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Posted: 4/18/2019 7:00:50 AM EST
12.5" KAK bbl. Factory Win 145gr FMJ, ejection is 4 o'clock at 8'
Recoil a bit more than 5.56, less than 7.62x39.

Just threw the PA red dot on there till I figure out what optic I want. 1-8 or 1-6, not sure yet.
KAK can on it because the 12" Larue rail I ordered turned out to be too long, going with a 10" I think.
Only problem so far is it will not reliably extract a live round, extractor slips over case lip. Needs a extractor donut upgrade. Older hard chrome Aim Surplus BCG
350 Legend recoil is mild.

350 Legend pistol 12.5"


Magpul 10rd, remove inner shoulder ribs, load to full capacity, feeds fine.
If you do not want to mod a poly mag you can get three rounds to feed from a 7.62x39 5rd or 10rd mag
Link Posted: 4/18/2019 8:36:44 AM EST
If the bolt is retracting too fast and the extractor is slipping - think about it - the brass hasn't relaxed from the chamber wall and is getting dragged out too early. If the brass isn't pushing the bolt face the unlock timing is too early.

Timing and gas pressure.

Harder brass isn't always an option so adjustable gas and a heavier buffer are often preferred.

And yah, the leftover parts of a previous build are sitting in the box sending telepathic messages . . . BRD is setting in again . . . they warned me this would happen. . .

Is there no cure?
Link Posted: 4/18/2019 8:54:51 AM EST
The extractor hook may not be far enough forward, or you have excessive head space.  It works when you fire it, because the case backs up a hair and the extractor can then snap over the rim.

Don't forget, that's a straight wall case with a .010" tolerance range between the Go and No-Go Gauges.  The brass is probably .003" or so shorter than the Go-Gauge, so if KAK has the chamber cut at the deep end of the range,
you've got quite a bit of head space there.  All that space means the extractor hook must be positioned accordingly.  The head space range should have been more like .005", similar to the 450 Bushmaster.

If a barrel manufacturer is smart, they will use the standard Go-Gauge, but make their own No-Go gauge that is only .005" out.

We'll probably be seeing some light primer strikes with the 350 Legend as well.

I'm curious to see how long the fired and un-fired cases are.

You may not be aware, but the 450 Bushmaster had it's share of light primer strikes in the early days.  That was due to Bushmaster cutting the chambers too deep, coupled with Hornady making the brass a bit shorter than need be.  They later lengthened the brass a hair.

Tony
Link Posted: 4/18/2019 10:00:34 AM EST
Tag for comments, interesting build.
Link Posted: 4/18/2019 10:55:15 AM EST
Attachment Attached File


Shows primer hit

Attachment Attached File

^ Did not measure before firing^
A single unfired round measures "1.7025.
Link Posted: 4/18/2019 11:02:07 AM EST
Very cool. But where did you get the Ammo?
Link Posted: 4/18/2019 11:15:16 AM EST
With a case length of 1.7025, if the chamber is cut to the minimum depth you'll have about 8 thousands head space.  If it's at the max in-spec depth, you'll have about 17 thousands head space.

You would need quite a bit of extractor reach to grab the rim if it's sitting 17 thousands off the bolt face.

It would have been nice if Winchester had made the brass a bit longer.

Tony
Link Posted: 4/18/2019 11:27:24 AM EST
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Very cool. But where did you get the Ammo?
View Quote
https://www.sgammo.com/product/350-legend-ammo/200-round-case-350-legend-145-grain-fmj-winchester-ammo-usa3501
Link Posted: 4/18/2019 12:02:28 PM EST
Can you measure the bullet diameter, and the case diameter of a loaded round at the very top of the case.

Tony
Link Posted: 4/18/2019 12:13:44 PM EST
Tony

Would not the case fireform to the chamber length?

The pre-fired is 1.7025 and post-fired is 1.7020, doesn't add??
Link Posted: 4/18/2019 1:39:27 PM EST
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Can you measure the bullet diameter, and the case diameter of a loaded round at the very top of the case.

