Powder burn rate and case capacity effect on accuracy?

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Powder burn rate and case capacity effect on accuracy?

Post by mpolans on Thu Jan 05, 2017 3:04 pm

It seems the most popular loads in bullseye tend to use faster powders, but has anyone actually studied if whether loads with faster or slower powders have any effect on accuracy?

Sort of related, it seems that most loads with faster powders seem to have smaller volume charges, while loads for a similar velocity with slower powders tend to higher volume charges.  I would think loads that take up greater volume in a case would tend to be more consistent and more accurate. Has anyone done any testing on this?

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Re: Powder burn rate and case capacity effect on accuracy?

Post by 10sandxs on Thu Jan 05, 2017 3:45 pm

But you have to use more of the slower powders, and many of us are... ahem.. frugal...

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Re: Powder burn rate and case capacity effect on accuracy?

Post by r_zerr on Thu Jan 05, 2017 3:58 pm

The faster powders provide the pressures needed and functionality for the low velocities typically desired. 
If one were to use a slower powder, the pressures would be lower, larger velocity variation, and lots more un-burnt powder.

-Ron

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Re: Powder burn rate and case capacity effect on accuracy?

Post by Wobbley on Thu Jan 05, 2017 5:10 pm

Years ago Ken Waters of Handloader magazine did that.  He found that powders as slow as Unique worked well.  This was in 38 with 148 WC.

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Re: Powder burn rate and case capacity effect on accuracy?

Post by rich.tullo on Thu Jan 05, 2017 5:27 pm

Slower powders, I found that W231 is very accurate but try shooting matches with it its about as sooty as can be under 5 gns. After a few shots you cannot see the red dot. 

VV320 is cleaner but you have to load to 4.5 gns or more to make it work where as WST is just as clean and softer at 4.1 gns.

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Re: Powder burn rate and case capacity effect on accuracy?

Post by james r chapman on Thu Jan 05, 2017 6:21 pm

WW231 is world class at 3.1 gr and 148hbwc. Millions of rounds proving it.
As BE is also.

You want 70% case capacity? Trail Boss donuts.

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Re: Powder burn rate and case capacity effect on accuracy?

Post by SteveT on Thu Jan 05, 2017 6:33 pm

I think one of the reasons Clays and WST are good powders is because they take up more volume and are less susceptible to position in the case. I've measured huge differences in velocity (150-200fps) using Titegroup by tipping the pistol forward or backward before the shot. I still use TG for service pistol and blasting ammo because I have several pounds (see note above about frugality) but have switched almost entirely to low density powders and I'm planning to work up some loads using IMR Trail Boss, now that it's available again.

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Re: Powder burn rate and case capacity effect on accuracy?

Post by dronning on Thu Jan 05, 2017 6:50 pm

Nice to see Clays mentioned, it doesn't seem to get much attention around here.  45 takes 3.6gr for a 200gr SWC & for .38 special either 2.5gr in a 148 gr HBWC or 2.9gr for the 158gr SWC.  Very accurate in my guns and not temp sensitive like many are.  I always thought is was cleaner than Bullseye.

It was pretty hard to find for a while so I switched over to WST last year (Clays is in stock at Powder Valley now).
- Dave

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Re: Powder burn rate and case capacity effect on accuracy?

Post by james r chapman on Thu Jan 05, 2017 7:04 pm

ClayDot is another one the worked great in .38 and .45

found the light 2.0-2.4 gr .38 loads didn't like to meter well in the Lee Discs so I discontinued.

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Re: Powder burn rate and case capacity effect on accuracy?

Post by rich.tullo on Thu Jan 05, 2017 11:14 pm

james r chapman wrote:WW231 is world class at 3.1 gr and 148hbwc. Millions of rounds proving it.
As BE is also.

You want 70% case capacity? Trail Boss donuts.
I agree I was just referring to 45acp BE loads under 5.0 GN. 

Nearly everything is dirty with a 38 special except for WST and VVN320. 

If you want to fill the case up Nosler says AA5 is the most accurate powder for the 185gn HP

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Re: Powder burn rate and case capacity effect on accuracy?

