Gunsmithing Setting headspace on a build.

[JCCinOhio]

I understand that you want the chamber to close on the go, and not close on the no-go.. but, wondering if there are intricacies in there to help possibly improve accuracy?

What I'd like to know is.. will it help to have the bolt barely close on a go gauge so as to minimize case expansion? I know that after you shoot the brass the first time you just bump it back a few thou.. but taking the .223 for example, the go at PTG is 1.464" and no-go is 1.467". So if I go all the way in till it won't close on the go, and then back it out till it barely closes, I'd think I have the tightest chamber possible? Am I thinking clearly? This moon phase gets me...

 

[DAVETOOLEY]

It won't have any effect on accuracy. Barrel quality and the chamber concentricity are 99 % of it.

 

[natdscott]

/thread.

 

[Supersubes]

Like Dave said, no accuracy improvement. For the sake of brass life I chamber my own barrels a bit on the short side, depending on the virgin brass size. Does it make any difference, probably not. Since I can control it on my end, I do. For example, my personal creedmoor chambers are go minus .001”(will not close on the go). Virgin lapua creedmoor brass is .0035-.004 short of go. Hornady is consistently the longest in virgin form, and would just touch in my chambers. I do this knowing that my sizing dies (I have several for creedmoor) will easily accommodate a shorter than go case, regardless of brass brand. I would not do this for just anyone if I didn’t trust their knowledge of sizing, or if they planned to shoot factory ammo.

 

[hereinaz]

Like Dave said, no accuracy improvement. For the sake of brass life I chamber my own barrels a bit on the short side, depending on the virgin brass size. Does it make any difference, probably not. Since I can control it on my end, I do. For example, my personal creedmoor chambers are go minus .001”(will not close on the go). Virgin lapua creedmoor brass is .0035-.004 short of go. Hornady is consistently the longest in virgin form, and would just touch in my chambers. I do this knowing that my sizing dies (I have several for creedmoor) will easily accommodate a shorter than go case, regardless of brass brand. I would not do this for just anyone if I didn’t trust their knowledge of sizing, or if they planned to shoot factory ammo.

I chamber on the shorter side for this reason-brass life reloading. I don't shoot factory ammo all that often, but I have had some that are hard to close the bolt on.

 

[Fig]

I "think", based on the round counts from my last two (shot out) barrels and my current one, that chambering as short as practical also allows you to increase your COL on the latter part of barrel life, chase the lands, and squeeze out several hundred more cartridges before precision chits the bed. I start checking the chamber with an OAL gage and lengthening my COL again after about 2000 rounds (or if groups start opening up). My last barrel was still holding good groups till I ran out of neck. I've found that a barrel can still look sharp all the way to the muzzle but gets shot out at the throat first.

 

[Sinocopa]

Good to know !

 

[flatland1]

I like to ream until I can just barely feel drag on the go gauge when closing a bolt that's had the ejector plunger stripped out of the bolt body, yet won't even start to close on the go gauge with a single layer of 3M Magic tape on it. I've done a barrel or two where I left the chamber a bit too short and then had some accuracy issues that went away after reaming a bit deeper.

 

[Easy_E]

Thanks for posting this was a question I had but didn't ask.

 

[natdscott]

To my knowledge, there is ZERO accuracy benefit to chambering a rifle that tightly, flatland. That said, the DOWNside is clear: lack of reliability with varied ammunition or with range grunge, vegetation, sand...basically ANYthing not found on a Benchrest firing line. While this is possibly mitigated by handloading every round that the rifle ever eats, life has a way of throwing curve balls, so a LITTLE cushion in space is not a bad thing.

Take 6.5 Creed as an example: the cartridge has a SAAMI range of 0.005". Not as tight as a Garand, but damned small just the same.

Do you NEED to put that right at the bottom? Or might it be okay to just put it kind-er in the middle? 0.002" over the bottom adds a bunch of reliability and costs virtually nothing in casing life. Casings are about 0.002" under the bottom, so that would put your TOTAL expansion on the first firing at 0.004", which is quite reasonable.

The OTHER side of the coin is that I have also set up a barrel too tightly and had issues until I fixed it. There was NO upside to doing that.

-Nate

 

[Supersubes]

To my knowledge, there is ZERO accuracy benefit to chambering a rifle that tightly, flatland. That said, the DOWNside is clear: lack of reliability with varied ammunition or with range grunge, vegetation, sand...basically ANYthing not found on a Benchrest firing line. While this is possibly mitigated by handloading every round that the rifle ever eats, life has a way of throwing curve balls, so a LITTLE cushion in space is not a bad thing.

Take 6.5 Creed as an example: the cartridge has a SAAMI range of 0.005". Not as tight as a Garand, but damned small just the same.

Do you NEED to put that right at the bottom? Or might it be okay to just put it kind-er in the middle? 0.002" over the bottom adds a bunch of reliability and costs virtually nothing in casing life. Casings are about 0.002" under the bottom, so that would put your TOTAL expansion on the first firing at 0.004", which is quite reasonable.

