6xc pressure signs

[billy308]

I was on this board a while ago with concerns about 6xc pressure signs. I'm shooting Sierra 107 gr,not moly)over 34-35 gr of H4350 in Winchester and Norma cases. That should be a mild load. I'm getting bright marks on the case head, sticky extraction, and loose primer pockets. Any advice? Thanks

 

[Mudcat]

That is a WUSS load so you shouldnt be having issues. What bbl do you have and round count?

John

 

[fivering]

Make sure you are not seating the rounds deeper than necessary.
That can really raise the pressure.

 

[billmo]

I was on this board a while ago with concerns about 6xc pressure signs. I'm shooting Sierra 107 gr,not moly)over 34-35 gr of H4350 in Winchester and Norma cases. That should be a mild load. I'm getting bright marks on the case head, sticky extraction, and loose primer pockets. Any advice? Thanks

What kind of accuracy are you getting from your rifle?

 

[Mudcat]

Make sure you are not seating the rounds deeper than necessary.
That can really raise the pressure.

One of the reasons i asked what bbl he is using and round count. There were a bunch of 6XC original bbls on the guns from the factory that had short throats due to dull reamers being used. If one tried to use a 115DTAC it led to rounds being WAY short and then pressure issues. Compound that with Norma/Tubb brass and we ran into some problems. I got a brand new bbl off my last rifle that had to be hit with a reamer....never fire a round out of it and its still sitting in the closet. lets just say I dont shoot Schnieders.

John

 

[billmo]

Good observation Mudcat. Bill

 

[FroggyOne2]

You know.. there is a reason why David stopped using those "S" barrels.. from what I hear.. He is now using "Rock Creek" barrels.

 

[billy308]

Thanks everyone! The rifle is a Tubb 2K from McMillan with the original barrel they put on at the factory. Maybe 800 rounds through it. Bullets are seated close to the lands but backed off a bit. Cases are trimmed to 1.87. No trouble chambering them, but the presseure signs have gotten worse with time. When I asked first about this,a year or so ago), just shiny marks on the case head. Now loose primer pockets and tough extraction of fired brass.

 

[mikecr]

That is a very light load.
How many times has this sticky brass been fired?
Could it be a die issue?

 

[Mudcat]

I bet its the bbl. I bet it was short chambered and your rounds are short and who know what else is going on with that thing now that it has 800 rds on it. Its exactly why I switched over to the Wilson bbls and believe in them so much that I keep them in stock and have sold a bunch over the last several years. For $235 you get a bbl thats just as accurate, will last just as long, costs half as much and doesnt give you fits!

If you have tried Win brass, try it. A bud had a S bbl that was doing this and we switched him from Tubb brass to Win brass and while the problem wasnt resolve till he stuck a Wilson bbl on, he did get to run hotter rounds.

Shooting 35grs of H4350 isnt going to impress any chronographs! Thats like running the 6XC at half throttle.

Have you borescoped that bbl?

John

 

[billy308]

Thanks again. Have used both Win brass,22-250, resized and fireformed into 6xc) and Norma 6xc. Get pressure signs with both. Die is Neal Jones, measurements taken from a fired case. Excellent! Haven't scoped the bore, but suspect the barrel may be the problem.
Any advice on re-barreling? Never done it. If it's just a matter of a barrel vise and wrench, no problem. But headspacing, lathe work etc are beyond my skills. Does McMillan still do the Tubb rifle?

 

[mikecr]

What velocities have you been getting?

 

[Mudcat]

BILLY; ADVISE, check head space. When 6XC first introduced we were setting up the chambers using 22/250 brass.,fire formed)every thing working OK.With the introduction of the new TUBBS and Norma brass the problems you describe surfaced.A head space difference of 10kAn isolated case you say. maybe,sounds suspicious to me..JIM

hmm...interesting thought. BUT, if he is having the same issue with the Win brass, would this be the case?

John

 

[Mudcat]

Any advice on re-barreling? Never done it. If it's just a matter of a barrel vise and wrench, no problem. But headspacing, lathe work etc are beyond my skills. Does McMillan still do the Tubb rifle?

If you can put a nut on a bolt, you can rebarrel a T2k! Takes longer to take off the sights and handguard than it does to put on a new bbl. I use a vise that my dad made which is nothing more than a beefed up Davidson/Tubb vise. You get the wrench with the gun. Taking off the OEM bbl can be tough sometimes, but use a extender on the wrench if need be and it will pop loose. When installing, be sure to have a nice amount of antisieze on there and torque it down till you feel your tricep pop/hurt, you are now good to go.