Tony
View Quote
Bullet
Attachment Attached File


Case
Attachment Attached File
Link Posted: 4/18/2019 2:48:41 PM EST
Seeing that the bullet measured .354" I wonder what your bore slugs?  I see Winchester shows on their website the bullet diameter is listed at .357".
Winchester 350 Legend
I have heard the correct bullet diameter is .355"?  Have you done any accuracy testing?
Link Posted: 4/18/2019 3:46:51 PM EST
Assuming the bullet is really .355, if you tried to shoot a .358 rifle bullet in that case, the diameter would end up .379".  The chamber reamer is .3789" at that point, so you could probably slam it into the chamber, but it would be difficult to extract by hand.

I've seen a lot of straight walled cases get shorter after the first firing, so the head space increases a bit with fired cases versus new.  If you're lucky, when you size it, it may grow a bit in length, but maybe not.

The case would fire-form to the chamber only if the side walls of the case stuck to the chamber and the case head backed up, thus stretching the case.  If the whole case slides back, it's not going to stretch the case.

Tony
Link Posted: 4/18/2019 4:05:10 PM EST
Donut and buna fairly worn. Got a refresh on the way. Attachment Attached File


Also no accuracy testing yet, just wanted to put a few down range to get the feel of the round. Chrono coming too.
Link Posted: 4/18/2019 4:27:42 PM EST
How 'bout a pic of the back side of the extractor?  Straight down from directly above.

Tony
Link Posted: 4/19/2019 5:41:52 AM EST
Link Posted: 4/19/2019 7:57:27 AM EST
See that shiny spot at the front of the extractor (top), that is where the back of the extractor was dragged across the barrel extension when you tried to manually extract a live round.  It did that, because the hook wasn't snapped over the rim of the case.

Tony
Link Posted: 4/19/2019 9:17:47 AM EST
You mean the clean spot, lol

I appreciate your forensic attention and input to this thread man. This bolt came out of a 16" 5.56 that I run a Hybrid on, that is why so dirty. Also the NiB really shows crud.

Have not talked to you in many years. I remember some conversation on assaultweb with you and one of my friends. '99 or '00
You were trying to figure out something case-wise about the not yet named 458 SOCOM
Have not checked on AW in many years.

Also, @tirod what are you doing hanging out in the fringe forums? We need some cover fire in the Saudi Purge thread man. Frickin_under_scores are running rampant. Dial up a rant tor two plz
Link Posted: 4/27/2019 8:43:40 AM EST
Switched the rail to a 10" Larue, fits better with the Mystic X
Attachment Attached File


Also swapped in a fresh ejector spring/buna/donut. Seems to have fixed unfired round extraction. Hoping to get in some trigger time today.
Link Posted: 4/27/2019 4:16:13 PM EST
Finally a few groups.
50yds, rested. 1-6 PA ACSS reticle. Nice glass actually.
145gr factory fmj, their intentional blaster ammo.
With Mystic X on it. Certainly minute of deer. Hand loads will tell more.

It's no threat to the benchrest community but it does shoot well enough to get game.

Love this round.

Attachment Attached File


Something weird happened and I had a case head separation. Shows high pressure indications.
Attachment Attached File
Attachment Attached File


Hammered that primer flat.
NIB BCG from Aim surplus
Link Posted: 4/27/2019 5:25:10 PM EST
I'd check your headspace.
Link Posted: 4/27/2019 6:54:53 PM EST
look at the case mouth of that failure.

definitely a headspace issue

ETA: please more pictures
Link Posted: 4/28/2019 7:24:36 AM EST
Discussion ForumsJump to Quoted PostQuote History
Quoted:
look at the case mouth of that failure.

definitely a headspace issue

ETA: please more pictures
View Quote
It looks crimped in in that pic but it measures 0.375 just like the rest of the spent ones.
Magnifying glass shows a slight ring line around the mouth.

