Gunsmithing Headspace question with Sig Cross factory 6.5C barrel.

[nickw]

I appreciate your thoughts and any help in advance.

I have an Sig Cross with a Factory 6.5 Creed barrel. Need opinion if I need to send it back to Sig for HS issue.

Back story- Rifle (new to me / used) shoots very well but I was experiencing some hard bolt open, cratering in primers and some shinny marks on case head (no round ejector marks) with some 6.5C ammo I had loaded for my Impact / Proof barrel combo. I thought it was the Lapua brass lower case volume but the load is not hot (41.8gr H4350 under. Hornady 147). I decided to try some different loads w/ 130 Berger Hybrids 1x fired Lapua brass from a different rifle with H4350, R26 and VV N160. Again, all mid-range powder charges. Same result. I was jumping the bullets .075 so tried some with .025 jump and had same result.

I had some factory Remington 140gr Core-Lokt ammo and it chambered fine and the bolt opened normally. I then measured the Remington brass I had fired with a Hornady Headspace Gauge and it was 1.530. I measured a piece of new Rem brass / anmmo and it was 1.529.5. As a comparison, I checked my Lapua brass from my Impact / Proof rifle and fired brass measured 1.532. I had bumped the shoulder of the Lapua brass .002 to 1.530 to load it in my Sig (In hindsight this wasn’t enough as the fired brass measures 1.530 out of the sig).

A guy in the Sig Cross forum mentioned having hard bolt lift with Peterson brass. He also said his bolt would not close on a go or no go gauge. His was an aftermarket barrel, but I decided to check the HS on my Sig’s factory barrel today. Bolt closed and opened VERY hard on Forster go gauge and didn‘t close on a no go gauge. I measured my Forster go gauge with Hornady HS tool and it measures 5.131.5-5.132. With this same go gauge in my impact 6.5C the bolt closes normally.

My Sig‘s head space is to short correct?

Thanks again.

 

[Smokin7s]

As long as they’re not sharing brass and your ammo in the sig will chamber better too short than too long.

 

[nickw]

As long as they’re not sharing brass and your ammo in the sig will chamber better too short than too long.

So you’re saying even though the bolt closes really hard on the go gauge, to just run dedicated brass for the Cross and fl/size bump accordingly? It makes me uncomfortable that the bolt closes so hard on a go gauge. New brass is only growing a 1/2 thou in the chamber. Pretty tight. I hear what you’re saying though. Thanks.

 

[Garvey]

So you’re saying even though the bolt closes really hard on the go gauge, to just run dedicated brass for the Cross and fl/size bump accordingly? It makes me uncomfortable that the bolt closes so hard on a go gauge. New brass is only growing a 1/2 thou in the chamber. Pretty tight. I hear what you’re saying though. Thanks.

"My Sig‘s head space is to short correct"

Correct.

You should have an easy cam-over with a go-gauge.

 

[Smokin7s]

So you’re saying even though the bolt closes really hard on the go gauge, to just run dedicated brass for the Cross and fl/size bump accordingly? It makes me uncomfortable that the bolt closes so hard on a go gauge. New brass is only growing a 1/2 thou in the chamber. Pretty tight. I hear what you’re saying though. Thanks.

My ts customs 22 creed doesn’t grow a measurable amount and closes tight on new alpha brass and snug on a go gauge.

 

[Supersubes]

That load may not have been bad in the impact, but thats WAY over max.

 

[nickw]

That load may not have been bad in the impact, but thats WAY over max.

Thank you. I realize that Hogdon says the max charge is 39.2 of H4350 in a 6.5C w/ a 130 and 41.8 with a 147. That said, it’s well established that you can safely load H4350 with a higher charge weight, many running between 41.5 and 42gr. I did load some 130s w/ 40gr of H4350 and 42gr of VV N160 in 1x Lapua brass and saw the same pressure. No pressure with the factory Rem ammo.

I guess I could just run Rem brass and keep the load below max since it works. I just didn’t like how hard the bolt closed on the go gauge. I’ve got no wiggle room in this chamber. I may just have a smith reset the headspace. Thanks all.

 

[Garvey]

That load may not have been bad in the impact, but thats WAY over max.

Hodgdon also says 40.0 gr of H-4350 is max under a 140 gr A-Max.

