Long headspace?

[mao0720]

Got a question about headspace. If your headspace is long, lets say 0.005 of an inch over max SAAMI for arguments sake, wouldnt the issue essentially be resolved when you resize your fireformed brass and only bump the shoulder back .002?

 

[DRNewcomb]

Assuming you are talking about a cartridge that headspaces on the shoulder, then if you fireform and either necksize or just bump the shoulder there will be no problem. "Headspace" is always relative to some standard. Shooting a cartridge fireformed to the chamber is essentially the same as shooting your own wildcat.

 

[CatShooter]

Got a question about headspace. If your headspace is long, lets say 0.005 of an inch over max SAAMI for arguments sake, wouldnt the issue essentially be resolved when you resize your fireformed brass and only bump the shoulder back .002?

Headspace are numbers are most important to manufacturers - once the guns is made, they loose most of their importance.

Consider Wildcats or Improved cartridges - the space between the bolt face and the case head can be 1/10" or more.

Once you have fired the case, then you work with what you have. There is no need to "bump" the shoulder unless it is affecting closing the bolt.

 

[mao0720]

Thanks gents. I have a custom 308 FT/R rifle that I had bult for me and the bolt closes on a NO GO gauge. When I first discovered that I was kind of freaking out about it. But, then I started thinking about the brass fireforming during the first firing and that Im only bumping the shoulders .002, so it should not be an issue now, untill I have to use new brass again. What I have, then, is essentially a long body 308 wildcat.

 

[DRNewcomb]

Thanks gents. I have a custom 308 FT/R rifle that I had bult for me and the bolt closes on a NO GO gauge. When I first discovered that I was kind of freaking out about it. But, then I started thinking about the brass fireforming during the first firing and that Im only bumping the shoulders .002, so it should not be an issue now, untill I have to use new brass again. What I have, then, is essentially a long body 308 wildcat.

A NO GO gauge is use by gunsmiths to tell them when to stop reaming the chamber. The bolt actually should close on a NO GO gage. It should not close on a FIELD gauge. The three gauges are GO, NO GO and FIELD. The GO gauge says, "you need to ream some more". The FIELD gauge says the chamber is to long to shoot with factory ammo.

 

[Tim Singleton]

GO: Corresponds to the minimum chamber dimensions. If a rifle closes on a GO gage, the chamber will accept ammunition that is made to SAAMI’s maximum specifications. The GO gage is essential for checking a newly-reamed chamber in order to ensure a tight, accurate and safe chamber that will accept SAAMI maximum ammo. Although the GO gage is necessary for a gunsmith or armorer, it usually has fewer applications for the collector or surplus firearms purchaser.
NO-GO: Corresponds to the maximum headspace Forster recommends for gunsmiths chambering new, bolt action rifles. This is NOT a SAAMI-maximum measurement. If a rifle closes on a NO-GO gage, it may still be within SAAMI specifications or it may have excessive headspace. To determine if there is excessive headspace, the chamber should then be checked with a FIELD gage. The NO-GO gage is a valuable tool for checking a newly-reamed chamber in order to ensure a tight and accurate chamber.
FIELD: Corresponds to the longest safe headspace. If a rifle closes on a FIELD gage, its chamber is dangerously close to, or longer than, SAAMI’s specified maximum chamber size. If chamber headspace is excessive, the gun should be taken out of service until it has been inspected and repaired by a competent gunsmith. FIELD gages are slightly shorter than the SAAMI maximum in order to give a small safety margin.

From Forster web site. If you haven't tried the field gauge you maybe just fine even with factory ammo not formed in this chamber.

 

[mao0720]

Hey thanks guys, I thought the bolt wasnt supposed to close on a NO GO gauge. Ill see if I can pick up a field gauge and check it out.

 

[RCurtis]

What I have, then, is essentially a long body 308 wildcat.

A quick glance at the rulebook (see below) would indicate to me that your chamber dimension or "wildcat" as you put it, violates both the spirit and the written intent of the rule. You were right to freak out about it and were it me I would return it to the person who did the chambering work for a slight set-back to bring it in to spec. This is assuming that you plan to compete in matches in the F-TR division.

