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Discussion Starter #1
As long as the bullet gets out of the barrel who do I care if the load is below the minimum? I am thinking of plinking, not defense or hunting, and not where power factor matters. I understand that higher pressure means more complete burning, higher spin rate, better consistency, and so on. I can't think of a safety reason, as long as the bullet clears the barrel.
 

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Detonation is the key reason one should stay within published load data ranges and not go below minimum safe and of course not above max safe unless you are a ballistics expert.

For rifle calibers, most of them burn medium to slower medium powders.

That means they usually can and do need more powder in the case to reach the optimal pressure and optimal chemically released gas volume.

The problem is when there is too much air volume to powder ratio within the cartridge, there is the risk of secondary ignitions.

Secondary ignitions are very bad because they alter how fast the powder is burned which affects pressure.

If the burn rate is significantly increased due to detonation, the pressure rises faster than the bullet can begin moving out of the case.

This creates a massive overpressure situation and can break the gun very violently.

So, in short the cartidge turns into a bomb.

Safe conventional ammunition depends on a predictable controlled burn, which is given by following crediable published load data.

Detonation is fact, not some folk tale.

People have been injured by it, so it's a life or death safety matter.
 

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Here is an excellent writeup on using light charges:
Gunwriters' Handloading Subsonic Cartridges, Part 1
There are some powders that are safe to load very light loads with, such as Bullseye, Trail Boss, Unique, 4895. However if you go too light you run the risk of a squib load that doesn't clear the barrel.

Detonation, or SEE (Secondary Explosion Effect) is real. Powder manufacturers will tell you not to go below minimum loads on most powders, so they know that it is real.
 

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Some powders like 296/H110 can have hazardous results down loaded. Unless you have pressure test equipment I would be cautious about varying from published data very much. If you do use some of the older established powders that have been tested for what you want to accomplish. jmho
 

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DrHenley Great article. Thanks for sharing.

To the OP. I only reduce load some rifle with shotgun powders. But with in listed data in my manuals.
 

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Discussion Starter #6
Thanks all. I was thinking in terms squib only. I am not a ballistician, however I get the gist. And once upon a time I saw the after effect of a small motor detonation (from quite a distance). It was impressive. Not to be trifled with.

I have Speer #14 and Lyman manuals. They often disagree on minimum load for same bullet weight (although often different BC for same same or similar SD). And powder manufacturers often quote different values yet. There doesn't seem to be consistency.

I don't think I am going to go too low. For my 1911s (45 ACP) I load for PF right around 165. For 45 LC out of my 2 Vaqueros with 4.62" barrel (older models, not the more recent ones that resemble the SAA) I find that 7.5 gr Unique driving 250 gr LRN from SNS results in average of 840 fps (200 rounds chronoed) with SD around 21 fps. I want to get down to around 750 fps. I'll step down to 7 gr Unique and maybe even 6.5 gr Unique and see where I end up. Lyman indicates 6.0 gr Unique at 595 fps for a similar bullet, also 6.3 gr Unique at 754 fps.
 

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For safe, reliable, reduced power loads it's really tough to beat Trail Boss. That's what it's designed for.
GH1😀
 

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+1 on Trail Boss, at least in revolvers.

I've not tried it in semi-auto pistols.

The odor is a bit unusual, sorta sweet smelling.
 

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+1 on trailboss, just keep in mind you will get the soot mark on the mouth of the case from not generating enough pressure to 100% seal the case. Doesn’t hurt anything but it will be there. I use a lot of trailboss for light loads in magnum cases so that I don’t get the ring that will affect chambering if magnum rounds if you shoot a bunch of special cases then switch to magnum.


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Another negative effect of downloading is cartridge case staining due to not enough pressure to seal the case in the chamber. This would make the fired cases very hard to clean.
 

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When downloading for .44 Mag and .357 you can look at the data for .44 Special and .38 Special as a guide. Give you a 'range' you work with to find the right load you are looking for. .45 Colt is already low velocity so hardly a reason to go under minimum unless you are firelapping. I found Trail Boss to be a good powder for that purpose. Trail Boss is also nice for light loads in big cartridges. Didn't care for it in the .38 on down calibers though.
 

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Discussion Starter #14
Trailboss is a fairly high burn rate powder with what is described by Hodgdon as high loading density. To me that means finely milled. It sounds pretty similar to Titegroup. I like Titegroup simple because it meters more consistently. Why does higher burn rate and finer milling allow for safely reducing the load? The charge is burnt more quickly with so less chance of detonation?
 

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Discussion Starter #15
Here's my 250 gr data with Unique
7.5 gr: MV=842 SD=26 ES=136
6.9 gr: MV=800 SD=19 ES=108
6.7 gr: MV=778 SD=22 ES=80
6.5 gr: MV=760 SD=22 ES=88

I'll get some Trail Boss and see how that loads for my 45 Colt stack up
 

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Of course you have to have enough powder to push the bullet out of the barrel, but you can go below the minimum listed load. Secondary Explosion Effect occurs in large capacity, bottle-necked cases with small amounts of slow powder; the primer pushes the bullet into the lands and then the powder ignites. In handgun cartridges this is not such a big issue BUT you have to work down the same way you work up; slowly and with appropriate powders. If you want a slow load use a fast powder DO NOT use small amounts of slow powder to create a slow load: H110/296 especially will not fully ignite with low pressure and you will end up with not only a bullet stuck in you barrel, but also a bunch of unburnt powder - if you are lucky. If you want a slow load get some fast powder (Tite Group, Bullseye, Titewad, N310 etc) start at the minimum load and work down. This is easy for revolvers, with semi-autos you'll reach a point where there isn't enough recoil to operate the action and you'll need to go to a weaker operating spring.

Hodgdon lists 3.1Gr. of Tite Group with a 55gr bullet for a light load in .223, now that is a light load.
 

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As long as the bullet gets out of the barrel who do I care if the load is below the minimum? I am thinking of plinking, not defense or hunting, and not where power factor matters. I understand that higher pressure means more complete burning, higher spin rate, better consistency, and so on. I can't think of a safety reason, as long as the bullet clears the barrel.
Semi-auto pistols and rifles need a certain amount of power to cycle the
action . The minimum loads usually do this .
Your guns and your loads .... when you start fooling around below minimum , be sure to bring a range rod with you so you can knock a stuck bullet out the bore. Sooner or later it will happen .
Gary
 

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Trailboss is a fairly high burn rate powder with what is described by Hodgdon as high loading density. To me that means finely milled. It sounds pretty similar to Titegroup. I like Titegroup simple because it meters more consistently. Why does higher burn rate and finer milling allow for safely reducing the load? The charge is burnt more quickly with so less chance of detonation?
What they mean by "high loading density" is Trail Boss fills up more of the case than other powders with an equivalent charge. The Trail Boss particles are large and donut shaped and the texture is very porous, thus a very low density powder, but allow a high loading density.

Not all powder measures work well with Trail Boss however. You need a powder measure that has a fairly large diameter hole to avoid bridging. I use an old Bonanza powder measure with Trail Boss that works wonderfully. Powder dippers work well with Trail Boss.
 
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