And every hand loaded 6.5 Creedmoor in the world running 41.5 to 43.0 gr.

 

[Supersubes]

Hodgdon also says 40.0 gr of H-4350 is max under a 140 gr A-Max.

And every hand loaded 6.5 Creedmoor in the world running 41.5 to 43.0 gr.

Compare the hodgdon 140 data with the 147 data. The heavier bullet with 1.8gr more charge makes exactly the same pressure as the 140. Bad data.

Hornady says 40.3 gr with the 147, and not in Lapua brass.

This site is loaded with shit data from people who have no idea what pressure is. Fortunately the OP is seeing it.

@nickw when the bolt wont close on a Go gauge, dont force it. Great was to gall the bolt lugs. If it doesn't fall closed easily, its out of spec, just stop right there. Fwiw, I dont think your chamber is the issue. Without velocities, we’re just guessing at this.

 

[nickw]

Compare the hodgdon 140 data with the 147 data. The heavier bullet with 1.8gr more charge makes exactly the same pressure as the 140. Bad data.

Hornady says 40.3 gr with the 147, and not in Lapua brass.

This site is loaded with shit data from people who have no idea what pressure is. Fortunately the OP is seeing it.

@nickw when the bolt wont close on a Go gauge, dont force it. Great was to gall the bolt lugs. If it doesn't fall closed easily, its out of spec, just stop right there. Fwiw, I dont think your chamber is the issue. Without velocities, we’re just guessing at this.

I appreciate the input. Always learning. Yes agree, shouldn’t have forced the bolt to close on go gauge. Lugs looked fine, but I hear you. I have velocities for 3 loads out of the Cross. 147gr ELDM, 41.5 H4350, Lapua brass, 2550fps. 130gr Berger Hybrid, 42.0 H4350, Lapua brass, 2630fps. Factory 140gr Remington CoreLokt, 2580fps. Factory Sig 18” barrel.

I called Sig today. No warranty available because I’m the second owner and I’ve fired reloads from the rifle.

Agree, don’t necessarily don’t think it’s the chamber, but HS is clearly short / not set properly at factory.

Appreciate the input.

 

[Garvey]

Compare the hodgdon 140 data with the 147 data. The heavier bullet with 1.8gr more charge makes exactly the same pressure as the 140. Bad data.

Hornady says 40.3 gr with the 147, and not in Lapua brass.

This site is loaded with shit data from people who have no idea what pressure is. Fortunately the OP is seeing it.

@nickw when the bolt wont close on a Go gauge, dont force it. Great was to gall the bolt lugs. If it doesn't fall closed easily, its out of spec, just stop right there. Fwiw, I dont think your chamber is the issue. Without velocities, we’re just guessing at this.

This site and Hodgdon, and printed manuals is not where I find out where pressure is. That happens on my rifle ranges. And one of them is in line with the loading bench. I can charge brass, and seat a bullet six feet from a rifle that is aimed down a range with berms at 100, 200, and 300 yards. Then drive 250 yards to a second range with steel set every hundred to 800 yards.

And no. It is not a pressure issue. If bare brass is only growing .0005" and a Go-gauge won't chamber, then the chamber is too tight. Which is the reason I jumped on Hodgdon's published data. I have exceeded their maximum many times, and done it safely, and make excellent shooting ammo.

 

[Ape_Factory]

I may just have a smith reset the headspace. Thanks all.

That's the beauty of the Cross, it's easily done.

 

[nickw]

That's the beauty of the Cross, it's easily done.

 

[FALex]

I've learned, even up until very recently, you can sometimes get away with swapping brass between different rifles, and sometimes you cannot. I found it hard to believe, but I have determined that it actually has to do with the portion of the case just above the extraction groove (moving toward the mouth), where the web inside the case would be.

Depending upon the chamber, that portion can expand, and allow cases to not further "seat" fully in one chamber, while they may still work in another chamber. This is just what I have found in terms of the only thing that makes sense. However, check your cases and let me know, because it'd be nice to have more of a sample size than 1.

 

[Xfrog]

I agree the chamber is too short. The statement above is also correct in that different companies cut different chambers. For instance my scar once fired brass must be completely resized if want to shoot it in several bolt actions. I used to reload the 308 lake city for my remmys. Now I shoot the lake city through a bolt first and separate from the autos.