WC868/870 and OBP-888 equivalents for the 20x102

45flaco · September 20, 2023, 02:24 PM

Hey guys.
Loading for a 20.
I have load data for WC868, WC870, and OBP-888.
None of these are available at a reasonable rate due to shipping.
However, US 869 is readily available and I have 32 lbs of it that was nearly free.
I know US 869 is a 20mm pulldown, but don't know if it is equivalent.

The first set of load data is for the TP bullets, such as PGU-30.
It calls for WC868 or WC870.
If US 869 is just repackaged WC868, the load data will be 585 to 605 grains, and I'd probably start at 875 or so.

The second load is for a Mk 244 Mod 0.
It requires OBP-888, which I can find zero information on and had never heard of before.
All I could find was that it comes from St. Marks.

If anyone knows of an equivalent to this, it would be fantastic.

Thanks,
Frank

Marco Califo · September 21, 2023, 07:31 PM

Savage does not have a 20mm clambering in their catalog. The FBI had 2 20mm rifles made. Did one of those hit surplus market?
WC872 is widely available, and was used in some 20mm loads. 8 lbs will cost you $100, plus hazmat.
In stock at https://www.gibrass.com/gunpowder.html
I am pretty sure you would run afoul of laws in California 0.787 caliber exceeding 0.50. I am aware of some data for surplus powders but not in 20mm.

**Unclenick** · September 22, 2023, 08:15 AM

Keep in mind that U.S. 869 is now sold as a canister-grade powder, so new lots will have been milled. This means the new lot was tested for burn rate and mixed with faster or slower past lots to adjust the burn rate to within 3% of a standard value set by the distributor and not the government. For that reason, I would expect it to be optimized for 50 BMG.

The WC (Western Cannon) and OBP (Ordnance Ball Powder, I believe) numbers out of the St. Marks plant are bulk powder numbers, so the burn rates are whatever they were when the powder came out of production, and they are not adjusted to the narrower range handloaders need in order to match published load data reasonably well. Bulk powders are sold to ammo manufacturers on the premise that the manufacturer will use pressure guns to tune their loads with it, and not rely on recipes, as the handloader normally does.

Occasionally, a bulk lot will have a large enough burn rate difference from the average that it winds up rejected for its intended application, being either too fast so that it can't reach the specified test velocity without going over pressure or too slow so that it can't reach pressure or velocity and still fit in the case. You have to be careful of surplus lots in case they were made surplus for that reason. With pull-down powder, on the other hand, you know at least that it was accepted for its intended purpose at one time and has simply been surplused because the ammo was either declared obsolete or aged past its stockpile expiration date (I've read the British use 20 years for spherical and double-base propellants, and 45 years for single-base powders and presume the U.S. uses similar numbers). However, you still don't know how close to average the burn rate is unless the seller has tested it and found it matched some existing data somewhere, as Jeff Bartlett appears to do. Just don't count on your loads to be the same from lot to lot, as even pulled-down bulk powder's burn rates can vary several times more than canister-grand powder burn rates do.

For the above reasons, if you use much surplus powder, you could do a lot worse than to invest in the Pressure Trace instrument, assuming they get it back in stock soon. It can be used on a 20 mm gun the same as on any other. If you have some good ammo for comparison, you can get a pressure number from it and load with the US 869 starting modestly and work up to that same peak pressure.

Marco Califo · September 28, 2023, 01:16 PM

TM 43-0001-27 (Google It)
Is what you want to read. It identifies the different 20mm rounds U.S. made. They specify powders and very general load ranges (I am told this is not actual loading data).

**Unclenick** · September 28, 2023, 05:44 PM

Marco, you can prove to yourself that it isn't real load data. Look up the 30-06 M2 Ball powder charge it gives for 150.5 grain (average) bullets, and the M72 Match load powder charge it gives for the 173-grain M1 Type bullet. They list the same 50 grains of IMR4895. Yet the detailed list of National Match loads by year using IMR 4895 shows 48.5 grains was the highest charge ever used in these loads, and 46.0 grains was the lowest, the difference being partly due to different burn rates for the different lots of powder and that, in turn affecting the actual velocities achieved when the loads were tuned to best accuracy. Also, by the time the 1970s rolled around, they had switched M2 to WC852. In that version there were different powder lots with charges ranging from around 53 grains up to lots with charges of around 58 grains. The latter lots were originally qualified only for machine guns, and not for the M1 Garand, though testing later concluded the Garand op-rod velocities resulting from it's higher muzzle pressure were generally acceptable. H380, which is the canister grade version of WC852, achieves M2 velocity with 53 grains.

Marco Califo · September 28, 2023, 06:42 PM

Ok. It is a general range, for information only, and spefically not load data. If your powder won't fit in a case, you can't load that much. I completely agree that using these surplus powders would be better with a pressure measurement of some sort.
I don't know where one would get 20mm brass or what the Primer spec is.
I have seen in OP's other posts, that this not a project an ordinary person would undertake. Then there is the "Why?".

