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Old 09-23-2015, 12:35 PM
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Default Crimp pressures on soft lead....

Some have asked if there is a difference on FPS with a light crimp vs a heavy crimp on soft lead bullets.

I have also wondered if it would up the fps if the bullet could stay in the case a bit longer, while the powder energy increased in the milliseconds that just happened.

Back in 5/25/2013 I did some test with my M49 38 snub nose with some soft Mag-Tech 158gr LRN bullets at 1.55" OAL.

x.x grs of Blue Dot with a medium crimp put out 812 fps.
.2 grs less powder with a heavy crimp put out 851 fps.
The x.x load with just .1 gr more powder and a heavy crimp was loaded into five cases.

Only three were fired, due to the recoil and fps printed on the chrony screen.
The three averaged 948 fps........ an 136 fps increase in fps.

Yes a HEAVY crimp on a soft lead bullet, can increase the fps on a load.
Use caution when at or near a FULL LOAD of powder or pressures.
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Old 09-23-2015, 02:13 PM
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Option C seems to duplicate the S&B 158g RN load.
That one in an LCR is not exactly what you'd call an all day range load.
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Old 09-23-2015, 03:53 PM
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Thanks for the info ! I've gone to a light crimp on my plinking 38 loads only because my concern for the crimp damaging the bullet during firing. I've noticed on spent cases with a heavy crimp I can still kinda feel the crimp in the case. I cast my own 105 gn Lee bullets under 3.7-3.9 grains of 700x. Very accurate. Occasionally ill get a little lead on the forcing cone but it's non issue for me. Oh...out of a model 66-3.
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Old 09-23-2015, 10:39 PM
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Default Good ole Cannelures.....

Crimping grooves and cannelures seem to be going out of style. You can heavy roll crimp without damaging the bullet. If you can seat the bullet deep enough a crimp over the beginning of the ogive works. To me it's only really necessary when loading 'hot ones'.

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Old 09-24-2015, 02:39 AM
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Quote:
Originally Posted by Nevada Ed View Post
x.x grs of Blue Dot with a medium crimp put out 812 fps.
The x.x load with just .1 gr more powder and a heavy crimp was loaded into five cases.

Only three were fired, due to the recoil and fps printed on the chrony screen.
The three averaged 948 fps........ an 136 fps increase in fps.
.

I'm curious what the results would be if you did the same test but with a fast powder. I'm guessing the heavy crimp is more meaningful when slow powders are used, irregardless of the bullet's BHN?

.
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Old 09-25-2015, 09:09 PM
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BLUEDOT37;

S&W M49 snub nose, 158 Lswc, cci500 primer, heavy crimp.

Bullseye 4.1 752 fps
w231 .... 5.0 816 fps
Green Dot xx 822 fps ( over Alliant data )

The faster powders came close but either the accuracy or the fps, failed to give results that were satisfactory to me.

Best results in the snub is with Unique or slower powders up to
and not including 10grs of 2400 that gave a "Shotgun" pattern and felt like a K frame load to me....... maybe 9.6 grs?
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