Cant say how many bbls I have changed on T2ks, but lets just say my bbl vice rarely gets removed from the loading bench. Between my rifles and a couple of buds, we have at least 8 T2ks that are burning up bbls at any given time, so it gets used a lot. I also dont hesitate to change out bbls at $235 a pop. Now, if we are talking Kriegers,which I have a few) I leave those on until they are totally toasted as I wring every last round out of those that I can.

John


John

 

[Mudcat]

What velocities have you been getting?

You should be getting 2900-3000 out of a 107 for 600 yards and back. I use 40.3grs of H4350 with a 107 for 3050fps. Its a really stout load but safe in my bbl and as accurate as anything else I have loaded up, so I use it. Anything hotter will toast my brass and I am too cheap for that! I dont strive for max speed, but when I get it, along with accuracy and brass life, I take it. For 300 yard rapids, I back down to 38.0grs for about 2850fps which makes for very smooth bolt work but still fights the wind well. My 200 yard loads are even more powder puffery! Why run hard when you dont have to? Might also explain why I get at least 2,500 rounds out of a bbl, sometimes up to 3,500.

John

 

[mysticplayer]

If you can, slug the bore. I had a tight bore 6mm pipe that ate bullets and gave lousy accuracy unless shot really slow.

A switch to a smaller diameter bullet and bugholes at 200yds at expected velocities.

A thou or two is a huge difference in bore diameter and almost impossible to see visually.

Jerry

 

[billy308]

Thanks all! Spoke to a very helpful person at McMillan, who suggested cleaning up the case necks before going to the $$s for a new barrel. Said there had been reports of tight chambers, stickiness, that were solved with neck-turned brass. One fact which suggests that this may be accurate is that the brass I'm using now only recently showed pressure signs, after 5-6 reloadings...could be the necks had thinkened up?

 

[mysticplayer]

If the chamber is too small vs your loaded neck diameter, there is a simple test.

Take your bullet and try to seat it by hand into a fired case.

If the clearance is too small, the bullet will not go into the neck. Will feel like after the case has been sized.

I like my bullets to just slide into the neck after firing. In a common factory rifle, the bullet will fall into the neck.

Unless the builder speced a turned neck chamber, that shouldn't be a problem but you just never know...

Jerry

 

[Mudcat]

Thanks all! Spoke to a very helpful person at McMillan, who suggested cleaning up the case necks before going to the $$s for a new barrel. Said there had been reports of tight chambers, stickiness, that were solved with neck-turned brass. One fact which suggests that this may be accurate is that the brass I'm using now only recently showed pressure signs, after 5-6 reloadings...could be the necks had thinkened up?

I can see why McBros will tell you that...ie, if what I found with my bbls to be true and they have a "out of spec" chamber, for lack of a better term at the moment, then yeah, taking brass of a case neck will do the trick. The problem with that solution, if its really a solution, is that every bbl I have used, 6XC or otherwise, on my T2ks have been just fine. And, if youre like me, the last thing you want to do is add another labor and time intensive process to preppin' your brass!

Basically the same BS story I got when I talked to them. Not being one to be BS'd or waste time farting around with them, I ended up having the bbl rechambered by a good smith, good shooter, good guy thanks to the help of another good shooter, good guy,wont name names cause I dont think they want folks calling them asking for rechambered T2k bbls!!).

John

 

[mikecr]

Sounds like BS to me also.
Tight neck chambers don't just happen by chance..
McBros can't be getting reports that some of their barrels are chambered tight neck.. Unless Schneider is providing finished barrels to them, and McBros is not checking them out.

Since I've personally been screwed twice by GS, and his lack of attention to detail, I surmise that this is the only way such sloppiness could happen.
But it would represent a serious flaw in McBros' business approach with 100 or so $4-6K guns per year.
And it would be the first time in my life I've run across someone with my kind of luck!!

That said, I'm happy with my T2K Schneider in 6xc. The only issue I had with it to begin with was Tubb's FL sizing die didn't work at all for the fired brass. I had to have a die made. I use 41gr of IMR7828 & 105vlds @ 2980fps
Great thing about this cartridge is that there are a ~dozen potential powder/bullet combos with it.

Good luck with your barrel issue. I'm sure another barrel would take care of it.