September 20, 2023, 02:24 PM	#1
45flaco Senior Member Join Date: November 19, 2017 Posts: 134	WC868/870 and OBP-888 equivalents for the 20x102 Hey guys. Loading for a 20. I have load data for WC868, WC870, and OBP-888. None of these are available at a reasonable rate due to shipping. However, US 869 is readily available and I have 32 lbs of it that was nearly free. I know US 869 is a 20mm pulldown, but don't know if it is equivalent. The first set of load data is for the TP bullets, such as PGU-30. It calls for WC868 or WC870. If US 869 is just repackaged WC868, the load data will be 585 to 605 grains, and I'd probably start at 875 or so. The second load is for a Mk 244 Mod 0. It requires OBP-888, which I can find zero information on and had never heard of before. All I could find was that it comes from St. Marks. If anyone knows of an equivalent to this, it would be fantastic. Thanks, Frank

September 21, 2023, 07:31 PM	#2
Marco Califo Senior Member Join Date: April 4, 2011 Location: LA (Greater Los Angeles Area) Posts: 2,602	Savage does not have a 20mm clambering in their catalog. The FBI had 2 20mm rifles made. Did one of those hit surplus market? WC872 is widely available, and was used in some 20mm loads. 8 lbs will cost you $100, plus hazmat. In stock at https://www.gibrass.com/gunpowder.html I am pretty sure you would run afoul of laws in California 0.787 caliber exceeding 0.50. I am aware of some data for surplus powders but not in 20mm. __________________ ............

September 22, 2023, 08:15 AM	#3
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	Keep in mind that U.S. 869 is now sold as a canister-grade powder, so new lots will have been milled. This means the new lot was tested for burn rate and mixed with faster or slower past lots to adjust the burn rate to within 3% of a standard value set by the distributor and not the government. For that reason, I would expect it to be optimized for 50 BMG. The WC (Western Cannon) and OBP (Ordnance Ball Powder, I believe) numbers out of the St. Marks plant are bulk powder numbers, so the burn rates are whatever they were when the powder came out of production, and they are not adjusted to the narrower range handloaders need in order to match published load data reasonably well. Bulk powders are sold to ammo manufacturers on the premise that the manufacturer will use pressure guns to tune their loads with it, and not rely on recipes, as the handloader normally does. Occasionally, a bulk lot will have a large enough burn rate difference from the average that it winds up rejected for its intended application, being either too fast so that it can't reach the specified test velocity without going over pressure or too slow so that it can't reach pressure or velocity and still fit in the case. You have to be careful of surplus lots in case they were made surplus for that reason. With pull-down powder, on the other hand, you know at least that it was accepted for its intended purpose at one time and has simply been surplused because the ammo was either declared obsolete or aged past its stockpile expiration date (I've read the British use 20 years for spherical and double-base propellants, and 45 years for single-base powders and presume the U.S. uses similar numbers). However, you still don't know how close to average the burn rate is unless the seller has tested it and found it matched some existing data somewhere, as Jeff Bartlett appears to do. Just don't count on your loads to be the same from lot to lot, as even pulled-down bulk powder's burn rates can vary several times more than canister-grand powder burn rates do. For the above reasons, if you use much surplus powder, you could do a lot worse than to invest in the Pressure Trace instrument, assuming they get it back in stock soon. It can be used on a 20 mm gun the same as on any other. If you have some good ammo for comparison, you can get a pressure number from it and load with the US 869 starting modestly and work up to that same peak pressure. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

September 28, 2023, 01:16 PM	#4
Marco Califo Senior Member Join Date: April 4, 2011 Location: LA (Greater Los Angeles Area) Posts: 2,602	TM 43-0001-27 TM 43-0001-27 (Google It) Is what you want to read. It identifies the different 20mm rounds U.S. made. They specify powders and very general load ranges (I am told this is not actual loading data). __________________ ............

September 28, 2023, 05:44 PM	#5
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	Marco, you can prove to yourself that it isn't real load data. Look up the 30-06 M2 Ball powder charge it gives for 150.5 grain (average) bullets, and the M72 Match load powder charge it gives for the 173-grain M1 Type bullet. They list the same 50 grains of IMR4895. Yet the detailed list of National Match loads by year using IMR 4895 shows 48.5 grains was the highest charge ever used in these loads, and 46.0 grains was the lowest, the difference being partly due to different burn rates for the different lots of powder and that, in turn affecting the actual velocities achieved when the loads were tuned to best accuracy. Also, by the time the 1970s rolled around, they had switched M2 to WC852. In that version there were different powder lots with charges ranging from around 53 grains up to lots with charges of around 58 grains. The latter lots were originally qualified only for machine guns, and not for the M1 Garand, though testing later concluded the Garand op-rod velocities resulting from it's higher muzzle pressure were generally acceptable. H380, which is the canister grade version of WC852, achieves M2 velocity with 53 grains. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

September 28, 2023, 06:42 PM	#6
Marco Califo Senior Member Join Date: April 4, 2011 Location: LA (Greater Los Angeles Area) Posts: 2,602	Ok. It is a general range, for information only, and spefically not load data. If your powder won't fit in a case, you can't load that much. I completely agree that using these surplus powders would be better with a pressure measurement of some sort. I don't know where one would get 20mm brass or what the Primer spec is. I have seen in OP's other posts, that this not a project an ordinary person would undertake. Then there is the "Why?". __________________ ............