The new 33XC & 37XC cartridges designed by David Tubb

[Jim Boatright]

I fear my earlier reply to this question from Skookum got lost when my internet service went down.

I cannot foresee any possible deleterious effects of shifting the tripping ring back about an inch behind the tip of any rifle bullet. For those bullets which can benefit from adding such a ring, it would not matter where it is relative to the ogive/body junction or any other break in the surface angles. The boundary layer L/T flow transition occurs after about 1.25 to 1.5 inches of laminar flow even for a flat plate in a wind tunnel. By shifting the transition point back about an inch, more of the bullet would experience the significantly lower-drag laminar flow.

One could ask David about this change, since he probably tried it.

 

[Deleted member 113831]

I fear my earlier reply to this question from Skookum got lost when my internet service went down.

I cannot foresee any possible deleterious effects of shifting the tripping ring back about an inch behind the tip of any rifle bullet. For those bullets which can benefit from adding such a ring, it would not matter where it is relative to the ogive/body junction or any other break in the surface angles. The boundary layer L/T flow transition occurs after about 1.25 to 1.5 inches of laminar flow even for a flat plate in a wind tunnel. By shifting the transition point back about an inch, more of the bullet would experience the significantly lower-drag laminar flow.

One could ask David about this change, since he probably tried it.

Thank you for that answer, it makes sense.

In light of what you've said, it would make sense also that Tubb would want to put the ring farther forward to market his ringing tool more effectively. Because you can't know what bullet will be ringed, the further back you place it, the more likely it will not work for any single particular bullet. I'm not knocking or criticizing that, I'm just drawing logical conclusions. As long as it still has the advertised effect, more power to him.

 

[Dave62677]

anyone know any gunsmith can to spin a 37xc bbl for AI AXMC ?

 

[wildcats]

anyone know any gunsmith can to spin a 37xc bbl for AI AXMC ?

If you have a reamer, i'm sure SAC,Mile High or Win Tactical can chamber one up for you.

 

[MACHTECH]

Anyone else building or already built a 33 or 37xc? I just received my brass for the 33xc and made a modified case for checking seating depth. Here is a comparison pic of the 33xc vs 375 cheytac:

Here's the 33xc with a 277 single feed cutting edge mtac in a CIP length AI mag:

Just wondering what action you guys chose to build on? It's definitely going to be a single feed cartridge unless you build on a cheytac length action.

 

[Bradu]

Anyone else building or already built a 33 or 37xc? I just received my brass for the 33xc and made a modified case for checking seating depth. Here is a comparison pic of the 33xc vs 375 cheytac:
View attachment 6969094
Here's the 33xc with a 277 single feed cutting edge mtac in a CIP length AI mag:
View attachment 6969099
Just wondering what action you guys chose to build on? It's definitely going to be a single feed cartridge unless you build on a cheytac length action.

Can you buy dies for the 33xc or are they going to have to be custom made?

 

[MACHTECH]

Can you buy dies for the 33xc or are they going to have to be custom made?

Dies are supposed to be available this week thru David's site.

 

[Bradu]

Dies are supposed to be available this week thru David's site.

I'm waiting to see if the Ultra 338 suppressor can be used with it first before I order one.

 

[MACHTECH]

I'm waiting to see if the Ultra 338 suppressor can be used with it first before I order one.

I'm waiting for the same thing. Hopefully we will get an answer this week. It will determine weather I thread my barrel for the 338 ultra or my Desert Tech (elite iron) 375 can.

 

[SharpsNitro]

Anyone else building or already built a 33 or 37xc? I just received my brass for the 33xc and made a modified case for checking seating depth. Here is a comparison pic of the 33xc vs 375 cheytac:
View attachment 6969094
Here's the 33xc with a 277 single feed cutting edge mtac in a CIP length AI mag:
View attachment 6969099
Just wondering what action you guys chose to build on? It's definitely going to be a single feed cartridge unless you build on a cheytac length action.

What COAL is that.

 

[Jim Boatright]

It looks like the 33XC chamber is 0.35-inch longer than that of a 338 LM, so COAL would run about 4.50 to 4.60 with long copper bullets seated out.

 

[MACHTECH]

What COAL is that.

