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Similar to @rambo-6mmrem question but different,
Is there a calculation for max projectile weight for barrel length?
For example, 6.5 Creedmoor, 1 in 8" twist, 18" barrel
Is it better to run 120, 130, 140, 143 ELD-X etc
Essentially i would like the best projectile/powder without pooing up the barrel with deposits
Cheers
Calculate the max length that your twist rate will stableise, then look up a table of bullet lengths in your cal, match length to weight and job done.
1:8 would do well with all those weights I imagine.
I've got a 20" 6.5CM Howa Alpine that I think is 1:8, I shoot 1/2 or better groups with 123 Amax's and thats with between 38gr and 42gr's of 2208 (ie a 10% powder spread)
I have found more twist is better than less.
Litz says more RPM = higher BC, & the velocity penalty is typically less than the usual ES.
Obviously in extreme situations too much twist is less than desirable, ie .224 40 grain @ 4500 fps in 1-8 or .375 350gr SMKs @ 3400 fps with 1-7 exit twist :oh noes:
No, what has a calculation is twist rate for projectile weight. Even shooting a heavy projectile with the right twist rate the barrel length will only determinate how fast you will need to "push the projectile" to achieve the velocity that will keep your projectile efficient out to long or extreme ranges.
Apparently, depending on how far you need to shoot the faster projectiles will go they will be supersonic for longer and efficient to the desired distance, cutting or having a short barrel length will only say you will need a "hotter" load to make your rig efficient.
My 0.05$c
Mac
Heavier calibers, such .308 upwards will have rifle especifications different for the purpose they are build for, a varmint 308 is likely to have a slower twist rate to push lighter projectiles faster at shot and medium range(bush or small fields(up to 300mt max?)), other 308 version designated to further distances the shooter will desire a faster twist so they can shoot heavier projectiles with less athmosferic influence in its path.
A heavier caliber such the .375 mentioned by KiwiGreg is categorised by me as a special caliber and as you can imagine it is designed to hit things at a very long distance. These calibers are designed with barrel length and twist rate ad equated to the purpose of the projectiles being used to reach those distances. Many people wanting a rifle to an especific purpose (long-extreme range) normally build the rig to suit their needs, a .308 or 300WM with 1:10 or 1:9 twist, a Creedmoor with 1:7(not really need, just example) a .243 normally 1:10 with a 1:8 or 1:7", a 7mm normally 1:9.5" to a 1:8.5" and etc.
Do a quick google about magnums and ultra magnums caliber, apparently the ultra magnums have a bit faster twist than the normal magnums.
Again, I hope I am of some help.
Agree faster twist generally better but don't go crazy on the fast twist direction. In terms of projectiles it also depends very much on your intended use - gongs vs game & what size game and range. The terminal performance of different pills and weights can be very different. If you're after a target bullet then this is of no consequence just focus on max BC & max velocity and find pill that you boom stick likes. If game and especially large game is the target then this will narrow down your choice quite considerably for 6.5 calibre. My own choice for 6.5 is 140gn partition for up close and 140 gn AMAX for +300 yrds.
Thanks for the replies. I probably should have had powder choice in my original post as well!
I suppose one of my concerns is that trying 2208 with 100gr Nosler BT, 120 AMAX and 129HSP the barrel had a light grey coating deposited at the crown.
While using 2209 and 140gr Interlocks and 143 ELD-X the deposit on the crown was black and a heavy scale that could be chipped off with my finger nail but took some considerable effort. This occurred with various powder charges!
That is another conversation that I will "TRY" to help later.Quote:
Originally Posted by Fireflite
I thought Litz said that too fast spin and you get large spin drift, but that the effect of spin drift disappears at longer distances i.e.gradually corrects itself over distance.Quote:
Originally Posted by Kiwi Greg
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.260 creedmore is a short action. My thought process would be this
-28" barrel max.
-1/8 twist because you need that to stabilise berger vld.
-if you want more mv then go the ackley improved route
-get a no turn neck. that is the best decision ive ever made.
What overall weight can you cope with? My rifle weighs a shitload but i dont care. Its pushing 140s as fast as possible without destroying brass but the barrel is 29" long and thick to stop it flexing. With a 260 you can match my 6.5x55 mv with a 26" shorter barrel and AI chamber. Getting a no turn neck should make it cleaner, barrel length needs to match the burn rate of your chosen powder. I'd use 2209 in a 260 for the medium burn rate and mid length barrel. Id use ELD-M for target and berger vld hunters for hunting. Those ELD-X dont beat the m's unless you can can jam enough powder in the case. That fancy BC is useless to me as my max load cant push them fast enough (2795fts)
Considering only velocity, the best powder burn rate is governed by the projectile and the chamber not barrel length. The "faster powder for shorter barrels" is mostly myth.
