Gunsmithing Headspace on a pre-fit question...

[santee116]

I recently assembled a pre-fit on my Bighorn Origin in 6.5 CM.

It threaded on smoothly no problems there, very little slop, torqued it to 75lbs. It will not close on the No Go. It will not close on the GO. It will close on a piece of virgin Lapua brass with no resistance. (The gauges are Clymer)

I will only be reloading for this rifle and my initial thought is run it as is and adjust my sizing die accordingly.

The manufacturer has agreed to adjust it, but would need my action and I would rather avoid that, if it's safe to shoot as is?

 

[Skunkworx]

You’ll be fine. Usually the real issue is when you can close your bolt on a no go gauge, then you have excessive head space which is a problem. You have the exact opposite issue, you have insufficient headspace.

insufficient head space has its own set of problems albeit different ones. Running factory ammo is probably a no go, but if you reload then it’s usually a non issue. Resizing brass may prove problematic if you cannot adequately bump back your shoulder enough. I know I’ve had this issue in the past and had to grind down my shell holder to add just a little more range. Other than that you should be ok.

 

[Mordamer]

It is safe to shoot.

If your sizing setup cannot push the shoulder back .002" then you might need to have the die or shell holder modified to allow more shoulder bump. This is unlikely as most full length sizing dies can push the shoulder back to at least where virgin brass shoulders are.

I think you'll be good to go.


Just to make sure, when you inserted the gauges you did remember to slide them under the extractor before closing the bolt? If not you could have gotten false readings.

 

[santee116]

It is safe to shoot.

If your sizing setup cannot push the shoulder back .002" then you might need to have the die or shell holder modified to allow more shoulder bump. This is unlikely as most full length sizing dies can push the shoulder back to at least where virgin brass shoulders are.

I think you'll be good to go.


Just to make sure, when you inserted the gauges you did remember to slide them under the extractor before closing the bolt? If not you could have gotten false readings.

Yep, slipped them under the extractor. I checked it when "hand tight" to begin with and it would barely close on the GO.

After torquing it would not close.

Thanks for the replies fellas, think I will shoot it and see about the re-sizing process. Like ya'll said, worst case I grind a touch off the shell holder or die.

 

[SBGreen0369]

i ran into this issue recently with a 6creed profit for an impact. barrel hand tight, GO gauge would barely close. NO GO would not close.

torqued barrel to 35 ft/lb per barrel makers recommendation.

issue ended up being a worn out reamer on their end and the chamber was not cut deep enough. took it out to fire and a projectile got stuck in the barrel because it was impending the lands. (i didn't fire the round. bolt was difficult to close to i tried to extract it and the case came out leaving the round stuck in the barrel.)

like the others have said above, it IS SAFE to shoot but id be interested to see how the groups look.

good luck man

 

[Mordamer]

i ran into this issue recently with a 6creed profit for an impact. barrel hand tight, GO gauge would barely close. NO GO would not close.

torqued barrel to 35 ft/lb per barrel makers recommendation.

issue ended up being a worn out reamer on their end and the chamber was not cut deep enough. took it out to fire and a projectile got stuck in the barrel because it was impending the lands. (i didn't fire the round. bolt was difficult to close to i tried to extract it and the case came out leaving the round stuck in the barrel.)

like the others have said above, it IS SAFE to shoot but id be interested to see how the groups look.

good luck man

What the barrel maker told you makes no sense. Maybe their reamer was worn, but that does not affect the setting of headspace. It can cause the bullet to get stuck as you experienced, but doesn't affect headspace.

 

[Steel head]

I set my barrels tight to the go gauge but I ensure the brass I’m planning to use is shorter than the gauge first.

 

[Lunchbox27]

You know... I should probably invest in a good set of gauges. Last 3 barrels I've spun on were solid (no issues), but after reading this it would be nice to have for the future.

 

[blb]

This is interesting. I have the same situation with neither Go nor No-Go gauges from Forster allowing my ARC Nucleus action to close on a PVA shouldered prefit. I could almost get it to close on the Go gauge, but not quite. I tried some snapcaps though and they worked fine. I haven't had a chance to try it with live ammo yet.

 

[Mordamer]

The reason this is most likely not an issue for hand loaders or people shooting factory ammo is that Virgin brass is almost always at least .004" shorter than a go gauge. There is generally about .004" between a go and no-go gauge. If your go gauge was just a little tight when the barrel was only torqued by hand then it probably crushed headspace by about .001" when torqued fully.

Take your comparator and measure your go gauge vs your virgin brass at the shoulder datum and you'll see what I am referring to.

 

[smoooth1]

Yep, slipped them under the extractor. I checked it when "hand tight" to begin with and it would barely close on the GO.

