Piston chat.. - Page 3 - M14 Forum

M14 Forum


Piston chat..

This is a discussion on Piston chat.. within the Art Luppino forums, part of the Gun Professionals category; Originally Posted by Capona tony, it doesn't eject brass as far? Or at a different clock position? The brass doesn't eject as far. Most of ...


Go Back   M14 Forum > Gun Professionals > Art Luppino

66Thanks
Reply
 
LinkBack Moderator Tools Display Modes

Old December 13th, 2016, 03:18 AM   #31
Super Moderator
 
tonyben's Avatar
 
Join Date: Apr 2007
Location: Beaverton, OR
Posts: 9,082

Awards Showcase

Quote:
Originally Posted by Capona View Post
tony, it doesn't eject brass as far? Or at a different clock position?
The brass doesn't eject as far. Most of it (the SPEER 125's) just kind of falls out of the action and it gently rolls off the bench.

Tony.

tonyben is offline  
Remove Ads
Old December 17th, 2016, 10:06 PM   #32
Lifer
 
2336USMC's Avatar
 
Join Date: Feb 2007
Location: The Road
Posts: 3,858
Art,

Could you give us an idea of what you consider a fast piston vs. a slow piston?

My old M1A, which has always shot as well as I could ask it to, currently has a piston (Sadlak) in a USGI unitized gas cylinder (Hueygunner) that, when I point the rifle up at 45 degrees and lock the bolt back, I can just say "Mississippi" then *click*. It's about a second or a bit less.

What would a fast or slow piston be, say in Mississippis?

Thanks from tonyben
2336USMC is offline  
Old December 18th, 2016, 04:56 AM   #33
Old Salt
 
lysander's Avatar
 
Join Date: Apr 2015
Location: North Carolina
Posts: 1,598
Quote:
Originally Posted by jywolfe View Post
Added a piston worksheet. Headed to the range and will update later.

Measured diameter at port, diameter at tip, total indicated runout from those locations, face concentricity and mass.

Note the difference in diameter for Brookfield Piston.
According to the drawings, only four of the listed pistons are to print.

#1, #5, #7, and the Bula

lysander is offline  
 
Old December 18th, 2016, 05:04 AM   #34
Old Salt
 
lysander's Avatar
 
Join Date: Apr 2015
Location: North Carolina
Posts: 1,598
Quote:
Originally Posted by XM25Ren View Post
Not an expert but I do know that the NM grooved piston was meant for the heavier bullets ie. 168 and 175. Anything lighter may not cycle the action.

REN
The stock GI M14 gas system is over gassed, for the average shooter in temperate weather. It was designed to work with the lowest possible expected port pressure in arctic climatic conditions, without lubrication.

It can leak, loose, have bleed off, a lot of gas before it starts to have serious trouble.

Thanks from tonyben, boomerpusher and BoltTrash
lysander is offline  
Old January 24th, 2017, 07:58 AM   #35
Platoon Sergeant
 
shooter86314's Avatar
 
Join Date: Dec 2013
Location: arizona
Posts: 341
piston tilt test surprise

Regarding my comments of early December in Post #10 in this thread:

Is it too late to return to that briar patch? I would like to report a recent experience which contradicts my comments above.

During the three years of my membership, I have read many comments about the value of the tilt test, which miffed me for several years because, as previously recorded, my gas piston fell ceremoniously when I had gas cylinder shims installed and fell rapidly with the gas plug removed or loosened. I attributed that to a condition recently described as "vacum drag." The tilt test is considered by many to be a "litmus test" of a rifle's operational health.

Pursuant to recent related discussions about shims, pistons, unitized gas cylinders, and egcetra, I removed my shim in preparation for my next range visit and testing. (I tapped my GC assembly forward gently to achieve a 5 o'clock finger-tight gas lock situation.)

As an after thought, I decided to conduct another tilt test (no shims, gas plug tightened sufficiently). Incredibly, the piston fell like a rock in both directions.

It appears to me now that there was no vacuum in the GC. Rather, the light tightening of the GC against the barrel shoulder and shim was distorting the GC!!

What do you all think?

I will soon report separately about changes since my last range visit.

Thanks from 2336USMC and rabbitone
shooter86314 is offline  
Old January 24th, 2017, 08:31 AM   #36
Lifer
 
Join Date: May 2006
Location: kerrville. texas
Posts: 2,941
Gas Cylinder installation

Installing the gas cylinder on the barrel in hopes of producing the best accuracy can lead to issues. In the attempt to install the cylinder in a non-movement position interferes with the normal slip fit of a standard grade rilfe cylinder installation.

