.300 win mag barrel length and twist...

[Deleted member 107666]

First Post on this forum, happy I found this place, seems like a wealth of info and thanks in advance for the suggestions.

I currently have a 6.5CM barrel being spun up at Proof. I ordered this when I was in Florida with intent on a mix of long range steel and deer, to replace a .308 I'd built.

Now, with western hunting on the mind, I've decided to cancel the 6.5 order and Proof is letting me switch my order to a .308 blank that I will have chambered for .300 win mag.

My only experience with .300wm is an old browning A-bolt I grew up shooting, but no clue on optimal barrel length (I know its debatable) and twist rate.

Can someone give me a few suggestions for specs (contour/twist/length)? This rifle will be packed in on hunts and will also spend time plinking steel.

I'm leaving towards 1:9 cut to 26" as a happy medium between weight/length and repeatable accuracy. Shooting for sub .5moa when it's back from the gunsmith.

Will eventually have to hand load to afford to shoot it at the range, but I figure it's cheaper than building both a 6.5CM and a .300wm...I cant afford both.

 

[gohring3006]

I would probably do a 26" 1-9 as well.
Case capacity will dictate how heavy I want to go with bullets. And for me, a 300 win mag has the capacity for bullets up to 225 grains. I would probably be shooting 208-215 grain bullets.

 

[NEMTHunter]

First Post on this forum, happy I found this place, seems like a wealth of info and thanks in advance for the suggestions.

I currently have a 6.5CM barrel being spun up at Proof. I ordered this when I was in Florida with intent on a mix of long range steel and deer, to replace a .308 I'd built.

Now, with Utah hunting on the mind, I've decided to cancel the 6.5 order and Proof is letting me switch my order to a .308 blank that I will have chambered for .300 win mag.

My only experience with .300wm is an old browning A-bolt I grew up shooting, but no clue on optimal barrel length (I know its debatable) and twist rate.

Can someone give me a few suggestions for specs (contour/twist/length)? This rifle will be packed in on hunts and will also spend time plinking steel.

I'm leaving towards 1:9 cut to 26" as a happy medium between weight/length and repeatable accuracy. Shooting for sub .5moa when it's back from the gunsmith.

Will eventually have to hand load to afford to shoot it at the range, but I figure it's cheaper than building both a 6.5CM and a .300wm...I cant afford both.

First off Welcome!

Is it steel or Carbon?

I would probably do a 26" 1-9 as well.
Case capacity will dictate how heavy I want to go with bullets. And for me, a 300 win mag has the capacity for bullets up to 225 grains. I would probably be shooting 208-215 grain bullets.

Agreed!!! ^^^

If its carbon do the extra 2" and go 28" Either way 26" or 28" it will do great.

 

[jpfrog]

A 1:9" is fine but when I rebarrel my 300wm I'll be looking to go 1:8" if possible so I can shoot the big solids like the 227gr Hammer Hunters (https://hammerbullets.com/product/308-cal-227g-hammer-hunter/), but with a 1:9" you can still shoot their 199gr and 214gr offerings.

I agree with going between 26-28" on length, especially if doing the carbon barrel over the steel.

 

[Deleted member 107666]

Thanks fellas, it's a carbon fiber wrapped, yes. I'm hesitant on 28" because with either a brake or supressor on there, its going to be incredibly long.

What are the drawbacks of 1:8 when shooting lighter loads? Do you sacrifice potentially tighter groups in exchange for being able to stabilize the heavier bullets. The higher BC would be nice in the mountains, but I'm stillhoping for a tack driver on the range with the lighter match bullets as well.

 

[L.Sherm]

Proof does not make a 1-8 30 cal only a 9, 9.4 10 in carbon and only a 10 in steel.
I would find out about there reamer if its saami or set up for the heavier bullets like the 210 or 215.
It's better to ask questions now than later when it's to late and you find out you have to seat the bullets really deep.

 

[WildRose]

First Post on this forum, happy I found this place, seems like a wealth of info and thanks in advance for the suggestions.

I currently have a 6.5CM barrel being spun up at Proof. I ordered this when I was in Florida with intent on a mix of long range steel and deer, to replace a .308 I'd built.

Now, with Utah hunting on the mind, I've decided to cancel the 6.5 order and Proof is letting me switch my order to a .308 blank that I will have chambered for .300 win mag.

My only experience with .300wm is an old browning A-bolt I grew up shooting, but no clue on optimal barrel length (I know its debatable) and twist rate.

Can someone give me a few suggestions for specs (contour/twist/length)? This rifle will be packed in on hunts and will also spend time plinking steel.

I'm leaving towards 1:9 cut to 26" as a happy medium between weight/length and repeatable accuracy. Shooting for sub .5moa when it's back from the gunsmith.

Will eventually have to hand load to afford to shoot it at the range, but I figure it's cheaper than building both a 6.5CM and a .300wm...I cant afford both.

1:9 and 26" is about ideal. You can add a couple of inches and shoot slower burning powders and maybe eek a bit more velocity out of it but it really isn't necessary.