4.40"

 

[surgeon260]

I'm waiting to see if the Ultra 338 suppressor can be used with it first before I order one.

Zak answered this question in another thread this morning. The 338 Ultra is good to go with the 33XC with 28" or longer barrels.

 

[jaybigboy34]

Zak answered this question in another thread this morning. The 338 Ultra is good to go with the 33XC with 28" or longer barrels.

Thanks! This is good to know!

 

[Backspace]

Has anyone finished up a 33XC yet? Interested to hear what everyone's results are. I'm also curious if the 300 berger hybrids (hunting or tactical versions) would hold together at 33xc velocities out of an 8.5 twist? Has anyone rented a 33xc reamer from Tubb? Does he have different reamers for both solids and lead core bullets, or only solids, and use a throating reamer for lead core bullets?

 

[Bravo6niner]

Has anyone finished up a 33XC yet? Interested to hear what everyone's results are. I'm also curious if the 300 berger hybrids (hunting or tactical versions) would hold together at 33xc velocities out of an 8.5 twist? Has anyone rented a 33xc reamer from Tubb? Does he have different reamers for both solids and lead core bullets, or only solids, and use a throating reamer for lead core bullets?

My gunsmith rented a reamer from Tubb. Yes Tubb has two different reamers available for solids and jacketed. If I remember correctly .100 for solids. I’m hoping here anytime I’ll have my barrel and can provide some data on velocity.

 

[Backspace]

My gunsmith rented a reamer from Tubb. Yes Tubb has two different reamers available for solids and jacketed. If I remember correctly .100 for solids. I’m hoping here anytime I’ll have my barrel and can provide some data on velocity.

Nice. Thanks for the reply. I picked up a 8.5 twist 36" 338 blank for a good deal in the for sale section. Working on piecing together a 33XC and playing with the 300 hybrids since i have a bunch. I know they supposedly had issues with the original ones coming apart at higher speeds but think that was addressed. I have no experience with either, so interested if anyone has pushed the current production 300s hard with good results yet.

 

[wildcats]

My gunsmith rented a reamer from Tubb. Yes Tubb has two different reamers available for solids and jacketed. If I remember correctly .100 for solids. I’m hoping here anytime I’ll have my barrel and can provide some data on velocity.

The solids .100 and the jacketed .250
His reamer neck dia shows a .378nk, on a loaded round im seeing .368 .
Why so much clearance?
338 lapua has the same .367-368nk loaded rnd and the saami is .371-.372 and the Crane,Socom is .373.

 

[MACHTECH]

I bought my reamer from Dave Manson and I believe the freebore is .250. I'm supposed to be getting my barreled action back from my Smith in a week or two. I'm still waiting on dies from David Tubb though. The seating die is available, but the re-sizer is delayed. They are telling me that it's going to be January now.

 

[craigos]

The solids .100 and the jacketed .250
His reamer neck dia shows a .378nk, on a loaded round im seeing .368 .
Why so much clearance?
338 lapua has the same .367-368nk loaded rnd and the saami is .371-.372 and the Crane,Socom is .373.

On his 6XC he has clearance for "Carbon buildup" ...

 

[wildcats]

On his 6XC he has clearance for "Carbon buildup" ...

I had some carbon buildup on my 338 Lapuas with a ..371-372 nk.
I would imagine how much more the 33xc will have with the .378nk

 

[Squibbler]

The solids .100 and the jacketed .250
His reamer neck dia shows a .378nk, on a loaded round im seeing .368 .
Why so much clearance?
338 lapua has the same .367-368nk loaded rnd and the saami is .371-.372 and the Crane,Socom is .373.

Dave's theory is that he wants to give enough clearance for the carbon build up that occurs around the neck in order to avoid pressure spikes. With the intended goal of consistently achieving single digit SD's.
When I first learned of the tolerances he was recommending for neck clearances I was shocked. I've been doing the exact opposite over the past few years and tightening the neck clearances to achieve higher accuracy potential. Would love to hear feedback from others that have the increased neck clearance on their reamers and the results they are attaining.

