A second headspace measurement thread

[BeeKay]

I inquired about this earlier but due to weather / acts of nature conditions and other situations, the thread began to get confusing.  

I bought some .308 Winchester headspace gauges recently and they're Clymer Go/No-Go gauges 1.630"/1.633" 

I have three uppers, including dedicated BCGs of various chamberings, which I may end up referring to, but I'd like to focus on my .308/7.62 KAK Barrel/BGC combination.

Prior to this, I haven't measured headspacing because the word online seems to be  -  If the bolt and barrel are from the same source, they're probably Ok.  But there are others online who say - Measure It Anyhow.     So what I have is a KAK Barrel and BCG that I've measured using my new gauges and that particular chamber has loose headspacing.    I emailed KAK and his only questions were "Did you buy it from us ?"  and  "Have you tried firing it ?"  Then he just told me it's probably okay - Keep using it.

 

I'll add - I tried chambering the Clymer Go/No-Go Gauges in a couple of other chambers and the bolt would close on the Go Gauge - But won't close on the No-Go

But this KAK Barrel/BCG is apparently loose  - What should I do ?            I'm somewhat familiar with headspacing, but not on rifles with bolts using locking lugs... So I'm aware of the case stretch issues etc ... I'm seeing that a check for a protruding primer is a good check and using a comparator to compare a fired case to the gauge ?

I'm not sure what the next step should be - I wish the tech guy at KAK would have been more helpful.

[98Z5V]

There are very small differences in different companies, with Go/No-Go gauges.  The only way to check on that might be "iffy" is to contact the barrel manufacturer, and ask them what specific gauges they use. 

And that can suck.  One company only uses Clymer gauges.  Once company only uses Forster gauges...  The list can go on an on. 

Here's the real deal.  Go needs to go, diesn't matter who it's from.  That stops you from a short chamber, and in an AR, with that recoil spring pressure chambering a round from locked-back - it CAN chamber a round on a short-ish chamber - THAT spikes your chamber pressure.  That's not good.

Make sure the GO gauge does go.  If the No-Go chambers...   take your chances.  Put a piece of scotch tape on the back of the gauge, and see if it'll chamber - that'll add 0.001" to the length of the gauge.

In-service weapons have a third gauge - the "Field" gauge.  That's for in-service weapons use only.  It's longer than the others, and accounts for throat erosion.  If you can chamber a Field gauge - that barrel needs to go.  On In-service weapons, if you chamber a No-Go, you try the Field.  No-Go just failed, but if the Field doesn't chamber, you keep shooting the gun...

Don't get wrapped around the axle about what some barrel manufacturer tells you, unless you specifically ask them what gauges they use to test, and you have those exact gauges, by brand.  Don't go buying different gauges, from all he manufacturers...   Just check your Go gauge from whoever you bought it from - ask here if your No-Go does GO...  and we'll figure it all out. 

4 hours ago, BeeKay said:

I'll add - I tried chambering the Clymer Go/No-Go Gauges in a couple of other chambers and the bolt would close on the Go Gauge - But won't close on the No-Go

This is exactly what SHOULD happen...

[98Z5V]

You never very specifically stated that the KAK barrel closed on the No-Go gauge...  Unless I missed it.  I didn't read that in your initial post. 

[BeeKay]

Yes - The KAK / KAK Bolt combination does close on the No-Go Gauge .

I tried creating a thread a few weeks ago,   And It's a fine line between NOT PROVIDING ENOUGH information and PROVIDING TOO MUCH info, and then creating confusion .

I've made guns that are chambered in Ackley Improved and Herrett wildcats, so I understand some basic things about headspacing issues.    But those builds were single shot, folding action guns using the .30-30 as the parent cartrige...   So it's time to expand my education 

At this point : I need to get a comparator and check the length of a fireformed case.

 

The thing that I'm uncertain about at this stage is :  How Much Excessive Headspace Is Tolerable  ?

I guess I'll find out after I fire it and measure a  fireformed case 

 

Additionally - I have a couple other barrels and bolts and I've tried checking the headspacing on those, using the Clymer gauges, and the bolt would  close on the GO GAUGE     -   and NOT close on the NO-GO GAUGE .  

13 hours ago, 98Z5V said:

You never very specifically stated that the KAK barrel closed on the No-Go gauge...  Unless I missed it.  I didn't read that in your initial post. 

 

[BeeKay]

There was a guy who posted here a few years ago, and he showed a pic of his bolt and the lugs were chewed up and his question was :  Is this normal wear for a few hundred shots ?

Everyone said : That's  DAMAGE  not  WEAR     -   That's the situation I'm trying to avoid   

 

So  - It sounds like excessive headspace by  + 003"  or so   -  Won't destroy my bolt  - But will cause case stretching or fireformed cases that can't be reloaded and shared with other rifles with a SAAMI spec chamber .

Do I have that right ?

I didn't mention that I'll be reloading the brass

 

Thanks for taking the time to clarify this stuff 

 

[BeeKay]

I have a home-made comparator now  -  It works well  -  I get repeatable results within .0005" , so it doesn't jiggle or go off center and create errors.

