Barrel Length vs Burn Rate.

[45/30-06OKIE]

I’m not even sure base obturation takes place with slow rifle powder and hard cast bullets. I don’t often recover bullets and don’t recall really looking for or recording any such thing the few times I did so maybe it does take place and I just never noticed. But it seems like the kind of thing that would be noticeable. If that makes sense.

That would show up as heavy "leading" of your bore , right? Or no?

 

[AJC1]

I’m not even sure base obturation takes place with slow rifle powder and hard cast bullets. I don’t often recover bullets and don’t recall really looking for or recording any such thing the few times I did so maybe it does take place and I just never noticed. But it seems like the kind of thing that would be noticeable. If that makes sense.

The amount of actual movement of material is very small in my understanding. If I had to describe it numerically it's a transition of a very tight fit to a small .001-.002 interference fit. I don't believe you could visually see the effect after the fact. Maybe somebody way smarter will be able to describe it better...

 

[Charlie98]

Faster powders which are slower in long barrels are also slower in short barrels. The ONLY differentiation being that a faster powder - while running slower - may promote less blast and flash at the end of the barrel than a slower powder which is still retaining higher driving pressure at the short muzzle.

But again, faster powders do NOT create higher velocity in shorter barrels than do slower powders.

It took me a while to grasp that concept (no additional velocity with a faster powder,) but to me the biggest benefit is more efficiency with a faster powder in a short barrel... that is, not so much blast and a better burn.

I load for 2 .308's... a 24" bolt gun, and my 16" M1a. Where I used to use one powder for both... IMR4895, I now use faster IMR3031 in the short barrel of the M1a, and IMR4064 in the longer barrel of the Savage. In each application, it's working better than one powder for both, on several fronts.

I also load the .348WCF for my 20" Browning 71. Big volume case, heavier bullets, in a rifle length barrel... H4831 was the most recommended powder to me. It was horrible... it was like an artillery piece going off every time. Making a huge change... I went to IMR3031, where the same everything worked better, including equivalent velocity in the short barrel. I really think the slow H4831 was toooo slow for the shorter barrel... but it probably works great in a 24" barrel.

 

[45/30-06OKIE]

It took me a while to grasp that concept (no additional velocity with a faster powder,) but to me the biggest benefit is more efficiency with a faster powder in a short barrel... that is, not so much blast and a better burn.

I load for 2 .308's... a 24" bolt gun, and my 16" M1a. Where I used to use one powder for both... IMR4895, I now use faster IMR3031 in the short barrel of the M1a, and IMR4064 in the longer barrel of the Savage. In each application, it's working better than one powder for both, on several fronts.

I also load the .348WCF for my 20" Browning 71. Big volume case, heavier bullets, in a rifle length barrel... H4831 was the most recommended powder to me. It was horrible... it was like an artillery piece going off every time. Making a huge change... I went to IMR3031, where the same everything worked better, including equivalent velocity in the short barrel. I really think the slow H4831 was toooo slow for the shorter barrel... but it probably works great in a 24" barrel.

Lol I shot a 155mm Blank once and they are only 1/3 of a charge and that still resonated in my chest a good bit. With normal ear plugs it wasn't that loud, but again, 1/3 charge. Dad was a Field Artillery Officer. P.S. you'd better keep off to the side or the reciprocation of the breech would take you out lol.

 

[GeoDudeFlorida]

That would show up as heavy "leading" of your bore , right? Or no?

Maybe. Maybe not. It depends on about a dozen factors: bore size, bullet size, lube, alloy, barrel twist, powder burn characteristics, pressure, velocity… leading is pretty typically a factor of bullet-to-bore fit more than anything else. What base obturation does is fit the base to bore tightly, blocking gas blow-by and bullet etching. But it isn’t necessary for a tightly fitted bullet to obturate at the base to seal; the fit is enough.

 

[Slamfire]

I prefer faster powders than slower in gas guns. It is all due to the timing of the mechanism. It is desirable to have low enough pressures at unlock that the case is not sticking to the chamber.

This is a 7.62 Garand barrel with a Garand gas cylinder and operating rod, on a Garand receiver (modified for box magazine). The cartridge was still a prototype 7.62 round.




you can see the bolt is unlocking before pressures in the chamber have reached zero. This is in fact, deliberate. Having some pressure in the chamber is desirable to "pop the cartridge out", but it is a balance. Too much pressure and the case rim gets ripped off because the case is still stuck to the chamber.

