Reloading for a 30" barrel?

[mdslammer]

Hi Guys,

I have been reloading for my current .338LM which has a 26" barrel. The current load consists of:
Lapua Brass, Federal 215M Primers, Berger 300gr. OTM Hybrids and H-1000 90.5 gr. OAL 3.680 / 2800 fps.

My new .338 LM is being finished up and will be here in a few weeks. It will have a 30" Bartlein barrel with a 1:9.35 twist.

What can I expect using this load in the new rifle? I assume a bit more fps but what else? Any concerns, pros / cons to be
aware of?

Any info would be greatly appreciated.

Thanks.

 

[Fuzzball]

Maybe another 150-175 fps. What else could change due to bbl length?

 

[Aimsmall55]

I've got a .300 win mag with a 30" Broughton 5c I had built for the 230 bergers. I'm zinging them at around 2980 fps. Pro: a fast barrel that will stand toe to toe with the .338 for 1500 yards or so.
Con: with my Shrewd brake, it's 32" long. Not the most compact rig.. I haven't even been able to find a "quality " case for it!

 

[mdslammer]

Maybe another 150-175 fps. What else could change due to bbl length?

Well, for one thing, how will this, if any, effect the powder burn rate?
How much more distance can I expect?
How much more accuracy, if any?

Just a few off the top of my head.

 

[oldfatguy]

New barrel is plenty of reason to do a new load work up. Your previous load might be best for your new barrel, might not.

OFG

 

[280nosler]

Accuracy - unless you were shooting with a loosey-goosey chamber factory barrel, don't expect 1/2 size groups just because of new barrel and 30 inches.
Distance - IF you use the same 300 grain bullet, you can expect probably another 90 yards between the 30 inch barrel and the 26 in term of distance to sub-sonic, but that bullet is well known to handle the change pretty well. You planning on shooting 1800 yards, because you will likely be down roughly 110 feet at 1800 yards.
Affects on Powder burn rate - pretty minimal. he smaller the diameter, the longer the barrel needs to be to burn the slow burning powder, but with a 338, I would guess that happens around 20-24 inches (burning is complete as it is going to be), but the gasses should continue to expand for another few inches, therefore the bullet is continuing to accelerate.

I am curious that you are using 90.5 grains, when berger calls for 85.2 to be a 104% fill rate. I based my calculations on a baseline of 2640 and 30" velocity of 2770, which is looks like you are already exceeding.

 

[mdslammer]

Accuracy - unless you were shooting with a loosey-goosey chamber factory barrel, don't expect 1/2 size groups just because of new barrel and 30 inches.
Distance - IF you use the same 300 grain bullet, you can expect probably another 90 yards between the 30 inch barrel and the 26 in term of distance to sub-sonic, but that bullet is well known to handle the change pretty well. You planning on shooting 1800 yards, because you will likely be down roughly 110 feet at 1800 yards.
Affects on Powder burn rate - pretty minimal. he smaller the diameter, the longer the barrel needs to be to burn the slow burning powder, but with a 338, I would guess that happens around 20-24 inches (burning is complete as it is going to be), but the gasses should continue to expand for another few inches, therefore the bullet is continuing to accelerate.

I am curious that you are using 90.5 grains, when berger calls for 85.2 to be a 104% fill rate. I based my calculations on a baseline of 2640 and 30" velocity of 2770, which is looks like you are already exceeding.

Thanks for the reply and info 280nosler.

As far as the load goes, I've had no issues as far as separated cases, blown primers, over pressure signs, heavy bolt lift, hard extractions etc.
I have had these problems when I tried loading at 91-91.5 grains.

 

[mdslammer]

I did find this info to be helpful from muzzle velocity/Wiki.

In conventional guns, muzzle velocity is determined by the quality (burn speed, expansion) and quantity of the propellant, the mass of the projectile, and the length of the barrel. A slower burning propellant needs a longer barrel to burn completely, but can on the other hand use a heavier projectile.[5] A faster burning propellant may accelerate a lighter projectile to higher speeds if the same amount of propellant is used. In a gun, the pressure resulting from the combustion process is a limiting factor on projectile velocity. A balance between propellant quality and quantity, projectile mass and barrel length must be found if both safety and optimal performance is to be achieved.