When I use the comparator to measure my No-Go vs a new unfired case,  the No-Go is only .001" longer - So that tells me something.

I'll dig thruogh my fired brass and see what I can find.  I have three .308s so it will be interesting to sort it. 

 

Thanks for helping to keep this project moving in the right direction.

[98Z5V]

32 minutes ago, BeeKay said:

I have a home-made comparator now  -  It works well  -  I get repeatable results within .0005" , so it doesn't jiggle or go off center and create errors.

When I use the comparator to measure my No-Go vs a new unfired case,  the No-Go is only .001" longer - So that tells me something.

I'll dig thruogh my fired brass and see what I can find.  I have three .308s so it will be interesting to sort it. 

 

Thanks for helping to keep this project moving in the right direction.

Getting it down to 5-10thou is pretty badass.  Very well done.  Half a thou.  Nice.

So, the No-Go gauge versus unfired is within 1 thou?  Measure a fired case, see where that thing comes up in comparison.  That's gonna tell your chamber, right there.

It's not uncommon for competition bolt gun reloaders to only load/bump shoulders a couple thou, 0.002?~0.003" - for their competition brass reloading.  Gas guns can have a shoulder difference 0.005", and that's not something that you'd look at as weird, or out of the ordinary.  Check your shot brass, man, see where it falls. 

[98Z5V]

Best user of a comparator gauge that I know of is @JBMatt - lets get him into this conversation and hear his info.  He's the most meticulous person I've ever met, for brass prep, and making badass handloads.  Bar none. 

[BeeKay]

Excellent - Thank You

I need to fireform some cases, because my .308 brass got mixed together between 3 different rifles, so it's hard to know for sure what I'm measuring .

But out of about 100 fired cases, I didn't see any that had proud primers.

I'm looking forward to following through on this.  With luck I'll get things dialed in to the point where I can share reloaded ammo between 2 or 3 different rifles with acceptable accuracy and reliability

[BeeKay]

On 1/15/2023 at 4:49 PM, 98Z5V said:

Best user of a comparator gauge that I know of is @JBMatt - lets get him into this conversation and hear his info.  He's the most meticulous person I've ever met, for brass prep, and making badass handloads.  Bar none. 

Do tou suggest that I send JBMatt a P.M.  ?

I did fireform some cases and it would be interesting to hear what someone who knows their stuff has to say.  Because now I have more questions.

Reloading brass is interesting and especially with rifles there can be a lot of details that make successful vs mediocre reloads.

Edited January 19, 2023 by BeeKay

[98Z5V]

I quoted him in that on purpose, to lure him in here and respond.  He's been busy.  I'll call his lazy ass and have him get in here and reply.  I might need to wake him up...  

[BeeKay]

I'm busy too - Otherwise I would have been done with this years ago

I'll be patient -  Thanks

 

[BeeKay]

I learned some tinngs about the sequence of events when a bullet is fired in a chamber with excess headspace, by building a TC Contender in .30-30 Ackley Improved.

The A.I. chamber has parellel walls so the case clutches the chamber under pressure. Ackley himself fired a round in a rifle ( in the lab ) with the lugs removed from the bolt, to demonstrate that. 

Excess headspace with that cartridge means stretching at the web . But if  loads are fired, that don't have enough  pressure to stretch the case, then the primer protrudes until the bolt face stops it.   Or the breech face.

But clutching the chamber walls doesn't happen with a tapered chamber, so there are different signs of excess headspace..

That may be relevant ?

[BeeKay]

So - At this stage of the game, I can say that this particular Barrel / BCG / Bolt combination, Positively has excessive headspace..

It's a .308 / 7.62x51  Barrel / BCG from the same manufacturer bought at the same time, but not as a package, as they don't offer a Barrel BCG package.

Fired less than 50 times

I performed the following tests and this Barrel / BCG Combo failed them all 

#1 ) Go / No-Go Gauge test : the bolt closes on the No-Go Gauge

#2 ) Tape on the No-Go gauge - Adding .002" thickness - Bolt still closes

#3 ) Light Primer Strikes

#4 ) Firing a new case with primer only, reveals primer protrusion of .010"

I tested my Go/No-Go Gauges in the chamber of another gun (Browning) and the test indicated results for a proper headspaced chamber.       In that same chamber a neck sized case from my AR won't allow bolt closure.

I have four AR-.308 Barrels - And I found one that has better headspace test results. But I haven't had a chance to take it out and fire it yet.  So I'm looking forward to seeing how that goes.

One of the things that I'm looking for is to be able to share neck-sized Reloaded Ammo with my .308 Browning lLever Action .    That may be expecting too much,though.  

I won't name the manufacturer unless someone asks, I've mentioned that in previous posts and I'm hoping that the company will correct the problem, so I don't want to sour my relationship with them....        I'm thankful that I followed some of the headspacing threads and decided to follow this step, because there are issues that came to the surface which would have been a source of future problems....   Another point of interest is that, The least expensive Barrel / BCG Combos that I have, passed the headspace test - BCA.    We'll see how they shoot.     I would have just broke down, and bought a new Barrel / BCG from Wilson, but I have four already.

Learning new things - Thanks for the helpful info