The case failure was from the 2nd shot out of a 10rd mag. Barrel was clean before first shot. Found the head and went to my gun bench and picked out the case body with a dental pick. Went back out and fired the 8rds in the mag fine. Then fired the 4 five shot groups in the pic. Still have not found the first case fired.

Attachment Attached File

Attachment Attached File

Attachment Attached File

Attachment Attached File


The other 20 fired cases/primers all look normal.

@moleman Only place I can find with gauges is PTG @$37ea for GO or NOGO or FIELD. Ah, the joys of a new round
Link Posted: 4/28/2019 8:33:22 AM EST
Let's talk about these case mouths.

Attachment Attached File


Were they crimped?
Were they overly deburred?
Or were they too long in the chamber?
Link Posted: 4/28/2019 10:09:43 AM EST
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Let's talk about these case mouths.

https://www.ar15.com/media/mediaFiles/1147/cases2_jpg-927195.JPG

Were they crimped?
Were they overly deburred?
Or were they too long in the chamber?
View Quote
New factory ammo right out of the box.
Link Posted: 4/28/2019 10:18:33 AM EST
Not really the right answer.

From that picture it looks like brass was pinched down in the chamber because it was too long. I may be wrong.

Take a look at this picture below I found.



If there is an interference fit the case mouth will be crimped and unable to release the bullet creating extra high pressure.
Link Posted: 4/28/2019 10:54:31 AM EST
Looks like a light crimp on the new ammo. Attachment Attached File


I measured the ID of the failed case mouth at .0350-0.352. The other spent cases measure up to 0.355
Link Posted: 4/28/2019 11:57:19 AM EST
Great thread fellas!

This thread is relative to one of my ARs...the 45 Raptor.  Same style cartridge that is headspaced on the case mouth.

Here's my questions on ARs that have headspacing that is set off of the case mouth vs. what you see in a standard headspaced cartridge.

What are the biggest problems in regards to keeping these ARs running smoothly?

Headspacing is absolutely critical?  (as it should be) But with the case shrinkage/growth from firing and resizing it seems like we have to be super careful when reloading for these guns.

Bullet crimp tightness is extremely important? I only reload for my 45 Raptor, but with the availablilty of over the counter ammo for a 350 Legend or 45 Raptor, do we need to be putting the micrometer to every brand/style of ammo we use in these casemouth headspaced guns?

What are some of the other important factors we need to pay attention to when shooting these straight walled case mouth headspaced cartridges? Such as the 350 Legend and the 45 Raptor

Thanks
Link Posted: 4/28/2019 1:20:47 PM EST
After seeing the 2nd set of pics, I'd do a chamber cast first to see what the case mouth step to freebore is and measure the case head against a new and the other fired cases.  It almost looks like the case mouths are slipping up past the case mouth step in the chamber. If that's the case it could very well pass a headspace check. That would explain why your rifle wouldn't grab unfired cartidges and your case head separation where if it were solely from high pressure you'd expect more flow into the ejector hole and likely the primer would fall out.    Seen reports of similar looking case mouths where guys were using a heavy roll crimp into the cannelure on a 357AR instead of the recommended  gentle taper crimp not into the cannelure.  Can't seem to find the pic of that at the moment, but the case mouths looked to have a slightly thinner stepped thickness look to them from getting pinched against the case mouth step by the bullet as it passed by. Different causes, but same end result.

Cerrosafe is easy to melt and use.  I use a metal jig and a tight fitting patch to block the bore, and plumbers putty to block off the locking lugs and make a little funnel in the barrel extension down to the chamber.  You can use thin carboard trough to direct the McDonalds hot coffee temp metal into the chamber  so you don't need to take the upper off.  Roto metals has more than enough for $10  https://www.rotometals.com/chamber-casting-alloy-ingot/  Brownells, midway and other places will have it also.  If you get another case head separation it can be used to grab onto the case so it can be knocked out, melted and reused.

