JT's Matrix Build

shepp · September 18, 2015

nevermind

Edited September 18, 2015 by shepp

Rsquared · September 18, 2015

Damn Wash, your spilling the beans on everyone....careful they may have to kill you;)

Nahh.......Wash is good. Afterall.....the "teams" are always ready on a moments notice............or already in place if on a defensive maneuver.

jtallen83 · September 19, 2015

Back on track here....

Got a notch cut in the buffer tube so it would go another turn. I cut deep enough, not on purpose, to get a second turn but then the carrier just hits the tube, I'm tempted to shave some from the top section of the extension tube so it clears. I have 75 cents in the tube so with that and the one turn added to the extension I have a strong 1/8th inch between the bolt face and the bolt catch when I pull it all the way back. It locks back when I hand cycle with a mag in it, but then it did that before. How does this sound? Any advice on shaving some to get another turn?

Got my bit set in, gas port is .0805 from measuring the #46 bit. that doesn't exactly fit the numbers on the bit size chart but the calipers and the bits are made in china so close is all I get.

If the rain goes away I'll test fire it in the morning as is and see if the extension depth was the issue before I start drilling and testing.

washguy · September 19, 2015

Im still thinkin undergassed.....what is the present port size..nevermind i see it above ....go bigger a lil Wash

Edited September 19, 2015 by washguy

98Z5V · September 19, 2015

Got my bit set in, gas port is .0805 from measuring the #46 bit.

On a rifle-gas 16" .308 barrel?!!? That's too damn small. That needs to go up to about 0.100" to cycle.

Shiit, I just gave away proprietary information.

jtallen83 · September 19, 2015

No love yet......I've made it to .0915 on the port size. Fired 10 rounds, the first shot there left the case in the chamber but all the rest pulled them out but only had varying degrees of ejection with none making it out of the rifle. One left the case laying on the mag with the carrier instead of the bolt being grabbed by the catch or the mag, pretty sure it was on the catch but the bolt went forward when I dropped the mag. sorry again for the crappy cell pictures.

Here is what the port looks like after the test;

I took 25 cents out then thinking the bolt may need more travel, I noticed some anodizing rubbed off on the lower just in front of the buffer that I didn't see before but it didn't get any worse after the last few rounds, I might have done it putting the buffer in and out???

Think I'll put the 25 cents back and drill a couple sizes bigger.

Am I missing anything?

Edited September 19, 2015 by jtallen83

washguy · September 19, 2015

almost there go bigger keep it lubed......what ammo? one cartridge at a time for lock back function ...be sure your gas block is lined up good

Wash

Edited September 19, 2015 by washguy

blue109 · September 19, 2015

almost there go bigger keep it lubed......
Wash

that's what she said....

washguy · September 19, 2015

that's what she said....

Always Brother ! JT here's the super secret gas port diameter thread from here a while back Wash

http://forum.308ar.com/topic/8090-i-have-a-new-ar10t-that-is-short-cycling-and/?page=2

jtallen83 · September 19, 2015

Progress! My gas port is now .955 on my chinese calipers. I ran 20 rounds of cheap ZQI with about a 75% success rate. It was short stroking some like this;

Raising hell with the finish on the front of the port......it is locking back on the bolt catch like it should on the last round but it leaves the brass sitting on the mag like this with the ZQI;

I ran 5 rounds of the Freedom Munitions reman. 175 gr match, no issues, bolt locked back with no brass in sight. Ran 5 rounds of the MK319 130 gr. same thing, no issues. Even with the cheap and varied ammo I hit 25 of 30 on the 100 yard 5 inch steel circles.

No new marks on the receiver by the buffer, I stuck with the 50 cents.

Do I bump it out a couple more sizes on the port or shoot some more to see if it breaks in? I'm thinking maybe .0975 on the port? I don't want to go any further than I need to as it shoots pretty mild right now but want the reliability 100%

blue109 · September 19, 2015

Be careful posting those port sizes...don't want any industry types learning your secrets

washguy · September 19, 2015

"I'm thinking maybe .0975 on the port".....go for it.... shooosh...dont tell anyone.....x- caliber team surrounded my home this am....Char beat em back .... x- caliber phone/forum/fleabay sales guy didnt even need that...she just bitch slapped him but if its locking back on last round and still leaves the brass right there sometimes...needs a lil goose in gas or also its still tight on the ejector/extractor? How many rounds shot now?

Wash

Edited September 19, 2015 by washguy

jtallen83 · September 19, 2015

80 rounds so far, back to the drill then the range again..................

washguy · September 19, 2015

80 rounds so far, back to the drill then the range again..................

