Powder Coat Bullet Accuracy

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Powder Coat Bullet Accuracy

Post by 10sandxs on 2/28/2016, 2:50 pm

First topic message reminder :

As the accuracy of powder coated bullets has been the subject of discussion of late, Al and I did a methodical study to determine the effects of powder coating on bullet accuracy.  To accomplish this, bullets were cast using a 5 cavity NOE mold # 453-200-SWC and a mixture of Wheel weight and linotype which when water dropped and aged gives a hardness of roughly 14 brinnell. Bullets from this mold and allow combination drop at 216 gr +/-.5 gr when I do my part well. 



These bullets were weight sorted into groups of +/-0.3 gr and the heaviest group was used for testing.  Of this group, half were lubed and sized with White Label Lube X-Lox2500+.  The other half were coated with polyester powder coat (red) sourced form www.powederbythepound.com.  Un-sized bullets were coated by the “Airsoft BB dry tumble” method and baked for 20 minutes at 420 degrees F. Thickness was determined to be between 1 and 3 thousandths by measuring coated and uncoated bullets prior to sizing.  Once baked and cooled, these bullets were sized using the same sizing equipment (Star) that the previous bullets had been lubed and sized in.



These bullets were loaded using IMI Match brass which had been cleaned and prepared using normal loading methods.  The load consisted of 4.5gr of Titegroup over a Federal Premium #150 Large Pistol Match primer seated to a depth of 1.230 +/-0.002 and crimped to 0.001 less than the body diameter with bullet seated.



This load was initially ransom rest tested from a base bolted to a concrete floor at an indoor range at 50 FEET.  Three ten shot groups ranged from 0.431” to 0.615” for this load.  The ransom rest on the indoor 50 YARD range consisted of the rest clamped to a 700 lb. (approximately) concrete and steel bench.  The test protocol consisted of firing 5 ten shot groups of powder coated and traditionally lubed cast bullets.  Previous 50 FOOT ransom rest testing indicated that within 1 or two “fouling” shots, the groups had stabilized and no significant effect was observed when switching between lubed and coated bullets (long line to short line simulation)



The test program was performed using two guns, a 45 I built on a Caspian frame and slide with a 5” Kart Exact Fit Barrel.  This was the gun used for 50 FEET ransom rest testing.  The second was a Rock River 6” gun that has shown excellent accuracy (>1.5”) in numerous previous ransom rest sessions.  The second set of experiments with the Rock River was conducted for reasons discussed below.  There was effectively no difference observed in the accuracy of these two guns.



Groups from the 50 YARD range were somewhat disappointing, ranging from a minimum of 2.065” to a maximum of 3.669”.  Interestingly, these extremes were fired using the same gun/ammunition combination so user error or rest stability are possible factors. In many cases groups were reasonable with the exception of one or two flyers.  To get a better understanding of the overall accuracy potential, group sizes are reported as both 10 shot and 9 shot groups.



Rock River powder – 2.466+/-0.072* and 2.153+/-0.235



Rock River lead – 2.825+/-0.578 and 2.356+/-0.522



Caspian powder – 2.589+/-0.672 and 2.008+/-0.426



Caspian lead – 3.088+/-0.289 and 2.231+/-0.422



* 4 groups, ran out of ammo.



In both guns for both 9 or 10 shot groups, power coating was MORE accurate in these tests by between .25 and .5” on average.  Of course there appears to be some issues with either load development or ransom rest technique/anchorage which may not be allowing the guns/ammo combination to be performing to their highest level.  I've also attached a graph of the average group sizes for all conditions for both 9 and 10 shot groups.



It should also be noted that while the average powder coat group size is better across the board then the lubed group size, the difference is still within the margin of error.  I interpret this to mean that while power coat may (or may not) increase accuracy, it certainly doesn’t negatively affect accuracy.



Now with all that said, I’m open to questions, critiques, comments or suggestions for future experiments.  Some things I’m planning, are to optimize load data for the range and bullet, chronograph testing to determine velocity and distribution. 

10sandxs

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Re: Powder Coat Bullet Accuracy

Post by Magload on 1/30/2018, 10:24 am

Thanks for this write up I have used both coatings for a couple of years till I started trying to shoot BE.  I am looking forward to shooting coated bullets again after reading this.  Don
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Re: Powder Coat Bullet Accuracy

Post by USSR on 1/30/2018, 11:06 am

And here is the tried and true method:

No Shake, No Bake:
Cast your bullets using an alloy suitable for the intended pressure/velocity.
Run you bullets thru your Lubrisizer at +.001" - +.002" above slugged bore diameter.
Properly lubed and sized, leaves zero leading in your barrel.
Who the heck uses barrel popple holes or external compensators?
If you want 50 FPS more velocity, add a tenth or two more powder if determined to be safe.
When I shoot, I expect there to be some smoke.

Don

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Re: Powder Coat Bullet Accuracy

Post by 10sandxs on 1/30/2018, 11:15 am

USSR wrote:And here is the tried and true method:


and this statement is the enemy of innovation...

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Re: Powder Coat Bullet Accuracy

Post by USSR on 1/30/2018, 12:58 pm

10sandxs wrote:
USSR wrote:And here is the tried and true method:


and this statement is the enemy of innovation...

Ah, but you have the solution to a problem that for the most part doesn't exist. Smile

Don

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Re: Powder Coat Bullet Accuracy

Post by 10sandxs on 1/30/2018, 1:32 pm

USSR wrote:
10sandxs wrote:
USSR wrote:And here is the tried and true method:


and this statement is the enemy of innovation...

Ah, but you have the solution to a problem that for the most part doesn't exist. Smile

Don
It may not exist for you, but it does for others

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Re: Powder Coat Bullet Accuracy

Post by Chris Miceli on 1/30/2018, 1:43 pm

I think the accuracy came from the White Label Lube X.  Smile 
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Re: Powder Coat Bullet Accuracy

Post by Cheapshot on 1/30/2018, 2:41 pm

igolfat8,
   Great information, thank you very much. I will be trying out the proccesses this weekend.

David

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Re: Powder Coat Bullet Accuracy

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