6mm BR headspace discrepancy

[Just Say Moe]

I’m confused. First I am a Pharmacist - not a machinist or gunsmith.....

I have a 6mm BR Remage barrel setup. Using the .350 bushing on my Hornady Lock N load tool, my Forster go gauge reads 1.158. I screwed the barrel on and set the headspace using the go gauge with the ejector removed. A fired Norma case ends up with a datum measurement 1.189 with some signs of case stretch. I reheadspaced the barrel and got approximately the same results. A different action also got about the same case stretch.

I found some new Lapua brass that measures 1.156. Obviously my action swallows the new Laupa brass. I reset the headspace using the Lapua brass. I haven't fired a round with this setup yet.

Now the datum COL measurement for loaded rounds at the lands using the Hornady tool have gotten longer even as the length of the “long” Norma brass is the same as new “normal” Lapua brass at 1.555. I would think the datum OAL of a loaded round would be shorter since I screwed the barrel in slightly while setting the headspace with Lapua brass.

1. Why was the brass from using the go gauge to set headspace so long after firing?

2. Why are the loaded round Datum COL’s with the new headspace longer and not shorter?

3. Are my measuring tools and or methods suspect?

4. My reamer print reads using the .375 bushing my headspace datum should be between 1.1456-1.1495. New Lapua brass is 1.135 which is shorter than what the reamer print says. I assume this is “room to grow” when the round is fired?

Many thanks for any replies.

 

[William Vogel]

I’m confused. First I am a Pharmacist - not a machinist or gunsmith.....

I have a 6mm BR Remage barrel setup. Using the .350 bushing on my Hornady Lock N load tool, my Forster go gauge reads 1.158. I screwed the barrel on and set the headspace using the go gauge with the ejector removed. A fired Norma case ends up with a datum measurement 1.189 with some signs of case stretch. I reheadspaced the barrel and got approximately the same results. A different action also got about the same case stretch.

I found some new Lapua brass that measures 1.156. Obviously my action swallows the new Laupa brass. I reset the headspace using the Lapua brass. I haven't fired a round with this setup yet.

Now the datum COL measurement for loaded rounds at the lands using the Hornady tool have gotten longer even as the length of the “long” Norma brass is the same as new “normal” Lapua brass at 1.555. I would think the datum OAL of a loaded round would be shorter since I screwed the barrel in slightly while setting the headspace with Lapua brass.

1. Why was the brass from using the go gauge to set headspace so long after firing?

2. Why are the loaded round Datum COL’s with the new headspace longer and not shorter?

3. Are my measuring tools and or methods suspect?

4. My reamer print reads using the .375 bushing my headspace datum should be between 1.1456-1.1495. New Lapua brass is 1.135 which is shorter than what the reamer print says. I assume this is “room to grow” when the round is fired?

Many thanks for any replies.

Are you measuring your bolt head to barrel clearance after headspace setting? Needs 0.005-0.007 clearance

 

[Just Say Moe]

Are you measuring your bolt head to barrel clearance after headspace setting? Needs 0.005-0.007 clearance

No - how is that done?

 

[jackieschmidt]

No - how is that done?

Screw the barrel in until it fits snug against a closed bolt. Slowly back it out about 1/8 turn. That will give you around .007 bolt nose to barrel clearance.

Chamber the headspace go gage. If the bolt falls, add a piece of .003 masking tape to the face of the gage untill it has feel. Hopefully, it won’t be more than 2 pieces.

The thickness of the tape is the true headspace. If it is more than .005, screw the barrel in a little and get it around .003 on the headspace gage. If the headspace is still excessive after you set the bolt nose to barrel clearance, then it is chambered too deep.

Forget about all of that datum line crap. Trust the headspace gage. If the barrel tenon nose is machined correctly, you should have no problems.

 

[Tim Singleton]

Like Jackie said
Trust your steel Go gauge
The tool you are using to measure the go gauge then the fired brass may be contacting the shoulder on the brass slightly different than on the GO gauge
Set the barrel with the Go gauge shoot away then adjust your dies to size whatever your cases come out to be
No need to overcomplicate things

 

[urbanrifleman]

Take the headspace gauge and add one piece of tape to the back. Run the barrel down on the gauge. Set it there. That's gauge plus two thou.

Two pieces of tape is no go.

 

[J.d. Popkes]

Primer removed from fired cases?

Go gauge plus tape like already mentioned.

Measure virgin vs fired. Probably less than.007 difference.

Be sure you can bump the shoulder after a couple firings.

Throw away all prints.

 

[Just Say Moe]

Primer removed from fired cases? no but I machined a dimple in the base of the measuring anvil to allow for any primer protrusion

Go gauge plus tape like already mentioned.

Measure virgin vs fired. Probably less than.007 difference. see below

Be sure you can bump the shoulder after a couple firings.

Throw away all prints. haha will do

I appreciate all of the replies. I get the picture now not to get lost in numbers!

Virgin = 1.158 Fired = 1.189 31 thou of stretch which is what concerns me. Some cases were starting to separate. This is with the go gauge and 2 pieces of tape as a no go.

