Is 250 gr LSWC lots different than 250 gr LRNFP?

[DesertRatR]

I loaded up 50 rounds of 45 LC 250 gr LRNFP with 8.5 gr Unique. The closet data in my Speer manual for Unique was for 250 gr LSWC, starting at 8.6 gr Unique. OAL listed for LSWC was 1.600". I set LRNFP OAL at 1.600" which put crimp right in the cannelure. Speed listed for 250 gr LSWC was 891 fps. I chronographed the 50 out of my Ruger New Vaquero. To my surprise average speed came in at 1014 fps with std dev 24 fps. Recoil was noticeably greater than the factory reloads I'd been shooting. After tumbling brass I checked and found none cracked or bulged. After sizing all brass looks good.

Why the > 10% speed increase for less powder than the manual calls for almost the same bullet? Both are same weight and same diameter at 0.452". I don't think it is all aerodynamics. I don't want to risk the gun nor my Henry.

 

[41 Mag]

The loads in the Speer manual might be for a softer swedged lead bullet which runs around a 9 BHN, where as the ones you might have loaded could be cast with a harder alloy. This would give more resistance hence more pressure.

Also just looked at my Lyman Cast Bullet manual, and the load listed for Unique and the 250gr RNFP is 6.0 - 9.0grs, and the 255gr SWC is listed at 6.0 - 8.5grs. These are both listed as cast from #2 Alloy.

Looking at the Alliant site listed load it shows 9.5 as the max load getting 941fps from their 5.5" test barrel. (Remember (IF) you use the data listed on Alliant's internet site you need to reduce by 10% as they are all top end loads.)

Your velocity could also vary due to barrel length, bullet fit, and lube differences. However I would think it is mainly due to being on the upper end of the data for Unique and that weight.

Hope this helps.

 

[CraigC]

I use them interchangeably.

Firstly, don't worry about the overall length, crimp in the groove. Secondly, I'm highly suspect of 8.5gr hitting over 1000fps. Rule of thumb with 250's and Unique in the .45Colt is 100fps for every grain of powder. The Speer data follows that trend. So you're about 150fps higher than expected. Some guns will shoot faster than others but that's a little much. Double check your powder charge and chronograph again under different conditions.

 

[Wil Terry]

WHY ??? Seating depth. READ your loading manuals, SIR. NOTHING causes changes more quickly than loading density.

And so it goes...

 

[Jesse Heywood]

WHY ??? Seating depth. READ your loading manuals, SIR. NOTHING causes changes more quickly than loading density.

And so it goes...

Seating depth (which is relative to OAL) is a number that does not work well in handgun ammo. Thus we adjust to fit the gun and works loads up, keeping rising pressure in mind.

 

[mdi]

I often use data for same weight, different shape lead bullets. I believe a 10% difference in actual measured velocity versus "book" velocity can easily be attributed to different guns. Your gun may be tight and the test equipment could be well worn...

For 30 years reloading for revolvers, I rarely, if ever measure OAL. I crimp in the crimp groove/cannalure and figger the bullet designers located the groove with case capacity in mind and not where it "looked good". Also I believe, in theory, that increased pressure resulted from "deep seating" but have never heard anything as to how much deep seating, as in tenths or thousandths of an inch equals a specific raise in pressure. How deep is too deep? I have though, seen and heard of bullets pushed back, waaay deep, when feeding and causing a kabooms...

 

[Sunray]

Speed listed in manuals applies to the firearm and barrel length used in the tests only. And manuals do change a bit over time. Different powder lots, ambient temperatures, etc will affect velocity.
However, 1/10th of a grain with handgun powders is enough to affect velocity a lot, but it won't affect safety.