There may be other advantages in reduced muzzel pressure etc with a quicker burn rate though.
So considering all the feedback, is 2209 the best option or would another power be better? Or do I just run a better cleaning regime?
your observation of grey deposit at crown - are you running a suppressor or brake by any chance ?
either one, but especially suppressor, can cause excessive carbon build up, most easily detected at the crown or muzzle but the gunk will be thru out the barrel. Your cleaning regime needs to take this into account. From my experience I would not expect a lot of difference between ADI powders like 2208 & 2209 in carbon build up, but could be better/worse if you changed brand of powders.
Maybe a good read regards barrel length and velocities.
6.5 Creedmoor- Effect of Barrel Length on Velocity: Cutting up a Creedmoor! | Rifleshooter.com
Those velocitys seem to ring true. I get 2790 fps with my 123 A-Max out of a 20" with DPT can.
No brake or suppressor used. It took quite a lot of effort to get the barrel clean again. Thanks for the replyQuote:
Originally Posted by chainsaw
Yes i read that a few times prior to load development (bloody good read) but didn't really highlight the issue I've experienced. Thanks for the on going help!Quote:
Originally Posted by PERRISCICABA
I disagree. It absolutely 100% is NO myth. The end user explosion when you pull the trigger is not the burn rate. That rate is a constant (it is a quantified number in quickload). Have a play with various combinations using that program and you'll see its no joke. If i try a huge charge of slow burning magnum powder down a short barrel with a light projectile, quickload will show you the pressure curve, and tell you that the projectile left the muzzle before the propellant had finished burning in your specified barrel length.Quote:
Originally Posted by sneeze
My old powder that matched the std barrel (2209 for a 24" barrel) would not be the best for my new 29" barrel for instance. I'm using 2213sc as it produces a safer pressure curve which can actually go higher than 2209. Choosing the projectile is the last thing I do. (But that's just me)
Also, when I reccomended 2209, that was an abbreviated reply as I'd run just about every combination for you in QL using all the better projectiles and powders. Same goes for the pill.
Iv got an ok understanding of burn rate and Iv had QL for quite a few years. My reference to reduced muzzle pressure with a faster burn rate was an example of why a faster burn rate might be desirable over best velocity. Probably not that relevant .Quote:
Originally Posted by Dead is better
If I understand it correctly? you are saying that 2209 will give better velocity in your 24" than barrel than 2213 because it has a higher percentage of propellant burnt?
So, I will try to explain in a different way, all the figure I will put here is fictional to a 308 caliber and you just "transfer your imagination to other calibers.
Imagine a drag race track, it is what I will call "the barrel", then you have the cars and I will call it "projectiles" and now you have the engine that I wil call "the powder".
You have a race track as long 260 meters(26" barrel) and a light little car (120grains projectile), you will load it with a "fast explosive engine) that will push this little car very fast thruout the 260 meters race track, why? Because it is a light car and the extreme velocity will take a short time to "burn" and take it all the way to the destination and still have enough "horse power" to take it further if necessary. The "down turn" of it is the track is too long so the explosive start and will only last and be effective for the first 200-220 meters (20-22") of the track but hold the speed further than that.
Then, you have the same track with a heavier car (190 grains) and need a more powerful engine to push it for the length of the hole track, so you get an engine (powder) with slower start but it will "push" the car with extreme power for a longer distance optimising the length of the track and the weight of the car.
Moral of the story: if you use the fast powder in a long barrel it will "work" for Just a percentage of the barrel, if you use a slower powder it will work for the hole length of a long. Artel but it won't be effective for a shorter barrel because, as the bullet already exit the muzzle the powder will still be burning the excess.
I will clarify my idea when I get home if necessary.
Cheers
Mac
But thats not how internal ballistics perform and the "engine driving the car to the end of the track" is the myth. With even the slowest powder the effect the burn has on the projectile is dropping rapidly after just a few inches of projectile travel down the barrel. The push the projectile has received has it accelerating to the end of the barrel but the rate of acceleration is decreasing.
The best velocity will come from the flattest pressure curve which will be from the slowest burning powder that is suitable for the particular bullet weight, irrespective of barrel length. Any powder still burning after the first few inches of projectile travel will not be enough to effect the rapidly dropping chamber pressure and have no real influence on muzzle velocity. Think of it as if the chamber was a balloon, the powder ignites and inflates the balloon which sends the projectile accelerating down the barrel. A fast powder will inflate the the balloon to its maximum( say 60.000 psi) but the burn is done and dusted so the balloon deflates rapidly. A slower powder will inflate the balloon to max but keep burning and hold the balloon at max pressure for a little longer and exposing the projectile to max presure for longer giving better acceleration
The key here is all of this takes place in the first part of the projectiles journey down the barrel so by the time its traveled a few inches its rates of acceleration are fixed.
