NAS3 5.56 Cases - Tikka 223 w/ 88 TMK

[B_Reynolds_AK]

Starting a new thread to address the issues I had with the NAS3 cases in my Tikka 223 with a 16", .100 fb, 1/7" twist bbl.

I loaded up 5 charge weights of N150 and 88 TMK's in the new NAS3 alloy cases, which Shell Shock indicates have
appx. 10% more powder capacity than standard brass.

The initial charge weight is what I've been using with ADI brass, 25.0 of N150. (2686 fps)

The first 3 loads ended up with "cookie cutter" holes in the Primers. I fired one more round and it did not go off.

On measuring the shoulders of ADI Brass and these, this is what I found.

ADI Resized: 1.361"
ADI Fired: 1.365

NAS Unfired: 1.351-1.355
NAS Fired: 1.359-1.362

What this is telling me is that the shoulder on the NAS cases are as much as .014" shorter than a fire formed case in my gun.
With what others have written in the 88 TMK thread, as well as from my research, this is causing an excessive chamber headspace issue.
Both the cookie cutter holes, from the primer slamming back into the firing pin hole, and the one misfire are both symptoms of this.

Velocites:
25.0 - 2704 fps
26.0 - 2764 fps
27.0 - 2840 fps



From Left to Right: 25.0, 26.0, 27.0. The ADI is a fired case with 25.0 and the 88 TMK.


I found two of the primer cutouts in my chamber.

 

[NWBLKTAIL]

Bummer this would have been pretty cool, but alas this is why things get tested.

Thanks for sharing I read your other post. I have had Peterson not form fully after first firing and shoulders varying in length. I can only imagine with harder alloy cases such as this the case hardly expands which probably also helps in aiding in the additional velocity via pressure.

Hopefully there comes a solution of some kind.

 

[Thegman]

The first 3 loads ended up with "cookie cutter" holes in the Primers. I fired one more round and it did not go off.

This last piece pretty much confirms the "too short case" hypothesis as the root of the problem.

 

[RockAndSage]

Separate from the case length problem, what primers are you using?

 

[B_Reynolds_AK]

Separate from the case length problem, what primers are you using?

Fed 205

To be clear, case length is fine. Shoulder to base length is the issue.

 

[RockAndSage]

Fed 205

To be clear, case length is fine. Shoulder to base length is the issue.

With the extra pressure, it might be worth considering trying magnum primers. The cups are made of a bit thicker material just for that.

 

[pods8 (Rugged Stitching)]

With the extra pressure, it might be worth considering trying magnum primers. The cups are made of a bit thicker material just for that.

But it’s not a pressure issue he is having, it’s the firing pin hitting the primer and pushing the case forward (since there is excess headspace) cartridge goes bang (sometimes) and the primer slams back into the bolt versus being against the bolt the entire time.

 

[JohnsIsl]

I’ll preface this by saying I know NOTHING about NAS cases. But just thinking about solutions.

What would be wrong with:
- Annealing (does this even work well with NAS?)
- Running an oversized mandrel - maybe two oversized mandrels
- Using a shoulder bump die (or two) that doesn’t actually bump the full shoulder but gets you to a point where you can chamber a round

You’d then have a ‘false shoulder’ that would keep the case from ‘bouncing’ and after 3-4 firings you may have a fully fire formed case. Maybe your full case length would be too short? Seems like a lot of work.

???

 

[B_Reynolds_AK]

I’ll preface this by saying I know NOTHING about NAS cases. But just thinking about solutions.

What would be wrong with:
- Annealing (does this even work well with NAS?)
- Running an oversized mandrel - maybe two oversized mandrels
- Using a shoulder bump die (or two) that doesn’t actually bump the full shoulder but gets you to a point where you can chamber a round

You’d then have a ‘false shoulder’ that would keep the case from ‘bouncing’ and after 3-4 firings you may have a fully fire formed case. Maybe your full case length would be too short? Seems like a lot of work.

???

None of that is relevant to the NAS3 Alloy cases, which are one time use. You don’t resize them. Load, Fire, Toss. If they don’t work in your chamber due to being undersized, then they just won’t work. I’m not sure of the cases I just got are under spec or if it’s an issue with my chamber. Either way, I’m getting 2715 fps now from 88 TMK’s in regular brass, so I’m sticking with those.

 

[JohnsIsl]

None of that is relevant to the NAS3 Alloy cases, which are one time use. You don’t resize them. Load, Fire, Toss. If they don’t work in your chamber due to being undersized, then they just won’t work. I’m not sure of the cases I just got are under spec or if it’s an issue with my chamber. Either way, I’m getting 2715 fps now from 88 TMK’s in regular brass, so I’m sticking with those.

