6.5 grendel 180?
- Thread starter Bman12456
- Start date
well, i'm enroute to becoming another date point. i've got an rwa 7.62x39 upper (stuck w mid-length gas system and their bolt i think) so ordered an ibi 6.5g hb 8 twist barrel at 0.125" and mid-length gas. intent is to burn cheap 7.62x39 and just swap barrels to go hunting with the 6.5g. i'll report back after everything shows up, weather warms up, and i can get a few rounds downrange. ps, i've been working with jerry at mystic precision to get the barrel and he's been excellent to work with as i've modified my order several times ...
I just wish TNA would do some kind of surface treatment on their 0.136" bolt instead of leaving bare metal... Just a thought but if you were to do a custom barrel (like an IBI) to put on a MCR, would there be any advantage to going to a mid or rifle length gas system if you were going to use an adjustable GB anyways? The recoil impulse (on the .223 carbine length barrels) is mild as is and you could further tune it down with the adjustable GB, so as to be easier on the rifle. Is there an advantage to mid and rifle length systems in an AR-180 that I'm missing (that isn't about compatibility with off the shelf barrels)?
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i think there are pros and cons. longer gas systems make for smoother action, and also keep the gas in the barrel for max propulsion of the bullet. a shorter system might make the recoil a little more pronounced but, as you state, the the recoil on the carbine-length wk/mcr is no biggie and can be managed with an adjustable gas block. i think the bigger issue is that there is a lot of wasted barrel at 18.6 inches with the gas port bleeding off energy 10" further back.
so, if building a distance/hunting rifle, a carbine gas system might be handicapping you. on the other hand, since we are constrained (currently) to piston guns, what kind of deflection is a 12" reciprocating rod putting on the barrel with each shot, impacting accuracy? and is it like a pistol where all that moving mass above the bore axis will introduce a bit of flip and and slow-down follow-ups? no idea really. now that i've determined that i'm stuck with a mid-length piston i've reduced my barrel order from 20" to 18.6".
so, if building a distance/hunting rifle, a carbine gas system might be handicapping you. on the other hand, since we are constrained (currently) to piston guns, what kind of deflection is a 12" reciprocating rod putting on the barrel with each shot, impacting accuracy? and is it like a pistol where all that moving mass above the bore axis will introduce a bit of flip and and slow-down follow-ups? no idea really. now that i've determined that i'm stuck with a mid-length piston i've reduced my barrel order from 20" to 18.6".
I wonder how many FPS you'd lose running a carbine length gas port vs mid or rifle? I definitely wonder if the longer piston would negatively affect accuracy. I expected these AR-180 variants to be markedly less accurate than an equivalent AR (because of the piston) and have been pleasantly surprised by that not at all being the case. I wonder if that's attributable to the shorter piston length?
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thanks. i found a used one (for around 50% less than the rwa upper currently on the ee ...). otherwise rwa will sell you whatever they have left (handguards mostly) but out of the business otherwise i think. an interesting rifle; gas system is much closer to the bore axis than a wk/mcr to the point where i wonder if it was appropriated from an ar in some manner, except the piston is a multi-part affair that i've not seen elsewhere. and the barrel is actually fixed in place by a plate instead of a barrel nut. the four #8-32 fasteners than hold the plate in place were a little chewed up (i don't think the receiver had been threaded all the way) so i cleaned up the threads and ordered new fasteners and hopefully it all holds together when required to.
i'll update on my build when i can make it go bang. i'd love to do some velocity testing, but the only guy i know with a chronometer is a bit of a choad (choat? chote? the vernacular is confusing) and my need to know that info is outweighed by his unpleasantness ...
That's insulting to toasters tbh
.330Dakota
CGN Regular
- Location
- Northeastern ON
Any updates?
islandhunter
CGN Regular
- Location
- princeton b.c.
I just finished up a grendel build
Sbi lynx with yugo stock , velocity trigger ( nice!)
Steel upper with tna bolt
20" odin barrel with tna rifle length setup
I just fired some quick tests outback and had good function with grendel mags. 10 round 7.62 pistol mags seemed hopeless. Ive loaded up some rounds to check for accuracy, will report back once Ive shot em.
The gun is a very soft shooter! Surprisingly only gained about 60 fps over my 16" grendels
Sbi lynx with yugo stock , velocity trigger ( nice!)
Steel upper with tna bolt
20" odin barrel with tna rifle length setup
I just fired some quick tests outback and had good function with grendel mags. 10 round 7.62 pistol mags seemed hopeless. Ive loaded up some rounds to check for accuracy, will report back once Ive shot em.
The gun is a very soft shooter! Surprisingly only gained about 60 fps over my 16" grendels
Nice! You may want to try the pistol magazines with less rounds; the spring tension of the fully loaded magazine could be causing feed problems. Is that the Kodiak Steel WK upper? If so, that's cool, since the first gen pop-in charging handle didn't fly out the same way the screw in one does, but it won't be able to gouge the steel charging handle track either. Are you planning on trying a Lynx upper later?
islandhunter
CGN Regular
- Location
- princeton b.c.
I will try loading a few less rounds, also I swapped in a blue 6.5g follower from a 5/10 grendel mag so hopefully that works. Yes its a steel kodiak upper, I couldnt wait for the lynx ��
the lynx lower is picky about mags. i built an x39 180 with an RWA upper and Lynx lower (the precursor to my 6.5G build, if my barrel ever shows up). i had two types of C-Products Defence (CPD) XCR x39 10-round pistol mags; early ones, and later ones labeled 'Duramag'. The early ones are just a smidge shorter and rock slightly in the magwell and don't feed worth a damn; the Duramag version feed fine. so your issue might not be 6.5G in x39 mags, but rather lower/mag compatibility.
islandhunter
CGN Regular
- Location
- princeton b.c.
Turns out the lower is being fussy with mags. Im unable to seat my cpd mags. loaded with the bolt closed. I have an elander 17 round 6.5g that will work.
I am having some feeding troubles even on loading the first round. It looks like the ejector pin is a bit too long and not allowing the case head into the bolt upon feeding. Going to sand it down like 1/32" or so, then try er out.
I am having some feeding troubles even on loading the first round. It looks like the ejector pin is a bit too long and not allowing the case head into the bolt upon feeding. Going to sand it down like 1/32" or so, then try er out.
islandhunter
CGN Regular
- Location
- princeton b.c.
I filed about .025" off the back end of the quare part of the mag catch that fits into the hole in the mag. Now Im able to fit the 10 rounder in loaded on a closed bolt.
Also, shortening the ejector .025" seems to have fixed the feeding issues. Im outta time for today but will load a bunch more up and give er a good test when I can.
i went mid myself. my thinking is that you are getting grendel for accuracy and hunting out to medium ranges. longer ranges you'll get a bolt gun. so, not a lot of benefit having a rifle-length system (ie, keeping as much gas as possible behind the bullet for more power at long range). also, with a piston system you'll see more opportunity for the piston to deflect the barrel when working (vs gas) so you want a heavy profile to the gas port (look what happened to the r18 when they put a pencil barrel on theirs - it flexed so much it was hitting the handguard). a heavy barrel out to rifle length is ... heavy. i thought mid a good compromise as carbine would make the action too violent (even if you can control the gas there is the concept of 'dwell' - how LONG before the system actions - mid gives a bit more time).
