Duel based powers

Discussion in 'Reloading Forum (All Calibers)' started by Bulletbob, Dec 5, 2018.

  1. Bulletbob

    Bulletbob

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    I have been told that duel based powders such as RL17 or 19 is hard on barrels. Is that true. It is Nitrocellulose and Nitrogen combined, I just spent $1200 on a new barrel, so I being careful.
     
  2. Mulligan

    Mulligan Gold $$ Contributor

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    I have not found that to be the case.

    CW
     
  3. Uncle Ed

    Uncle Ed

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    The military uses double base powders and with all the deterrent coatings the peak flame temperature is slightly lower with ball powders. The down side is the double base powders are more temp sensitive vs single base powders.

    Example the military switched from RL15 to IMR-4064 for their long range 7.62 sniper ammunition. This was due to the wide temperature swings in Iraq and Afghanistan.
     
  4. Mulligan

    Mulligan Gold $$ Contributor

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    RL-16, and RL-23 are both as stable as any powder I have used.
    CW

    Edit
    Has anyone tested AR-comp for temp stability?
    CW
     
  5. Uncle Ed

    Uncle Ed

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    Below the number to the right of the type powder is the fps change for each degree of temp change.

    [​IMG]
     
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  6. hambone1971

    hambone1971

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    I have just over 2650 rounds through my Savage 12FV 6.5 CM using RL-16 still shooting 1/2 MOA if that helps. I haven't looked at it with a bore scope and don't really want to. I can tell you the throat/lands/rifling has move forward .125 in after all those shots.
     
  7. Meangreen

    Meangreen

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    Where did this info come from?
     
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  8. MagnumManiac

    MagnumManiac

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    Double base powder, pound for pound, produce a fair amount more energy AND gas.
    Their true constituents are nitrocellulose and nitroglycerin.
    Single base powders are just nitrocellulose, they also produce a hotter flame and are slightly less dense than double base powders
    Ball powders produce the coolest flame, the reasons are quite obvious, it is very small in relation to stick type powder.

    It is not 100% correct to say double base powder is harder on barrels or not. It depends on the quantity and HOW it is used.

    Cheers.
     
  9. dminn1

    dminn1

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    What barrel costs $1200? Is it a carbon wrap?
     
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  10. Mulligan

    Mulligan Gold $$ Contributor

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    @Bulletbob,
    I had a similar question a couple of years ago, @BoydAllen shared some good informantio with me and in the end I have used a lot of the Alliant powders. I have had no issues with faster barrel wear, additionally there may be some lubricity benefits from using a double based powder.
    Maybe Boyd will share a little of what he knows on the subject.
    CW
     
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  11. KevinThomas

    KevinThomas

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    With any given cartridge, the single most important factor in barrel life is bullet weight. Heavier bullets are considerably harder on barrel life than lighter bullets, and will show throat erosion far quicker than their lighter countparts. They also generally run higher BCs, and greater sectional density, both of which are often highly desirable attributes in selecting a projectile.

    I’ve used both single and double-based powders in a whole range of cartridges, for all types off shooting, and never seen any real differences in bore life due to what I believe was the type of powder used. Bullet weight, very definitely, but again, you use the bullet that suits your needs the best. Barrels are nothing more than temporary, perishable tooling. Use them as needed, and once they’re done, replace them, simple as that.
     
  12. JRS

    JRS Gold $$ Contributor

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    Duel base swordmens_duel_base_by_freekissforall.png
     
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  13. Laurie

    Laurie

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    There are a LOT of factors at play here, of which double-based formulation (or what are more accurately called 'high-energy' powders such as the Viht N500 series in some cases) is only one - barrel material (stainless is much softer than chrome-moly steel and hammer forging as in most mass manufactured factory rifle tubes hardens it further); size of case/charge v bore size; peak pressures employed; rate of fire / barrel heat reached; weight of bullet as Kevin rightly says.

    Then there are 'double-based' and double-based propellants. The original 1890s British government arsenal produced 'Cordite' ran on a 60% nitroglycerin, 35% nitrocellulose and 5% mineral jelly recipe and basically wore barrels out in 1,000 rounds. (I believe the original US smokeless loading, that for the 30-40 'Krag' 220gn round was loaded with something similarly high in NG and wore barrels out just as quickly.) It was amended to roughly reverse those NC and NG shares in later ammunition marks, but will still wear a barrel out in say maybe 3,000 rounds - and that's for a 45,000 psi number. Most Alliant powders by comparison run at under 10% nitroglycerin content, some at as little as 5%. Some Viht 'High-Energy' grades are 'hot' though - ~40% NG in N540 according to the 'Handloader' magazine profile of this product some years ago.

    The question I can't answer is how does one compare a very high pressure 'hot' single base powder load against a similar performance but lower pressure one from a D-B / high-energy powder? As an example, in those low expansion ratio designs using heavy bullets in say 6.5, 7mm calibres that need slower burning powders, Viht N560 will provide similar MVs to the 4350s, 4831s and similar, but often according to QuickLOAD at considerably lower PMax values. I wore my first 308 Win FTR rifle barrel out in ~2,500 rounds that included a lot of Berger 185s over Viht N550 and a lot of bench time that got barrels much hotter than in the UK's pairs shooting F-Class. Despite the slowfire mode and low UK ambient temperatures, I have friends wearing stainless 308 match barrels out just as quickly (sometimes faster!) in today's FTR competition using very high pressure single-based powder loads under 185s and 200s in small primer Lapua 'Palma' brass.