While I'd do the chamber cast first, do you have access to a lathe?  Straight wall case gauges are easy to make out of O1 or pin gauges but you need to be able to cut them perfectly square and to a precise length.
Link Posted: 4/28/2019 2:11:43 PM EST
Thanks everyone especially moleman, yeah I already have the entire set of gages coming from PTG will let you know what it does.
No problem pulling the bbl. Never used cerrosafe but knew of it.
Link Posted: 4/28/2019 8:35:41 PM EST
When you get the gauges, you need to check the length to make sure they are correct.  And make sure PTG didn't chamfer the front edge too much, or they will drop too deep.
And while you're at it, you better check the diameter of the gauges as well.
Link Posted: 4/28/2019 9:51:41 PM EST
Discussion ForumsJump to Quoted PostQuote History
Quoted:
I measured the ID of the failed case mouth at .0350-0.352. The other spent cases measure up to 0.355
View Quote
That's extra strange. There is no way the case mouth of a fired cartridge would be smaller than the diameter of the bullet it fired.
Link Posted: 4/29/2019 9:42:47 AM EST
Happy2shoot,

Except that it is smaller. The case failure it the other point of information.

It tells you that the cartridge did not headspace on the case mouth.
Link Posted: 5/3/2019 1:13:58 AM EST
interesting.

I know the KAK barrels are threaded to 5/8 instead of 1/2.

Does that seem to be better?

I can't quite comment on the possible short comings of the new cartridge.  Or the case seperation, case mouth damage. Maybe things are just a little too new at this point?
Link Posted: 5/3/2019 6:03:21 AM EST
My pic but edited by moleman [thanks]

Dosen't look good guys.

Anyway, some measurements.
Chamber mouth 0.3785"
Whatever the next thing is 0.3685" [a mini step? Help me moleman]
Leade 0.3565"

Attachment Attached File


Contacting KAK, will keep updating.
Link Posted: 5/3/2019 7:31:11 AM EST
The .3685" step shouldn't be there and is what is causing your issues.    My best guess after talking with a buddy who's a top notch machinist is that the rougher was fed in too far and left that shoulder.  I'd stop shooting it and send it back.
Link Posted: 5/4/2019 8:46:13 AM EST
Send the pictures to KAK, they should take care of you.

Yikes though, how did that even happen?

Would the reamer be cut improperly like that?
Link Posted: 5/4/2019 1:04:34 PM EST
That doesn't make me feel real great about my KAK barrel I just got.  Think I will start with the CMMG 16" first.

Actually I might get some cerrosafe before I put either together
Link Posted: 5/4/2019 3:07:52 PM EST
I got a GLFA 18 inch barrel last week. 40 rounds absolutely no issues. All brass looks good. Haven’t checked accuracy yet but functional test was 100%. I’m going to cancel my cmmg order.
Link Posted: 5/4/2019 8:23:38 PM EST
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Yikes though, how did that even happen?
View Quote
Did you read the post before yours?  The rougher was fed in too deep.

Tony
Link Posted: 5/5/2019 5:55:16 AM EST
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Send the pictures to KAK, they should take care of you.
...snip...
View Quote
President of KAK replied to my email, sent return label.
Link Posted: 5/7/2019 6:46:38 AM EST
A friend at work bought a 16" KAK 350L bbl same time I did. Told of my issues, decided to check his with a chamber cast, same problem. Identical dimensions too.

Attachment Attached File
Link Posted: 5/7/2019 11:45:28 AM EST
Ran too deep with boring bar on rough or if using a rouging reamer.  Either way, you figured it out.  Good for you on not assuming.
Link Posted: 5/7/2019 2:04:39 PM EST
One more thing.  My gauge numbers for my Manson 1.711" Go  1.7205" No,    PTG 1.711" Go   1.7142" No

SAAMI  350 LEG is 1.710"(min) - 1.720"(max).

