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Very Hot Topic (More than 25 Replies) Rolling Block conversion to .223 (Read 4135 times)
KWK
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Re: Rolling Block conversion to .223
Reply #60 - Jul 11th, 2019 at 6:48pm
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Depending on the pin material, numbers indicate they are possibly the weakest link, might bend, crack or fail before large scale failures of the blocks.


Again, based on the failures marlinguy and I have read about, a catastrophic failure is nearly always in the breech block at the stress riser at the corner, not the pins. In cases where failure is limited to yielding, it's possible that occurs elsewhere; perhaps he's seen a few such.

What alloys Remington used in each part I can't say, and this could affect the results.
  

Karl
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Bill Lawrence
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Re: Rolling Block conversion to .223
Reply #61 - Jul 11th, 2019 at 7:56pm
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RM Maker, let's leave aside Vall and KWK's arguments for now and just concentrate on your points to me.  If one or both pins should fail, even if it didn't "blow up", wouldn't the action no longer work and wouldn't gases very likely blow back in the shooter's face?

Bill Lawrence
  
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RB Maker
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Re: Rolling Block conversion to .223
Reply #62 - Jul 12th, 2019 at 9:05am
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Bill
The chance of both pins failing in double sheet is theoretically possible but very unlikely
What happens in structural failures is that one member may start bending or yielding to its limit then typically the surrounding structure starts receiving the stress and spreading it over a larger area
Letís say for conversation sake both pins sheared off at both blocks
The hammer roller kinda drops down into the receiver, the breech roller depends on the hammer roller location
If the hammer is down in the firing position, the breech roller has to go down into the receiver as well
Not sure how these position would look at the moment the pins fail
Donít think they would exit the receiver as both rollers are somewhat shaded from a direct exit path
I would think the breech roller pin is more likely to bend causing the breech block face to open up and potentially releas pressure at a perpendicular direction to the shooters face
Would not want either scenario
To bust the pins in a catastrophic mode pressures would have to be well above 85 kpsi  not sure  a load can get ther
  
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Chuckster
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Re: Rolling Block conversion to .223
Reply #63 - Jul 12th, 2019 at 10:20am
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Trying to stay out of this because I don't have a Roller or drawings.
Just a couple of comments: There is no such thing as shear yielding. That is why scissors and shears work.
Hopefully the side walls would yield in bearing before the pin shears. Don't see a bending load on the pins.
The hammer pin has a higher load than the block pin.
Guessing the block cracking at the sharp corner is a tension fatigue failure which can occur at lower stress levels.
FWIW,    Chuck
  
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marlinguy
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but they sure are neater!

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Re: Rolling Block conversion to .223
Reply #64 - Jul 12th, 2019 at 10:41am
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Seeing the picture of the Tipmann block, it looks more apt to fail than an original with the wide cut through it. That @1/4" wide cut removes a lot of strength in the area most prone to failure. Leaving two "ears" that the pin pivots on makes it even more likely for those ears to fail under higher pressures.
  

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