    If you use the extra heat and energy of some double-based powders to the very safe maximum, they will wear a barrel out quickly especially with heavy bullet loads. I think the OP may be thinking of horror stories of the Nitrochemie manufactured Alliant Re17 which not only has around 10% NG content, but more crucially has Nitrochemie's advanced 'EI' deterrent infusion technology applied which stretches the period that the burning rate is controlled out far longer than with conventional surface coated powders. This sees the period of maximum heat / pressure applied to the throat / rear barrel areas extended to give considerably higher MVs within SAAMI pressures, but applies the heat and pressure to a longer section of barrel for a longer time duration. In some cartridges it gives what initially seemed incredible MV increases - 200 fps in the 6XC with 105-115s, 150 fps or so in 284 match loads with 180s. But there is definitely no free lunch in internal ballistics and people who made full use of this capability paid for it with rapidly enhanced barrel wear. I suspect - but don't know for certain - that if you ran Re17 loads at same MVs as say H4350 equivalents, this lower pressure (than H4350) combination won't wear the barrel any faster than the single-based propellant loading, maybe even slower!

    We have a fair few people in Europe using Viht N560 in the 260 Rem, Creedmoor and similar with 140s and providing they don't go mad on pressures / MVs, their barrels last as long as those on other people's 6.5s as far as I can see - in fact some get longer barrel life than most.
     
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  14. Bulletbob

    Bulletbob

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    The $1200 cost was Barrel, chambering,crowning and installing a muzzle break. Barrel is a R4 Brux 1-8 6.5MM it cost alittle over $450. Price caught me a bit off guard as well.
     
  15. Bulletbob

    Bulletbob

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    Yes I agree, but replacing is easier said than done, I just spent $1200 replacing mine. Counting barrel and machining.
     
  16. Bulletbob

    Bulletbob

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  17. Bulletbob

    Bulletbob

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    You my friend are a Doctorate, of ballistic information, I so wish that you lived in North Alabama. So thank you so much for this very detailed information. My favorite loads in my 6.5x47 is 40 Grns of RL17 on a Berger 140gr Elite Hunter, and a CCI 450 primer, this gets me 2850 fps. with SDs of way less than 10fps. And 40 Grns of H4350 with the same combination of bullet and primer,This gets me 2760fps, and both like .020 off the lands. Accuracy is much better than this old boy can shoot. So from what I am learning from you is, this should be fairly barrel safe. Thanks so much for the mountain of knowledge. Thanks Bob
     
  18. Laurie

    Laurie

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    Thinking further on Alliant's older powders, in this case Re15 which is actually Swedish Bofors manufactured Norma 203-B with a different label on the tin, I have direct experience of very good barrel life with this powder in a moderate pressure load. This powder is one of the higher nitroglycerin content Bofors / Alliant grades at around 12.5% by weight, enough to cause people to panic nowadays, but not back in the 80s, 90s when we got frightened less easily (and were more ignorant about these matters too. :) )

    Around 25 years ago when I shot GB 'Target Rifle' ('Fullbore' sling shooting in US shooting speak) I bought a newly rebarrelled Musgrave RSA target rifle from a club member who'd had to give up shooting on health grounds. It had an almost new Australian Maddco stainless barrel, button rifled job - very popular in GB TR circles in the '90s - reckoned to only have 150-200 rounds down it.

    I soon worked a load up that shot very well for me. Can't remember the brass, probably Norma or Lapua, CCI-200 primer, the original 155gn Sierra MK and Re15, 45gn of it if my memory is right. There was no QuickLOAD or affordable chronographs back then but the maximum distance I shot over in those days was 600 yards, and nearly all my main club's comps were at 300. I kept it for half a dozen seasons and some 1,500-2,000 rounds and then sold it on to another member of the same club - a guy I still see regularly on the range and who still shoots the same rifle with the same barrel, and with the same load. He won't put as many rounds down that Maddco in a season as I did, but a conservative guesstimate says it must have at least 6,000 rounds down that barrel now and if it was the wrong side of 7,000 I wouldn't be too surprised. It's a mild load, but was all that's needed for short/mid-range, and the current owner tells me it still shoots better than he can hold a sling-supported smokepole and he's never had to change the load.

    As Uncle Ed says in post #3, Re15 IS temperature sensitive, as I found when I used it in 223 with very hot 90gn VLD loads and started carrying the ammo around in hotter weather in a cool bag, but North Yorkshire in northern England is just a tad less warm than Afghanistan in high summer, so again that was never an issue I or my successor with the 308 even considered never mind worried about in our ignorance. It remains one of my favourite powders in its class, although I rarely load anything these days that uses powders with this burning rate.
     
  19. Laurie

    Laurie

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    Way too hot and humid for me Bob - I'm a very delicate flower and much too used to the northern English climate to transplant myself there. :)
     
  20. BoydAllen

    BoydAllen

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    Generally, it is my understanding that the typical double based powder has some percentage of nitroglycerine and that that raises the flame temp, which may accelerate throat erosion, but if we are truly in pursuit of the best performance/accuracy, I do not think that this should be a primary consideration when it comes to powder selection. As to any lubricant effect. I have not heard or read that.
     
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