Longer barrels give the propellant force more time to work on propelling the bullet.[5] For this reason longer barrels generally provide higher velocities, everything else being equal. As the bullet moves down the bore, however, the propellant's gas pressure behind it diminishes. Given a long enough barrel, there would eventually be a point at which friction between the bullet and the barrel, and air resistance, would equal the force of the gas pressure behind it, and from that point, the velocity of the bullet would decrease.

 

[pjparker]

+ 1 for oldfatguy's response. You need to do a new work-up for the new rifle. New chamber, throat and bore are all variables to be considered, and if radically different ( and here we are considering just a few tenths to be radical ) you could experience some serious pressure issues. Barrel length should be the least of your concerns.

Paul

 

[mdslammer]

Yes, I realize I will have to do a complete work up for my loads for this new rifle. But that wasn't the question for this post.
I was asking what noticeable difference(s) I could expect going from a 26" barrel to a 30" barrel for those who have reloaded for both lengths.

+ 1 for oldfatguy's response. You need to do a new work-up for the new rifle. New chamber, throat and bore are all variables to be considered, and if radically different ( and here we are considering just a few tenths to be radical ) you could experience some serious pressure issues. Barrel length should be the least of your concerns.

Paul

 

[Aimsmall55]

Yes, I realize I will have to do a complete work up for my loads for this new rifle. But that wasn't the question for this post.
I was asking what noticeable difference(s) I could expect going from a 26" barrel to a 30" barrel for those who have reloaded for both lengths.

Noticeably; a lot longer damn barrel that looks pretty unproportional. Not trying to be a jerk but your asking questions that nobody can answer. For instance , how in the hell are we supposed to know if its going to be more accurate...?
If your that concerned, get Quickload and that should answer alot of what your asking about

 

[Fuzzball]

* "Burn rate"? You mean of the best powder? That won't change.
* "Distance" will be determined by the elevation of your sights and what ever trivial effect an extra 150-175 fps produces - not much
* There will be no direct effect on accuracy but longer barrels are obviously more flexible than short ones of the same diameter so it may be more difficult to develop an equally accurate load for it.

Off the top of my head.

 

[mdslammer]

* "Burn rate"? You mean of the best powder? That won't change.
* "Distance" will be determined by the elevation of your sights and what ever trivial effect an extra 150-175 fps produces - not much
* There will be no direct effect on accuracy but longer barrels are obviously more flexible than short ones of the same diameter so it may be more difficult to develop an equally accurate load for it.

Off the top of my head.

Hey Fuzzball,

Thanks very much for taking time to reply with some useful information.

 

[Fuzzball]

You're welcome.

As for "useful information", that always varies by how much you're unaware of. I have assumed you already know that even with your large volume case and the slowest burning powder the pressure will peak at maybe 5" of bullet travel, not 28" down the tube.

 

[Josh Smith]

Hello,

I handload for 30" barrels -- Mosin-Nagants.

I'm finding that the burn is almost complete with, say, Varget and similar powders. For them, 24" to 26" barrels seem to be best. Loads using Varget and 150 grain bullets hover around 1.5MOA, with a couple touching MOA.

However, when I switch to heavier bullets -- Hornady Match, SMK, etc, around 174grn, the precision becomes apparent. Very tight groups result when backing with a slower powder like H4350.

Please remember that when I talk about these rifles, they're only precise so far as battle rifle are precise. Handloading and shimming the actions, which includes a pressure pad on the barrel, allows me to bring the precision from three or four MOA to keeping up with current-production hunting rifles of similar caliber.

I do like the longer barrel for the longer sight radius, but I'm assuming you're using a 'scope, so that's immaterial for you, I guess.

Just some random thoughts to chew on.

Regards,

Josh