After torquing it would not close.

Thanks for the replies fellas, think I will shoot it and see about the re-sizing process. Like ya'll said, worst case I grind a touch off the shell holder or die.

Unless I missed it somewhere, this is a standard pre-fit, not a shouldered prefit?

 

[santee116]

Unless I missed it somewhere, this is a standard pre-fit, not a shouldered prefit?

Shouldered prefit. No barrel nut.

 

[Banango]

This sounds more like a negligence when measuring headspace or your actions tolerances are a little shorter than normal. What action is it?

 

[Banango]

I just re read and saw the action. Measure the tennon and see if its .890 in length and go guage protrusion should be .135 for a total length from guage to shoulder of 1.025"

 

[Banango]

Heres the blue prints directly from bighorn on the origin. This should help you figure out where the tolerances are out.

 

[bschneiderheinze]

I have 2 6brx’s and one is slightly tighter than the other you can’t interchange ammo the tighter will have a very tight bolt close and wont extract I think after a couple hundred fire forming rounds it will get better. I don’t use a no go just some tape.

 

[dustingaunder]

Could be the gauge. If the guy that cut It used a different gauge there could be tolerance between them. See if you can borrow a different gauge? If you’re only reloading a thou short isn’t going to sink you if you make sure you bump even new brass if it needs it to be reliable.

 

[Praeger]

Just treat it as a short chambered barrel and hand ream to your desired final headspace. Much easier than too long headspace. I followed this process before I bought a lathe. Criterion cut a short chambered barrel for my Badger M2013. I rented a reamer, and it took about 15 minutes. You don't even need to remove the barrel from the action.

https://rifleshooter.com/2017/01/installing-a-short-chambered-barrel-on-a-remington-700/

 

[santee116]

Follow up: Took it to the range today and it shot great. Just at good as any other custom barrel I've had. I was able to bump the shoulder back 2 thousands on the fired brass with the die, no problem.

Seems good to go.

 

[Ledzep]

Most case/ammo makers set the ammo headspace to the minimum spec to ensure they'll fit in min-spec chambers.

Head space on the short end is purely for function (if it's too tight it won't fit). Safety is really only a concern for long head space. If virgin cases easily chamber I wouldn't sweat it.

 

[Digetydog]

My Origin Action Instructions instruct me to remove the extractor before using the headspace gauges for my 280AI. For the life of me, I cannot find any instructions on how to remove the extractor. My Google/YouTube skills have completely failed me. I know how to remove the bolt head, but not the extractor.

Can anyone provide good guidance?

 

[Ledzep]

My Origin Action Instructions instruct me to remove the extractor before using the headspace gauges for my 280AI. For the life of me, I cannot find any instructions on how to remove the extractor. My Google/YouTube skills have completely failed me. I know how to remove the bolt head, but not the extractor.

Slide the gauge under the extractor and everything will be fine. They just don't want you to try to close the bolt and have the extractor snap over the steel HS gauge because it will ding the face of the extractor.

 

[MDof2]

Just treat it as a short chambered barrel and hand ream to your desired final headspace. Much easier than too long headspace. I followed this process before I bought a lathe. Criterion cut a short chambered barrel for my Badger M2013. I rented a reamer, and it took about 15 minutes. You don't even need to remove the barrel from the action.

https://rifleshooter.com/2017/01/installing-a-short-chambered-barrel-on-a-remington-700/

This. And then this again.

 

[Carl_Ross]

My Origin Action Instructions instruct me to remove the extractor before using the headspace gauges for my 280AI. For the life of me, I cannot find any instructions on how to remove the extractor. My Google/YouTube skills have completely failed me. I know how to remove the bolt head, but not the extractor.

Can anyone provide good guidance?

Bighorn extractor removal

I know it’s a dumb question but how do I remove the extractor on a bighorn origin?

www.snipershide.com

It's not a video but it isn't hard either. As usual much easier after you get it once. I have used a push pin or the point of a compass to depress the plunger.

That said, Ledzep is right, you can absolutely slip the rim under the extractor. However, if it slips out, stop and reset don't just force it. It only takes once to bugger the face of the extractor in my experience.

 

[Digetydog]

Bighorn extractor removal

I know it’s a dumb question but how do I remove the extractor on a bighorn origin?

www.snipershide.com

It's not a video but it isn't hard either. As usual much easier after you get it once. I have used a push pin or the point of a compass to depress the plunger.

That said, Ledzep is right, you can absolutely slip the rim under the extractor. However, if it slips out, stop and reset don't just force it. It only takes once to bugger the face of the extractor in my experience.

Thank you. It is good to know if I ever need to replace one.