SKB,
Looks like you have it well tuned for that whitetail.
I found this data shot with a 40-90. Its a pretty close comparison:
Goex express Fg no compression
Lo 1371
hi 1403
Av 1384
Es 32
Sd 11.7
Goex express with .218 compression
Lo 1397
Hi 1426
Av 1409
Es 29
Sd 11.3
Swiss Fg no compression
Lo 1369
Hi 1383
Av 1374
Es 14
Sd 5.4
Swiss with .180 compression
Lo 1383
Hi 1395
Av 1391
Es 12
Sd 4.7
Note the ES & SD numbers.
The SD on the Swiss is consistently in the single digits were as the Express is double digit while the ES is considerably higher across both loads for Express. Playing around with a few variables my lower those numbers.
Tinker,
One item that is very diffrent between then and now are primers. As the BPCR folks will tell you primers can make a significant diffrence when working up a load.
This all has to do with how BP and Nitro based powders are ignited. BP is best ignited by flame or heating particles to incandescence were as nitrocelulous based powders are best ignited by heated gasses.
Just a side note:
Remember - never use the word DETONATE when refering to BP or smokeless propellants. DEFLAGRATION is the proper term. Its when the grains are ignited on the surface and burn towards the center.
Detonation, on the otherhand, is when a pressure wave travels through the material at or near the speed of sound. The wave then triggers the chemical reactions within the explosive.
Any composition that detonates is bad, bad, bad.
Now back to primers:
So with the variation of ignition between BP and nitro based powders its a no brainer that they require diffrent primer criteria.
Here is a small comparison between mercury fulminate used in BP primers old to lead azide primers as used today:
Temperature of combustion.
4105 degrees C, Mercury fulminate
3180 degrees C, Lead azide
Calories of heat evolved (unit of weight?)
420, Mercury fulminate
684, Lead azide.
In addition the duration of the flame with mercury fulminate could be extended by certain additions to the compound and that is what BP likes a nice hot flame of long duration. Sort of like running your finger through a candle. Do it fast and it won't hurt. Do it slow and ouch!
One other factor was the popularity of Berdan primers. V. the Boxer primers we use today. The Berdan design may have acted to diffuse the flame and cause ignition on a much broader surface rather than a narrow deep penatration of the charge. Today some BPCR shooters use primer wads that work to achieve the same result.
Now lets look at Curtis & Harvey:
By the end of the 19th century 1800's the best English-made sporting powders were urtis & Harvey and Chilworth Gunpowder.
However, with the advent of smokeless powders By the end of the 1890's the demand for fast burning sporting powders had just about ceased in the U.S.
No U.S. based powder company ever produced moist-burning powder to match Curtis & Harvey and many of the German powders. From the 1870's through the 1880's it was common for commercial cartridge companies to load the fast sporting powders in thier pistol caliber cartridges. By around 1890 the commercial cartridge loading companies switched from using the more expensive sporting powders in their pistol cartridges and switched to rifle burn rate powders. To compensate for the slower burn rate they simply went to the next lower grain size in the rifle powder.
Curtis & Harvey continued to produce a sporting burn rate powder up until about 1970. Around 1970 they could no longer purchase buckthorn alder wood from suppliers in Spain. That forced them to change to commercial charcoal and powder quality suffered greatly.
This slow powder was prepared with the commercial charcoal that was greatly inferior to the glossy buckthorn alder charcoal that C&H had charred and prepared "in-house". Its also the stuff compared with Dupont back in the 1974 in the Lyman black powder book and was actually slower. However, if you can find a pre-1970 can it will be good powder.
Best regards,
Terry
Last edited by THARPER; 07/15/08 10:51 AM.