 

[wildcats]

Dave's theory is that he wants to give enough clearance for the carbon build up that occurs around the neck in order to avoid pressure spikes. With the intended goal of consistently achieving single digit SD's.
When I first learned of the tolerances he was recommending for neck clearances I was shocked. I've been doing the exact opposite over the past few years and tightening the neck clearances to achieve higher accuracy potential. Would love to hear feedback from others that have the increased neck clearance on their reamers and the results they are attaining.

I'm going to tighten it up a bit and go with the .373.5 nk. i can always slightly turn the necks if i want an extra 001-2 clearance

 

[Dan Warner]

There is nothing wrong with having that much neck clearance. While the game of Palma is in it twilight, it was common place to run excessive neck clearance on the 308. It was mostly mandated and not the shooters choice, but it functioned just fine. The downside it the amount that he brass is worked. David is simply trying to make it an easy setup so folks don't have issues. After all, it is somewhat of a production process he has. On the other hand, however, if one pays enough attention to their cleaning regiment, carbon build up should not be an issue. But given the fact that the slower powders of today, used in the larger cases, are extremely dirty, there is certainly a method to the madness. Until there is a replacement for these fouling powders (and we are working on that), it is not all together a bad way to go.

 

[Jim Boatright]

I agree, Dan. Also I never recommend any type of neck turning when it can easily be avoided with adequate neck clearance and best quality brass, say about 3 thousandths more than the loaded round. I also avoid "pull type" neck expanders in precision reloading and always use "bushing type" partial neck sizing, usually 2 or 3 thou less than the loaded round neck OD. That will provide the maximum possible bullet pull without resorting to crimping the case necks. Always check your case lengths and keep them trimmed to 10 or 20 thou shorter than the maximum for your chamber. Otherwise, you can easily blow up the gun.

 

[Bravo6niner]

Picked up my barrel from Mile High today. Hoping to get it out this weekend and send a few down range. Plan on trying h50bmg and 277 mtac’s.

 

[Squibbler]

Picked up my barrel from Mile High today. Hoping to get it out this weekend and send a few down range. Plan on trying h50bmg and 277 mtac’s.

Keep us updated

 

[THEIS]

Picked up my barrel from Mile High today. Hoping to get it out this weekend and send a few down range. Plan on trying h50bmg and 277 mtac’s.

Hi,

Bravo---where did you get your seating die from?

Sincerely,
Theis

 

[Long Range 338]

W

Picked up my barrel from Mile High today. Hoping to get it out this weekend and send a few down range. Plan on trying h50bmg and 277 mtac’s.

Putting on an AXMC?

 

[Bravo6niner]

Hi,

Bravo---where did you get your seating die from?

Sincerely,
Theis

Picked up the seater die from Tubbs website

 

[Bravo6niner]

W

Putting on an AXMC?

Yes sir

 

[THEIS]

Hi,

Shit I thought for some reason he had mentioned mid January.....

Sincerely,
Theis

 

[Bravo6niner]

Hi,

Shit I thought for some reason he had mentioned mid January.....

Sincerely,
Theis

The sizing die is due out mid January ?

 

[Bravo6niner]

Sent one round out of the 33xc early this morning before heading to work. 124.2 grs h50bmg with mtac 277 seated for .015 jump. No stiff bolt and very faint ejector mark.

Hoping I can run a quick ladder tomorrow.

 

[Bravo6niner]

Sent one round out of the 33xc early this morning before heading to work. 124.2 grs h50bmg with mtac 277 seated for .015 jump. No stiff bolt and very faint ejector mark.

Hoping I can run a quick ladder tomorrow.

FYI 30” Bartlein 8-7 gain

 

[Milepost]

Sent one round out of the 33xc early this morning before heading to work. 124.2 grs h50bmg with mtac 277 seated for .015 jump. No stiff bolt and very faint ejector mark.

Hoping I can run a quick ladder tomorrow.

Any extraction issues with a fired case?

 

[Bravo6niner]

Any extraction issues with a fired case?

No extraction issues with that one. I have a small ladder loaded up but not going to get it ran today. Hopefully tomorrow I can. When I do get it done I’ll report back

 

[Bravo6niner]

Got out to the range today to run the ladder. I had about a 3300da, 39F, and full value 5-6mph wind. Target distance 510yds. Velocities from the ladder kinda have me puzzled still but the only brass prep I did was run a .0025 mandrel in the case. Nonetheless accuracy seems to be good. Never encountered stiff bolt lift but a faint ejector mark was noticeable on all pieces of brass.

