Powder burn rates and barrel length

[360hunt]

So I have a new 30-06 carbine 18.5" to load for.
All data in my manuals are for longer barrels 24"-26" . I would think I'm going to have alot of unburned powder in the shorter barrel.
Would you use faster powders than recommended to compensate for this?

Thanks

[Dean2]

All the powder is burned in far less than 18.5". The issue with the shorter barrel is you have less length where the expanding gases are enclosed and acting on the bullet, that is why a faster powder is recommended in shorter barrels. It builds pressure faster and hits peak pressure sooner allowing for more velocity out of the shorter barrel. It has nothing to do with being able to burn all the powder, that happens with the fastest or slowest. I would stay with recommended powders but use the fastest powder that still produces top velocities with the desired bullet weight. Hope this helps.

For example, with a 150 grain bullet I would pick Benchmark over 4350.

[360hunt]

Originally Posted by Dean2

All the powder is burned in far less than 18.5". The issue with the shorter barrel is you have less length where the expanding gases are enclosed and acting on the bullet, that is why a faster powder is recommended in shorter barrels. It builds pressure faster and hits peak pressure sooner allowing for more velocity out of the shorter barrel. It has nothing to do with being able to burn all the powder, that happens with the fastest or slowest. I would stay with recommended powders but use the fastest powder that still produces top velocities with the desired bullet weight. Hope this helps.

For example, with a 150 grain bullet I would pick Benchmark over 4350.

That does help
Thanks

[amosfella]

Originally Posted by Dean2

All the powder is burned in far less than 18.5". The issue with the shorter barrel is you have less length where the expanding gases are enclosed and acting on the bullet, that is why a faster powder is recommended in shorter barrels. It builds pressure faster and hits peak pressure sooner allowing for more velocity out of the shorter barrel. It has nothing to do with being able to burn all the powder, that happens with the fastest or slowest. I would stay with recommended powders but use the fastest powder that still produces top velocities with the desired bullet weight. Hope this helps.

For example, with a 150 grain bullet I would pick Benchmark over 4350.

Not necessarily correct. My friend and I had 45-70 guns. He had the 24" barrel and I had a 18.5" guide gun. We loaded some rounds with IMR 7828 (IIRC?) and all the powder would burn in his gun, but I still had unburned powder in the cases in my gun.

We were trying to get black powder equivalent in the guns.

[YYC338]

Originally Posted by amosfella

Not necessarily correct. My friend and I had 45-70 guns. He had the 24" barrel and I had a 18.5" guide gun. We loaded some rounds with IMR 7828 (IIRC?) and all the powder would burn in his gun, but I still had unburned powder in the cases in my gun.

We were trying to get black powder equivalent in the guns.

I'm not entirely sure barrel length was the issue here. IMR 7828 is an extremely odd powder for a straight (almost) wall case like the 45-70.

Why did you use that one?

[Dean2]

Originally Posted by amosfella

Not necessarily correct. My friend and I had 45-70 guns. He had the 24" barrel and I had a 18.5" guide gun. We loaded some rounds with IMR 7828 (IIRC?) and all the powder would burn in his gun, but I still had unburned powder in the cases in my gun.

We were trying to get black powder equivalent in the guns.

So first off, where did u find published data for 7828 in a 45-70. Second, 7828 is a REALLY slow burning powder, far slower than anything usually used in that cartridge. If you were trying for BP equivalent loads u should have been using 4759, Trail Boss, reduced 4895 loads or real black powder. There are also low pressure trap door loads published. Finally unburned powder in the case indicates an ignition problem. When most people talk about unburned powder they are talking about unburned grains in front of the muzzle. My bet is you aren't crimping, and using regular rifle primers and not getting complete ignition. 7828 is notoriously difficult to light off. Even in the 7 Rum I have to use FED 215 primers as CCI mag primers won't light off the 95 grain charges reliably. What the longer barrel length is doing is masking the poor ignition of this far too slow powder.

[catnthehat]

Originally Posted by 360hunt

So I have a new 30-06 carbine 18.5" to load for.
All data in my manuals are for longer barrels 24"-26" . I would think I'm going to have alot of unburned powder in the shorter barrel.
Would you use faster powders than recommended to compensate for this?

Thanks

Don’t Screw around with anything but load book data!
The only difference you will see between the 24” and 18.5” barrels is some velocity , that’s it the pressures will be the same as will the powder burn with the same powder but a longer barrel
You will be fine going with published load data .
Cat

[Nyksta]

A faster burning powder and a slower burning powder both will lose about the same velocity as the barrel is shortened to 18.5". Use the powder with the highest velocity in the book for your bullet weight, and if you dont like that powder, try the next fastest.

[huntinstuff]

I experimented with this

I had a 22” barrel on a Sako 3006

I had it cut/recrowned three times to see if it affected accuracy

I got nervous at 20 inches and stopped lol

Made the rifle lighter and accuracy was unaffected.

I was using 180G Nosler Partition PPT with 57g of RL 22 and federal magnum primers.

[prarie_boy1]

Originally Posted by huntinstuff

I experimented with this

I had a 22” barrel on a Sako 3006

I had it cut/recrowned three times to see if it affected accuracy

I got nervous at 20 inches and stopped lol

Made the rifle lighter and accuracy was unaffected.

I was using 180G Nosler Partition PPT with 57g of RL 22 and federal magnum primers.

