 2Thanks -
 1 Post By RET DEP 04 -
 1 Post By Phil McGrath
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October 5th, 2011, 08:06 PM
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#1 | | Platoon Commander
Join Date: Jun 2011 Location: Houston
Posts: 405
| NM Piston - question answered
What is the difference between a NM piston and a standard one?
Last edited by BagemTagem; October 6th, 2011 at 09:53 PM.
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October 5th, 2011, 08:25 PM
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#2 | | Lifer
Join Date: Sep 2010 Location: Northern Ca
Posts: 2,488
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On the Sadlak NM piston I believe there is a groove that equalizes the gas pressure for a "smoother more consistent action". Read the info lower on the attached for specifics. http://www.amazon.com/Sadlak-Industr.../dp/B003MA61T4
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October 6th, 2011, 10:08 AM
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#3 | | Fire Team Leader
Join Date: Jun 2006 Location: Arkansas
Posts: 208
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Has to do with pressure curves for ammo with 168gr+bullet weights IIRC.
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October 6th, 2011, 01:02 PM
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#4 | | Platoon Commander
Join Date: Jun 2011 Location: Houston
Posts: 405
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So then it begs the question, was there a usgi NM piston
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October 6th, 2011, 09:07 PM
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#5 | | Old Salt
Join Date: May 2004 Location: Salem, Or
Posts: 1,863
| Quote:
Originally Posted by BagemTagem  So then it begs the question, was there a usgi NM piston | No, but there was a drawing and drawing # assigned, Sadlac makes a piston per the NM drawing #. Standard USGI pistons were hand grooved by unit armorers. I have both a std USGI piston that was hand grooved and a Sadlac TiN grooved piston I cannot tell and niether can my rifle what shoots better. YMMV.
There is a feelable differance in the rifles recoil, a std piston is sharper akin too a slight jab too the shooters shoulder, a grooved piston is more of a shove/push too the rear.
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October 6th, 2011, 10:07 PM
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#6 | | Platoon Commander
Join Date: Jun 2011 Location: Houston
Posts: 405
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awesome info...thanks around!!! Quote:
Originally Posted by BigEd63 Has to do with pressure curves for ammo with 168gr+bullet weights IIRC. |
can this be verified?
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October 7th, 2011, 07:23 PM
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#7 | | Old Salt
Join Date: May 2004 Location: Salem, Or
Posts: 1,863
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The groove came about while firing ammo that weighted more than 190grs, the atempt was too slow down the op-rod and prevent cracked rec heals. The name that I heard connected too the groove was Bill Donovan, even thou the 190 still didn't work well there was a side effect less barrel deflection.
There is a short slow motion vid on you-tube of a M1a firing, in slow motion you can see a few things going on at the same time, one is the gas system, it pulse 6 times with each firing from each ring on the piston as it travels too the rear, you can also see the barrel flex/whip up and down from each venting, in real time this looks like on event, with a groove piston there is one continous pulse and the barrel flexes less.
I think this time frame was when std barrels were the norm, medium and heavy barrels flex/whip less do to there added mass, that doesn't mean they don't flex, add a grooved piston too any barrel weight and the noodle effect is minimized that much more.
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October 8th, 2011, 11:56 PM
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#8 | | Platoon Commander
Join Date: Jun 2011 Location: Houston
Posts: 405
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So what do you think something like this is worth? 40, 50, 70, 80?
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October 9th, 2011, 02:34 AM
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#9 | | Lifer
Join Date: Jan 2009 Location: Long Island NY
Posts: 7,891
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The only one making them right now is sadlak and they list for $55.90.
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October 9th, 2011, 07:09 AM
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#10 | | Lifer
Join Date: Dec 2003 Location: Upstate NY
Posts: 2,768
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They started popping up again a couple years back. They got popular for a little bit until people figured out that they won't cycle reliably with bullets <168grs.
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October 9th, 2011, 07:14 AM
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#11 | | Grunt
Join Date: Aug 2010 Location: Cincinnati, OH
Posts: 99
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Didn't Broofield Precision Tool make an improved piston for the M25? Any idea what the improvements consisted of? Difference in plating techniques, perhaps?
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October 9th, 2011, 08:38 AM
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#12 | | Old Salt
Join Date: May 2004 Location: Salem, Or
Posts: 1,863
| Quote:
Originally Posted by 30Caliber They started popping up again a couple years back. They got popular for a little bit until people figured out that they won't cycle reliably with bullets <168grs. | In some rifles, its a you need too try one first or loan one from a shooting buddy and see if your load works with it or not, both pistons I have work in both of my rifles with loads as lite as 125grs.
If it doesn't work out they sell pretty quick in the PX so your not out alot of coin.
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