277 mtac @ .015 jump
H50bmg powder

I had one “flyer” at 2 oclock which I’m assuming was my error. Last two on the left I dialed over so my colors for those rounds didn’t get mixed up, (saves me a trip to the target) only have 5 sharpie colors that show up well on cardboard.

I shot one round at a 100 to check zero, one on steel at 510, then proceeded with ladder

 

[jaybigboy34]

What are you going to do when you run out of H50bmg powder?

 

[MACHTECH]

What are you going to do when you run out of H50bmg powder?

This is going to be an issue for a lot of elr guys! I found a supplier that had (5) 8-pounders left in stock and grabbed them all. Once that's gone, I'll be in the same boat.

 

[GIXXER2000]

I am going to Shot Show and plan on speaking with HODGDON about 50 BMG as are a number of other people. Its not that the powder is not being made it's just the HODGDON is not importing it. The powder is made by ADI of Australia so it can be made available again if the demand is there it's just up to them if they think it's worth bring it back.

 

[Bravo6niner]

What are you going to do when you run out of H50bmg powder?

I have enough 50bmg for a couple barrels so no worries in the short term.

 

[Dan Warner]

I am working on an alternative the the Hodgdon brand. We have used is quite a bit already and it is almost identical in burn rate, but is much cleaner. I will know more about it as the discussions are had at Shot and will keep you posted once I have details.

 

[GIXXER2000]

I have 18 pounds of H-50BMG so would be very interested in and alternate powder if HODGDON decides not to import more of The H-50BMG. I guess it just comes down to what come out of SHOT.

 

[SIDS01]

Good shooting Bravo6niner. I'd send the guy that chambered the barrel a case of beer too.

What is your barrel length and the cartridge OAL?

 

[Bravo6niner]

I am working on an alternative the the Hodgdon brand. We have used is quite a bit already and it is almost identical in burn rate, but is much cleaner. I will know more about it as the discussions are had at Shot and will keep you posted once I have details.

Any word on the 285 flatline release dat

Good shooting Bravo6niner. I'd send the guy that chambered the barrel a case of beer too.

What is your barrel length and the cartridge OAL?

Barrel length is 30”
Rough OAL is 4.4”

Base to ogive is 3.502”

 

[Long Range 338]

What are you going to do when you run out of H50bmg powder?

Has anybody tried the surplus pulldown powders in these cartridges? Should be approx the burn rate needed, but are they a dirty powder?

 

[Dan Warner]

The 285 grain .338 Flatline is scheduled to be released at Shot Show. Working to build inventory and get the website squared away right now.

I think you will find the military surplus powders to vary substantially from one lot to the next; enough so that you won't like the results. Any yes, it can be quite dirty, but it depends greatly on witch one you use. We found 872 to be pretty consistent (all be it a bit slow) for what we were testing. 880 was way to slow any insanely dirty. I have to wonder about authenticity too, on this stuff, given how much its handled. Can never quite be sure that its the same all the time, or mixed, or mis-labeled, or ...

 

[badassgunworks]

U can get Cheytac cases with rebated rims for the Lapua .585 bolt face...I believe Peterson. The reason Dave developed his new case is the Cheytac case was designed for the .408 and at .375 it is way overbore and u end up with a cartridge that has a low fill ratio with higher peak pressures. So, overbore, poor fill ratio, and high chamber pressure all lend themselves to less chance of broad stable nodes which equate to high ES and SD equalling poor accuracy at range. His goal was to design a cartridge with perfect fill ratio for .375 that's optimized for modern powders like H1000 that are less temp sensitive trying to get the best ES/SD

Not at all true. the 375 cheytac is not overbore. Case fill % is higher then that of the xc in 338. The 375 cheytac runs very low S.d.s with quality load development its around 4 fps. The Xc cartridge is a good design tried and proven Prior to Tubb... and was a great choice to the use of his Tubb Gun design sence it wont take a cheytac round. the 375 xc is underbore and could use more capacity .

 

[Dave62677]

37xc brass and die available yet?