Did you run any loads over the chrony? I’d be curious to see the diff in velocity as the barrel was shortened. I had a .30-06 re barrelled about 6 years ago and decided on 22” finished length really didn't notice much of a velocity diff from the 24” factory barrel it had previously and the rifle feels better in the hands with the 22” barrel of a slightly heavier contour.

[huntinstuff]

Originally Posted by prarie_boy1

Did you run any loads over the chrony? I’d be curious to see the diff in velocity as the barrel was shortened. I had a .30-06 re barrelled about 6 years ago and decided on 22” finished length really didn't notice much of a velocity diff from the 24” factory barrel it had previously and the rifle feels better in the hands with the 22” barrel of a slightly heavier contour.

No chrony

I was only interested in accuracy

It was unaffected

[marxman]

Don’t change your powder, if loaded to the same pressure the slower powder will still give more velocity because there is more of it. A faster powder will theoretically give you less muzzle blast because the exit pressure is lower and there is less gas produced, loaded to the same peak pressure I mean

[Pathfinder76]

Originally Posted by huntinstuff

I experimented with this

I had a 22” barrel on a Sako 3006

I had it cut/recrowned three times to see if it affected accuracy

I got nervous at 20 inches and stopped lol

Made the rifle lighter and accuracy was unaffected.

I was using 180G Nosler Partition PPT with 57g of RL 22 and federal magnum primers.

Why would accuracy have been affected?

[YYC338]

Originally Posted by chuck

Why would accuracy have been affected?

Possible change in barrel harmonics?

[sako1]

Originally Posted by chuck

Why would accuracy have been affected?

A longer barrel means you are closer to the target 😁

[marxman]

Originally Posted by 360hunt

So I have a new 30-06 carbine 18.5" to load for.
All data in my manuals are for longer barrels 24"-26" . I would think I'm going to have alot of unburned powder in the shorter barrel.
Would you use faster powders than recommended to compensate for this?

Thanks

To answer your question no you don’t need a faster powder to burn it. If it doesn’t burn right it’s because of low pressure caused by a powder that is too slow or not enough of it. If it won’t reach high pressure in the first few inches it won’t finish burning no matter how long your barrel it will leave husks or yellowish Unburnt powder down your barrel

[Pioneer2]

About Elmer Keith when he was test firing .50 BMG's at the Ogdon plant.He said he was sweeping up unburnt powder off the table with wisk and a dust pan.So depending on the powder /gun it may not all be consumed in the barrel.

[Pathfinder76]

Originally Posted by Pioneer2

About Elmer Keith when he was test firing .50 BMG's at the Ogdon plant.He said he was sweeping up unburnt powder off the table with wisk and a dust pan.So depending on the powder /gun it may not all be consumed in the barrel.

Elmer Keith had about one powder to choose from.

[Dean2]

Okay, simple proof of what I said. Work up a max load in 4350 with 150 grain bullet out of an 18" barrel. Measure velocity. Work up max load with Benchmark and all other components exactly the same. Measure velocity. Also assess both max loads for accuracy. Come back and tell me which was faster and more accurate.

Last one I proved it with was a 20" barrel 308. With a 130 grain bullet and 4895 I can get 3150 fps, 1/2" groups and no pressure signs. With Varget and CFE the best I could get was 2900 fps before pressure signs showed up, accuracy at 2900 was about 1 inch. According to Hodgdon's load data, out of a 24" barrel max velocity with Varget should be virtually the same as it is with 4895, but 4895 is significantly faster burning. It also tolerates reduced loads well for playing around with cast bullets.

I have done the same validation with short barreled 375s that burn north of 80 grains of powder, as well as short barreled 300 Win Mags. Once you actually try it you will be surprised what using the correct burn rate powder, within the published range of powders and loads for that cartridge, will do for the performance of your short barreled guns.

[marxman]

Originally Posted by Dean2

Okay, simple proof of what I said. Work up a max load in 4350 with 150 grain bullet out of an 18" barrel. Measure velocity. Work up max load with Benchmark and all other components exactly the same. Measure velocity. Also assess both max loads for accuracy. Come back and tell me which was faster and more accurate.

Last one I proved it with was a 20" barrel 308. With a 130 grain bullet and 4895 I can get 3150 fps, 1/2" groups and no pressure signs. With Varget and CFE the best I could get was 2900 fps before pressure signs showed up, accuracy at 2900 was about 1 inch. According to Hodgdon's load data, out of a 24" barrel max velocity with Varget should be virtually the same as it is with 4895, but 4895 is significantly faster burning. It also tolerates reduced loads well for playing around with cast bullets.

I have done the same validation with short barreled 375s that burn north of 80 grains of powder, as well as short barreled 300 Win Mags. Once you actually try it you will be surprised what using the correct burn rate powder, within the published range of powders and loads for that cartridge, will do for the performance of your short barreled guns.

Well I can’t argue that I have not done short and long barreled comparisons. I did look at hodgdons site though and 4350 is 120 FPS faster than benchmark in a 24 inch barrel. If it loses 30 FPS per inch that’s a loss of 180 FPS at 18 inch barrel length. The benchmark can only lose 10 FPS per inch or a total of 60fps to arrive at the same velocity as the 4350 both in 18 inch barrel.i say it’s not possible that the 4350 loses velocity that much faster and that in the hodgdon gun the 4350 is still faster. No doubt the benchmark is more efficient though it uses 80 percent of the powder to get 95 percent of the velocity

[Pioneer2]

Originally Posted by chuck

Elmer Keith had about one powder to choose from.

Point being all powder is not necessarily burned in the barrel. His reputation and life experiences would make him an expert IMO.