Powder Recommended for Long Barrel 6.5

[gasrat]

Picked up a 6.5 today with a 29” Hart Barrel on it. Plan on running 140 ELD-M through it and was looking for slower powder suggestions other than what I have on hand, which is H4350, R16 & Varget.
I have some 4831SC that I’m thinking may be my best bet with that much of a tube. What says you? Any information is appreciated.

 

[Steel head]

Case capacity is an important factor and H4831 fills the case before You get a good speed often in mid size 6.5 cartridges.
I’d look at R16 & 26 and IMR4451

 

[gasrat]

I’ve got plenty R16, so I’ll give it a go. I run it in my 26” 6.5. Didn’t know if it would suffice for the longer barrel or would burn to fast.

 

[264win]

Rl 26
H4831
H1000 (will be over 100% case capacity)
VV 560

 

[spife7980]

The best powder for a given caliber and chamber size is always going to be the best powder regardless of barrel length. Your H4350 and RL 16 on hand are the default choices for a reason.

 

[gasrat]

The best powder for a given caliber and chamber size is always going to be the best powder regardless of barrel length. Your H4350 and RL 16 on hand are the default choices for a reason.

I was under the impression I needed a slower burning powder for the longer barrel length. Appreciate the clarification.

 

[spife7980]

The majority of the speed comes in the first few inches, like 70% of it and 90% is in the first 10 inches. The rest of the barrel is just a marginal increase compared to the overall velocity. What’s 25 fps per inch when it’s already going 2,000+ fps?

I’d show some quick load graphs but I’m walking to my car on my phone but you can google and see where the speed gets made.

 

[264win]

The powders op mentions are fine for any barrel length.
Slower powders may offer a little more speed and possibly a bit more barrel life ( RL 16 is pretty fast in 6.5 cm and 7-08)

 

[Greenday4537]

The majority of the speed comes in the first few inches, like 70% of it and 90% is in the first 10 inches. The rest of the barrel is just a marginal increase compared to the overall velocity. What’s 25 fps per inch when it’s already going 2,000+ fps?

I’d show some quick load graphs but I’m walking to my car on my phone but you can google and see where the speed gets made.

Is that true for all calibers? Cause my 16" barrel RAR in 5.56 is like 250-300 fps slower than published values. I don't expect to get the actual values but that's a heck of a difference.

 

[spife7980]

Is that true for all calibers? Cause my 16" barrel RAR in 5.56 is like 250-300 fps slower than published values. I don't expect to get the actual values but that's a heck of a difference.

It’s about the ratio between the mass of what you are pushing (the bullet), the in the chamber, and then the amount of volume created behind the bullet as it moves down the barrel. It’s about most efficiently and ideally filling that volume behind the bullet with the gasses from burning powder: what’s in front of the bullet (barrel length) has no effect on what’s already happened to the bullet.

Too fast of a powder and you fill that space too quickly and pressure spikes up high. Too slow of a powder and you have more space created behind the bullet the powder can burn and fill up time so you get pressure sagging behind.