Reloading the 277 Fury 6.8x51 SIG Hybrid Case

[khuber84]

I noticed a sharp edge there at the steel brass junction. The steel must be thinner there also so it makes me wonder if that sharp edge flex outward and act like a knife cutting into the chamber.

Almost like a belt line is what I was told. I would guess it's due to dissimilar expansions causing a pinch there possibly.

 

[xsn10s]

Almost like a belt line is what I was told. I would guess it's due to dissimilar expansions causing a pinch there possibly.

Could be. But I believe the steel is a smaller diameter than the brass. And I don't see the steel expanding except MAYBE the thin part where it meets the brass. But that's just a wild guess on my part. All I can say is yes it's like a belt line and starts out very faint. And grows more defined with each firing. And then at the top of the belt line a very sharp line forms. I can catch my finger with that line. I stopped using them at that point.

 

[walk2112]

Could be. But I believe the steel is a smaller diameter than the brass. And I don't see the steel expanding except MAYBE the thin part where it meets the brass. But that's just a wild guess on my part. All I can say is yes it's like a belt line and starts out very faint. And grows more defined with each firing. And then at the top of the belt line a very sharp line forms. I can catch my finger with that line. I stopped using them at that point.

Good info. You remember about how long it took for the marring to show up? As in how many rounds on a one chamber?

 

[xsn10s]

Good info. You remember about how long it took for the marring to show up? As in how many rounds on a one chamber?

It was my 260 AI and I have a total of 12X rounds fired including fire forming and load development. It was forty cases total so I'd say I noticed a faint band around the 2nd to 3rd cycle of firing. Early on my fourth cycle of firing is when I could catch my finger in the defined thin line on the top of the "band". That is when I stopped using them. So 120-130 maybe total? My barrel is a stainless Rock Creek barrel which is very accurate. Frank messaged me back and forth and I asked about using chromoly barrels, nitrided barrels, and chrome lined. He didn't like chrome lined barrels due to possible accuracy issues. The other combinations helped delay the issue but it's still going to happen.

 

[xsn10s]

Let me also say others plan to use the hybrid cases on older barrels to test if their chambers get marred too. Or so they said in LRH forums. So that's something to consider. I really had high hopes for these cases. I still have them on the shelf.

 

[walk2112]

Dang, I’ve been wanting to shoot the crap out of them in my 7-08 but should have figured there’s no free lunch. I was thinking it would take more rounds than that to cause any issues. Thanks for info.
Not really interested in marring the chamber of my stainless featherweight barrel, maybe I’ll just try 10-20 for science in that barrel

 

[xsn10s]

Dang, I’ve been wanting to shoot the crap out of them in my 7-08 but should have figured there’s no free lunch. I was thinking it would take more rounds than that to cause any issues. Thanks for info.
Not really interested in marring the chamber of my stainless featherweight barrel, maybe I’ll just try 10-20 for science in that barrel

That was my plan too. Run them in my Howa Superlite 7-08 and my Rem PSS 308. I shelved them to see if Sig or someone comes up with a solution. I estimate I have well over 10k rounds through my PSS since 1991. But my family bought that rifle for me when I returned from the Army so it has great sentimental value. It has great possibilities. We'll have to see what the future brings.

 

[HandgunHTR]

Let me also say others plan to use the hybrid cases on older barrels to test if their chambers get marred too. Or so they said in LRH forums. So that's something to consider. I really had high hopes for these cases. I still have them on the shelf.

I am at 120 rounds through my 7-08AI between fire forming and load development. I am shooting one of my Lapua brass cased cartridges after every 20 rounds to see if the issues shows up in my barrel (Bartlein). So far, the one I just shot looks like my "baseline" cartridge (fired before I started testing the hybrid brass). If the issue is going to show up, it should be shortly as I am going to be pushing the pressures up during load development.

I also have some Remington brass that I may shoot in it as well as Rem brass tends to be a little softer than Lapua, so maybe it will show a defect sooner.

 

[xsn10s]

I am at 120 rounds through my 7-08AI between fire forming and load development. I am shooting one of my Lapua brass cased cartridges after every 20 rounds to see if the issues shows up in my barrel (Bartlein). So far, the one I just shot looks like my "baseline" cartridge (fired before I started testing the hybrid brass). If the issue is going to show up, it should be shortly as I am going to be pushing the pressures up during load development.

I also have some Remington brass that I may shoot in it as well as Rem brass tends to be a little softer than Lapua, so maybe it will show a defect sooner.

Good deal. How many fire formed rounds in those 120 rounds? I'd say for me 40 rounds fire formed, I jam the bullets hard to get a good fire form. About 18 rounds load development max divided in 3 round groups. And about 124 rounds total fired, So 66 rounds of higher-pressure loads. I saw a rub mark which looked like a "band" on the steel section of the hybrid case. which lead me to keep an eye out.

 

[HandgunHTR]

Good deal. How many fire formed rounds in those 120 rounds? I'd say for me 40 rounds fire formed, I jam the bullets hard to get a good fire form. About 18 rounds load development max divided in 3 round groups. And about 124 rounds total fired, So 66 rounds of higher-pressure loads. I saw a rub mark which looked like a "band" on the steel section of the hybrid case. which lead me to keep an eye out.

100 of those were fireforming rounds with a 139 grain Hornady BTSP jammed 0.010" into the lands and a medium charge of Vectan 7000 powder (I have a bunch that I got cheap and it works great for fireforming stuff).

The other 20 were for load development using H4350 and a 162 grain ELDM at 0.020" off the lands. I have another 20 loaded up with Varget to try during the next range outing.