Add to this the use of shims and the cylinder can be put under stress, using the popular method of having the lock hand tight to 5 oclock. Now three things have been added, peening and shims and a tight lock..

This combination of modifications often puts stress on the cylinder, this stress influences the piston, which accounts for slow piston action.. To make matters more difficult the heat changes all of the above.

What does all this mean?

Always check piston fall when the barrel up to temp, at least ten rounds fired.. If the piston is dragging, slow or jerky now is the time to change pistons, "Piston Change out".

The above may be ther reason the Army used the "Pull Forward" system insrtalling the gas cylinder, in stead of shims.. Sometimes the Army makes good decisions.. The shim system is excellent but can require making adjustments to the lock going from 5 to 5:15 and so on..

The lock is not a hand tight one position for every rifle, you have mess with it sometimes.. Art

art luppino is online now  
Old January 24th, 2017, 10:38 AM   #37
Old Salt
 
Killashrub's Avatar
 
Join Date: Nov 2014
Location: Polk County, Florida
Posts: 1,258
Interesting. I will keep that info in mind.

I always make sure the pistons fall free when cleaning. I guess I will keep it up.

Killashrub is offline  
Old January 24th, 2017, 12:55 PM   #38
Lifer
 
POLACK's Avatar
 
Join Date: Aug 2016
Location: south east Florida
Posts: 2,449
Quote:
Not sure it was worth our time, but we still talk about the all-day nearly-straight rod
>sigh<

POLACK is offline  
Old January 24th, 2017, 01:08 PM   #39
Lifer
 
Join Date: May 2006
Location: kerrville. texas
Posts: 2,941
Anybody know how to

Move my Thread on cyl installation to a new Thread// Would appreciate it being done... Art

art luppino is online now  
Old February 26th, 2017, 11:35 PM   #40
Platoon Sergeant
 
shooter86314's Avatar
 
Join Date: Dec 2013
Location: arizona
Posts: 341
ArtL said:
Quote:
After this test was conducted the results indicated free flowing pistons out performed non free flowing pistons in across the course Match M14's, it was not detrmined as to why.
I found this statement very interesting. Do you recall whether these "non free flowing" pistons were on rifles with shimmed gas cylinders, which might contribute to bending of the GC or binding of the pistons?

shooter86314 is offline  
Old March 15th, 2017, 08:35 AM   #41
Super Moderator
 
Phil McGrath's Avatar
 
Join Date: May 2004
Location: Silverdale, WA.
Posts: 7,468

Awards Showcase

Quote:
Originally Posted by shooter86314 View Post
ArtL said:

I found this statement very interesting. Do you recall whether these "non free flowing" pistons were on rifles with shimmed gas cylinders, which might contribute to bending of the GC or binding of the pistons?
I doubt it.

Phil McGrath is offline  
Old March 15th, 2017, 11:12 AM   #42
Lifer
 
Join Date: May 2006
Location: kerrville. texas
Posts: 2,941
Just as fussy....

This subject is an interesting one because there are many variables. One such variable is the cylinder lock, just how tight should this cyl. lock be torque on???

We all know about the hand tight to X position "o clock referance".. It is possibel to torque the lock on so tight it will "Kink" the barrel, don't know whatit would do to the cylinder.. Don't do that..

One of the things I like to do on my own rifles is to stone both the contact sides of the lock and the receiving face of the cyl.. Not being a Collector, I'm not concerned about the parkerizing being removed. Also, I make sure there are no spurs on the edges of both parts.. This is a final hand fitting method.. Once stoned smooth,i I continue to stone until lock finger tightens to just past 5:00, that puts it about 5:15 to close to 5:30. Yes, I know, that's not kosher, well maybe not, but it produces fine shooting rifles.. Art

Thanks from hytekrednek and boomerpusher
art luppino is online now  
Reply

  M14 Forum > Gun Professionals > Art Luppino

Moderator Tools
Display Modes


Similar M14 Forum Discussions
Thread Thread Starter Forum Replies Last Post
Can You Spot the Difference? lysander The M14 23 April 13th, 2016 05:52 AM
what is wrong!!?? Capt Mullet Accuracy 64 October 27th, 2014 12:07 PM
M14 Gas Pistons, Maintenance and their effects on Accuracy Gus Fisher Gus Fisher 69 August 22nd, 2014 07:28 AM
Dwell time as it pertains to the M14 and how to adjust it... tonyben The M14 23 November 25th, 2013 07:08 AM
Simple Gas Piston Accuracy Test i8mtm Reference 44 February 21st, 2013 08:38 AM



Top Gun Sites Top Sites List