So as a general rule, I use the fastest powder commensurate with standard pressures and velocities in my gas guns.

If you really want to increase your velocities, increase the length of your barrel. The tactical 308 rules for FClass have weight limits. Seen fellow shooters out there with 30 inch long, thin barrels, getting their 155 grain bullets above 3000 fps in a 308 Win. They need the bullet to go that fast. They were using Varget at the time, heard H4895 is popular, no one is using IMR 4350 from what I can tell. There is sort of a sweet spot in powder capacity, max pressure, and burn rate.

 

[Charlie98]

Maybe. Maybe not. It depends on about a dozen factors: bore size, bullet size, lube, alloy, barrel twist, powder burn characteristics, pressure, velocity… leading is pretty typically a factor of bullet-to-bore fit more than anything else. What base obturation does is fit the base to bore tightly, blocking gas blow-by and bullet etching. But it isn’t necessary for a tightly fitted bullet to obturate at the base to seal; the fit is enough.

Couldn't have said it better myself.

 

[Beck]

...I’m wondering if more velocity could be gained by using a bit faster powder in the shorter barrel.

The simple correct answer is YES! Modern powders are quite versatile when it comes to matching barrel length to pressure and velocity. The old way of thinking that slower is faster in longer barrel lengths is still correct, but powders have come a long way in terms of launching projectiles to greater velocities while staying within SAAMI or C.I.P. pressure guidelines. We've come a long way baby!

 

[AJC1]

The simple correct answer is YES! Modern powders are quite versatile when it comes to matching barrel length to pressure and velocity. The old way of thinking that slower is faster in longer barrel lengths is still correct, but powders have come a long way in terms of launching projectiles to greater velocities while staying within SAAMI or C.I.P. pressure guidelines. We've come a long way baby!

Your going to need evidence to substantiate that claim.

 

[Beck]

Your going to need evidence to substantiate that claim.

I could write a book my friend. There's no magic or hocus pocus to it. It's common knowledge by now. Of course there are always some who are not quite up to speed. I can't fix that. I would have to be paid by the hour to try.

 

[GeoDudeFlorida]

I could write a book my friend. There's no magic or hocus pocus to it. It's common knowledge by now. Of course there are always some who are not quite up to speed. I can't fix that. I would have to be paid by the hour to try.

Fine. Write a book, get it published, have it independently reviewed, and get your credentials in the public. Then you might be able to justify being a jerk. But I doubt it.

 

[Beck]

Fine. Write a book, get it published, have it independently reviewed, and get your credentials in the public. Then you might be able to justify being a jerk. But I doubt it.

A jerk is something none of my friends and associates would think of me as. On web forums like these words that are meant to be light-hearted and good-natured often don't translate well in text alone. I consider myself among friends on this forum, unless I learn otherwise.

PS: I would have to write a book in this instance. But better yet reference a book or professional journal, but I don't have any links handy off the top of my head this time of night. It'll come to me later. Of coarse I could be a jerk and not share the information. Leave people wandering in the dark... but that's just not me.

 

[Varminterror]

I’ll also call @Beck to the bench - because the claim he’s making is unsubstantiated BS.

We have data provided here in this thread which proves out the fact faster powders at equal max pressures will yield slower velocities. We have many users here - myself included - shooting these powders in these barrels of various lengths and absolutely proving the common MYTH he is lying about here to be wrong.

This drama of “I could write a book, and would have to do so to explain it,” is BS. Just grandstanding. Pump out a few example loads in various barrel lengths with sufficient evidence that the results more likely came from a Chronograph instead of your tailpipe, and your claim would be supported. But that won’t happen, because it doesn’t.

 

[Charlie98]

If you look at published load data, most are listed by top tested velocity... then look at the powder listings. It almost always goes from slowest powder (highest velocity) to faster(est) powder (lower velocity.) There are probably minor exceptions, and that could just be between testing methods, etc.

 

[45/30-06OKIE]

If you look at published load data, most are listed by top tested velocity... then look at the powder listings. It almost always goes from slowest powder (highest velocity) to faster(est) powder (lower velocity.) There are probably minor exceptions, and that could just be between testing methods, etc.

