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<  16ga. Ammunition & Reloading  ~  SP16 Wad And Straight Hulls
gjw
PostPosted: Sat Jul 05, 2014 4:05 pm  Reply with quote



Joined: 09 Sep 2006
Posts: 863
Location: NoDak

Hi all, so according to spr310's spreadsheet (which are great, BTW!) is states that the SP16 was is not a good choice for straight walled hulls.

My question is why?

Just curious.

Thanks as always!

Greg
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Dogchaser37
PostPosted: Sat Jul 05, 2014 4:43 pm  Reply with quote
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Joined: 08 Aug 2011
Posts: 1946
Location: Central CT

Unless you use large grained powders like 800-X, powder can migrate past the overpower cup, and will not be used to propel the payload.

I have been successful using 800-X, Blue Dot and Longshot with the SP-16 wad in Federal and Cheddite hulls. A firm crimp is essential for these combinations to work.

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Mark
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AmericanMeet
PostPosted: Sat Jul 05, 2014 5:06 pm  Reply with quote



Joined: 26 Apr 2010
Posts: 3172
Location: NCWa

The SP16 is slightly narrower than most of the other wads, so when used with thin, straight sided hulls there is not a good pre-ignition seal. On firing the wad flares out to seal the bore, but as noted by DC, the problem occurs prior to firing, particularly with fine grained powder that can sneak out between the hull and wad, thus being of no use for generating pressure behind the wad. While this powder movement occurs mostly when the shells are bouncing around, I have noticed powder can come alongside the wad if the wad is moved rapidly down into the hull when loading. Prior to seating the wad, the hull contains powder and air. If the wad is slam-dunked down into the hull, the air gets forced out of the hull and as it's leaving it can take some powder with it. Best to take a little time and keep the full charge in place.
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16gaugeguy
PostPosted: Sun Jul 06, 2014 7:15 pm  Reply with quote
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Joined: 12 Mar 2005
Posts: 6535
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If good load performance is desired, then firm crimps are always mandatory regardless of the components being used. However, there is more to it than this. So please follow on if you will.

The SP16 and R16 wads are both 1st generation designs from the 1960's. The design is rather primitive in comparison to later, more modern wad designs. In fact, most of Remington's 1st generation wad designs have been withdrawn from the reloading component market. The SP16 is but one of just a scant few survivors. It is still offered as a component on a limited basis, so us 16 ga diehards Laughing can reload the 16 ga. RGL hull. Who can say how long it will still be available though.

The skirts at the base of the SP16 and R16 wads are small and not nearly as generous and supple as those found on later wad designs like the WW16AA wad, it's clones, and close copies like the DR16 wad, as well as the later Remington wad designs. Also, the wad base cups on the underside of the SP16 and R16 wads are rather flat and shallow unlike the more hemispherical wad bases found on later wads.

These 1st generation wad base skirts obturate well enough to produce a good seal if used in a Remington polyformed hull or any other which also has a smaller inside diameter (like the now defunct compression formed WWAA hull). These older Remington wad designs can be problematic if used in any hull with a larger inside diameter due to this lack of suppleness. This is especially true when using finer grained ball and stick powders. It is less so if used with most flake powders though.

One solution is to place a very thin (.005-7") overshot card wad of the proper diameter on top of any charge of fine grained powder before seating the SP16 or R16 wad. A very thin card wad will help prevent powder migration but should not interfere with the gas seal once the pressure has built up enough to obturate the wad base skirt. The card will be blown into the wad base, and the skirt will flare out enough to seal the gases until the wad and shot leave the bore.

Be advised. Average peak pressures may be increased to some extent if none of the available powder charge is lost to migration before ignition. How much is anyone's guess. However, a prudent reloader will reduce his powder charge by a few grains at first and test the load to see if pressures drop enough to cause incomplete burning and excessive unburned powder residue. If so, then a full charge can probably be safely used.

Also, it is never wise to modify any load recipe which already produces maximum pressures. Anyone who does this is on their own.
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