375 Cheytac flattening Fed 215s

KCORBIN

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Hello I’m new to the 375 rifle and had one just built.
Stiller tac408/31” bartline 8twist/xlr chassis.
I’m using Lehigh 353 match solids with h1000. I started pressure checking single rounds due to little to no info on this caliber starting with 116gr of H1000 and had flattened a primer with mild ejector swipe and a muzzle velocity of 2830. I was thinking that this is way too slow and that if I continue to back the charge down why not just shoot my 338 Lapua? Any thought or suggestions would help thanks
 

spamassassin

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How far are you from the lands? Are you jamming the bullet into the rifling or even just not giving much of a jump? I've seen pretty consistent need to jump monometal bullets a little farther than cup-n-core and learned to not jam them ever. I hypothesize that this is due to the increased engraving energy required of metals like brass/bronze/copper that while soft compared to steel are nowhere near as easily malleable as lead and so don't deform as easily. I've seen exactly the opposite tendencies with cup-n-core bullets with really thin jackets seemed to suggest they like to be closer to the lands or even jammed into the rifling. YMMV but I betcha a little comparo with your seating depth (ignore group size and MV, just look at pressure signs) against a seating depth that's farther from the lands might show something interesting.
 
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KCORBIN

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20 thousands off the lands I’m using Peterson new brass also. I would think that seating further into the case would cause the pressure to be more? I’m not even trying for groups yet. I thank you for the advice, this thing has been one of the more challenging endeavors I’ve taken on. I’m also going thru the whole extractor bending issue that I’ve read about.
 

j-huskey

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Did the gun builder offer suggestions on loads ?

Did Lehigh ?

If not, whose advice and education created the working plan for the rifle ?

Who's advice suggested H1000 versus a much slower powder ?

The 375ct on whatever reamer David Viers used is pretty much the 308 of bigger bores when loaded with 125,-6,-7or 128 grains of Retumbo, behind a 350 Sierra.

This will much in part be determined on reamer dimensions to case dimensions where too tight tolerances are used.
Too tight will definitely run pressure up faster and instead of increasing velocity, will destroy cases and potentially the rifle.

Not knowing any more than you posted, it's very difficult to offer comments beyond these, from a 12 year CT owner and shooter.
 

clcustom1911

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I've never done anything with your cartridge. Just here to pose a thought.

How much is your brass growing at the datum from the unfired to the fired size?

Phrased differently: what is the headspace for your chamber compared to the headspace for your new brass?

For me when doing my Magnum brass for the first firing theres some primer flattening nearly 100% of the time that does not appear on further firings of the same brass.
 
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j-huskey

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Dies your chamber have .030" over the case dimensions, or .015" per side ?

If it does, does your reloading die return the case to this dimension ?

Can you drop a bullet into a fired case mouth and it drop freely in ?

Is the reamer throat cut a sharp land cut common to copper jacketed bullets or a gradually tapered cut land that creates an easier entry into the lands ?

Lots of things with solids and generally any caliber.

Have you experienced something like this in other reloading ?

Your mention of 338lap indicates you have experience with bigger boomers.

My nightmare was a 338Xtreme, wildcat on the ct case, factory running a 266 grain solid at 3350fps, 145 grains of BMG50, and .400" free bore b4 the bullet started to engrave. It's on it's way to becoming 375#2, fwiw.
 
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KCORBIN

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Ok so I’ll try and answer what you guys are asking thank you by the way.
H1000 is all I have available at this time
The machine work was done by Mirage ELR
I have 2 thousands neck tension on my loads
I have only loaded for the Lehigh bullets so far.
as far as the plan for the rifle it’s been based of what is available really. The community is very small.
I would have to reach out to mirage and find out what reamer profile they used?..
I know the case shoulders blow forwards 6 thousands. I sent new brass for the smith there to test fire and check with. I purchased Whidden dies. Bought a tap and made my own modified case to measure coal(I use a comparator also). I have resized my spent brass but have not used any so far. I’ve just been using new Peterson brass to do the initial testing. It does resize down I did not take any base measurements. I’m starting think that even if I found some Retumbo that the charge weight would still not be were I’m wanting to be.
 

j-huskey

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None of our 375 crew has had any luck w H1000.
And you wont be able to find "if" it is 'that h1000 pressure curve' causing your problems until you can try what most people consider the 375 go to powder, retumbo, or another slower powder than h1000.

I would try a resized case next, just to see if CLcustom1911's post method gives you a different result, but....

