JT's Matrix Build

[washguy]

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. 

you are right...just jacking with the sales guy 

We didnt need the physics of gas porting in relationship to barrel building......just an answer about JT's barrel and its specific gas port problem

instead we get a sentence like this....."Did you know if the changes by .001" it will change your gas port size by .010"?!?  Did you know changing your twist can change your gas port size .004"?!?  There is so much to gas porting and thinking what works for one barrel will work for the other, may work in some situations, but not gun barrels.".........but not gun barrels?  HUH?    then all the crap that gas port dimensions are super secret.....sure      Wash

[blue109]

Don't worry wash, I got your joke ;)

 

Hope we didn't chase them off with two posts. That might be a record! If he just nutted up and said "yea, we didn't take into account the fast pressure drop of that configuration, and will reconsider our port size" They would get a high five, and a better product to boot. Shame when pride gets in the way of progress. 

Edited September 20, 2015 by blue109

[washguy]

Don't worry wash...,I got your joke ;)

Whew    I was worried bout that      Wash

[jtallen83]

GOT IT! No short strokes ejected everything I fed it, all the previously mentioned ammo plus 168gr FGMM, Fiocchi 175gr match, and Winchester 180 gr power point. I went to the .1005 port size, that stopped the short stroking with the remanufactured stuff but was still leaving most of the ZQI sitting on the mag:(

I gave it a sprinkle of Armalite love with an extractor spring and the issue was solved. The ZQI still doesn't eject with the authority of the the MK319 but it reliably made it off the bench. 9 different types of ammo in 100 rounds and no issue. Last 20 were a mag full of Radway Green as fast as I could get on target, no issue. Now I have to find a box of the "still case" ammo and see if the rifle runs with it.

I appreciate all the support here, without you guys it would have taken much more time and money to get where I am, if I got here at all! Thank You All!

[unforgiven]

Congrats brother,way to go..

[jtallen83]

    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 . 

I used my calipers for getting the numbers, the drill bits didn't come close to hitting the sizes they should have been. I checked the calipers on a 1 inch gauge I have in a micrometer set, it isn't right every time but most often it is. Sometimes it would be +/- .0005.

I for sure had an extractor spring issue that was fixed with the Armalite spring but I'm pretty sure I needed the extra gas as well. The remanufactured stuff would short stroke every few rounds and the ZQI still doesn't eject with the authority I'd like to see but the other types and M80 ball stuff is fine.

Still not sure I understand why the MK319 started functioning fine when it did, bad spring and all??????

[98Z5V]

GOT IT! No short strokes ejected everything I fed it, all the previously mentioned ammo plus 168gr FGMM, Fiocchi 175gr match, and Winchester 180 gr power point. I went to the .1005 port size, that stopped the short stroking with the remanufactured stuff but was still leaving most of the ZQI sitting on the mag:(

I gave it a sprinkle of Armalite love with an extractor spring and the issue was solved. The ZQI still doesn't eject with the authority of the the MK319 but it reliably made it off the bench. 9 different types of ammo in 100 rounds and no issue. Last 20 were a mag full of Radway Green as fast as I could get on target, no issue. Now I have to find a box of the "still case" ammo and see if the rifle runs with it.

I appreciate all the support here, without you guys it would have taken much more time and money to get where I am, if I got here at all! Thank You All!

Hell. Yes. 

Glad she's running.  Glad you didn't have to send it back to get it solved, too. 

[jtallen83]

I neglected to shoot any groups for accuracy but even with the wide variety of ammo a center hold on 5 inch steel at 100 yards gave me 90 hits out of the 100, lots of just catching the edge but under the circumstances I'll take it.

As soon as I restock the match ammo supply I'll get a 100 yard 2 round group pictured for Breastroker and a 20 rounder for the rest of you!;)

Edited September 20, 2015 by jtallen83

[washguy]

Woot    way to go JT .....        Wash

[Malig8r]

Congratulations JT!!! Glad to hear she's up & running. You're right, sure are a lot of old 308 sages around here that are willing to help out. Makes this site pretty great!

[survivalshop]

  Good job , JT .          Its hard to concentrate on shooting groups when having malfunctions . Takes your mind out of it . 

Edited September 21, 2015 by survivalshop

[shepp]

I neglected to shoot any groups for accuracy but even with the wide variety of ammo a center hold on 5 inch steel at 100 yards gave me 90 hits out of the 100, lots of just catching the edge but under the circumstances I'll take it.

As soon as I restock the match ammo supply I'll get a 100 yard 2 round group pictured for Breastroker and a 20 rounder for the rest of you!;)

accuracy will come later you got the most pressing issue solved, good job!!

 

i was reading thru the past days posts here and wondered if you went to big could you used an adjustable block, think wash ended up answering that with a yes, I'm  not as dumb as I thought lol!

