To Blish or not to Blish...

[deerslayer]

Well I doubt anybody runs without a blish lock anymore but we do have an answer on what it does to the recoil... It absorbs it! If you refer to my previous post on recall all I did was replace the blish lock I have a 28 bolt set up then do the same test using the same recoil spring.

[TSMGguy]

What are the five small pieces of metal?

[giantpanda4]

Actually it transfers it, not absorbs it!

 

Had the lock not been de-earred (Van Gogh'ed?) the load path stays between the bolt face and the receiver thru the lock. The Van Gogh'ed lock allows all of the energy to transfer to the rear of the receiver where the .22 bullet was sitting in place of the buffer.

 

Good work on creating a visual reference for what the bolt system actually does!

[The1930sRust]

So, a '21 actuator had less pressure at the rear? R

[deerslayer]

Excellent observation. Overall energy transferred to the whole receiver is the same, just spread out more or concentrated at the back.

 

TSMGguy, The little pieces of metal are squished 22 lead bullets, and the other piece is a de-eared blish lock (or Van Gogh'ed... That's funny..). See previous post for details of the experiment.

 

So yes the 21 had the least of all energy transferred to the back of the receiver.

[ppgcowboy]

Is that because it is lighter, it being the actuator.

[giantpanda4]

Well, Dan said "So yes the 21 had the least of all energy transferred to the back of the receiver."

To clarify that (or really confuse it) , it means least amount of energy through the buffer to the back of the receiver. The buffer in his case was a .22 bullet. All of the energy goes thru the receiver at some point.

 

Two issues here - Blish vs. VanGogh and 21 vs. 28.

 

By taking the ears off, the Blish lock does nothing to connect the bolt group to the receiver mass - so the buffer (bullet) gets smashed a lot because that is the major load path (the spring being the other path).

Add the ears and now the whole receiver system is accelerating back until the pressure drops and the lock disengages with the receiver. A lot of the force now has dissipated since the bullet exited the barrel.

 

Remember energy is force x time. Force is mass x acceleration.

So in the case of the 21 vs 28, the 21 actuator mass is less and that means it accelerates faster to the rear, but it encounters a stronger spring than the 28. Energy is the same, less mass but bigger spring means faster cycling and more energy going into the spring rather than the buffer as seen by the squished bullets.

[The1930sRust]

[rpbcps]

Well, Dan said "So yes the 21 had the least of all energy transferred to the back of the receiver."

To clarify that (or really confuse it) , it means least amount of energy through the buffer to the back of the receiver. The buffer in his case was a .22 bullet. All of the energy goes thru the receiver at some point.

 

Two issues here - Blish vs. VanGogh and 21 vs. 28.

 

By taking the ears off, the Blish lock does nothing to connect the bolt group to the receiver mass - so the buffer (bullet) gets smashed a lot because that is the major load path (the spring being the other path).

Add the ears and now the whole receiver system is accelerating back until the pressure drops and the lock disengages with the receiver. A lot of the force now has dissipated since the bullet exited the barrel.

 

Remember energy is force x time. Force is mass x acceleration.

So in the case of the 21 vs 28, the 21 actuator mass is less and that means it accelerates faster to the rear, but it encounters a stronger spring than the 28. Energy is the same, less mass but bigger spring means faster cycling and more energy going into the spring rather than the buffer as seen by the squished bullets.

 

Mike,

That is well explained, I appreciate that.

 

Stay safe

Richard

Edited September 22, 2020 by rpbcps

[deerslayer]

From my other posting on this can you run the numbers to get the speed of impact of the various bolts? I've been too tired lately to dust off my physics...

 

 

 

Well..a nine pound sledgehammer lifted up 6 inches squished the bullet down to 0.1295 inches... So we're talking 4.5 footpounds of energy to more than replicate the recoil force.

[giantpanda4]

Not bad - but you make the assumption that the "squishing" is linear, and it ain't!

 

We sure have invented some cool new engineering terms here!

[thirtyround]

Thank You Gentlemen for the time and effort here. I cant get enough of this subject, The Thompson just doesn't disappoint regardless of what one does with it. JB

[Adg105200]

Interesting topic, and very interesting way using the bullet squish method to help visualize the forces!

 

Andrew

[mnshooter]

Very interesting that the M1 and 28 have identical squishes.

Would expect the blishless M1 would be much closer to the earless 28, everything else being identical.

 

 

Also interesting: Blishless is not found in any dictionary. Did this forum produce a new word?

[Arthur Fliegenheimer]

If there were a firearm testing equivalent of Todd Osgood's Project Farm youtube videos, this subject would be a must see. The Missourian Osgood is adept at configuring systems to measure stresses on mechanical and non mechanical consumer items.