increasing headspace on newly installed factory original fixed shouldered barrel

[1mechanic]

Let's say there is no saftey issue. Some other problems I see. If the gun is not stainless steel. The stainless shim will cause dissimilar metal corrosion. Had a guy bring me a blued R700 with stainless action screws. It was a nightmare getting those out and had to repair the screw holes on the action. The other is the shim will eventually become damaged with repetitive recoil. Have it corrected properly.

If this was a remington or rem clone. I have bought extra thick recoil lugs and milled them to correct this exact issue. No room for short cuts in rifle building.

I don't believe in shimming it and I think the best course would be to rent a reamer but that shim will not fall or get beat out by recoil it would be firmly wedged between the barrel and recoil lug.

An example would be shimming valve springs on an engine they aren't even permanently wedged in because the spring dances around on them.

Shimming the carrier bearings on a rear end are thin and not even hardened like the valve spring shims and the don't get damaged.

Shimming is stronger than you think but it does change other measurements on an action that could be detrimental.

 

[DUCKMAN11]

i have not found much information here on this topic or much of anywhere else for that matter so thought to pose this question.

recently i removed a very tired 308 win barrel off my howa 1500 to replace with another brand new fixed shoulder factory barrel i had in my safe of the same caliber. what i have found is the barrel fits perfectly as expected but the headspace is tight and needs to be increased by .005

i do not not want to mess with the bolt and decided to shim the barrel increasing headspace by .005 using one 18-8 ss steel arbor shim with 1'' id (perfect for od barrel thread diameter) and 1.5'' od. the receiver od at point of barrel action contact is 1.34''. i plan to shave down the excess shim for a better smoother fit.

in doing so i have now perfect headspace after tightening the barrel to 35-40 psi (i never tighten beyond that as i have found it excessive and unnecessary).

my question here since i have never shimmed a barrel before on a bolt action of this caliber and have yet to fire the newly changed rifle have i made a grievous mistake which will potentially give me trouble?

typically aftermarket barrels come with a barrel nut allowing fine adjustment for headspace. how is this setup using a barrel nut to adjust barrel depth into action any different than shimming a fixed shouldered barrel?

You should be fine safety wise. I've seen guys decrease the BTO or headspace by sanding down recoil lugs or increasing headspace by using thicker recoil lugs on rem700 style actions. That's essentially what you are doing.

Quit telling people how good Howa's are... you are driving up the prices on the 2nd hand market!

 

[Hugnot]

From the back of my head:

Contact between stainless & chrome-moly steel:
from wikipedia
"Dissimilar metals and alloys have different electrode potentials, and when two or more come into contact in an electrolyte, one metal (that is more reactive) acts as anode and the other (that is less reactive) as cathode. The electropotential difference between the reactions at the two electrodes is the driving force for an accelerated attack on the anode metal, which dissolves into the electrolyte. This leads to the metal at the anode corroding more quickly than it otherwise would and corrosion at the cathode being inhibited."

Both stainless & chrome-moly steel share the same general location at the middle of the Anodic Index, & that means an even balance between most cathodic and most anodic. The potential is just not there for any electrolytic exchange.

Want to see potential at work?- go to copper (.35) & zinc (1.25) with some acid.

Some kind of Loctite other than blue ?

Increasing headspace is best done by making the chamber deeper using a finish reamer. This may be done by hand turning using no-go & go gauges. A shim will increase headspace but will also increase the gap between end barrel face/surface & bolt end including bolt face, plunger ejector & extractor. A replacement barrel might have correct headspace and bolt not close as any clearance between barrel face & bolt end (nose) would not exist.

Grinding down a shell holder is a fix for an excessively short chamber. I have a 6mm AI that was chambered to allow a crush fit to FF brass. The crush fit required excessive crush, so I ground down a shell holder that lives in the same box with the F/L 6mm AI die.

 

[RuninL8]

Same argument could be made against barrel nuts. I think experience has proven that such an argument will fail.

Are you saying that the .005 won't matter that's the argument?

 

[ntsqd]

No, I'm saying that a shim moves the barrel in exactly the same way that a Savage barrel is moved by threading it in or out before locking it in place with the nut. Both the head-space and the bolt to barrel gap are effected identically. The same it true if substituting a thicker or thinner recoil lug (were this not a Howa).

 

[Rocketeer77]

i have not found much information here on this topic or much of anywhere else for that matter so thought to pose this question.

recently i removed a very tired 308 win barrel off my howa 1500 to replace with another brand new fixed shoulder factory barrel i had in my safe of the same caliber. what i have found is the barrel fits perfectly as expected but the headspace is tight and needs to be increased by .005

i do not not want to mess with the bolt and decided to shim the barrel increasing headspace by .005 using one 18-8 ss steel arbor shim with 1'' id (perfect for od barrel thread diameter) and 1.5'' od. the receiver od at point of barrel action contact is 1.34''. i plan to shave down the excess shim for a better smoother fit.

in doing so i have now perfect headspace after tightening the barrel to 35-40 psi (i never tighten beyond that as i have found it excessive and unnecessary).

my question here since i have never shimmed a barrel before on a bolt action of this caliber and have yet to fire the newly changed rifle have i made a grievous mistake which will potentially give me trouble?

typically aftermarket barrels come with a barrel nut allowing fine adjustment for headspace. how is this setup using a barrel nut to adjust barrel depth into action any different than shimming a fixed shouldered barrel?

You're going to seal 60,000 psi on a 0.005" steel washer and to add to your woes you don't tighten the barrel to the correct torque? Have fun

 

[ntsqd]

I'm thinking that there is a fundamental lack of understanding in just how all of this works.