You know, now that I think about it, your are right about that. Cause I'll see Titegroup at the bottom of the list and CFE Pistol or Accurate No 7 at the top.

 

[Charlie98]

You know, now that I think about it, your are right about that. Cause I'll see Titegroup at the bottom of the list and CFE Pistol or Accurate No 7 at the top.

The truth shall set you free. I know, I was a BS caller... until I did my own research, now I'm a true believer.

 

[AJC1]

You know, now that I think about it, your are right about that. Cause I'll see Titegroup at the bottom of the list and CFE Pistol or Accurate No 7 at the top.

Always compare apples to apples. I found crossing manuals didn't work because nothing is the same including barrel length. Normalizing data from different sources is no small or easy task.

 

[bltmonty]

No. This is an old “gun counter fool’s myth,” which truly needs to die.

Faster powders which are slower in long barrels are also slower in short barrels. The ONLY differentiation being that a faster powder - while running slower - may promote less blast and flash at the end of the barrel than a slower powder which is still retaining higher driving pressure at the short muzzle.

But again, faster powders do NOT create higher velocity in shorter barrels than do slower powders.

I have heard this many times, but I reload six rifle cartridges for 15" T/C Encore barrels (308, .223, 7mm BR, 6mm BR, 6-5-284, and 350 magnum), and in EVERY case, I get the fastest velocity using the fastest-burning powder, as shown in Lee and other reloading manuals. It's documented carefully on my chrono. I don't go past the published load data, and I never get the published veolocity data for the longer barrels on the short Encore barrels, but it's certainly the results I have seen. I have mostly the same experience loading for shorter pistol barrels with 9mm and .40, though it's not as consistent as the rifle cartridge. I don't know the science, but I cannot agree with the above statements.

 

[GeoDudeFlorida]

I have heard this many times, but I reload six rifle cartridges for 15" T/C Encore barrels (308, .223, 7mm BR, 6mm BR, 6-5-284, and 350 magnum), and in EVERY case, I get the fastest velocity using the fastest-burning powder, as shown in Lee and other reloading manuals. It's documented carefully on my chrono. I don't go past the published load data, and I never get the published veolocity data for the longer barrels on the short Encore barrels, but it's certainly the results I have seen. I have mostly the same experience loading for shorter pistol barrels with 9mm and .40, though it's not as consistent as the rifle cartridge. I don't know the science, but I cannot agree with the above statements.

Okay, so, the fastest powder currently available is Accurate (formerly Royal Scot) Nitro 100. The new, improved formula has flash suppression and improved stabilizers but neither Royal Scot nor Accurate saw the need to deprecate the existing data.

If the faster powder = faster bullet theory is true, then test it out and post the results. Load up some of your SBR loads with Nitro 100 to exceed the slower powder velocities at lower than slower powder pressures and let us know how that goes.

 

[Varminterror]

I have heard this many times, but I reload six rifle cartridges for 15" T/C Encore barrels (308, .223, 7mm BR, 6mm BR, 6-5-284, and 350 magnum), and in EVERY case, I get the fastest velocity using the fastest-burning powder, as shown in Lee and other reloading manuals. It's documented carefully on my chrono. I don't go past the published load data, and I never get the published veolocity data for the longer barrels on the short Encore barrels, but it's certainly the results I have seen. I have mostly the same experience loading for shorter pistol barrels with 9mm and .40, though it's not as consistent as the rifle cartridge. I don't know the science, but I cannot agree with the above statements.

You’ll be the first guy in history of specialty pistol reloading to actually prove it.

But you’re not the only person out there shooting specialty pistols. It just doesn’t happen - the data is out there.

The fact you’re referencing Lee data, eh. Ok…

 

[bltmonty]

You’ll be the first guy in history of specialty pistol reloading to actually prove it.

But you’re not the only person out there shooting specialty pistols. It just doesn’t happen - the data is out there.

The fact you’re referencing Lee data, eh. Ok…

If you want me to start, here I go--in my 15" barrels, fastest velocities among the five top velocities in 350 magnum is AA 2230; fastest in 6mbr is among top five is 4895; fastest in .224 is VN 120; fastest in 6/5-284 is HH 4350; fastest in .308 in VN 133. In all of these loads, I could not get to maximum load per the load manuals (Lee and others) or I would get pressure signs; and velocities were at least 15% off published velocities. But the faster powders were clearly faster than the slower powders with same bullet in 15" barrels. Just saying they are speciality barrels and doubting Lee does not change the well established burn rates and the chronos I have recorded in these barrels. Sorry to burst your bubble.

