Discussion in 'Reloading Forum (All Calibers)' started by Ironworker, Sep 14, 2018.
Is Re#15 a double based powder ? It doesn't say either on the container.
Yes RL15 is double base, look at MSDS sheets
Thought double base powders were harder on bbls ,as where a couple of shooters say IMR 4064 is a barrel killer ?
The military switched from RL15 to IMR-4064 in their long range sniper ammunition. This was because RL15 was more temp sensitive in Iraq and Afghanistan. And as far as double base or single base powders being barrel burners that depends on the peak flame temp for a given caliber...
Early double base powders contained more nitroglycerine than many pistol powders contain today. And today double base powders develop the same approximate peak flame temp as single base powders.
Hey Uncle Ed... How can you tell from the MSDS ?
It has 7.5% nitroglycerin content by weight, a modest level that will have no significant effect on barrel life if pressures are reasonable. It may heat the barrel up a little quicker in rapid fire than an equivalent single-based nitrocellulose only type and that can affect wear.
Double-based powders mostly got their dreadful reputation in the early days of smokeless powders. The original 1880s British Cordite had a 58% nitroglycerin, 37% nitrocellulose, 5% petroleum jelly recipe and burned barrels out in ~1,000 rounds. Even Cordite MD, a gentler substitute introduced in the early 20th century had 30% nitroglycerin content. The US propellant utilised in the 30-40 US Army (Krag) had a similar high NG content although I've never seen a % quoted. There are high-energy handloader's grades around today with 30% or so NG content but they are exceptions to the rule, Alliant Reloder series powders, Norma grades, and the new IMR 'Enduron's all use the ingredient but in single figure percentages or just getting into double figures in the higher performance variants such as Re22, Norma MRP and URP.
All ball / spherical powders are double based hence Winchester, some Alliants, Hodgdon 'Sphericals', Ramshot and Accurate ball grades, and all US military smallarms ammo propellants since 7.62 was adopted in the 1950s with a few special purpose exceptions such as sniper grades. Extensive studies have shown that double-base ball powders and single-based extruded equivalents produce very similar barrel lives in 7.62 and 5.56mm military weapons whose ammunition is loaded to NATO STANAG specifications.
Temp and corrosive, and friction maybe can erode barrels. If the temp is the same, what, how can the content change the barrel erosion rate ??
Nitroglycerin contains considerably more energy than nitrocellulose (hence its use in 'high-energy' types such as the Viht N500 series). It also burns hotter / produces higher temperature gasses than straight nitrocellulose grades and as it is denser than a same size kernel single-based grade can pack more energy into the case if room is an issue. All of these factors may see a greater volume of higher temperature gas produced and hence more barrel wear.
Put temperature strips on the barrel ahead of the chamber (or just feel it with one's hand) and it soon becomes obvious that some powders heat the barrel faster than others. With single figure percentage nitroglycerin shares though, these 'mild' double-based types such as Re15 have a negligible (if any) effect on barrel life at modest loadings if the type of shooting doesn't involve long strings that heat the barrel up both rapidly and to very high temperatures. In fact as they are more 'energetic' than equivalent single-based equivalents, many loadings that produce satisfactory MVs for the user may be running at appreciably lower pressures than their single-based equivalents producing similar velocities so this factor may offset the higher burn temperature.
220 Swift is the bad boy cartridge I'm burning this powder in.
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