 

[Darryle]

I'm thinking that there is a fundamental lack of understanding in just how all of this works.

I see your point, the reference points all change regardless of how you adjust the chamber.

The action stays static and you move the barrel in or out to establish headspace, whether you use a nut, shim or the thickness of the recoil lug, it is essentially the same outcome.

As far as carrier shims and valve shims, the carrier adjusts side load of the ring and pinion, once the caps are torqued down, relatively little load on the shims. The pocket shims under valve springs are much thicker and are constantly lubricated, I have seen them fail, while rare, I don't know that I have ever seen them thinner than .015".

This has been a very enlightening discussion

 

[pavementends]

Touched on I think but lost in the noise. .005 too little head space. A .005 shim will not increase the head space by that amount. The barrel will contact the face of the receiver sooner but the amount the headspace changes will be determined by the pitch of the barrel threads. At least that is what a tired old brain remembers.
Have fun.

 

[Luckyshot7]

If I had a headspace supposedly 0.005 too short, I would go down the following list of options from top to bottom (best to worst)

1. send the barrelled action back to the smith/barrel supplier for correction
2. Just bump the shoulders 0.005" more in the sizing die and shoot it as-is
3. Hand reamer rental and DIY lengthen the headspace
4. Use a shim

If the shim was already in hand from the beginning? Maybe I'd do that right away.

Worst thing that would happen is that you find out very quickly that the case head is not not supported enough. I'm assuming that adding 0.005 of clearance is not going to really matter at all there. But it's not my gun or my face either

 

[1mechanic]

You're going to seal 60,000 psi on a 0.005" steel washer and to add to your woes you don't tighten the barrel to the correct torque? Have fun

That 60,000 psi is sealed by the barrel steel the shim only has the pressure of how tight the barrel is torqued to.

 

[1mechanic]

I see your point, the reference points all change regardless of how you adjust the chamber.

The action stays static and you move the barrel in or out to establish headspace, whether you use a nut, shim or the thickness of the recoil lug, it is essentially the same outcome.

As far as carrier shims and valve shims, the carrier adjusts side load of the ring and pinion, once the caps are torqued down, relatively little load on the shims. The pocket shims under valve springs are much thicker and are constantly lubricated, I have seen them fail, while rare, I don't know that I have ever seen them thinner than .015".

This has been a very enlightening discussion

I see your point on the shims on the carrier don't have much pressure on them but I have worked in several other things where shims have a lot of clamping pressure on them and they do not fail or get damaged. They aren't moving they are just a spacer.

 

[Revolting Peasant]

From the back of my head:

Contact between stainless & chrome-moly steel:
from wikipedia
"Dissimilar metals and alloys have different electrode potentials, and when two or more come into contact in an electrolyte, one metal (that is more reactive) acts as anode and the other (that is less reactive) as cathode. The electropotential difference between the reactions at the two electrodes is the driving force for an accelerated attack on the anode metal, which dissolves into the electrolyte. This leads to the metal at the anode corroding more quickly than it otherwise would and corrosion at the cathode being inhibited."

Both stainless & chrome-moly steel share the same general location at the middle of the Anodic Index, & that means an even balance between most cathodic and most anodic. The potential is just not there for any electrolytic exchange.

Want to see potential at work?- go to copper (.35) & zinc (1.25) with some acid.

Some kind of Loctite other than blue ?

Increasing headspace is best done by making the chamber deeper using a finish reamer. This may be done by hand turning using no-go & go gauges. A shim will increase headspace but will also increase the gap between end barrel face/surface & bolt end including bolt face, plunger ejector & extractor. A replacement barrel might have correct headspace and bolt not close as any clearance between barrel face & bolt end (nose) would not exist.

Grinding down a shell holder is a fix for an excessively short chamber. I have a 6mm AI that was chambered to allow a crush fit to FF brass. The crush fit required excessive crush, so I ground down a shell holder that lives in the same box with the F/L 6mm AI die.

Exactly. Well written explanation, better than I could have done. Thank you.

I have rec bolts, receivers, barrel lugs, and barrels/barrel devices that are all of dissimilar metals. CMoly recievers with stainless barrels and vice versa. All manner of different combinations. Never have I seen any dissimilar metal corrosion and I've taken them apart and swapped parts around on a regular basis for years. And then bolted the whole mess in an aluminum chassis or bedding block. Still no problem.

 

[Revolting Peasant]

Whole lotta knee jerk reactions every time someone does something a bit different without stopping and thinking a minute about what is actually happening.

The shim isn't a gasket. It's not holding pressure back. It's a spacer. If you continued the thread out further on the barrel shank and added an adjustable barrel nut, you would be doing the same thing. Moving the barrel/chamber shoulder datum point away from the bolt face to adjust the headspace. Barrel nuts do not blow up or blow off due to pressure. Why would a shim?
Torque on the barrel to the receiver makes no difference on the ability to contain pressure. You can use a barrel nut style barrel, with no nut. Screw it in and set the headspace to a go gauge , and shoot it with the barrel just sitting in the receiver. It's not going to blow up. It's not gonna rocket off downrange. Torque (to a shoulder or with a barrel nut) just gives you a repeatable index and assures the barrel doesn't loosen over time and use.
Yes, you have to look and make sure you do not move the barrel out so far you have too much unsupported brass at the bolt face. But the amounts of adjustment we are talking here will not do that. Again, you could do the same with a barrel nut install.
Go back through this thread and count how many quality information posts are in here. Not trying to single out anyone but stop and think a minute before typing. Yes, discussion is good and educational but read and think please. Just for a minute.