enlarge gas port...?
 

Currently, my M1S 16" Whisper doesn't fully cycle. It will extract but not strip the next round from the mag. I swapped out the rifle length buffer spring (I use an A2 stock) for a carbine length spring, but to no avail. Got me thinking I'm not getting enough gas in the action, so why not try and enlarge the gas port a little in an effort to get that gas? So, with that in mind, what numerical size is the OEM port, and what would be the reccomendation to go up to?


BTW, I know some have mad e a fix by using a carbine length buffer, but I don't like the idea as it lets the carrier travel too far back in the extension tube.

i use an a2 stock and a m1 upper. i took some weight out of my buffer first. second try i cut 1/2 off the spring. cycles fine now.

Cycle
 

I like to swap lowers around so I'm working to make mine cycle without modding the lower in any way. My gas port on my M1S is a little over .123 and I wouldn't go bigger than that.

I spent 7 hours at the range yesterday (I have new video too :) ) and did a lot of experimenting.

GET MAGPUL PMAGS !!!!! I've had trouble getting rounds to pick up from all other mags, The PMAGS took the magazine feed problem out of the equation.
Once I eliminated that I started on bullet weights and powders.
All bullets weights and powders picked up the next round. Every one of them. I never had a mis-feed all day. The big thing for me was getting the bolt to lock back after the last round..
My gas port is in the carbine position. I tried 4 different powders and 4 different bullets
Powders ... A-2400, H-110, W-296 and AA-1680
Bullet weights.... 150gr JSP, 168gr SMK, 175gr SMK and 220gr SMK.

What I found was the slower the powder the better results I had. The best results came with 1680. The 2400 and 296 I got from friends but I bought the H-110 and AA-1680. Once I use up the H-110 I'll just buy AA-1680.

I got all to cycle and strip cartridges from the magazines. Anything faster than H-110 would not lock the bolt back after the last round no matter what bullet I used. H-110 with a 175 SMK @ 1500/1550 fps (890 Energy ft/lbs). would lock the bolt back half of the time. AA-1680 with a 220 gr SMK @ 1000/1050 fps (499 Energy ft/lbs) locked it back all of the time. Even with the adjustable gas tube turned down within 1.5 turns from full closed.

So after my experimenting here has how I got my M1S 300 fireball upper to feed as well as my other findings.

#1 Magpul PMAGS just rock !!

#2 energy ft/lbs. had no effect on getting the bolt back far enough to lock back. The sub-sonic 220gr SMK with 499 fed and locked the bolt back the super-sonic 175gr with 890 only locked it back half of the time.

#3 Bullet shapes and weights and shapes had no effect on feeding the 150 gr JSP's all fed just fine. This is the one area I need to do more experimenting as I have never tried a bullet lighter than 150 grains

#4 All of my bullets were loaded with a 2.170 max. OAL, My M1S is short to the lands.

#5 2400 was just too fast even with 12gr of the stuff behind a 220 SMK the bolt would not lock back. Powders in the H-110 range are the cut off point in my gun. W-296 was close to working every time. H4227 may be the perfect powder ????? I haven't tried it yet but if the powder burn rate charts are correct it may be so. for me AA-1680 is the way to go.

#6 None of my brass showed any pressure problems. but 13.7 gr of H-110 behind a 175 gr bullet was as hot as I got. That was 1500 fps in my gun. I'm using cut down Remington UMC .223 brass cut down and reformed.

#7 both lowers were DPMS one with an A2 stock and the other with a TAPCO adjustable stock


Temps from 76 to 91 degrees , Sunny to overcast.

I hope this helps ... I feel your pain.

ditto on the magpul mags. i forgot those are the only ones that worked for mine too.

Thought about pulling some of the weights out of the buffer, just haven't done it yet. I was kinda hesitant to cut some coils off the spring though... What the hell, I'll try it.

I've got a pile of PMags.

Video
 

http://home.comcast.net/~kdiver/whisperSTEEL.wmv


175gr SMK over 13.3 Grains of H-110 as you can see that cycled every time but did not lock the bolt back on the last round..


What loads are you shooting ????

Good luck ...

.
Reduced power recoil spring from wolff
fixed my short and the bolt is held back on the last round.
.

http://www.gunsprings.com/1ndex.html

Glad you got it working. I too was sold on magpul mags, but twice now, a couple days apart with different bullets and lengths I've had a couple misfeeds, the bullets tipped too far down and didn't quite get the feed ramps, this is with standard feed ramps(not M4). 2.150" and 2.225" OAL with 125TNT and 160gr bullets.


Jon

I ended up taking apart one of my JP low mass buffers and weighing it (about 85 grams) and then taking a stock rifle length buffer and pulling the weights out of it. Found a long section of aluminum rod at a hardware store and cut a piece to fit in the gutted buffer. Came out to within one gram. I'll try it out next time I have the whisper at the range.


Ordered some sierra 220's also to replace the hornady 208's, and I'm gonna try AA1680 instead of H110. Keep watching this thread for updates.

Looking for a recipe for a with Sierra 220's and AA1680 now... Any suggestions?