First I would measure the web on new cases, then flat primer fired cases and see if web growth is present, leading to loose primers and lost cases.

If the web growth is there, you are stuck until you can change powders. Jmhe

VR and best to you .
 

j-huskey

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Curiosity. Mil headspace on a 762 is 1.630, high end go 1.634, and field service is 1.638.

Cases fired in 1.638 are definitely not intended to reload, because of case stretch to fill that .008.

Any other caliber, headspace jump over .003 or .004 can give the same results AND can give the flattened primer signs of excess pressure when it is no more than headspace jump. You said you had. 006.

So, eliminating web growth and firing a resized fired case might give you a different result, wont know until you resize the shoulder bump no more than .002 and fire some of those.

Will wait to hear results.
 
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steve123

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It's like if you used any powder that was too fast for a particular cartridge.

At least you didn't have to wait a year until a suitable solid projectile came out like I had to do back when 375CT was in its infancy.

I used US869, AA8700, and some BMG powders that just caused barrel wear because they were so temp sensitive. I had to just walk in the shots to make hits.

Looking back I should have just waited till I got my hands on Retumbo which ended up being the best powder at the time.
 

KCORBIN

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Ok maybe a little more volume and less movement in the chamber I’ll bite. Going to be a little bit I found that I need order another neck bushing for my resized brass. (Not enough neck tension bullets dropping into case)Has any one here found a good smith to barrel 375? Other than Mirage... Just curious.
 

j-huskey

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@Geno C.
Who built your Snipetac?
 
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timintx

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Wrong powder, way too fast , you need to use H50 bmg or RL 50 or same speed powder anything faster is getting dangerous pressures and no velocity, with Reloader 50 you should have velociies in the 3100 fps area before you see pressure, much safer with the right powder.
 
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timintx

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every gun can vary a good starting point for a 350 grain bullet is 138gr,
on my cheytacs and ended up at 145 of RL50 at 3280 FPS , hints of pressures at 3330 with a cutting edge 350 mth ,in a 36 inch barrel

Timintx
 

biffj

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Like the others I'm thinking H1000 is the problem. I've not been able to get it working in my 338 Lapua so I sure wouldn't run it in the 375.
Friends are running H50BMG, WC872 or RL50 as they are much more suited to the bigger cartridge and longer barrels.

Frank
 

j-huskey

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Like the others I'm thinking H1000 is the problem. I've not been able to get it working in my 338 Lapua so I sure wouldn't run it in the 375.
Friends are running H50BMG, WC872 or RL50 as they are much more suited to the bigger cartridge and longer barrels.

Frank
Jfwiw, a LONG time ago, H1000 with a 250 grain in a armalite ar30, fat chamber 338 Lapua, was known to work. But, it was not a first line choice and never caught on. Some of the old load data pops up from time to time on 338L. I wish it did not.

When you consider H1000 works well in a 6.5-284, it's hard to think about it seriously in a bigger case. Jmho
 

biffj

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I think I'm running about 103gr of RL33 in my Lapua mag with 250gr matchkings. This same rifle wouldn't run 88gr of H1000 with the 250s and velocity was about 150 fps or more slower. My 33XC is running 122gr of RL 33 and I'm getting ready to go to the RL50 as a test. Going by my friends 375 cheytacs the RL50 might be a good choice. The VV powders are great too when you can get them. Not always easy to find so if you get one that works buy a decent quantity.

Frank
 
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KCORBIN

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My logic is I run 93.9 gr H1000 in my 338 using 250 smk that’s upper 2900ish FPS and 78-80 gr H1000 using 285A max but it’s slow 2780 FPS out of a 10 twist 26” barrel. I’ve got 2lbs of RL50 and H50 in route so I’m pumped never thought I’d be using black powder lol
 
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timintx

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My logic is I run 93.9 gr H1000 in my 338 using 250 smk that’s upper 2900ish FPS and 78-80 gr H1000 using 285A max but it’s slow 2780 FPS out of a 10 twist 26” barrel. I’ve got 2lbs of RL50 and H50 in route so I’m pumped never thought I’d be using black powder lol
I hope your not using black powder
 

Geno C.

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@Geno C.
Who built your Snipetac?
I missed this.

I had a local friend spin the barrel for me on this one. I have a reamer now though.

Like everyone else has said, the powder is the problem. All the ones listed by others will work much better for you. RL33 is another to consider with the lighter 375 bullets in the 350gr range.