Post by joy2shoot on Fri Jan 06, 2017 8:57 am

SteveT wrote:I think one of the reasons Clays and WST are good powders is because they take up more volume and are less susceptible to position in the case. I've measured huge differences in velocity (150-200fps) using Titegroup by tipping the pistol forward or backward before the shot...

That's good to know since Titegroup's advertising says "powder position in large cases (45 Colt, 357 Magnum and others) has virtually no effect on velocity and performance".

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Re: Powder burn rate and case capacity effect on accuracy?

Post by mpolans on Fri Jan 06, 2017 2:35 pm

Hmm, so for less dense, slower burning powders, it sounds like AA5, Trail Boss, Unique, Clays, and WST are some options.

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Re: Powder burn rate and case capacity effect on accuracy?

Post by desben on Fri Jan 06, 2017 3:32 pm

mpolans wrote:Hmm, so for less dense, slower burning powders, it sounds like AA5, Trail Boss, Unique, Clays, and WST are some options.


I would not call WST a slow powder!

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Re: Powder burn rate and case capacity effect on accuracy?

Post by desben on Fri Jan 06, 2017 3:37 pm

r_zerr wrote:The faster powders provide the pressures needed and functionality for the low velocities typically desired. 

That! You want pressure to properly upset the bullet and seat it in the barrel grooves, but you don't want the velocity which increases recoil. Slower powders would either give too much velocity or not enough pressure. There's a sweet spot in the relation between bullet hardness, pressure and accuracy.

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Re: Powder burn rate and case capacity effect on accuracy?

Post by messenger on Fri Jan 06, 2017 7:17 pm






If you want to fill the case up Nosler says AA5 is the most accurate powder for the 185gn HP

My Les Baer ransoms right about an inch with 8.5gr AA#5 under a Nosler JHP

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Re: Powder burn rate and case capacity effect on accuracy?

Post by mpolans on Sat Jan 07, 2017 2:55 pm

desben wrote:
r_zerr wrote:The faster powders provide the pressures needed and functionality for the low velocities typically desired. 

That! You want pressure to properly upset the bullet and seat it in the barrel grooves, but you don't want the velocity which increases recoil. Slower powders would either give too much velocity or not enough pressure. There's a sweet spot in the relation between bullet hardness, pressure and accuracy.
Ah, but the other factor I was considering was a compensator. Traditionally, the knock on them for bullseye is that the most popular .45acp loadings don't produce the gas volume to make it worthwhile. I'm wondering if using slower less dense powders (and lighter bullets) will yield more consistent velocities and as good or greater accuracy, while also making a compensator more effective, which should help on timed and rapid fire. 

I've noticed someone else talking about using 155gr. SWC bullets (not related to compensators), and while I have my doubts about their potential accuracy, what with their smaller bearing surface, if they're accurate, I know they will have a noticeable effect in a compensated gun based on my circa late 1980s IPSC experience with the old Vic 152gr SWCs (for those of us who were to scared to run major power factor .38 super when it was new on the scene).

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Re: Powder burn rate and case capacity effect on accuracy?

Post by rich.tullo on Mon Jan 09, 2017 10:14 am

I tried a Clark Barrel and Comp once, I did not gain any accuracy and it was unreliable under 4.0 gn BE with a #10 recoil spring. I seem to recall 4.5 WST was the round it cycles. 

150s with 4.8 gn of BE or 5 gn of wst may do it but will it print at 50 yards and if the comp gets dirty will it become less accurate? 

If you are looking at reducing recoil 3.6 of BE over a 185 HP LSWC is pretty manageable.

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Re: Powder burn rate and case capacity effect on accuracy?

Post by mpolans on Mon Jan 09, 2017 12:32 pm

rich.tullo wrote:I tried a Clark Barrel and Comp once, I did not gain any accuracy and it was unreliable under 4.0 gn BE with a #10 recoil spring. I seem to recall 4.5 WST was the round it cycles. 

150s with 4.8 gn of BE or 5 gn of wst may do it but will it print at 50 yards and if the comp gets dirty will it become less accurate? 

If you are looking at reducing recoil 3.6 of BE over a 185 HP LSWC is pretty manageable.
Out of curiosity, when you tried the Clark comp, were you also using a slide-mounted optic?

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