FPS variance in loads


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JimGun
March 9, 2010, 03:24 PM
Hodgdon recipe for a 200 gr LSWC calls for min. 4.4 gr of Winchester 231 for 771 FPS. Using Berry’s plated SWC oaded with 4.4 gr Winchester 231 I obtained an avg of 570 fps. Since this is the minimum load I will be moving up, but what factors would cause such a disparity between the Hodgdon recipe and the actual fps?

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rcmodel
March 9, 2010, 03:32 PM
For one thing, the Hodgdon starting load data you used is for a grease lubed lead bullets.
But you are shooting Copper Plated bullets.

Copper has a higher coefficient of friction then greased lead.

Berry Bullets suggest you use low to mid-range jacketed bullet data, not lead bullet data, for that reason.

See this Berry FAQ for recommended load data to use:
http://www.berrysmfg.com/faq.aspx?n=633800

rc

Walkalong
March 9, 2010, 03:51 PM
That's it. At that low level, make sure each bullet leaves the barrel. It's getting close to low enough to stick one.

ants
March 9, 2010, 08:00 PM
I've loaded some really low velocity loads like JimGun. The bullet seems to roll down the barrel, fall aimlessly to the ground and walk over to the target, where it climbs up and lazily pokes a hole somewhere in the paper, then it goes and sits down somewhere for a rest.

At least that's what explains the random pattern of holes all over the target.

Walkalong
March 9, 2010, 10:48 PM
I have had 125 & 158 Gr .357 bullets leave the barrel of a 6" Trooper Mk III at less than 400 FPS (Chroned), but I have had them stick as well. Those 200's have a lot of bearing surface, and 500 FPS is close to sticking one.

The bullet seems to roll down the barrel, fall aimlessly to the ground and walk over to the target, where it climbs up and lazily pokes a hole somewhere in the paper, then it goes and sits down somewhere for a rest.
The best description I have heard yet. :)

Seismic Sam
March 11, 2010, 05:19 AM
I've loaded some really low velocity loads like JimGun. The bullet seems to roll down the barrel, fall aimlessly to the ground and walk over to the target, where it climbs up and lazily pokes a hole somewhere in the paper, then it goes and sits down somewhere for a rest.

At least that's what explains the random pattern of holes all over the target.
I had something similar happen to me in trying to figure out if some strange primer signs in my 50GI 1911 were pressure signs or just artifact from the humoungous cartridge cycling in a 1911 gun. Since I wasn't about to use a $3,000 gun with heavier charges to see what happened, I came up with a unique and somewhat perverted solution. I shot my trial 50 GI loads in a 500 Smith with cut-up and ground down (to 20 mils) moon clips. Obviously, I could do anything i wanted here with a 50 GI and the gun wouldn't blow up. Now, the really revolting thing about doing this is that whn you fire the round, the bullet rattles down a full 1.5" of chamber before it hits the end of the cylinder and the forcing cone in the barrel. :barf: First load I shot chronoed at about 350 FPS, and there was a discernable pause between the BANG! and the SPLAT!! Didn't see the bullet stick its thumb out to hitch a ride, but maybe I just wasn't looking good enough. I ran the powder charges all the way up until I was getting 1,000 FPS out of the Smith, with the primer and the case looking fine, so whatever was going on in the 1911 was case motion atrifact. Alex Zimmerman, owner of Guncrafter industries, was both amused and grateful for my data.

JimGun
March 11, 2010, 11:51 PM
I thank all of you for your comments. I increased the load to 5.0 grs of Winchester 231. Chronoed speeds avg 651 fps. however, they still didn’t rack the slide back to eject the empty casing. shooting this rounds out of my Ruger Blackhawk w/ 71/2” barrel I avg wa 741 fps.
Keeping the same 5.0 gr load I went back and adjusted my seater die on my RCBS to give a tighter taper crimp and my XD ejected all but three rounds. This leads to another question. What is the proper crimp for a brass-plated SWC?

Walkalong
March 12, 2010, 11:13 AM
A light taper crimp is all you need.

Assuming .45 ACP, 5.0 Grs of W-231 and a Berrys 200 Gr SWC should work the action of a stock gun. 741 sounds reasonable, depending on the barrel length etc, etc.

It is possible your sizer is oversized or your expander is too big rsulting in poor neck tension. Check that.

Try 5.3 Grs W-231 at 1.260 O.A.L. with a light taper crimp.

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