Pressure "Tuning"

Page 2 of 2 Previous  1, 2

Go down

Pressure "Tuning"

Post by Hammbone on Tue Dec 05, 2017 9:03 pm

First topic message reminder :

I load for 9mm and 38spl.  I just picked up QuickLOAD and I'm going through the stages of getting acquainted and tuning powder burn rates to match my chrono results.
In the quest for the most accurate round, I've been doing lots of reading - mostly about rifles. But I figured hey, a pistol is just a really short rifle.

Ultimately, here's my question: When looking at pressure, should I tune the load to SAAMI specs, or to the BHN of the bullet (Like the "Lee Precision Modern Reloading 2nd Edition talks about).  

For 9mm I've mostly use Hi-Tek coated hard cast lead bullets, but recently started experimenting with Xtreme copper plated bullets. Both are advertised having a BHN of 18. Which upon linearly interpolating Lee's chart, gives me a compressive strength of 22,980psi.  Obviously SAAMI max pressure is 35,000psi for 9mm.

Side Note: The other think I'm looking at is barrel dwell time. I'm looking to see if it correlates to the resonance frequency of my barrel. I've calculated it using the "closed pipe" method.  3F = 0.512ms. I have a load that has a 0.522ms barrel time that is VERY accurate. Problem is, it's too slow to meet power factor for IDPA or IPSC if I ever get a chance to compete. -I digress.... this is a topic for another thread.

Hammbone

Posts : 6
Join date : 2016-06-11

Back to top Go down


Re: Pressure "Tuning"

Post by fpk on Tue Dec 12, 2017 9:18 am

Wouldn't the bushing on a 1911 barrel make the "resonance" theories as applied to free floated rifle barrels at least completely different, or even non-applicable? 

Also having been in the benchrest game, this stuff does make sense for a free floated barrel, but the practitioners of this theory tend to use tuners and not a calculated barrel length. Now there is certainly a long and rich history of load tuning that is done, but again, experimentally determined on a per setup (gun w/installed barrel), by setup, basis. Even in this system, there are several elements that effect the ultimate accuracy of the rifle that are beyond any model I have ever heard discussed.  Things like erosion of the lands, torque on barrel, temperature/humidity, etc. make it currently impossible to calculate the behavior or this system down to benchrest accuracy, which is thousands of an inch in a five shot, five target aggregate. 

Finally, it is pretty clear that we are so far from that level of accuracy with pistols that none of this matters.

fpk

Posts : 143
Join date : 2017-04-26
Location : Texas

Back to top Go down

Re: Pressure "Tuning"

Post by Tim:H11 on Tue Dec 12, 2017 11:31 am

To the origonal post: 

First off, like CR said, pistols aren’t short rifles. They behave differently. Everything behaves differently. Two barrels cut from the same chunk of steel made one after the next on the same machines by the same guy won’t behave the same. Maybe close. 

Looking for pressure and dwell time and frequencies and all this technical data may be interesting and useful in its own way some how but at the end of the day all you simply need is a load that groups good in your gun. 

You can try different powders and amounts of powder and bullets and seat depth but “will it group?” Is all that matters. Power factor: ok - but that’s a different sport ... velocity... nice to know but again if you have a good load in theory on paper but it doesn’t group then what good is it? 

Load, test, shoot, analyze, change one variable, repeat. Don’t get hung up on the science. It’s a black hole not many return from.
avatar
Tim:H11

Posts : 1439
Join date : 2015-11-04
Age : 30
Location : Columba, TN

Back to top Go down

Re: Pressure "Tuning"

Post by LenV on Wed Dec 13, 2017 5:53 pm

Rolling Eyes



To kinda quote Rober84210 "yea, it's winter"
avatar
LenV

Posts : 3137
Join date : 2014-01-24
Age : 68
Location : Oregon

Back to top Go down

Re: Pressure "Tuning"

Post by Tim:H11 on Wed Dec 13, 2017 7:00 pm

Len! lol!!!
avatar
Tim:H11

Posts : 1439
Join date : 2015-11-04
Age : 30
Location : Columba, TN

Back to top Go down

Re: Pressure "Tuning"

Post by Magload on Wed Dec 13, 2017 7:06 pm

Len I think that is going to cause standing waves if the frequency isn't right.  Don
avatar
Magload

Posts : 1174
Join date : 2016-11-18
Age : 71
Location : NE Florida

Back to top Go down

Re: Pressure "Tuning"

Post by LenV on Wed Dec 13, 2017 10:08 pm

Not a problem Don. I have almost 3/8" I can move it back and forth to find the sweet spot.
avatar
LenV

Posts : 3137
Join date : 2014-01-24
Age : 68
Location : Oregon

Back to top Go down

Re: Pressure "Tuning"

Post by Jack H on Thu Dec 14, 2017 12:40 am

Perhaps in 22s the different brands fire and bend the barrel in different ways to group in different places.
avatar
Jack H

Posts : 1573
Join date : 2011-06-10
Location : Oregon

Back to top Go down

Re: Pressure "Tuning"

Post by Sponsored content


Sponsored content


Back to top Go down

Page 2 of 2 Previous  1, 2

Back to top


 
Permissions in this forum:
You cannot reply to topics in this forum