[jtallen83]

I'm anxious to see if the Wolf ammo will function, as soft as the ZQI cases come out I don't think I'm heavy on the gas but I guess this could change as I get more rounds in. I'd have to go back and add them up again but I think I'm near 200 rounds so it should be pretty settled in now. I won't drive the final pin in the G block till I'm 100% sure it will not need to come off till the barrel needs changed, then I'll be bugging Tom for those "hand drill" installation instructions that Geissele says won't work;)

The wife just put in an order for a 5.56 build for her. She has arthritis real bad in her hands  so I'll be looking for soft shooting and large, easy to manipulate controls, but that will be a while and another thread............

[Rsquared]

Out-Fucking-Standing JT! Glad to hear you've got her running.

[unforgiven]

Great job brother Jt.

[jtallen83]

Did some ammo function tests and checked some for accuracy today, all at 100 yards. Ran 20 rounds each of Perfecta 147 gr. FMJ, "still" case COLT 168 gr. FMJBT,Federal XM80, and a 3 rounds of Freedom Munitions 175 gr match( I'll save the explanation of why only 3 rounds for the end.)

Here is 20 rounds of Perfecta, started with a cold bore and shot them as fast as I could get back on target, as the barrel heated it opened up but still managed just a hair over 2 MOA;

The Colt functioned fine but the group was not worth a picture.

XM80 held just under 2 MOA on a 10 shot string at a brisk pace, missed 2 out of the remaining 10 on the dueling tree, again at a brisk pace.

I ran into issues with the Freedom remanufactured 175 gr. match. The first round keyholed on the target and did not extract. I sent the bolt back home after removing the magazine and had to mortar the rifle to get the case out. Next round hit good and extracted but the third round failed to extract and mortaring it took off enough rim that I had to call it a day and use the wood dowel at home. It popped right out with just a whack from my palm. I noticed that beside both issues coming from Freedom remanufactured stuff both cases were head stamped TAA 06 with the NATO cross. I thought the NATO stamp would mean it was good to go even being Taiwan stuff but when I compare the rim thickness with all the other brass I have the only other type with as thin a rim is POF stuff and it still functioned so I think the brass may be softer on the TAA cases. For now I'm going to chalk the issue up to junk remanufactured ammo, I have noticed that this last batch was not up to the usual standard for accuracy in my AR-10 but I have never had a keyhole before on any ammo?????

I'm also seeing the same odd look on the primer I pictured early in the thread, a crater look but no flattening. I'm betting the firing pin hole is a touch oversized. Is this something to concern myself with?????

When I get some more quality match stuff I'll try some 5 shot groups with time to cool in between and see what the barrel will do then, so far though I'd call it a 2 MOA barrel.

[blue109]

Friends  don't let friends shoot reman. 

[washguy]

Friends  don't let friends shoot reman. 

No crap!   shame on you JT                 all the hard work gettin your piece workin...and you're shootin crap ammo       Wash

[jtallen83]

Now my Armalite has eaten everything I fed it without issue, I never used more than a box of any of the crap steel stuff but always want to know if it will work in any weapon I have. I used to have good results with Freedom but this last batch has been problems. Guess I'll wait for the times they have new Fiocchi or Igman to do my brass trading with them from here on, the last 100 rounds that I have of this batch will have to be run in the AR-10, Ethel does just fine with it.

That said any weapon I own will not be a picky bitch, if I say shoot it it better listen or hit the road, I want reliability above all else, there may be a time when I will not have a choice.

[blue109]

I'll shoot steel all day before I shoot reman. I feel the same way, and want my gun to be able to shoot junk, but I just don't trust that stuff. 

[jtallen83]

Freedom treated me right for last couple years, it was very accurate and always functioned fine, I had tried a box of HSM tracers but the cases all split at the neck so I never touched their stuff again. This last batch had some bullets with deformed tips and the great accuracy I'd seen went out the window, looks like I'm done with the remanufactured regardless now, and anything from Freedom Munitions for that matter. Sucks though cause I just don't have time for the reloading bench anymore.

[jtallen83]

I ran the 4+ boxes of Freedom Munitions 308 remanufactured 175 gr. match through a case gauge, 1 out of 5 were either proud of the gauge or fell in to far with the neck sticking out the other end. On one case the whole rim stood proud. Freedom has obviously lost their quality control standards. The keyhole still has me puzzled, never seen that in my life and I used to run some very hot to very mild handloads in my old bolt guns and shot plenty of rounds through pitted bores on old rifles. What the heck could cause this???? 175 gr HPBT through a 16 inch 1-10 twist should not have any issues.

[jtallen83]

Just realized I never posted any pictures of the rifle after completion, still need an extended mount for the Bushnell SMRS 1-6.5X scope that I have for it.

[MikedaddyH]

JT how much does the complete rig weigh ?

And no its not a BS question. I have one that is similar with a different buttstock.

[blue109]

Damn jt....that's a sexy beast. Love it.just need to collect on a few recent deals and I can order my barrel.