Freebore Discussion

[Boisedoc]

Some questions about this. Was finishing up a 300 WSM rifle build and debated about a SAAMI vs custom freebore. It seems the freebore physics is more complicated than simply pushing the bullet out gives more space for more powder. My question is have any of you fired the same powder, same bullet combo with a long freebore vs a SAAMI chamber and seen the difference?? Seems logical that there would be; however the only article I've ever seen testing the theory seemed to refute the adage.

 

[nealm66]

I had this conversation with bugholes when I was helping a friend put a 6 creed together. They said the 1000 yd guys found the saami to be best. Something I've noticed with 230 and 250 Atips in 2 different 300 prc's is a huge jump if loaded to max coal. At 20k off, they run about 3.84 and have to be single fed. Also noticed Berger 245's are very forgiving with seating depth. Hornady's eldx as well.

 

[Mikecr]

I haven't done your test, but I don't feel like this is complicated.

Weatherby has designed on this decades.
They want max MV, so they go very overbore capacity combined with extreme length freebore.
This, to produce a large & broad pressure curve, that does not hit a sharp point of peak.

Point blank BR competitors do just the opposite, not because they want a sharp peak, but to flatten a peak into heavily diminished returns.
Diminished returns equals diminished variance of returns, and just like that -they don't even have to weigh their powder.
They get away with it because their cartridge is a tiny little underbore. Not a hunting cartridge.

That's 2 opposite extremes in this regard.

 

[Mike D Texas]

Some questions about this. Was finishing up a 300 WSM rifle build and debated about a SAAMI vs custom freebore. It seems the freebore physics is more complicated than simply pushing the bullet out gives more space for more powder. My question is have any of you fired the same powder, same bullet combo with a long freebore vs a SAAMI chamber and seen the difference?? Seems logical that there would be; however the only article I've ever seen testing the theory seemed to refute the adage.

I've never owned a straight 264 Win Mag but my improved version with and additional .210" of freebore is a screamer and a shooter.

I can comfortably run 156 EOL at 3350 and have pushed to over 3400fps but accuracy is better around 3340-3350.

 

[L.Sherm]

I had this conversation with bugholes when I was helping a friend put a 6 creed together. They said the 1000 yd guys found the saami to be best. Something I've noticed with 230 and 250 Atips in 2 different 300 prc's is a huge jump if loaded to max coal. At 20k off, they run about 3.84 and have to be single fed. Also noticed Berger 245's are very forgiving with seating depth. Hornady's eldx as well.

Your talking a whole different ball game between a saami 300 PRC and a saami 300 wsm

 

[Dot_3]

Scott Saterlee talks about this on Modern Day Sniper podcast. Can't remember which one. He has been experimenting with measuring freebore in fractions of inches as opposed to speaking about a few thousandths. It's an interesting podcast. He talks about having a load jumping three miles that shoots the same from day one until the barrel gives out, without ever changing seating depth. It's something I'm going to experiment with on my next barrel.

Obviously you can throat one to load long and also jump far to maximize case capacity, but you're running into mag length issues and may have to pick one over the other unless you put a short action round in a long action receiver.

Experimenting is expensive these days but would make for a good one.

 

[nealm66]

Your talking a whole different ball game between a saami 300 PRC and a saami 300 wsm

It is. I was just trying to warn about the different bullet designs that have a lot of jump per design. And also the conversation with bugholes with the 6 creed was along the same lines and what they're standing on it was. I believe weatherby uses a type of forcing cone if I remember correctly when I was considering 6.5-300. Sorry, didn't get much sleep last night lol

 

[L.Sherm]

Theres nothing gained by having more of the bearing surface stuffed below the neck shoulder junction.

 

[nealm66]

Unless the bullet you want to shoot becomes so long it's a single feed only

 

[L.Sherm]

Unless the bullet you want to shoot becomes so long it's a single feed only

Thats called **** poor planning unless its intended.
Is it gaining anything?

 

[Boisedoc]

It's a difficult conundrum if you're like me and not sure what bullet you may ultimately wind up shooting. The ELDX line has LONG bearing surfaces. Something like a hammer is short. To seat an ELDX at the neck junction would make a heck of a jump for a lot of other bullets.

 

[nealm66]

Making the freebore long in the 300wsm might become a problem for feeding is what I'm saying. Plus, some bullets like the Atips are likely going to push the max coal even with a saami. At least that's my thoughts. I'll leave it to L.Sherm to better guide as he is definitely more knowledgeable than me

 

[VinceMule]

So, should a long range hunter be shooting a single shot due to mag constrictions? I can not remember last time I shot more than one round on a deer.

Wyatt makes a 4" mag internal mag box for Rem 700s.

Most of the cartridges I shoot like to be seated very close to the lands.

 

[L.Sherm]

A 300 wsm really has no reason to be built on a short action these days.
I look at rifle builds this way, pick action, barrel, reamer, components and smith to give me every advantage to it shooting really well. Why stack something against you.