(b) F-Class Target Rifle (F-TR) - A rifle restricted to the chambers of unmodified .308 Winchester/7.62mm
NATO or unmodified .223 Remington/5.56mm X 45 NATO cartridge cases.

Rick Curtis

 

[mao0720]

Im gonna have to disagree with you on this one. I do plan to compete with the rifle, but will be limited to local club matches. My intent was never to create a wildcat cartridge, nor was it to alter the 308 win cartridge in any way. I gain no advantage from this long headspace. The reason I said it was like a long 308 wildcat was just because of fireforming affect of having the longer than normal headspace. We're literally talking about a few thousandth of an inch here, not enough to change poweder capacity by enough to increase velocity. I may still have the smith set back the barrel, depending on what kind of measurements i get on fired, unsized brass (all of my brass right now is FL sized already).

 

[Erik Cortina]

Im gonna have to disagree with you on this one. I do plan to compete with the rifle, but will be limited to local club matches. My intent was never to create a wildcat cartridge, nor was it to alter the 308 win cartridge in any way. I gain no advantage from this long headspace. The reason I said it was like a long 308 wildcat was just because of fireforming affect of having the longer than normal headspace. We're literally talking about a few thousandth of an inch here, not enough to change poweder capacity by enough to increase velocity. I may still have the smith set back the barrel, depending on what kind of measurements i get on fired, unsized brass (all of my brass right now is FL sized already).

Your chamber is a modified 308 chamber, not on purpose, but still a modified 308 weather you agree with Rick Curtis or not.

 

[mao0720]

Ok. I understand where you guys are coming from. So long as my rifle is safe to shoot then I am not going to worry about it. I wont be going to nationals or any other high level matches, so I dont think it is a big deal. If it is not safe to shoot then I will have the barrel set back a touch to correct the headspace.

I read on another site that the bolt should not close on a NO GO gauge, but DRNewcomb say it can close on a NO GO but not on a FIELD gauge. Can anyone clarify?

 

[Keith Glasscock]

I disagree. The chamber most likely still falls within the SAAMI max headspace, thus, it is still "unmodified." Go take a look, last time I did the headspace tolerance scared me.

The intent of the rule was to prevent people from bringing improved cartridges, that give them a ballistic advantage, based on the 308 to the line and competing in F/TR. This would not qualify as improved any more than using small primer Lapua palma brass does.

 

[Erik Cortina]

Ok. I understand where you guys are coming from. So long as my rifle is safe to shoot then I am not going to worry about it. I wont be going to nationals or any other high level matches, so I dont think it is a big deal. If it is not safe to shoot then I will have the barrel set back a touch to correct the headspace.

I read on another site that the bolt should not close on a NO GO gauge, but DRNewcomb say it can close on a NO GO but not on a FIELD gauge. Can anyone clarify?

It's called a NO GO for a reason, emphasis on "NO".

The main issue you may run into is that your die will not resize the base of your brass because you will have to adjust it out due to longer headspace. I would take it back to your "gunsmith" and have him fix it.

 

[Tim Singleton]

As stated in the post above
Even a field gauge is slightly shorter than maximum saami spec. So even if it closes on a field gauge which is longer than a No go. It still maybe be with in saami spec. Which would be with in the ftr rules.


I'm with Busdriver on this one.

Maybe you should cast the chamber and take some measurements.

 

[Scott Harris]

If I"m reading the SAAMI 308WIN cartridge print correctly, the SAAMI spec can vary up to .007 from the minimum dimension and still be in spec. My 308WIN GO & NO-GO gauges vary .004. So, the chamber can still be in spec if it exceeds the NO-GO. The problem is you have no idea by HOW MUCH the chamber exceeds the NO-GO when the bolt closes on it...could be .001 or could be .010. This is why I think you should insist that the NO-GO not fit...then you know it is in spec for sure.

I've used four of the top smiths in the nation, as listed on this website, to do chamber work for me. I have learned that:
1. Most of them do not have NO-GO gauges. They usually tell me they use the "scotch tape trick" on the GO gauge....but see item 2. below.
2. About 1/2 the finished chambers I receive allow a bolt to close on the NO-GO gauge.