With most "in  stock"  gauges ive used since '94 they have always have had a 0.0000" - +0.0010" on the Go.   The No is Max and this number has swayed a couple tenths to as much as -0.0040" short of SAAMI max with different manufactures.  You will typically find "field" at max SAAMI headspace for rimless cases with a shoulder.   Now all that said it depends on the gauge manufacture.  They have their own tolerances and ideas where they think certain gauges should be held too in the SAAMI standard.

All four of the big reamer gauge companies have always been helpful, just ask them where their gauge dimensions ad tolerances are.
Link Posted: 5/7/2019 2:28:25 PM EST
One more thing.  My gauge numbers for my Manson 1.711" Go  1.7205" No,    PTG 1.711" Go   1.7142" No

SAAMI  350 LEG is 1.710"(min) - 1.720"(max).

With most "in  stock"  gauges ive used since '94 they have always have had a 0.0000" - +0.0010" on the Go.   The No is Max and this number has swayed a couple tenths to as much as -0.0040" short of SAAMI max with different manufactures.  You will typically find "field" at max SAAMI headspace for rimless cases with a shoulder.   Now all that said it depends on the gauge manufacture.  They have their own tolerances and ideas where they think certain gauges should be held too in the SAAMI standard.

All four of the big reamer gauge companies have always been helpful, just ask them where their gauge dimensions ad tolerances are.
Link Posted: 5/7/2019 8:16:24 PM EST
You gotta be really careful when dealing with straight wall cases and chamber gauges.  You can measure the gauge end-to-end all you like, but if the diameter of the gauge is a bit undersize and the leading edge is chamfered, it will blow your reading all to hell when in actual use.

The above poster did not mention the diameter of the gauge or the chamfer on the leading edge, which is extremely critical with a straight wall cartridge gauge.

Tony

P.S. For the Cliff Notes...the Manson gauge has a ten thousands swing and the PTG has three.
Link Posted: 5/7/2019 9:01:07 PM EST
Here's a pic for you guys.  This is a pair of 450 Bushmaster No-Go Gauges from the same manufacturer.  Both of them are the exact same length, but they are both undersize in diameter.

A loaded 450 Bushmaster cartridge is about .478" at the case mouth and the chamber reamer is .481" at that point.  But these gauges are both only .474" in diameter which is 7 thousands under the chamber diameter.

The gauge would still work even though the diameter is undersize, until you factor in the chamfer on the leading edge of the right hand gauge.  It drops too deep and ends up being at the same depth position as the Go-Gauge.

The manufacturer of the gauges should have looked at the chamber reamer drawing or measured a loaded round, and made the gauges about .479" in diameter.  Then they could de-bur or give them a light chamfer on the leading edge and all would have been good.

I've been in this business 20 years and it's pretty clear, there is a serious disconnect between the guys that make barrels, make reamers/gauges, and make ammo.

Tony

Link Posted: 5/8/2019 6:01:31 AM EST
Besides the two barrels I personally chamber cast I know of another on a local Michigan forum, same problem. My 12", friends 16" and local forum guys 18" barrels.

Anybody with a KAK 350 Legend barrel please check your chamber.
Link Posted: 5/9/2019 8:27:15 AM EST
Did the roughing reamer go in too far?  Or, did the finish reamer not go in far enough?

According to SAAMI.

Link Posted: 5/11/2019 5:15:09 AM EST
Barrel refunded, search for new one begins.
Link Posted: 6/12/2019 6:18:10 PM EST
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Barrel refunded, search for new one begins.
View Quote
That's good that they refunded you. Sounds like you aren't the only one having problems

Failed To Load Title


This guy had a 9mm barrel reamed and gas port drilled to spec.

Sounds like there is a lot of confusion regarding what Winchester is claiming that this is and what it's spec actually is. While the bore is supposed to be .357.  It looks like they actually went with .355 and chocked it up to tolerance.
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