I remember you post on LRH showing your brass. That is what prompted me to shoot a brass-cased load after every 20 shots of hybrid-cased. Looking to see if I can replicate the issue.

 

[xsn10s]

100 of those were fireforming rounds with a 139 grain Hornady BTSP jammed 0.010" into the lands and a medium charge of Vectan 7000 powder (I have a bunch that I got cheap and it works great for fireforming stuff).

The other 20 were for load development using H4350 and a 162 grain ELDM at 0.020" off the lands. I have another 20 loaded up with Varget to try during the next range outing.

I remember you post on LRH showing your brass. That is what prompted me to shoot a brass-cased load after every 20 shots of hybrid-cased. Looking to see if I can replicate the issue.

Every 20 round check is a good idea. Just a heads up I looked at Frank's PM to me and here is what he said:

"At around 560 rounds the groove is a .001” deep. At 760 rounds fired the groove/ring in the chamber is about .002” deep.".

 

[Eric_F]

Sorry if this isn't allowed, but I posted some hybrid cases resized to 6.5 CM for sale if anyone is interested. These from are the more recent, heavier batches from AM.

WTS Thread 'Hybrid 6.5 CM-6.8x51 Fury cases'

Aug 9, 2025

I have some 6.8x51 aka 277 Fury cases I resized to 6.5 Creedmoor for sale. Neck turned to ~0.014". Weight sorted to 155-160.5 gr each.

109 are 1x fired (annealed and resized)
100 are sized but unfired

The fired cases were mostly a mild load (for the case pressure) of 44 gr H4350, which got 2750 fps with 140gr in a 20" Tikka.
Looking for $210 shipped.

• Eric_F
• Replies: 2
• Forum: Guns Classifieds

 

[walk2112]

Makes me wonder if there’s a difference between shooting hybrid cases that have been resized/fired several times vs resizing them and making them a 1 time use piece of brass in terms of how quick the marring would show up. Hypothesizing that the repeated firing/reshaping around the brass/steel junction could eventually allow for more easy movement there I.e. more force transferred to chamber wall under pressure and result in quicker marring maybe?
Would be very hard to prove out without two identical setups and load recipes.

Every 20 round check is a good idea. Just a heads up I looked at Frank's PM to me and here is what he said:

"At around 560 rounds the groove is a .001” deep. At 760 rounds fired the groove/ring in the chamber is about .002” deep.".

 

[Mike D Texas]

Every 20 round check is a good idea. Just a heads up I looked at Frank's PM to me and here is what he said:

"At around 560 rounds the groove is a .001” deep. At 760 rounds fired the groove/ring in the chamber is about .002” deep.".

So is this creating a groove in the barrel or a ridge in the barrel? If it’s a groove, does it really even matter?

 

[xsn10s]

So is this creating a groove in the barrel or a ridge in the barrel? If it’s a groove, does it really even matter?

It's in the chamber. And it eventually causes hard bolt lifts.

 

[longrangelead]

Sorry if this isn't allowed, but I posted some hybrid cases resized to 6.5 CM for sale if anyone is interested. These from are the more recent, heavier batches from AM.

WTS Thread 'Hybrid 6.5 CM-6.8x51 Fury cases'

Aug 9, 2025

I have some 6.8x51 aka 277 Fury cases I resized to 6.5 Creedmoor for sale. Neck turned to ~0.014". Weight sorted to 155-160.5 gr each.

109 are 1x fired (annealed and resized)
100 are sized but unfired

The fired cases were mostly a mild load (for the case pressure) of 44 gr H4350, which got 2750 fps with 140gr in a 20" Tikka.
Looking for $210 shipped.

• Eric_F
• Replies: 2
• Forum: Guns Classifieds

is "54gr H4350" a typo? I'm getting 2960 with 45gr, 21" barrel and noticeable bolt lift at 45.5gr w/130 ELDM's.

 

[Eric_F]

Sorry yes! 44 gr, I'll correct

is "54gr H4350" a typo? I'm getting 2960 with 45gr, 21" barrel and noticeable bolt lift at 45.5gr w/130 ELDM's.

 

[Eric_F]

So after all the talk on this thread, I pulled my barrel and definitely have a gouge at the base of the chamber where the steel case head sits. This was after 233 rds of hybrid 6.5 CM.If I get bored I'll find some soft brass and fire it a few times, see how much it takes to get clickers.

It also makes me curious if I have the same in my dies, I've formed 300+ hybrid cases in my Type S die.

 

[walk2112]

So after all the talk on this thread, I pulled my barrel and definitely have a gouge at the base of the chamber where the steel case head sits. This was after 233 rds of hybrid 6.5 CM.If I get bored I'll find some soft brass and fire it a few times, see how much it takes to get clickers.

It also makes me curious if I have the same in my dies, I've formed 300+ hybrid cases in my Type S die.
View attachment 921778

Whoah, damn that’s significant!

 

[khuber84]

So after all the talk on this thread, I pulled my barrel and definitely have a gouge at the base of the chamber where the steel case head sits. This was after 233 rds of hybrid 6.5 CM.If I get bored I'll find some soft brass and fire it a few times, see how much it takes to get clickers.

It also makes me curious if I have the same in my dies, I've formed 300+ hybrid cases in my Type S die.
View attachment 921778

I heard last year the hybrid brass did this to chambers. It was only one sample, but now this is 4 or 5 occurrences I've observed. This obviously isn't the way. Imagine what it'd do in full auto form in military applications after 1-2k rds.

To me, that almost looks like gas cutting. Maybe pressure is getting out the steel/brass junction and etching thr chamber a bit each firing.

For science sake, do you know someone nearby with a saami 65cm reamer? Would be interested if you took the reamer and spin it in with a T handle, if any that deformation would disappear.