AR disease strikes again

[stagpanther]

Seems like it's pretty common to see the range of bullets used as being from .355 to .357, and the occasional foray into .358. SAAMI chamber specs indicate a bore of .346 and groove of .355, I'm kind of interested what the implications on case flow might be since presumably you need to crimp the mouth which is also what the case headspaces off of.

I also have noticed some posts indicating people are using 9mm muzzle devices--shaw itself warns to use a 40 caliber device which makes sense to me.

[P Flados]

Stag,

Ok now you touched on a nugget that Winchester has really fouled up.

Yes it headspaces on the mouth.

Yes the brass must be the correct length.

Yes any crimp needs to be minimal.

Winchester has shipped a lot of target ammo with both under length and over length brass.

Under length brass can result in a FTF.

Over length brass causes the case to jam into the throat and hold onto the bullet instead of releasing it. Lots of flattened primers, split cases, etc.

With Winchester ammo, some are measuring case length on each new round. Any over length case is set aside, disassembled, trimmed and reassembled.

For my 357AR, I set my seating die for flare removal without really trying to crimp at all.

Early on you should probably make up some dummy rounds using once fired brass. If the bullets are easy to seat in the cases, they may be less secure than needed. If so, cycle the heck out of the dummies while checking the round for any change in OAL. Do this for each brand of brass you use and the smallest bullet diameter you will be using.

If you need to crimp, keep it to the least amount needed.

[stagpanther]

Early on you should probably make up some dummy rounds using once fired brass. If the bullets are easy to seat in the cases, they may be less secure than needed. If so, cycle the heck out of the dummies while checking the round for any change in OAL. Do this for each brand of brass you use and the smallest bullet diameter you will be using.

If you need to crimp, keep it to the least amount needed.

Good advice, thanks for that.

[FrankenMauser]

I have been using cast in my guns. I actually do not have a 350 L, I have a 357AR (350 L with slightly shorter brass, 0.358 bore and uses 0.223 brass) and bunch of 357 Max.

That's the problem. You know what you have.
The .350 Legend guys generally don't. At best, they're leaning on SAAMI specs. (As is evident in the discussion link I posted.)

.350 Legend is loaded by Winchester with .355 bullets, which most people assume to be groove diameter.
But it isn't the case. People that have slugged their barrels have found .354-.359" groove diameters.

To make matters worse for cast bullet shooters, even properly made barrels, that actually meet SAAMI spec, have throats that taper from up to 0.359" to as small as 0.353". (Because the cartridge is supposed to take .357" bullets in the throat, but is spec'd for a .355" groove diameter, with +/-0.002" tolerance.)
So, even in most "proper" barrels, there will be blow-by with a .357" bullet, until it fully seals in the throat/leade. ...And the guys that size to .356" or .355" will just make things worse.

[mehavey]

How many folks in this discussion thread speak from actually having a 350 Legend ?

[stagpanther]

I definitely value everyone's experience and opinions--that's why I solicit it when dipping my toes in something new to me. My previous straight wall case experience in AR's has been dealing with pistol cartridge carbines, and I certainly learned a lot from those--like P Flados says I get best results when I can seat a bullet with enough neck/case tension so that I don't need to crimp or minimally crimp if at all possible yet maintain headspace. However, the legend runs close to the same pressures as the 223 rem and is a DI lock-lug system, so it's potentially "sportier" as to the consequences when something goes sideways. Despite all the criticism blow-backs get, they do dump and dissipate their lower pressures almost immediately in the upper receiver once the carrier starts back.

The biggest question I have in my mind now--where's the load data?

[stagpanther]

More thoughts I'm just throwing out into cyberspace: it appears that Winnie decided to make the legend "backward compatible" to accommodate conventional 9mm bullets, for which I've read posts of criticism directed at them. I'm not so sure that's a bad idea rather than expecting the market to genuflect to some new bullet spec that's so close to the 355 that they probably are not going to do it IMO. I've dabbled in the 9 x 25 Dillon for quite some time and have driven 9mm bullets up to nearly 3000 fps out of a Glock--the 9mm bullet can potentially be delivered with very good velocity and energy, as well as accuracy out to 100 yds and beyond but obviously the shooter needs to know when that bullet goes over the cliff performance-wise since it will bleed velocity and energy very quickly after a certain point. That said, most 9mm bullets are not designed to stabilize and stay together at those velocities.

[stagpanther]

Just noticed that Hornady's 170 gr interlock popped back into available at midway and jumped on 4 boxes of those.