 

[Just Say Moe]

Like Jackie said
Trust your steel Go gauge
The tool you are using to measure the go gauge then the fired brass may be contacting the shoulder on the brass slightly different than on the GO gauge
Set the barrel with the Go gauge shoot away then adjust your dies to size whatever your cases come out to be
No need to overcomplicate things

Thanks this is what I did but the cases started having rings around them towards the base and some were starting to separate.

 

[J.d. Popkes]

I appreciate all of the replies. I get the picture now not to get lost in numbers!

Virgin = 1.158 Fired = 1.189 31 thou of stretch which is what concerns me. Some cases were starting to separate. This is with the go gauge and 2 pieces of tape as a no go.

You can use virgin brass as your gauge too. I don’t know what is going on with the situation but if you pay attention to your measurements there’s not a problem with using the brass instead.

 

[mudduck]

I appreciate all of the replies. I get the picture now not to get lost in numbers!

Virgin = 1.158 Fired = 1.189 31 thou of stretch which is what concerns me. Some cases were starting to separate. This is with the go gauge and 2 pieces of tape as a no go.

I would suggest you not fire any more until u know for sure want the issue is. If you installed as Jackie says sounds like it’s not correct

 

[Just Say Moe]

I reset the barrel today using they suggestions. Loaded up a few rounds and went under the house and blasted the dirt.... and ended up with fired cases of 1.1675 - with about 9 thousands of stretch. Much better than 30.

This is my "starter" rifle and the next barrel I get will be shouldered. My first batch of brass was Norma, so when I felt comfortable with my system (and learned the step up from reloading hunting to target ammo) I got some Lapua brass and I don't want to ruin it!

You guys are the best!

Moe

 

[AlNyhus]

This is my "starter" rifle and the next barrel I get will be shouldered.

A solid move for lots of reasons.

Good shootin' -Al

 

[spike-55]

tighten her up a little more till you get about 4-5 thou stretch and you will be good to lock it down tight
stan
set your sizing die up to bump the shoulder back just till it chambers smoothly, probably around 2 thou and go have fun.

 

[NorCalMikie]

You planning on using "factory loaded ammo"??
If SO, headspace gauge.
If NOT, set it where YOU want it.
I prefer "snug" headspace. That way, less brass to move when bumping the shoulder.
None of mine could chamber factory loaded ammo on a bet.

 

[Just Say Moe]

You planning on using "factory loaded ammo"??
If SO, headspace gauge.
If NOT, set it where YOU want it.
I prefer snug headspace. That way, less brass to move when bumping the shoulder.
None of mine couldn't chamber factory loaded ammo on a bet.

100% Handload!

thanks

 

[mikecr]

I think your chamber is too deep.
That screwing the barrel in more is merely causing you to run out of breech clearance (that Jackie mentioned).
Possibly making you 'think' that you're at 0 HS on the go gauge, while you're still too long to chamber shoulder..
Did your barrel finisher use YOUR action to chamber your barrel?

 

[dellet]

The answer to your original question “are your measuring methods suspect” is yes.

Assuming you are using the Hornady tool with the dummy case, most of your confusion is probably there.

Have you measured case base to shoulder datum of the Hornady case? Most likely it will be different than the same measurement on your brass. Best is to make a custom case based on a fired case, sized as you will actually shoot it.

You have two things going on. Headspace, bolt face to shoulder contact point in the chamber, and bolt face to bullet contact at the lands. You said that you are seating the bullet to touch the lands. Technically you are headspacing off the bullet, not the shoulder of the brass. In a perfect world, or brass sized the same, both points would be touching. That’s why the Hornady tool case needs to be the same size as what you shoot to have any real meaning.

The cartridge overall length Should remain constant with the bullet touching the lands. That’s base to bullet ogive. But headspace could vary, base to shoulder. That’s why it is possible to to have different headspace measurements and the same overall length. When you are loading to a touch or jam, the headspace is determined more or less by neck length, the distance from the shoulder to bullet ogive. More neck, less body, is more headspace, more gap between case shoulder and chamber. The bullet is touching.

More body, less headspace will give You the same overall length, with the same bullet touch.

This is easier seen with a jump. The jump distance will change with a headspace change when moving the shoulder. As base to shoulder distance changes, you push or pull the neck back and forth.

The Hornady gauge gets even less precise if the shoulder angle is different than the brass you are shooting.

There is a learning curve to learning to use the tools and being able to trust the measurements, that curve is reduced by using a case sized as it will be shot. I would bet that measuring the Hornady case might clear up a lot of your confusion.

 

[STS]

If you have .031 of stretch the first thing I think of is that you didn't get the go gauge snapped into the extractor before you tightened the nut. Your go gauge was stopping on the extractor, not the bolt face.
Edit to add, you can check this by putting an witness mark from the barrel onto the nut with a Sharpie marker. When you tighten it up make sure the go gauge is against the bolt face then tighten. If the witness mark is in a different place, you found the problem. Good luck.
If you have pressure problems with it when you get it squared away, try a Beta Blocker.

 

[Old Navy]

I didn't search this here but I seem to remember some or one of the Remage barrel makers were sending the barrel out too long (cut too deep) and you needed to cut .010" off to properly headspace it?