Cheytac barrel lives

[bohem]

On the topic of melonite coating a 338/408 CT barrel I figured to start a new thread so as not to totally hi-jack the other one, NotAGuru and I were trading posts about this and some similar range capable 30's.

IIRC NAG's expectation of bore life was 1800-2k rounds for a well pampered barrel. What are people getting from the 375 CT and how would you guys mind chatting it up a bit on the life of a 338-408?

Sure it's an expensive round to shoot, but if the barrel life is 800rd like I believe was hinted at in a thread on 338-408 bullets, I'm akin to think that the extra performance might not be worth killing expensive barrels like that, at least to me.

I'm probably going to be looking at building a larger bore long range rifle in the 338/408 or 375CT type calibers. One of the other things I was thinking was that maybe I should consider necking the 50 down to a 408 caliber for some extra powder capacity to throw those 429gr bullets a little faster. Along the lines of the 416 Barrett idea, but with non-proprietary brass/bullets/loads

 

[Tyler Kemp]

Re: Cheytac barrel lives

I was told 2k for my 338 Lapua Improved and your round will be MUCH hotter than mine. You better be really nice to it to get 2k.

 

[The Mechanic]

Re: Cheytac barrel lives

.375 period.

 

[jpmuscle]

Re: Cheytac barrel lives

sounds interesting. I like the idea of trying to neck down the 50 for more capacity, ive been wondering why nobody has done it yet. Would pressure be a concern?

 

[crumpett]

Re: Cheytac barrel lives

Has anybody considered the M48 spotter case necked to 416, I've been tossing that around for a while.

 

[djd]

Re: Cheytac barrel lives

On necking the 50 cal down, Dave Viers has played with that idea. He didn't go down to .338 though. I have had a 338/408 for 3+ years now, but it gets little use anymore. It was decided at CheyTac (Dean and I) that .375 would be as far overbore we wanted to go commercially at the time. It would vaporize some lead core bullets, so we made a 270 gr. solid which most data was complied with. You'll enjoy experimenting with it.

DJD

 

[arnygollott3]

Re: Cheytac barrel lives

I have often wondered (dreamed) of a 416 Barrett Case necked down to drive the .375 ultra high BC bulletts faster than ever before...but barrel would be pretty short I imagine.

 

[pc3]

Re: Cheytac barrel lives

Its been done here in Australia a few times on Jongmans actions .50 cal necked starighth down to .375..............Very high speeds and barrel life around 500 rounds. Had read/heard that this round was approaching 5000 fps but I cant verify that.

It was VERY flat shooting LOL

 

[arnygollott3]

Re: Cheytac barrel lives

Yeah...that is FAST but I would hope that the 416 case could push the heaviset 375 bullets to 3600+ FPS and possibly 1000+ rds...still a barrel burner, but that is the cost of doing business with that level of performance.

Oh well, just an idea...

 

[The Mechanic]

Re: Cheytac barrel lives

arnygollot3 I am sure NotAGuru can make a barrel for you. He has done some experimenting with this kind of thing. Don't dream, do.

 

[arnygollott3]

Re: Cheytac barrel lives

Mechanic, point well taken, but my AR10 build starts next, then I have another pistol purchase to make, once the non-experimental pieces of my collection are filled...then I might be able go out on the experiemental branch of my hobby.

I also put my ELR project on hold while the 375 Cheytac barrel twist rates/bullet lengths(designs) were being tested, but that seems to have quited down lately. Earlier this summer there was alot of chatter about bullets/twist rates but I have not seen much lately.

I have MUCH to learn and practice before I am capable of starting a project like that...

 

[The Mechanic]

Re: Cheytac barrel lives

I think a lot of the "chatter" has slowed because the bugs are pretty much worked out and now the fine tuning starts to come into play on the .375 and .408. I think bullet design and playing with load development is going to take it the rest of the way.

 

[jpmuscle]

Re: Cheytac barrel lives

is there still alot of work being put into the .408? I kinda have gathered that more emphasis is being put into the .375 in terms of furthering development.


but a .375 solid projectile moving 5000fps gives me a woody. It would be interesting to see what that would be capable of doing at range.

 

[steve123]

Re: Cheytac barrel lives

More like 3100fps give or take a few.