This has been disappointing to me as I have to mail out all the gear and it is time-consuming and frustrating to fix sloppy mistakes. This is even more frustrating because I send MY GO and NO-GO gauge and always request they make sure to use the gauges. You would think that properly using the GO and NO-GO gauge would be standard procedure for any decent smith.....that has not been my experience.

 

[mao0720]

So I bought a hornady headspace gauge kit today and measured my Go and NO GO gauges. WAY UNDERSIZED!!! GO was 1.620, NO GO was 1.625. I stacked scotch tape on the no go gauge until it read closer to proper dimensions at 1.633, and suddenly the bolt wouldnt close on it! Go figure!

 

[BillPa]

So I bought a hornady headspace gauge kit today and measured my Go and NO GO gauges. WAY UNDERSIZED!!! GO was 1.620, NO GO was 1.625. I stacked scotch tape on the no go gauge until it read closer to proper dimensions at 1.633, and suddenly the bolt wouldnt close on it! Go figure!

Your gauges might be fine, the tool inserts not so much.
http://forum.accurateshooter.com/index.php?topic=3808270.msg36188490#msg36188490

Bill

 

[CatShooter]

I found the same thing with mine - some dingle-berry at Hornady used a countersink to break all the edges of the inserts.

Any measuring tool should be expected to accurately measure what it is intended to measure, unless it is stated in the instructions... "This gauge is intended to measure comparative/relative headspace, and not absolute headspace, and is not intended to be used for determining true measurements."

IF... the tool was intended for comparative/relative measurements, then there would be no need for using bore holes that are accurate, and to the SAAMI standard... any ol' hole would do (that doesn't sound right, but you know what I mean).

It is more likely that at the manufacturing stage, the manager of the final assembly folks (at a whoppin' minimum wage + 20%) thought they should finish the inserts so they looked "nice", and take the rough edges off the inserts.

I would gladly pay 3 times the price if the inserts were made of stainless steel and properly faced and lapped as a last step.

But, there is a light at the end of the tunnel.

If you take a 12" square piece of plate glass, and a #600 (or finer) silicone carbide "Wet-n-dry" paper, and some light oil, you can lap the inserts to remove the counter sunk section, and the gauge is 98% more accurate.

 

[DRNewcomb]

Ok. I understand where you guys are coming from. So long as my rifle is safe to shoot then I am not going to worry about it. I wont be going to nationals or any other high level matches, so I dont think it is a big deal. If it is not safe to shoot then I will have the barrel set back a touch to correct the headspace.

I read on another site that the bolt should not close on a NO GO gauge, but DRNewcomb say it can close on a NO GO but not on a FIELD gauge. Can anyone clarify?

You are talking about thousandths of an inch. The standard use of the three gages are that the GO gauge is used to tell the gunsmith that the chamber is too short and to keep turning the reamer. When the bolt will close on the GO gauge he slows down and starts using the NO GO gauge, as the bolt just begins to close on the NO GO gauge he will stop. The two gauges indicate the minimum and maximum dimensions for a new, factory chamber. After some shooting it is normal and safe for the bolt to close on a NO GO gauge. This does not indicate that the gun is unsafe. That job falls to the FIELD gauge, which indicates that the camber has grown to more than allowable specs. This only applies to factory ammo. If you are handloading and sizing your cases to shoot in this particular chamber the FIELD gauge does not indicate an unsafe condition by itself. However, if a factory rifle's bolt would close on a FIELD gauge, I would want to know why before shooting it, even with necksized reloads.

The whole theory of headspace is that, if it is more than allowed, the base of the factory cartridge slams against the bolt head with a hammer-like blow which, over time, can cause the lugs to crack and eventually fail. By keeping the fit of the round in the chamber within specs you make the loading and unloading of the bolt lugs a much more smooth action without the hammer-like impact.

 

[shortgrass]

Someone is thinking way too hard about this!!! If common sense still prevailed in this country, this thread would NOT exist. For a chamber cut to SAAMI specifications, the bolt should CLOSE on the "GO" head space gauge,,,, the bolt should NOT CLOSE on the "NO-GO" head space gauge.