected to the same government mandated proof testing, and yet they were shipped out blued.

The USGI TSMG was either blued right over the raw machined steel or sand blasted and then blued.

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Originally Posted by Tobor

BrianQ,
Could you refer me to the M1 Carbine reference where this is explained?

While there were only two entities manufacturing TSMG's during WWII, Savage and Auto Ordnance, and 10? entities manufacturing Carbines, it is odd that there wasn't a standardized finish that would be utilized for all factories for USGI small arms. Many USGI TSMG owners still believe their Parkerized Thompsons' sport the factory finish.

Phosphating is the same as Parkerizing (which was a proprietary process of the Parker Rust Proof Company just as " Du-Lite" is the name of a refinishing product) and would require that the parts be sandblasted first or the finish won't adhere. This would be a time consuming process and the parts would require protection from rust while awaiting the phosphating. There is no prep required for bluing other than the parts being clean. To machine a part, and then blue it is much faster than Parkerizing. The time savings in the middle of a war would surely tend to favor bluing, especially when the factories are already set up for bluing. The TSMG was subjected to the same government mandated proof testing, and yet they were shipped out blued.

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Why are you digging in your heels on this, questioning decisions and processes of nearly 70 years ago? It is what it is. One of the early carbine manuals had the phrase 'a peculiar shade of neutral gray' describing the obviously Parkerized finish. Yes, we know that Parkerizing is Zinc Phosphate.