Also, what made you go with Lehigh? Just curious. But their stated bc for that bullet is highly unlikely.
 
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biffj

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After building a pretty good bunch of barrels for the DT's I can tell you that the reamer makes a huge difference. I have friends with a wide variety of reamers for the 300 win mag and they all have different throat configurations. Some were done to use special bullets or different weights and others for different reasons. The powder load and seating depth that is just tits in one will blow primers in another. This just means you need to work out your load, bullet and COAL for yourself. You started with H1000 which isn't a bad thing so moving on to find the one that works is what you're doing. Keep us posted on progress too.

Frank
 
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oneshot.onehit

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I would say it a powder thing as well, but from the original question posted are we talking about a standard 375 Cheytac or the improved - 375 Snipetac? At the end of the day these are still two different animals when recommending powders and related speeds while working with someone who is new to the 375s.

Cheers
Oneshot.onehit
JH
 

KCORBIN

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I missed this.

I had a local friend spin the barrel for me on this one. I have a reamer now though.

Like everyone else has said, the powder is the problem. All the ones listed by others will work much better for you. RL33 is another to consider with the lighter 375 bullets in the 350gr range.

Also, what made you go with Lehigh? Just curious. But their stated bc for that bullet is highly unlikely.
I’m running the Lehigh just based off cost using a solid copper to get a feel on what the gun likes
 

KCORBIN

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I’ve run the RL33 in a 300 win mag and it’s too temp sensitive for my liking I would have never guessed trying in a 375. Worth a try but like the idea of temp stable powders
 
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KCORBIN

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I would say it a powder thing as well, but from the original question posted are we talking about a standard 375 Cheytac or the improved - 375 Snipetac? At the end of the day these are still two different animals when recommending powders and related speeds while working with someone who is new to the 375s.

Cheers
Oneshot.onehit
JH
Yes just CheyTac
 

Geno C.

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I’ve run the RL33 in a 300 win mag and it’s too temp sensitive for my liking I would have never guessed trying in a 375. Worth a try but like the idea of temp stable powders
I would think it’s a little on the fast side too but a couple guys around here running the improved version are or were using it with good results, so that should work in a slightly smaller case as well.
 

j-huskey

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RL33, ok, we may have gotten a bad lot, but, it has not worked for any of my crew, in anything it was intended for. We have given up on it.
VVN570 worked super where RL33 has not.
Retumbo still is king for us in 375CT. My 32" barrel loves it. Couple folks did ok with BMG50 in a 36". I didnt get the results I wanted with it.
 

Geno C.

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I formed my brass with Retumbo under 377s first charge and swatting depth I tried was 1/3 moa easily
 

biffj

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I wasn't recommending the RL33 for the 375, just noting that it works well in my 338 Lapua mag where the H1000 was less than useful. I figure if the H1000 won't do in the 338 than it won't work in the 375 for sure.
I think RL50 is the best next step for the 375. I'd really say go for the H50BMG but its not available. Try the N540 VV or which ever powder was recommended above if you can get it too.

Frank
 

Geno C.

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I wasn't recommending the RL33 for the 375, just noting that it works well in my 338 Lapua mag where the H1000 was less than useful. I figure if the H1000 won't do in the 338 than it won't work in the 375 for sure.
I think RL50 is the best next step for the 375. I'd really say go for the H50BMG but its not available. Try the N540 VV or which ever powder was recommended above if you can get it too.

Frank
He was referring to my suggestions of 33 I think
 

oneshot.onehit

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Geno
We were pushing the 361 grain Flat Lines at a easy on the primer pockets/brass at 3020 to 3070 fps mattering on which rifle with excellent results proven in the 2 mile stuff using the RL33. 375 Snipetacs

Oneshot.onehit
 
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KCORBIN

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Geno
We were pushing the 361 grain Flat Lines at a easy on the primer pockets/brass at 3020 to 3070 fps mattering on which rifle with excellent results proven in the 2 mile stuff using the RL33. 375 Snipetacs

Oneshot.onehit
What length barrel and twist might I ask?
 

Geno C.