 

[AJC1]

If you want me to start, here I go--in my 15" barrels, fastest velocities among the five top velocities in 350 magnum is AA 2230; fastest in 6mbr is among top five is 4895; fastest in .224 is VN 120; fastest in 6/5-284 is HH 4350; fastest in .308 in VN 133. In all of these loads, I could not get to maximum load per the load manuals (Lee and others) or I would get pressure signs; and velocities were at least 15% off published velocities. But the faster powders were clearly faster than the slower powders with same bullet in 15" barrels. Just saying they are speciality barrels and doubting Lee does not change the well established burn rates and the chronos I have recorded in these barrels. Sorry to burst your bubble.

So your barrels cannot perform normally with book standard loads and your results are a further aboration of that problem.

 

[bltmonty]

another data set to burst some bubbles. In these six 15" encore barrels, the cartridges that have bore diameters closer to the cartridge case width (350 magnum and .308 win) performed differently regarding powder burn rate and velocity than the cartridges that have wide case diameters in comparison to the bullet diameter (6.5-284 and 6mmbr). Using the fastest powder in the top 7-10 best velocity loads from Lee, VN, and Hornady, I get near long-barrel velocities in the 350 rem mag and .308 winchester (with no pressure signs), but with the 6.5-284 and 6mmbr (skinny bullet and fat case), the velocity spread between the fastest powders and best velocities powders is much closer.

Stated differently, fat bullets and skinny cartridges perform differently than skinny bullets and fat cases regarding powder burn rates, velocities, and barrel lengths--at least in these 15" rifle cartridges. If someone can explain why the factory produced TC encore barrels contradict the accepted truths of burn rate, barrel length, and velocity, please tell me.

And don't even bother telling me that I don't know how to reload--I reload for 23 different cartridges, using A&D medical lab powder scale, best cases, best bullets, meticuluous case preparation and loading, best dies, and best reloading presses.

 

[GeoDudeFlorida]

another data set to burst some bubbles. In these six 15" encore barrels, the cartridges that have bore diameters closer to the cartridge case width (350 magnum and .308 win) performed differently regarding powder burn rate and velocity than the cartridges that have wide case diameters in comparison to the bullet diameter (6.5-284 and 6mmbr). Using the fastest powder in the top 7-10 best velocity loads from Lee, VN, and Hornady, I get near long-barrel velocities in the 350 rem mag and .308 winchester (with no pressure signs), but with the 6.5-284 and 6mmbr (skinny bullet and fat case), the velocity spread between the fastest powders and best velocities powders is much closer.

Stated differently, fat bullets and skinny cartridges perform differently than skinny bullets and fat cases regarding powder burn rates, velocities, and barrel lengths--at least in these 15" rifle cartridges. If someone can explain why the factory produced TC encore barrels contradict the accepted truths of burn rate, barrel length, and velocity, please tell me.

And don't even bother telling me that I don't know how to reload--I reload for 23 different cartridges, using A&D medical lab powder scale, best cases, best bullets, meticuluous case preparation and loading, best dies, and best reloading presses.

Fantastic! Get it authenticated by a trusted source, tested in an independent lab, published and independently reviewed and it will carry some weight. I suggest sending your data and methodology to someone like Brian Pearce who can at least reproduce the results and comment on them.
Because until you get some credibility, it’s all just hot air. Anonymous posters on internet websites are not credible sources. As much as I may like y’all I would never just blindly trust any loading data posted here - or anywhere else. Trust but verify.

 

[Walkalong]

I have heard this many times, but I reload six rifle cartridges for 15" T/C Encore barrels (308, .223, 7mm BR, 6mm BR, 6-5-284, and 350 magnum), and in EVERY case, I get the fastest velocity using the fastest-burning powder, as shown in Lee and other reloading manuals. It's documented carefully on my chrono. I don't go past the published load data, and I never get the published veolocity data for the longer barrels on the short Encore barrels, but it's certainly the results I have seen. I have mostly the same experience loading for shorter pistol barrels with 9mm and .40, though it's not as consistent as the rifle cartridge. I don't know the science, but I cannot agree with the above statements.

At the same pressures? That's the catch.