Well… now I know more about NAS3 cases. Thanks.

 

[BLJ]

Have you contacted the manufacturer? I’d be curious to hear their thoughts.

I’m getting 2715 fps now from 88 TMK’s in regular brass, so I’m sticking with those.

This might work.

 

[Steve300xcw]

With the extra pressure, it might be worth considering trying magnum primers. The cups are made of a bit thicker material just for that.

Rem 7.5's letcha get away with a lot..

 

[B_Reynolds_AK]

Personally, I’m not going to pursue using them with this gun. Hopefully others can check the NAS cases out and find this useful.

 

[Schmo]

I’ll be testing them in two Tikkas next month and will report here

 

[ACHILLES]

Eventually I’ll try the nas3 5.56 cases. I would think the simple solution for the excesses headspace issue is to kiss or lightly jam the bullet into the lands. If you don’t want to be in the lands then load .001-.002” off the lands.
Also a thicker cupped primer wouldn’t hurt like a cci450 or 41, rem7.5, or br4

 

[Fireflyfishing]

ADI Resized: 1.361"
ADI Fired: 1.365

NAS Unfired: 1.351-1.355
NAS Fired: 1.359-1.362

How much stretch are you getting on virgin brass vs the NAS3 case?

 

[ezwy]

I think they are supposed to be used with no 41 primers. Not saying that would solve a headspace issue, but one less variable

 

[wind gypsy]

My shell shock 556s case got delivered over the weekend. With the Hornady 0.330" comparator, they are measuring 1.449" on avg with seemingly consistent measurement variance of less than 0.001 +-.

Creedmoor sports (in starline brass), ADI, and AAC loaded factory ammo all measure 1.456" with the same comparator. Fired brass measures 1.458"ish. That is fired in a wylde chamber fitted (not prefit) by manzella.

Pretty lame that they are that short.

 

[wind gypsy]

Eventually I’ll try the nas3 5.56 cases. I would think the simple solution for the excesses headspace issue is to kiss or lightly jam the bullet into the lands. If you don’t want to be in the lands then load .001-.002” off the lands.
Also a thicker cupped primer wouldn’t hurt like a cci450 or 41, rem7.5, or br4

I'm skeptical of seating depth consistency to do such a thing especially with virgin cases that you cant uniformly size the necks on and soft pointy bullets that are easily deformed by seating stems if there is much for seating pressure. And i just hate trying to be exactly at the lands.

@B_Reynolds_AK - I posted in a thread about loading with these cases on the Hide to see if anyone else has seen it or if this most recent run is just out of spec. Curious if the mfr has anything to say about it if you contact them. I do wonder if your prefit barrel isn't set more towards the mid or higher range of headspace tolerance to avoid having ammo fail to chamber. Clearly not an issue with most typical case dimensions..

SAAMI says 0.007" total case dimension tolerance base to shoulder datum. Just seeing that these are 0.006" to 0.007"+ shorter than the 3 different factory ammo cases i measured is a pretty good indication they are out of spec to me. I'd be surprised if all the factory ammo is being churned out right at maximum case size but I've not looked into such things in the past. Also - Clearly the hornady 330 comparator isn't a perfect tool for measuring actual 330 datum as my measured values are off by about 0.010" compared to SAAMI spec.

 

[ACHILLES]

I'm skeptical of seating depth consistency to do such a thing especially with virgin cases that you cant uniformly size the necks on and soft pointy bullets that are easily deformed by seating stems if there is much for seating pressure. And i just hate trying to be exactly at the lands.

@B_Reynolds_AK - I posted in a thread about loading with these cases on the Hide to see if anyone else has seen it or if this most recent run is just out of spec. Curious if the mfr has anything to say about it if you contact them. I do wonder if your prefit barrel isn't set more towards the mid or higher range of headspace tolerance to avoid having ammo fail to chamber. Clearly not an issue with most typical case dimensions..

SAAMI says 0.007" total case dimension tolerance base to shoulder datum. Just seeing that these are 0.006" to 0.007"+ shorter than the 3 different factory ammo cases i measured is a pretty good indication they are out of spec to me. I'd be surprised if all the factory ammo is being churned out right at maximum case size but I've not looked into such things in the past. Also - Clearly the hornady 330 comparator isn't a perfect tool for measuring actual 330 datum as my measured values are off by about 0.010" compared to SAAMI spec.

Valid concerns. Using a nitrided mandrel on the necks before loading will help with seating tension and uniformity. I personally would seat a few thou long on the first round then go back and seat everything thing within +-.001”. But I know most won’t want to take that much time. In that case just running the mandrel through the necks then seating .003-.004” off the lands should still fix the headspace issue and give you more wiggle room on seating depth.