 

[Kogapsp]

Re: Cheytac barrel lives

Just make sure the case neck length is longer this will buy you at least a few hundred or more rounds of barrel life.

kn

 

[bohem]

Re: Cheytac barrel lives

Thanks guys, I was away for the weekend and I'm glad to see this didn't totally die already.

I figured that a 408/50BMG would be about as far overbore as I would want to go on a 50BMG parent case. The 375 just struck me as too small for 250gr of powder behind it.

FWIW, the 338/408 at 3500 fps has been done by Kirby Allen. He's saying that the 300 SMK's come out at that speed, and running the data through JBM, it's still at 1500 fps at sea level and 3000y so I'm guessing it's a 3500y subsonic transition.

I took the data on some of the GS bullets and assumed a little better velocities with the higher BC's and according to Pejsa's equations it should be a 4000y transition to 1100fps.

I never dreamed 5000 fps from a 375 projectile was possible, that's like a ballistic wet dream. Though, 500 rounds would be a little on the short side for that kind of barrel. I'm almost done with a slow twist barrel for a 22-284 and I'm hoping to get around 5200 or slightly better with the 35 Vmax, I just hope it holds together long enough to get over the chrono.

 

[djd]

Re: Cheytac barrel lives

Just FYI...I built a 224/284 for the gun rag writter Ross Seifried, for his article in "Handloader" mag. I also built one for my self. It vaporized all light weight bullets except the 55 gr. Nosler when kept about or below 4300 fps. Mostly I used heavy, or solid bullets with it since it had a 1x7 twist. That was 6 years ago and bullet technology has changed.

It was a true 1/4 moa rifle, but opened to 1+ moa at 600 rds. Good luck!

djd

 

[Triggerfifty]

Re: Cheytac barrel lives

Hi guys,

This has been discussed to some degree about high velocity on this site. My observations have been that the faster your drive a bullet, the faster it slows down. You gain some supersonic range (the definer of maximum effective capability range) with higher velocity, BUT, as the projectile slows down faster, the shape of the trajectory changes more and the LESS capable a shot is due to the extreme fall angle of the shot at long ranges.

This affects the danger space of the shot, and the steep the fall angle, the less the danger space, which means the distance to the target must be very precise.

Numbers:

Supersonic range of the 375 CT at 3150 fps = 2800 yards SAC, fall angle is 3.5 degrees.

Supersonic range of the 375 CT at 4000 fps = 3400 yards SAC, fall angle is 5.0 degrees, the diff between being a difference of 7 meters of danger space, THAT 7 meters difference makes laser range finding a serious challenge at only 3400 meters, change that distance to 5000 meters and range finding becomes nearly impossible, without a 4 point GPS offset range finding activity.

Now there's something

Trigger

 

[Triggerfifty]

Re: Cheytac barrel lives

DJD,

That 22/284 was awesome to see shoot. Funny that solids was the only thing the radar could grab ahold of, jacketed bullets were dust in the air and the radar team couldn't track dust!! Very awesome gun/bullet combination, well done!

Trigger

 

[bohem]

Re: Cheytac barrel lives

T50- that's some excellent insight to the range questions, thank you.


djd- I am building the 22/284 with a 1:14t adams and bennet barrel to see if I can break a mile per second with the light bullets. The faster twist shilen is on order but hasn't come in. It will be a 1:8 for shooting the 80gr or so bullets.

I went with the really cheap A&B in a slow twist simply to make an attempt at keeping the bullets together at closer ranges, not more than 400y. Since I have the reamer and I'm doing the work myself it was more or less an academic exercise in "how fast can we go" at the expense of a cheap barrel blank.

Primarily, I want to shoot some watermelons and water balloons inside of 50y with it just for kicks, but my aim for the 80gr bullets is something for chucks out to about 600 or so. It'll more than likely be a range toy/safe queen with very little hunting.

 

[Triggerfifty]

Re: Cheytac barrel lives

that sounds like great fun! Vapor at a higher level

 

[bohem]

Re: Cheytac barrel lives

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Triggerfifty</div><div class="ubbcode-body">

that sounds like great fun! Vapor at a higher level

</div></div>

Thanks, I hope so

I'll be sure to put up some videos of eggs when it's done.