[P Flados]

Originally Posted by stagpanther

The biggest question I have in my mind now--where's the load data?

There is data at:

http://www.hodgdonreloading.com/data/rifle

[stagpanther]

I missed it first glance--thanks!

[stagpanther]

Kudos to Joebob's--they got my parts to me yesterday before anyone else has even notified they are ready to ship. Shipping of orders has appeared to ground to a halt from about 3/4 of the orders I made--but this is SOP I've noticed over the years for this time of year. I expect the build to be complete sometime mid-January at this rate.

[stagpanther]

Stupid is as stupid does--I just called EAB to ask about the barrel, it was listed on their site as "in stock, ships Dec 6!" when I ordered it--I just found out what that ACTUALLY means is Shaw has them and will be shipping them to EAB on the 6th.

[brasscollector]

Pretty sure that's going 1000 miles in the wrong direction...

[stagpanther]

Pretty sure that's going 1000 miles in the wrong direction...
__________________
He may look dumb, but that's just a disguise.
-Charlie Daniels

OMG! That's right, thanks for reminding me about what happened last year. The shortest direction between two shipping points in the US is the opposite direction of a straight line connecting them.

[44caliberkid]

Can Shaw tell you what groove diameter they are using?

[stagpanther]

Can Shaw tell you what groove diameter they are using?

It's on their website, I believe. I'm not worried about it as long as they can say they are within SAAMI specs. I will do a cast of the chamber and the leade before I asemble.

[stagpanther]

Since EAB didn't have the barrel or magazine in stock--I decided to cancel the order and go with a Faxon barrel instead. The Faxon is a lighter contour--and is also 20" instead of 18". Never tried Faxon before--kinda curious how they are. Interestingly, it too has a carbine gas system. The Faxon barrel also has an oddball thread pitch--1/2 x 28--so it took me a while to find a suitable comp--ended up selecting a .375 comp from Rex Silentium with a thread adaptor to fit the barrel muzzle.

[stagpanther]

I just had a conversation with a very well-respected manufacturer of custom rifles who just finished a 350 legend project for a client (semi-auto)--he gave me head's up to watch out for the headspace specs which apparently (if I understood him correctly), following winchester's specs, have a max beyond what one would normally would expect to find in an AR. I'm starting to get concerned, I'm already baffled by the seeming lack of standards in the chamber and bore reamer dimensions--getting the "224 valkyrie deja vue all over again feeling."

[9x19]

Yep, more of those interest-stopping details that I ran into.

[mehavey]

"...watch out for the headspace specs which apparently (if I understood him correctly), following
Winchester's specs, have a max way beyond what one would normally would expect to find in an AR."

I'm a little confused there.
Is he saying people are reaming significantly deeper than 1.710" case mouth stop?

[stagpanther]

I'm a little confused there.
Is he saying people are reaming significantly deeper than 1.710" case mouth stop?

What I understood is that between the chamber's headspace datum (mouth) and the face of the bolt the specs allow for headspace that is in excess of what you might typically find for a bottleneck AR cartridge (I don't recall any DI AR build I've ever done exceeding .005 to .006 without a no-go gauge closing). I've heard that there are several different reamers "out in the wild" so that (my interpretation) could possibly be a contributing factor; I ran into a similar variations issue (unrelated to headspace) when I jumped on the 224 valkyrie bandwagon early on in that there was some variation in the reamers manufacturers were using which made it difficult to sort out "what's what."

[mehavey]

There's a 10-thou tolerance on the case length (1.700 - 1.710), and the same on chamber headspace (1.710- 1.720)
Interestingly, the 45 ACP case has 10-thou on the case, 20-thou in the chamber; similar for the 9mm

[stagpanther]

There's a 10-thou tolerance on the case length (1.700 - 1.710), and the same on chamber headspace (1.710- 1.720)
Interestingly, the 45 ACP case has 10-thou on the case, 20-thou in the chamber; similar for the 9mm

Exactly--point being that that much potential headspace in a higher-pressure locking bolt semi-auto set-up is beyond what I've ever encountered, and why I was told to watch it closely. Keep in mind I'm not "pulling the alarm" until my components get here and I've had a chance to measure everything.

[mehavey]

As long as the bolt closes leaving within-spec base/web containment, the straightwall case length/headspace has minimal effect.

Watching case length is therefore important -- though I've seen little/none over about 300 (first-time) firings.

So far.....

[stagpanther]

As long as the bolt closes leaving within-spec base/web containment, the straightwall case length/headspace has minimal effect.

One hopes so-- Could introduce other nags like how well extractor works for cycling.