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#1 Grey Crow

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Posted 03 September 2005 - 08:58 PM

Being an avid 1911 owner and shooter, and replacing the main springs frequently pending model and number of rounds fired.
I was just curious as to how frequently Thompson springs should be replaced.

Its possible with the WH receivers, that failure to replace springs more frequently could be part of the problem with cracked receivers. Granted the metal is a part of the equation as well.

In a few previous threads I've noticed its time to replace when they stop working.

Just a thought.
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#2 PK.

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Posted 05 September 2005 - 07:07 AM

If the lock and its slots in the receiver are correct (often not), the energy of firing will be reduced to a safe level by the time the various parts allow the free travel of the bolt. Obviously we are talking ’28 model here.

Because of field constraints, the easiest way to check the spring is to measure it’s overall length. GI manuals say 10.25” is minimum. This assumes that the spring has not been cut (it should have 69-72 coils). This spec is the same for ’28 & M1. Some manuals show a slightly different length spec.

A kinked spring should never be used. A little wave is ok, but the straighter the better.

If the fit of the pilot and receiver are correct, there should be little evidence of pilot canting. If you place the pilot into the receiver without the spring, the free end should move in a circle of (I’m estimating) about 1/8” max. If it’s loose, you risk spring kinking and the wear problems Phil noted above. Most kinked springs are caused by sloppy assembly/ disassembly techniques.

FWIW

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#3 Grey Crow

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Posted 05 September 2005 - 08:05 AM

Thanks for the replies.

The same should work for other auto loaders and MG's as well I would think.

The 1911 crowd most likely arrived at the same answer the same way. Then through observation narrowed it down to an approximate amount of rounds fired and replacement.
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#4 deerslayer

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Posted 05 September 2005 - 11:19 AM

I remember seeing a spring pressure graph in Tracy's book (I think).
Dan
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