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Firing Pin Spring Coil Count - Colts


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I'm pretty new to the forum, so please excuse me if this is a silly question.

 

I've been pouring through Mr. Davis' Amateur Guide (since I'm even less than an amateur) and on pg 141 it mentions the 1921 firing pin spring is 32 coils vs 30 for the 28N and that the 28N spring is longer (though no length was mentioned). Referring to the Spring detail print (rev 2 dated Sept 1, 1921) on page 93 of Mr. Hill's Ultimate Guide, it shows that the spring is 30 coils of .031" music wire with a free length of 2.50 +/- 0.050".

 

Which is the correct number of coils, or did it vary in production? It seems a difference of two coils is quite a bit and at 12 coils/in, that would equate to a difference of 0.167" which is over 3X the allowable tolerance on the print.

 

Sorry for getting into the minutiae and thanks in advance for any help!

 

Doug

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Just to keep things interesting, I guess, the firing pin spring for No.133 shown on page 16 of the Amateur's Guide appears to have 31 coils. #133 had to have been manufactured prior the Sept 21, 1921 drawing rev 2 (30 coils). Maybe Colt was less concerned about coils than the overall length (which is reasonable since length, spring rate, and solid height are the most important characteristics)? Just trying to figure out the 30 vs. 32 coil question.

 

The reason I ask is that while I haven't bought a gun (yet), when I do I want to make sure I know the correct spring for a spare parts kit depending on if I get a 21 (preferred) or an Overstamp. Yes, I know the Herigstad metal box and brushes I have are not original, but parts for the gun itself I would want to be as correct as possible.

 

Thanks again for any advice for Me the Novice!

 

Doug

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I have to correct my original post in that the Amateur Guide says the 28N spring is slightly shorter, not longer as I stated (which makes sense based on coil count). Sorry for the error. I blame senility.

Edited by DFisch
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DFisch,

Thank you for purchasing my book. I do hope you find it useful as you study and look for that perfect Colt's. And welcome to the world of Auto-Ordnance paper.

 

I agree the recoil spring on NO 133 appears to have 31 coils. Or maybe 31 and a half coils rounded up to 32 coils during the spring inspection part of the manufacturing process. Those that study the Colt's era Auto-Ordnance paper are aware of statements in the handbooks, catalogs and other paper items that do not match with the reality of the gun or accessories. Probably the biggest mistatement or lie is the C drums do not work in the 1928 NAVY model. Shown below is the 1928 NAVY insert for the Auto-Ordnance 1929 Commercial Price List and Catalog. Note how the firing pin springs are still referenced as being differert between the models - Green Arrows. More importantly, note how the magazines are also referenced as being different between the two models - Red Arrows. While I appauld your attention to detail, I would not let the number of coils on a firing spring be a deal breaker on an otherwise original Thompson gun that is the model, variation and price you desire.

 

As mnshooter states, "There is no such thing as too much minutiae in this forum." You are going to have a great time on this forum. Again, thank you for purchasing my book. I hope to meet you at one of the upcoming Thompson Shows & Shoots.

 

1929 Insert Rear with arrows.jpg

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Hi Doug,

 

I decided it was a good time to count mine up. So I took pics of 4 Colt's guns.

#5177 27A Quite sure original internals. Possibly mixed up with other original St. Louis guns, no way to tell.

#7463 21AC Colt internals but not original to #7463

#6781 21AC Colt internals but not original to #6781

#6077 21A Colt internals but not original to #6077

 

Best I could tell, all have 30 coils....

firing pins.jpg

Edited by giantpanda4
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Thanks, Mike! I’m starting to feel bad with everyone tearing their guns apart just to check the springs!

 

It’s interesting to see the difference in the free length of the four springs even though the coil count is the same. Of course 100 years of compression could easily have that effect.

 

Thanks again for everyone’s help! I love this forum!

 

Doug

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Giant Panda, thanks for the photo.

 

Now, if you will just remove the Cutts from a 1921 Colt with an original serial-numbered barrel that appears to have never been removed,

 

and let us know if it shows to have been "pinned" twice....

 

We will all rest easier...Phil

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