375 SMK in hand today

[davewilson]

finally saw the 375 match king today.looks about like the others. might be a little on the short and fat side.very short bearing surface with a fairly long boat tail.it's about 350 grains. they probably need to make it a little longer.

 

[Fiftydriver]

I have some for testing in my 375 AX and 375 AM. I am not overly optomistic about their performance.

Like you said, very short baring surface and at the velocity I will be driving them to, I am a bit concerned. In the 375 AX, they should work well but not in the AM.

In talking with the head research man at Chey Tac about my opinion of them, the first thing I told him was that they needed to jump the bullet weight up to 375 grs. His reply was that is exactly what he wanted but Sierra said these were as heavy as they had the ability to make.

There have been some issues with these bullets in early testing and they are working on a new design with a heavier jacket. I assume from that that they were having bullet failure in flight.

Now looking forward to Richards heavy 375s more then ever when they get up and running, especially his Al. Tipped versions!!!

Got the same impression you did seeing the 350 gr SMK in 375 cal. I think they could have made the BT a bit less aggressive which would have helped in baring surface length as well and probably not dropped BC a huge amount.

I would be suprised if these bullets have a BC much over .600. That said, compared to what else is currently out there, that is a huge boost in ballistic performance for a 375 cal bullet with conventional lead core design.

Kirby Allen(50)

 

[Roll-Yur-Own]

I'm making a 350 grain 375 bullet out of copper alloy. It is longer than the sierra since the alloy has a lower specific gravity.

Anyone interested in trying some out, let me know. They will be $1.75 each.

 

[davewilson]

i'm told the BC is somewhere around .8 based on one test session at 1100 and 2300 yards. again that's only one test. my buddy wouldn't give me any because he only got 50. he was a little disappointed, of course wanted a couple hundred so he could do some real testing.i guess 50 is plenty if they're coming apart.

Roll-yur-own, could you post a pic of your bullets? have you shot any? what twist do you need for a monolithic 350 gr/ 375 cal bullet?

 

[Black Diamond 408]

11.5 twist, should have the lost river bore size to go with them. .0002 bigger.

Dave

 

[Roll-Yur-Own]

Not out of a 375/408. I have shot my 338 bullets out of a 338/408 and they were lights out. 11 or 11.5 twist should work fine. They are just under 2" long.

These are not pure copper they are leaded copper alloy. Same as CheyTac is using. Fouling is minimal.

The cool thing about these solids is that they are lighter than jacked bullets. So you get a higher BC with a lighter.
For example my 195 308 bullet has a BC of .715 (YMMV) which is just over a 240 SMK but still only needs a 10 twist.

I also did not design these for hunting, so I don't really know what they will do on game.

BC should be over .8, but I haven't done testing.

How do I post a pic?

 

[davewilson]

can you tell us what kind of accuracy you mean by lights out? i hope you didn't miss the target so bad that you hit the light bulb! /ubbthreads/images/graemlins/grin.gif

 

[Black Diamond 408]

Chey-tac is using 11.5" twist on their 375-408 rifle, 350grn LRB or the new Sierra prototypes. Barney Lawton made the barrels for them in LRB bore dia. The same spec barreled action was sent to Sierra for the bullet development. I'm not sure what bullet Barney said they were testing a couple weeks ago, but they shot a 8 shot group that was 16" at 2400yds, i think he said Sierra's.

Dave

 

[Fiftydriver]

BD,

Yes that was the sierra bullet they were using for that group at 2400 yards. Only problem is that they need to keep the velocity down to keep it accurate from what I hear.

Kirby Allen(50)

 

[Fiftydriver]

Dave,

I know there are several things that go into producing BC but just from looking at these bullets next to a 300 gr 338 SMK, there is no way in heck they will get anywhere near .8 in BC.

THey are only a few thou longer then the 300 gr SMK and ALOT fatter. If they break .650 in BC I would be amazed.

Kirby Allen(50)

 

[biggjake]

I just got off the phone with Joel Russo,who is stocking my XP-100 for me.and he was calling from Bruce Baer's shop,who has several guns made up in 375-408,and a good supply of the new Sierra's for testing.Hopefully,They will be able to see how these bullets shoot,and using bullet drop,be able to at least get an idea of what kind of BC these things have.My decision to build a 375-408 is based entirely on being able to buy good,high BC bullets for it.And I have no intension of spending a buck a bullet.

Kirby,do you know just how involved a procedure it actually is find out a bullets exact BC?I've heard things like tests using radar and such to really get it right.Evidently,it's a pretty complicated and costly procedure.

 

[Fotis]

[ QUOTE ]
I have some for testing in my 375 AX and 375 AM. Kirby Allen(50)

[/ QUOTE ]

Kirby:

What is the ballistic potential of these designs? Got any #'s yet?

 

[Fiftydriver]

Biggjake,

From what I have heard talking with some that are pretty close to Bruce Baer is that he is getting extremely good accuracy performance with the 1st generation 350 gr SMK but he had to limit velocity to get it because of the thin jackets in that first version. That is why there is currently a 2nd generation design being made.

Sierra said nothing heavier then 350 gr could be made so they are just going with a stouter jacket and possibly some slight design changes but basically they will be the same as the original, just heavier jackets to handle the velocity potential.

With the price of copper and lead these days, and the weight of these bullets, you may pay nearly a buck a bullet no matter what bullets you shoot!!!

I agree, the limiting factor on the 375 right now is bullet selection. If the right bullets get on the market, in my opinion, it will be superior to the 338 cal for extreme range shooting.

Only real way to test true BC is to use a doppler radar over the entire flight of the bullet. I am sure Sierra or Chey Tac will be having this done on these bullet. I do not know how expensive it is to be honest but I sure its not cheap. Getting access to one is the hardest thing I would imagine.

Again, I would be amazed if the 350 gr SMK has a BC over .7 but it may. Just have to get some in the air and see how they drop.

Kirby Allen(50)

 

[Fiftydriver]

I expect my 375 AX to match the 378 Wby.

The 375 AM will give the same performance boost as say a 338 AM does over a 338-378 Wby, at least a solid 300 fps velocity advantage with heavy bullet weights so whatever the 378 Wby will get you, add at least 300 fps and there you have it.

Can not say for sure until bullets get in the air.

Kirby Allen(50)