You're gonna be golden this time Wash

Edited September 19, 2015 by washguy

survivalshop · September 19, 2015

Wooooooow , Those look like the same extracting & Ejection problems I was Having with the Wilson Bolt . It would lock the Bolt back like it should on last round & the open case would be laying on top of the mag follower .

First change the Ejector spring , I did & it cleared right up . Did you get a battery for your Digital Calipers ? , Measure the Ejector spring length & look at my Bolt thread for photo's of my issues .

jtallen83 · September 20, 2015

Wooooooow , Those look like the same extracting & Ejection problems I was Having with the Wilson Bolt . It would lock the Bolt back like it should on last round & the open case would be laying on top of the mag follower .
First change the Ejector spring , I did & it cleared right up . Did you get a battery for your Digital Calipers ? , Measure the Ejector spring length & look at my Bolt thread for photo's of my issues .

I did get the calipers up and running so I'll try to get comparisons for your measurements.....been busy drilling and shooting.

jtallen83 · September 20, 2015

Drilled the port to .0975 and ran 20 rounds. Interesting results when I compare things to SS's thread on the face it would seem to be the same extractor issue. 10 rounds of ZQI, 8 stayed on top the mag, 2 just dribbled out onto the bench. 5 rounds of Freedom reman. 175 gr. Match, 1 short stroke, 2 laying on the mag and 2 made it off the bench. Here is the interesting string, MK 319 130 gr. penetrator round, all 5 ejected strongly, banging off the wall at 3 O'clock from the rifle, and then hitting me in the face. I knew this stuff felt a little hotter in my other rifles but there was a real dramatic difference today. These MK 319's are specifically designed for short barrel rifles, that combined with the lighter bullet and I would have thought the pressure would have been less but obviously I thought wrong.

If it is the extractor/ejector issue then why would the MK319 function so well? The Freedom reman. stuff is all in LC cases so there shouldn't be any or much difference in the case

The next bit size up I have measures .0985 then after that it hits .1005. I'm going to at least give the next size up a try. I'll also bring more of a variety of M80 ball stuff, FN, Radway, Indian from 1974 I think???? and some Pakistani stuff that seems pretty hot.

So close but yet so far...........

washguy · September 20, 2015

JT you are close,but you prolly got Survival 's problemo also...check the spring....you're bout to cross the finish line brother Wash

jtallen83 · September 20, 2015

Posted up the bolt measurements in SS's d. wilson thread. I'm going to give a spare Armalite extractor spring a run in this bolt, it is longer and a good bit stiffer. My extractor hook measurements are way off his but then that could be the measuring tool. The fact that the MK 319 ran so well makes me think a bit more gas will be a big help. Fingers crossed for the range trip tomorrow!

washguy · September 20, 2015

Yeppers gas it up.....just a touch...remember it will affect your twist rate though

Wash

98Z5V · September 20, 2015

The next bit size up I have measures .0985 then after that it hits .1005.

Skip the 0.0985" and just hit the 0.1005", brother. It'll run all the stuff you're shooting, then. Go right to it.

98Z5V · September 20, 2015

Clint at Fulton designed this config a long time ago - LONG time ago. Criterion made his barrels for it. He dropped that barrel config, and Criterion as since released a version again. Between those two companies, they know what's up. And their port diameter was above 0.100"...

survivalshop · September 20, 2015

98 is correct , but do you have a precise measuring tooling to say your hole is what the dill size is ? If you get my meaning , it could be larger than you think already & I had the same Ejection issue & did nothing to my Gas Port size & just changed a spring & it fixed the issue . If I had my choice of drilling the gas port or changing the spring , well , the spring can be changed back to what was in there .

The high pressure ammo may be a clue or it really is HP for your set up & slamming the BCG back hard & that slamming would Extract or throw any case out of the rifle . Just think , if you go to big on the gas port , you can always use an Adj. Gas Block & with the Gas tube ID, you can only get so much gas Volume & pressure through it .

blue109 · September 20, 2015

Yea...I'd probably stop with the drilling and make sure the bolt is working right. Hate troubleshooting several issues at once, but if it's locking back empty you are close.

Edited September 20, 2015 by blue109

DNP · September 20, 2015

To be fair Wash, he essentially said changing the twist rate will change the pressure and require a different gas port. Not that the gas port changes the twist rate. I guess the theory is a tighter twist causes more friction equating to a slightly slower moving projectile and allowing more dwell time? Not sure I buy it, but that's all I can figure for how it would affect it. You'll see bigger velocity differences in your loads than you would from the twist rate I would imagine. That might be a nice comparison test though. Same load through different twist rates ...checking velocities. Lighter loads are going to need a bigger port, hot loads may be fine where you're at. You'll have to decide what you want to feed it. The hot loads may be a little harsher on the system, but at least it'll eat the light stuff.