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Geno
We were pushing the 361 grain Flat Lines at a easy on the primer pockets/brass at 3020 to 3070 fps mattering on which rifle with excellent results proven in the 2 mile stuff using the RL33. 375 Snipetacs

Oneshot.onehit
Yep, Ed and I have had lengthy conversations about it before I got started
 

secondofangle2

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wrong powder, way too fast. No point in building a 375 if you're going to run 300 WM powder in it.
 

jasent

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Geno
We were pushing the 361 grain Flat Lines at a easy on the primer pockets/brass at 3020 to 3070 fps mattering on which rifle with excellent results proven in the 2 mile stuff using the RL33. 375 Snipetacs

Oneshot.onehit
I’m getting the same speed with the fl in my 37xc. 32” 1:10
120gr h1000
 

IntoTransonic

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Magic with the 361 flatlines is with 50BMG. Full full case, no pressure even at 100 degrees.
7 twist. 36” Bartlein barrel.
3140 FPS.
popcorn load. This has been a winning combo.
good luck and great shooting.

Chris Schmidt
Tennessee
IG: ChrisSchmidt_elr
 
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KCORBIN

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It seems like you either a 1-10 twist or a fast 1-7 or8 seems to be common. When planning to build I was under the impression that the slower twist handle the jacketed bullets better and the fast twist was solids.

Does anyone have any published data on this caliber? I understand that it’s a wildcat , but it is a popular unique cartridge.

Another thought I had was (regarding pressure issue) is it like a 300 win mag that you can machine free bore into the throat to run the longer heavy bullets. I see the all comes back to previous question regarding who did the machine work and what reamer they used.

Just some deep thoughts waiting for my powder to come.
 

j-huskey

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My rifle was initially built by RW Snyder Gunsmithing and I bought the complete rifle from him, off the Hide, new, 15ish years ago. It's on a Lawton action.

The 10 will handle either jacket or solid in the 350 - 360 range with no problem.
Because that was the most available bullet weight at the time 10+years ago, the 10 twist became pretty much standard in 375 offerings. It's pretty forgiving with a lot of bullets.

Early 375 ammunition was made by Jamison for Cheytac, and was a 350ish grain solid.
Cheytac's history is not the usual success story. If the pre scout archives were available, it was all laid out here.
Look up 408 Cheytac on Wiki and that's about as good as it gets, and in a Google search, old Hide articles pop up, read to your hearts content.

The Jamison Cheytac ammo at one point was all that was available and we owners were all glad when Sierra brought out their match king.
Jamison brass, Bartram brass, Peterson brass, fun fun....not.

Dies, more fun. Viers built mine, and Whidden built my newest seater die.

I have no clue what dimension reamer CT initially used or Snyder.
My personal PTG reamer is built off fired cases from my Viers chamber.

The Jamison ammo was HOT.... we lost primer pockets on first firing. That was expensive and it hurt....

When I got David Viers to rebarrel my rifle, the 10 twist was his recommendation to handle both Sierra and solid.
David was building rifles under Viersco and Black Diamond rifles and had his own 338 and 375 Wildcats, called Snipetac, running higher speeds than CT.

So was Kirby Allen, Allen Magnums, and there was one more big boomer builder but I forget...

Based on what Viers and Allen knew then and what we know now, the CT is slow, slower than what is needed to go two miles. CT was designed for 2000 yards and it does that very well.

As bullet weights get heavier and longer, the twist rate has to get faster to keep the bullet stable at extended ranges, and the manufacturer of the bullets will recommend the twist rate. This is not specific to the 375, but all calibers. So, 10, 9.5, 9, 8, 7, are all out there.

And, the heavier the bullet, the longer it is, the faster the twist needed, and special seater dies. And a longer throat for a longer bullet. And it can get you some more velocity.

So many variables and options.

A few answers to your questions offered here. VR
 

j-huskey

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1 mile to 2000, can be done less expensively with a 338Lapua and 300 Berger hybrids, whidden pointed.

2500 to 3000, the 375 does pretty well. With the right solid and load combo. Getting iffy at 3k.

Past 3k, the 416 Barrett case is a good start.

That is what that it.
 
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Geno C.

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My current barrel is a 1-10 and it shot the 377 extremely well. They didn’t make the transonic transistion at all for me though. I stepped back to a 350 to see if I can remedy that
 

j-huskey

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My current barrel is a 1-10 and it shot the 377 extremely well. They didn’t make the transonic transistion at all for me though. I stepped back to a 350 to see if I can remedy that
Dont think the 10 will do it, wondering if my two 9.5 replacement tubes will.......
Havent put them on yet.... the other barrels still shoot too well. Just know I'm stopped around 2500 with what I'm pushing depending on elevation when I get to shoot.
Beer virus has limited shooting travel, and my buds went 416 with serious intent to go to Ko2M. And that stopped some 375 load playing. Is what it is.

At KC, not much of a writer.
 
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