It does drop but it's still there, adding velocity right till the last mm.
I agree that bullet weight / type is just as important and deffinately effects the pressure generated. He'll, I was surprised to see the 140 bergers have a higher mv than the 140 Amax. Still don't quite know why as the seating / powder etc was all the same.
Say you're right. Does this mean short barrel guys should start using magnum powders because they have flatter pressure curves?
Agree with you 95%, what you can help me to understand now is, in the case of those people shooting thruout short barrels why or when a slower powder "help" keep the pressure curve till the end of the barrel if the total length is not optimised to the for it?Quote:
Originally Posted by sneeze
I do acknowledge all the things "we" are talking here and "I" personally don't have a QL software to check all the possible data and variations the combinations will give "us". I am learning more and more here.
Cheers
Mac
Yes some pressure is available till exit which is why longer barrels give higher velocity but the amount of pressure available is determined early in the process. As the projectile travels down the barrel the internal volume available grows substantially and quickly becomes to great for any still burning powder to have any affect.Quote:
Originally Posted by Dead is better
It depends on the chamber and projectile. In simple terms for example if 2217 gives the best velocity for a particular 338 300gr combination in a 28 inch barrel it will give the best velocity in a 22 inch. There is no free lunch, you cant chop a barrel , throw in a faster powder and get velocity back without running higher peak pressure or dropping bullet weight. Be nice though eh, I could have a 15 in 7mm remag pushing162 amax with BM2Quote:
Originally Posted by Dead is better
A slower powder will generally give a flatter curve and therefor more area under curve( it will provide peak pressure for a longer time) proving more initial push for want of a better term, better acceleration. How far away the muzzle is has no affect on how fast or hard the bullet can accelerate. You do have to be able to fit enough in the case though which is why we cant just use US 869 for everything, it has to match the chamber and projectile.Quote:
Originally Posted by PERRISCICABA
.308 Win Barrel Cut-Down Test: Velocity vs. Barrel Length « Daily Bulletin
If what you're saying was true, the above experiment would not have documented a 261fts drop in mv when they sawed off the barrel from 28" all the way down to 16". They average was a loss of 22.5fts loss per inch
So, the powder ain't burning past 3 or 4 inches but that really is semantics. The bullet is still accelerating all the way up so a shorter barrel does leak a crap load of wasted 'expanding gas' shall we call it.
Your post did make me go looking and a lot of guys find unburnt powder but that's due to the oxygen being depleted apparently and nothing to do with barrel length
The propelant creates its own oxygen as it burns.
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Yes if you chop a barrel you loose velocity. Iv said that already. Yes you may not be burning all of the powder because of the shorter barrel and there could well be some kernels that didn't ignite and yes there will be more gas wasted as you put it, (more muzzle blast). They are all symptoms of a shorter barrel.Quote:
Originally Posted by Dead is better
None of which changes the fact that you can not win back velocity by switching to a faster burn rate. .
You have QL, while its not prefect it normally gives a good indication
6.5 creedmoore 140gr amax.
2213 46.88gr for 60184psi. in a 28inch barrell propelant burnt =98.27% for vel of 2958fps.
drop it to a 20 in barrel and we get propelant burnt =95.85% for vel of 2738.
Load and chamber pressure remain the same
If I use 2209 (slightly faster) 44.74gr for 60211 psi
20 inch barrell propellant burnt =97.39% for vel of 2713fps
So with 2209 in a 20 inch we have a higher percentage of propellant burnt slightly higher chamber pressure but LESS velocity.
Let me eat my pie in peace haha.
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I just focussed one way (up) and never thought to try to tweak the same powder backwards to a shorter one.
I tried your numbers but wasn't able to replicate them exactly as my seating distance is different
So I tried mine. I'd have to say if I was using a 20" barrel i'd not bother with 2209 because i'd want max speed over a quieter / more cost effective load. MV is king in my books (use 2213 in either barrel)
We're only talking about 10ft/sec here though. I got 25ft/s gain for the 20" barrel and 35ft/s for the 29" which I use. The longer barrel mattered MUCH more. I have a 260ft/s gain which sounds right
I then had a play to see if the powder above more but there is a limit. That powder is bulkier and has less return for granule so case capacity did hem me in ultimately.
I'd have to take my swede and make it an Ackley for a measly 53ft/s return and all that for an extra 4.5gns per round.
Its probably one of the most common misconceptions in reloading.You see it posted a fair bit, theres another thread asking about powder for a short barrel running now. .
I can say from experience that humble pie is more palatable warm than when its left to go cold.:thumbsup: