Chopped barrel now short stroking

G

Gas Can

CGN Regular
Rating - 100%
125   0   0
I chopped my barrel to 18 3/4", added a Dlask A6 muzzle brake(bored out for .308), and a Marstar Navy front gas lock sight. Now she fails to fully cycle. She will eject the case and re-#### the hammer but the bolt does not go quite far enough back to pick up the next round or lock the bolt back after the last round.

Before the chop she was fine.

Gas port lines up properly, passes the 30 deg test, piston moves nicely, nothing riding on the stock that I can see.

At a bit of a loss. Has any had to open up the gas port alittle after a chop??

Thanks in advance

Gas Can
 
Silly question... Do the gas port and hole in the barrel line up... It has happened where they don't so you aren't getting full gas..
 
With the shorted barrel, the dwell time for the bullet in the barrel is not as long as it was with the extra inches. Also gage check the pistol and the cylinder and see if the pistol is undersize and the cylinder oversize, this is very common with the chinese guns.

You might need to drill a larger gas port but try changing the pistol or cylinder first.

And this my friends is what occurs when you screw with a perfectly good design and try to make it better.


Scott
 
I had that problem and after I gave it a damn good oiling (not the piston or cylinder) it was good to go.
 
Simple fix - short stroking

Gas Can said:
I chopped my barrel to 18 3/4", added a Dlask A6 muzzle brake(bored out for .308), and a Marstar Navy front gas lock sight. Now she fails to fully cycle. She will eject the case and re-#### the hammer but the bolt does not go quite far enough back to pick up the next round or lock the bolt back after the last round.

Before the chop she was fine.

Gas port lines up properly, passes the 30 deg test, piston moves nicely, nothing riding on the stock that I can see.

At a bit of a loss. Has any had to open up the gas port alittle after a chop??

Thanks in advance

Gas Can
Click to expand...

Cut one coil off the oprod guide spring - shoot - if crap out - cut another - shoot etc - you shouldnt have to cut more than 3 coils - If you fear battering - get a marstar buffer -

armscare.jpg

swingerlh.gif
:cheers:
 
Please email me and we'll get you thru this. No offense to the advice given here but I'm not in agreement. Do not drill your gas port and do not cut any springs.
First thing to do is make sure that the valve on the side of your gas system is open, with the screw slot set in a vertical position. Then email me. My advice is free
 
2nd thing to check is the gas plug itself. Have you cleaned it recently? Also inside the piston itself. Use of apropriate size drill bits are the armourers tools for properly cleaning built up carbon from these parts. Carbon build up in plug and or piston is a leading cause of short stroking
I have NEVER in my time spent working on these rifles, found any situation which would require oversizing a gas port nor have cut the recoil spring. If the rifle functioned fine before the modification, there must be a simple explanation for the current issue. Bullet dwell time is a non issue once the bullet passes the port.
 
M14Doctor said:
Please email me and we'll get you thru this. No offense to the advice given here but I'm not in agreement. Do not drill your gas port and do not cut any springs.
First thing to do is make sure that the valve on the side of your gas system is open, with the screw slot set in a vertical position. Then email me. My advice is free
Click to expand...

Thomas - U have worked on many more of them than me and I agree with you- Piston cleanliness if hole lined up first and foremost - and if the op rod isnt binding due to out of index - but if so - chop spring will work -simple fix- replacements are easily available -
Every short stroke M14 norc timed correctly I have had has been cured with spring chop - If track burrs exist, replace the spring when the burrs wear smooth - or do valve grinding paste to smooth the track - or let the shooting do the work -
Sadlak pistons in chinee gas cylynders short stroke - put in a standard piston and no spring chop needed -
I titled the post - simple fix - cheap also-
Harder but proper fix - fix the cause of the short stroke - usually op rod drag due to op rod not timed to gas piston due to op rod guide off kilter cause of bad placement or bad barrel index - I have yet to see a bad hole line up with unshimmed - have you ? - Rarely rough machined track with proper indexing , but I have had a few -
swingerlh.gif
 
M14Doctor said:
2nd thing to check is the gas plug itself. Have you cleaned it recently? Also inside the piston itself. Use of apropriate size drill bits are the armourers tools for properly cleaning built up carbon from these parts. Carbon build up in plug and or piston is a leading cause of short stroking
I have NEVER in my time spent working on these rifles, found any situation which would require oversizing a gas port nor have cut the recoil spring. If the rifle functioned fine before the modification, there must be a simple explanation for the current issue. Bullet dwell time is a non issue once the bullet passes the port.
Click to expand...

+1

There shouldn't be any need to modify gas port. This isn't an AR where the hole to gas tube varies by length.

There shouldn't be a requirement to shorten oprod spring.
 
One thing I should correct in my statement on bullet dwell... It's true that the shorter barrel will change the gas pressure profile.
This does affect gas system sensativity to a degree. This means judicious monitoring of carbon build up inside the body of the gas plug and piston.
I'll double check and if wrong I'll get back to you but there is no difference in barrel port size or gas system dimension between an M1a standard versus a socom 16, so in theory, inthese rifles, it is gas port location that dictates gas profile, not barrel length.
 
Yup

M14Doctor said:
One thing I should correct in my statement on bullet dwell... It's true that the shorter barrel will change the gas pressure profile.
This does affect gas system sensativity to a degree. This means judicious monitoring of carbon build up inside the body of the gas plug and piston.
I'll double check and if wrong I'll get back to you but there is no difference in barrel port size or gas system dimension between an M1a standard versus a socom 16, so in theory, inthese rifles, it is gas port location that dictates gas profile, not barrel length.
Click to expand...

Yep yep - It is not hole size - to much blast with that much powder/pressure for barrel length - non issue - dimension same same - (if I am not on mars lol) - but absolutely -carbon build up differs --lemme know if springfield tells you of different hole sizes --they wont tell me sh!t
army_lg.jpg
swingerlh.gif
 
I have NEVER in my time spent working on these rifles, found any situation which would require oversizing a gas port nor have cut the recoil spring. If the rifle functioned fine before the modification, there must be a simple explanation for the current issue. Bullet dwell time is a non issue once the bullet passes the port.

Thomas has chopped at least as many M14 rifles into shorties as I have. Between us, we have done A WHOLE LOT OF SHORTIES. And like he says,
I have never had to drill out a gas port or cut any coils off any of my shorty builds.

Look elsewhere ...
something simple has been changed during the shortification.

PS: WHAT AMMO ARE YOU SHOOTING?
WHAT ELSE HAS CHANGED?
 
I have the same problem.

Before I chopped mine it didn't work much, the stock was contracting the receiver one side and the ferrule to another. When I chopped nothing changed of course. I prefered to wait for a new stock to test reliability.

Then I received one of Thomas's CQB stock:cool:, now it shoots like a house on fire with good ammo, but it still fail to feed sometimes with certain ammo and always with some other. Exact same failure as the original poster.

Fed American Eagle 150gr FMJ : fail to feed at every round, I don't mind since this ammo patterns like buckshot

Remington accupoint 165gr: fails sometimes like 3-4 rounds out of 20, great accuracy

Winchester ballistic silvertip 168gr: about same failure rate as the previous ammunition, great accuracy again here

Hornady match 155gr palma: failure is slightly higher than previously almost half the rounds, can land every round on top of the other at 100 yards


Quite strange: First with the original gas system (all lined up good) it didn't work at all, the gas cylinder seemed to be rough when the piston slid in, so I've put on a USGI cylinder with an ajustable gas plug (a likely culprit), i've shimmed the assembly snug, and dropped a sadlak TiN coated piston; it did work from time to time from this point... I've put on the original norinco recoil spring since the first fail to feed, i'm sure the wolff spring is way too strong anyway. The USGI bolt doesn't bind and moves freely. And the op rod guide doesn't seem to put pressure on the op rod and the rod passes the test.

I'll get an ordinary gas plug soon to retest the whole setup, sucks to have such a cool rifle that shoot good too but doesn't work at all. :bangHead:

My gunsmith brought up the idea of enlarging the gas port and to not touch the spring, wasn't sure back then... What is the normal diameter for a gas port.
 
Sadlak pistons

Sadlak nm pistons are for hi powered Match ammo - Mike says they are not for surplus ball or other low power ammo. I saw short stroking even with his non grooved piston. A swap back to a standard piston solved the short stroking.
swingerlh.gif
 
Note taken, but the hunting ammo I've listed aren't they a lot more powerful than any lighter FMJ or surplus load available and yet it does short stroke from time to time, the problem may be lying somewhere else too, since it DOES work from time to time with this piston and a brand new cylinder.

I'll change a few parameters, if it still fails, I'll get an ordinary piston
 
Advice to those purchasing aftermarket pistons...
Sadlak pistons are designed for USGI cylinders BUT are compatable with some chinese cylinders. Your rifle will tell you.
Sadlak NM grooved pistons were specifically designed for use with 180 grain and higher ammunition and not intended for use with standard ammo.
My advice is to not rush to replace your norc piston.
 
.

Thanks gang for the advice.

I don't want to cut or drill anything, was just asking about the port.

The op rod guide was removed for the chop, but put back on with the same pin. I did take out a 0.005" shim after switching to the Navy gas lock, but the port and assembly are bang on.

The action does lock and unlock under its own weight with the spring removed at around 45 deg, even in the stock(without the trigger assembly).

The receiver was not removed.

I will check the gas system for carbon buildup.

I am shooting SB, and FNM surplus along with hand loads.

Thanks again

Gas Can
 
You must log in or register to reply here.
Back
Top Bottom