The OTHER side of the coin is that I have also set up a barrel too tightly and had issues until I fixed it. There was NO upside to doing that.

-Nate

It was already mentioned that this isn’t wise on a gun that will eat factory ammo. For the handloader though, we set the headspace clearances during sizing, just as we would after the first firing in a longer chamber. The go/no go window is small, and what we’re talking about here is smaller still. I don’t buy the accuracy issue thing on a shorter chamber. GO plus .002 (or .001, .003 etc) and all is well, but GO minus .001 and the thing won’t shoot? I don’t buy it. Something else was going on if you had accuracy issues in that scenario.

 

[Killswitch Engage]

put a piece of scotch tape on the head of your go gauge and set it so it closes with slight resistance. that is go +.002 happy place

 

[natdscott]

It was already mentioned that this isn’t wise on a gun that will eat factory ammo. For the handloader though, we set the headspace clearances during sizing, just as we would after the first firing in a longer chamber. The go/no go window is small, and what we’re talking about here is smaller still. I don’t buy the accuracy issue thing on a shorter chamber. GO plus .002 (or .001, .003 etc) and all is well, but GO minus .001 and the thing won’t shoot? I don’t buy it. Something else was going on if you had accuracy issues in that scenario.

I am well aware of what was already mentioned, because I too can read. On review, you may note that my response was crafted, and staged, as one of DIRECT response to flatland's post. It was also made out of a desire to re-emphasize and offer my own take on why setting headspace to a reasonably moderate dimension is an asset.

Please do re-read: I didn't say I had ACCURACY issues with that rifle. It was 1 to 1.1 MOA with even ball ammo.

The issue was that it would not FUNCTION with several casings. You can buy it, or you can not buy it, but if the fucking round won't chamber because you didn't leave "enough" room (that definition being varied)...then that is, by ANYONE'S definition, a significant detriment to that rifle's accuracy.

"GO minus 0.001" will very GD well not chamber a round at +0.001. Not without a mallet.

I don't need to be lectured on handloading as it pertains to FL sizing and casing lengths. Given that I tell my smiths where to stop the reamer because I have often already bought the brass intended for that barrel and measured it....I guess I have a handle on that dimension.

put a piece of scotch tape on the head of your go gauge and set it so it closes with slight resistance. that is go +.002 happy place

Yup. There are some other methods, but this one works with surprising accuracy compared to it's humble appearance.

-Nate

 

[Supersubes]

I am well aware of what was already mentioned, because I too can read. On review, you may note that my response was crafted, and staged, as one of DIRECT response to flatland's post. It was also made out of a desire to re-emphasize and offer my own take on why setting headspace to a reasonably moderate dimension is an asset.

Please do re-read: I didn't say I had ACCURACY issues with that rifle. It was 1 to 1.1 MOA with even ball ammo.

The issue was that it would not FUNCTION with several casings. You can buy it, or you can not buy it, but if the fucking round won't chamber because you didn't leave "enough" room (that definition being varied)...then that is, by ANYONE'S definition, a significant detriment to that rifle's accuracy.

"GO minus 0.001" will very GD well not chamber a round at +0.001. Not without a mallet.

I don't need to be lectured on handloading as it pertains to FL sizing and casing lengths. Given that I tell my smiths where to stop the reamer because I have often already bought the brass intended for that barrel and measured it....I guess I have a handle on that dimension.



Yup. There are some other methods, but this one works with surprising accuracy compared to it's humble appearance.

-Nate

No need to be a smart ass about it. You were ambiguous about what “issues” you were having, and you quoted flatland, who had accuracy issues.


"GO minus 0.001" will very GD well not chamber a round at +0.001. Not without a mallet”

Does this point really need to be made? I don’t think anybody in the room fails to grasp the concept that an out of spec/oversized round won’t fit in an out of spec/undersized chamber. It’s probably worth noting that the same out of spec round won’t fit in an IN-SPEC but minimum chamber. I’m sure you already know this, but you made what I thought was an odd point....

We agree on almost everything here, which is primarily reliability. Nobody beats that drum more than I do.

 

[Rubicon Precision]

I like to ream until I can just barely feel drag on the go gauge when closing a bolt that's had the ejector plunger stripped out of the bolt body, yet won't even start to close on the go gauge with a single layer of 3M Magic tape on it. I've done a barrel or two where I left the chamber a bit too short and then had some accuracy issues that went away after reaming a bit deeper.

If you can feel the go gauge while fitting the barrel, chances are it's not going to close on go when the barrel is torqued down. Personal stuff, probably won't matter unless you are shooting factory ammo or find out your sizing die won't bump the shoulder. Customer stuff, that's not a good place to be.

 

[FCrifles]

Go + .003 before barrel torque. This could go either way a little bit depending on barrel torque used.