If you are one of those guys who's going to jump on the newest, latest, highest BC bullet you might consider 1:8 or 1:8.5 because in all likelihood someone will come up with a grossly heavy for caliber high BC offering in the future but for anything else the 1:9 should be more than ample.

If you just want a nice 6.5CM or .260 you don't need to go custom, there are some great factory offerings out there that will shoot better than 99.9% of the guys and gals that get behind them.

 

[Deleted member 107666]

Proof does not make a 1-8 30 cal only a 9, 9.4 10 in carbon and only a 10 in steel.
I would find out about there reamer if its saami or set up for the heavier bullets like the 210 or 215.
It's better to ask questions now than later when it's to late and you find out you have to seat the bullets really deep.

I believe it ships as a blank, forgive my ignorance, but if that is the case, I can work out those details with my gunsmith when he chambers it?

 

[WildRose]

I believe it ships as a blank, forgive my ignorance, but if that is the case, I can work out those details with my gunsmith when he chambers it?

I'm pretty sure they all come already rifled and lapped.

The "blank" refers to final finishing.

 

[L.Sherm]

I think I was under the assumption you were having proof do the build for you my bad if that's not the case, anyhow still ask questions about the reamer who ever doing the "smith" work and make sure it's what you want. Performance wise there definitely not all the same.
A 1-9 will be just fine for a 300 win.

 

[MagnumManiac]

I would steer clear of SAAMI reamers and order a 'A191' reamer.
You will thank me later, trust me.
As to barrel length and twist, I prefer 26"-28" with a 1-10" twist. I shoot 230's in 28/30/32" 1:10" twist barrels every other week with ZERO issues regarding twist rate.
Sure, a 1:9" twist will give some margin for error, but a 1:10" twist IS actually fast already in 30 cal.

Cheers.

 

[johnlittletree]

I like a 28 inch barrel with a 1:8 to 1:10 twist. You are only limited in bullet weight by twist, barrel length and how you set up the chamber. It depends on what bullet maker you plan on using and if it is a hunting bullet, hybrid or VLD target bullet! Because each barrel maker has massive differences from one to the next you might have best luck with your Brux Barrel in 1:10 but maybe you need to use a 1:9 from Hart to get the same velocity, SD and some sort of accuracy with similar load.

Normally I will call the barrel maker I want to use and have a good idea of what I want but I do not shake my fist at my barrel maker and start barking at him what I want. I will give him a call tell them what I think I want and why and then ask them what they think! They supply barrels to a lot of high end smiths and competitors and most of them are shooters too. Most of all they know their product and what it likes and does not like. Twice I have been talked into a slower twist than I thought I wanted. The thing is they know their product better than I do. So far so good. That said I tend to like a faster twist than most to allow for a heavier VLD bullet that I know is just a matter of time! A lot of rifles end up becoming kind of obsolete when major changes in technology for powder, primer, and bullet construction. I do not think anyone would have predicted the huge increase in the bullet weights available today for the 223/5.56 20 years ago. When this happens unless you rebarrel you are limited in what you can shoot through the rifle well!

My F-Class rifle has a 32 inch cut rifled barrel. It is 6.5mm and it has fairly slow 1:9 or 1:9.5. It shots Berger 6.5mm 140 VLD's no problem. If it was shorter or from a different OEM it might be a different story. You see this all the time with .308Win/7.62 NATO some guys are happy as a kit at the beach with 1:12 and some want 1:8.

So I like to go a little bit faster than what ever is the norm. Most factory rifles go the other direction and are a tad slower than is ideal. Some projectiles are known to favor bore dimensions that are anything but standard you saw this a lot in Palma decades ago. Back when Palma was all the rage almost ever barrel maker had internal diemensions specific to Palma based on the 155gr 7.62 bullet in use. by some requiring .3065 for tight grove. Who would have ever thought? So think about what you want but also future proof your rifle!

If you are going with a carbon wrapped/spon barrel from Proof you might as well take advantage of the reduced weight and aim for a finished length of 28 inches unless you think the area you will hunt will not support this length. 1:10 will Stablize Berger 230gr bullet so anything 1:10 to 1:8. I have 2x 1:8 barrels in 30 Cal and have never had a problem with it being "two fast". As I see it the point of a carbon spun barrel is that you can go with a larger profile or longer barrel and still have the same weight as a shorter or thinner profile all steel barrel. I have owned a lot of 300 Win Mag rifles over the years and I think 26 inches is the minimum I would go with if I really wanted to push the performance! Plenty of companies in the past offered 24inch magnum barrels but I think today's norm is 26 for most magnum rifle! 20 years ago there was no such thing as a VLD 230gr bullet for 30cal. If you had a 220gr for 30 cal it was a round nose soft point.

 

[johnlittletree]

Sorry the above is so sloppy. I have a fever and do not feel well.

 

[Deleted member 107666]

Awesome Info and thank you for including reasoning behind your thinking along with the suggestions. I emailed Proof today with my wish-list and asked them for inputs. I'll post what I get in response.

Initially I asked for sendero, 26", 1:9...will be sure to check weight difference between 26 and 28. I'm trying to stay under 10lb with this rifle. I have a TBAC on my wishlist as well, and if I go that route, I think 28" and a TBAC Ultra 7 is pretty dang long