Sigle base vs. double base powders

[GSP7]

What are the benefits and disadvantages over the other?

Seems I just read a conflicting opinion . I thought ive been reading that Double base powders(nitroglycerin added) do produce higher velocities but can burn hotter and lead to more throat errosion , where as single base powders (nitrocellulose only) will generaly be easyer on throat wear.

Some guy on another site just stated that double base powders burn cooler and cause less throat errosion. Im thinking this is a false statement...

 

[jlmurphy]

I'd say that you have it correct, I have been using more of the Hodgdon's Extreme line of single based powders instead of the Alliant Reloder double based line in cartridges with heavy bullets.

 

[Laurie]

The benefits from double-base are the increased energy; greater load density possible as the N-G treatment adds weight so that you can pack a heavier weight charge into a volume-limited case for any given kernel size / configuration; longer shelf life as D-B powders only deteriorate very slowly in storage. (I pulled the bullets on a load of WW2 era .30-06 M2 ball some years back. Those loaded with IMR-4895 S-B stick powder were full of a black liquid 'goo' and were corroding the cases from the inside out; 1943 dated WW ammo loaded with the original D-B ball powder were perfect - the powder was in such good condition, it looked as though it could be reused despite being 60 years old.)

Downsides are increased cost (sometimes) and increased flame temperatures - but only if not treated by the manufacturer to avoid this occurrence. Also, in my experience, some examples such as the Viht N500 series can be 'stickier' than the base S-B N100 version so don't meter as accurately in powder measures.

Every ball powder on the market is D-B as are all Alliant Reloder series rifle powders.

In practice, where you have directly comparable versions - which means the Vihtavuori powders - you find that the addition of N-G does change the powder behaviour. N500 powders are noticeably slower burning than their N100 counterparts in practical terms despite being shown as having identical burning rates in the manufacturer's manual and data sheets, so you have to use a bit higher charges to get the same MV and a bit more still to get the promised increases. It can change the performance characteristics in a particular application. Having tried N160 in .243 Win with 100gn bullets and got good results, I found that N560 gave poor accuracy, large ES spreads and massive muzzle flash and blast with the same components. Other times round, the N500 powder works better than the N100 from the off - so you can't treat them as identical performers but with one that gives a bit more MV than the other. My 'feeling' is that most N500 loads work best at maximum loads / pressures, while the untreated versions are more flexible. D-B powders may be slightly dirtier than S-B from the same basic N-C base as they have additional additives.

Wear and tear wise, I've no concerns about increased erosion from modern D-B powders except insofar as increased perfromance = shorter barrel life, all other things being equal. D-B powders were once notorious for rapid barrel throat erosion, but that was a long, long time ago. Equally, I don't buy into longer barrel life claims - it's the bullet weights you're running, the MVs they're running at, and the pressures you need to achieve them that determine 99% of barrel life. Speed costs!

Find the powder that gives you the results you want and don't worry about its composition.

Laurie,
York, England

 

[ronemus]

Double-base powders have a flatter pressure curve: the nitroglycerin burns quicker, and the nitrocellulose slower. This can be used in two different ways. Loaded to the same muzzle velocity, peak pressure is reduced and with it peak temperature. Loaded to the same peak pressure, muzzle velocity is increased due to the extended burn. If you go for the velocity increase you pay a price in throat erosion since the peak pressure is maintained longer; however, if you load for the same velocity erosion is generally reduced since peak pressure and temperature are lower. There's no free lunch - you can't have it both ways.