Understanding headspace

[Hunthigh1]

Storytime:

I have an old cheap Mossberg ATR 30-06 rifle that has been my GO-TO hunting gun for 15+ years. Yeah yeah, I know it's not a Tikka. . . A few months ago it began to not fire reliably. I cleaned the bolt assembly and firing pin area thoroughly. This did not fix it so I sent it to Mossberg for service/inspection. They sent it back with a new bolt in it. I had recently purchased a set of Forster brand headspace gauges for a different antique rifle I am working with. When I received the Mossberg with the new bolt I dropped the NO-GO gauge in the action and it closed without resistance. I then dropped my FIELD gauge into the action and it closed without resistance.

I sent a video of the aforementioned checks to Mossberg and they replied that they have their own gauges and the rifle was inspected to be safe......

How is this possible? Doesn't this mean the rifle is unsafe to fire since it closed easily on a "field" gauge? Is Mossberg gaslighting me?

 

[hereinaz]

Yeesh, I would have more conversations and try to send it back to be checked again and get headspace reduced if possible for precision, let alone safety.

Is your field gauge smaller than SAAMI maximum? It could be you. I know some field gauges are SAAMI maximum, so that leaves questions. But, I know some no-go gauges have different tolerances based on brands.

They could technically be within SAAMI, so you might not get a resolution you want. If it has long headspace, the brass is gonna grow regardless of safety issues.

 

[Hunthigh1]

Thanks for the response. I will check maximum against the below gauge sizes.
Yeeesh is exactly what I thought!

My gauges are:
FORSTER brand no go = 2.0547"
FORSTER brand field = 2.0577"

The action closes easily on both.

 

[Hunthigh1]

Mossberg responded to me sending a video closing the action on the aforementioned gauges.They said they checked headspace with their own tools and the gun is fine.

This doesn’t really give me confidence and I’m wanting to send it back in but may get the same result…..

I’m terrified of the rifle blowing up. Largely because I don’t understand how it can be safe if my field gauge goes into battery with ease

I guess I need a gauge at 2.0587” rather than 2.0577?

Since 2.0587 is SAAMI max?

 

[Weldor]

following

 

[BBob]

I’m terrified of the rifle blowing up.

Tell us how the rifle is going to blow up with an extra thousandths of an inch or two of clearance?

 

[Hunthigh1]

Tell us how the rifle is going to blow up with an extra thousandths of an inch or two of clearance?

I don’t know, and am not claiming to. Hence the thread asking question's. It seems to me that if I feel no resistance on a field gauge, the rifle could be well beyond saami spec, and therefore unsafe?

 

[BBob]

It sounds like you have not proven out that it exceeds SAAMI maximum but the manufacturer says it doesn’t with their gages and they have stated they are willing to hang their hat on that assessment. Excess headspace is not going to make it “blow up”. How many multiple thousands of cases have wildcat handloaders fired over the years blowing shoulders out let’s say .100” or more without them blowing up? There are many reasons for excess headspace being bad or undesirable but “blowing up“ isn’t one of them.

 

[wapitibob]

Put tape on the back of the field gage, 1 at a time and you’ll have a rough idea where it’s at.

 

[TaperPin]

If it bothers you this much I’d sell it or have someone fix it.

Doesn’t the ATR have a barrel nut? If you don’t have iron sights it’s as easy as cracking the nut, adjusting headspace a few thou, making sure the recoil lug is aligned properly and tightening the nut. Your barrel thread is 20 tpi so each full 360 degree turn of the barrel is .050”. That’s 7.2 degrees for every thou of headspace, which is easy peazy with an electronic angle finder and simple clamp on the barrel to index off of. With iron sights a smith will turn a full thread-worth of metal off the barrel shoulder and back of the tenon, and run a reamer in for proper headspace.

I know nothing about Mossberg, but the fastest way to fix a quirky gun is often to sell it locally and buy another used one for roughly the same price. As long as it goes bang and Mossberg has given its blessing, most guys won’t care what the headspace is.

 

[Hunthigh1]

Thanks for the response guys. Sounds like my concern is excessive and that the rifle is safe to shoot.

It sounds like you have not proven out that it exceeds SAAMI maximum but the manufacturer says it doesn’t with their gages and they have stated they are willing to hang their hat on that assessment. Excess headspace is not going to make it “blow up”. How many multiple thousands of cases have wildcat handloaders fired over the years blowing shoulders out let’s say .100” or more without them blowing up? There are many reasons for excess headspace being bad or undesirable but “blowing up“ isn’t one of them.

Thank you for the response. Sounds like I’m good to go on this rifle from a safety standpoint.

 

[Hunthigh1]

Put tape on the back of the field gage, 1 at a time and you’ll have a rough idea where it’s at.

Great idea. I’ll play with that.

 

[Hunthigh1]

If it bothers you this much I’d sell it or have someone fix it.

Doesn’t the ATR have a barrel nut? If you don’t have iron sights it’s as easy as cracking the nut, adjusting headspace a few thou, making sure the recoil lug is aligned properly and tightening the nut. Your barrel thread is 20 tpi so each full 360 degree turn of the barrel is .050”. That’s 7.2 degrees for every thou of headspace, which is easy peazy with an electronic angle finder and simple clamp on the barrel to index off of. With iron sights a smith will turn a full thread-worth of metal off the barrel shoulder and back of the tenon, and run a reamer in for proper headspace.

I know nothing about Mossberg, but the fastest way to fix a quirky gun is often to sell it locally and buy another used one for roughly the same price. As long as it goes bang and Mossberg has given its blessing, most guys won’t care what the headspace is.

All stuff I didn’t know. Thank you!