Small Rifle v Small Rifle Magnum

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Small Rifle v Small Rifle Magnum

Post by JimTom » 03 Apr 2022, 12:54 pm

G’day Gents

I am just perusing some reloading data for my 300AAC as I am about to do a few trials with different projectiles, and in doing so, noted that there is a discrepancy between different manufacturers data with the use of small rifle primers, and small rifle magnum primers.
For example, ADI, and Hodgdon have small rifle magnum primers listed, whereas Speer and Hornady have small rifle primers listed.
Any of you knowledgeable gents hazard a guess why, and for a case where the load is circa 17 grains of powder, would it make much difference in your opinion?
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Re: Small Rifle v Small Rifle Magnum

Post by rc42 » 03 Apr 2022, 2:46 pm

There are numerous test videos on Youtube, some using high end pressure test equipment, comparing different primers and they all find that the explosive force from the primer is insignificant compared to the propellant powder so changing primers does not affect load data, despite all the nay-sayers that will warn you to work up loads again.

Magnum primers burn a little hotter and longer so are better suited to slower powders which is probably why you are seeing different recommendations but it's unlikely to make any real difference.

Another important consideration is the cup thickness and its ability to withstand higher pressures in the case. For CCI primers, small rifle (and small pistol magnum) have a cup thickness of 0.020" whilst small rifle magnums are 0.025", that extra thickness also need a harder firing pin hit than most pistols can manage but all rifles should be OK unless springs have been lightened.
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Re: Small Rifle v Small Rifle Magnum

Post by JimTom » 03 Apr 2022, 3:14 pm

Thanks mate, I will use the listed primer for the powder I am using however like you, I don’t think it would make a massive difference.
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Re: Small Rifle v Small Rifle Magnum

Post by bladeracer » 03 Apr 2022, 3:59 pm

JimTom wrote:G’day Gents

I am just perusing some reloading data for my 300AAC as I am about to do a few trials with different projectiles, and in doing so, noted that there is a discrepancy between different manufacturers data with the use of small rifle primers, and small rifle magnum primers.
For example, ADI, and Hodgdon have small rifle magnum primers listed, whereas Speer and Hornady have small rifle primers listed.
Any of you knowledgeable gents hazard a guess why, and for a case where the load is circa 17 grains of powder, would it make much difference in your opinion?


Could just be what they tested with.
I prefer magnum primers.
If you have both try them both and see if you prefer one over the other.
These days, use what you have.
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Re: Small Rifle v Small Rifle Magnum

Post by JimTom » 03 Apr 2022, 4:14 pm

Fortunately I do have a sufficient supply of both.
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Re: Small Rifle v Small Rifle Magnum

Post by Oldbloke » 03 Apr 2022, 7:31 pm

JimTom wrote:Thanks mate, I will use the listed primer for the powder I am using however like you, I don’t think it would make a massive difference.


That's my understanding too. Never used magnums myself.
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Re: Small Rifle v Small Rifle Magnum

Post by Wyliecoyote » 03 Apr 2022, 7:42 pm

My experience with SR primers has been more to do with long range benchrest than field shooting where any old powder will do. With the likes of 6BR, Dasher or GT it is my findings that the magnum SR primers reduce pressure allowing more powder to gain more speed with the 103 to 108 grain range of pills. CCI 450s are pretty well much the standard and more recently the Sellier& Bellot have become more common especially amongst the 6.5 CM Fclass guys.
Where the danger lies is replacing the magnum primer with a standard SR primer on that existing load where the pressures often rupture the cup or loosen the pocket or both. In high intensity cartridges like those stated, it is advantageous to go with the magnum primer just purely for the cup strength, but also for a more complete burn where you will see across the board single digit ESs when CCI 450s are used. Rem 7 1/2s also fall into this category but are not as consistent as the CCI or S&B
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Re: Small Rifle v Small Rifle Magnum

Post by wanneroo » 04 Apr 2022, 5:08 am

In 300 Blackout I exclusively use CCI #41 primers which have a harder cup to prevent slamfires in semi and full autos and apparently use whatever chemical composition small rifle magnum primers use. CCI says use small rifle magnum data for any loads using CCI #41s so it's basically about the same thing.

From the research I did years ago, it was said in using such magnum primers back loads down a half a grain.

I have always developed my loads around CCI #41s and by default small rifle magnum primers.

To me in a way 300 Blackout is not too dissimilar from loading for 357 Magnum and for Magnum loads we use Magnum primers.
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Re: Small Rifle v Small Rifle Magnum

Post by wanneroo » 04 Apr 2022, 5:16 am

JimTom wrote:Thanks mate, I will use the listed primer for the powder I am using however like you, I don’t think it would make a massive difference.


When I duplicate loads from manuals using similar equipment and they use standard small rifle primers and I use #41s, I am typically about 50-100 feet per second faster with 300 Blackout loads. It's a difference, how massive is up for debate.

Glad you brought this up as I probably need to address this in one of my upcoming 300 Blackout videos on Youtube.

At one point years ago I did get some regular small rifle primers that I used and as I recall I used a bit more powder to get the same velocity.
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Re: Small Rifle v Small Rifle Magnum

Post by JimTom » 04 Apr 2022, 5:46 am

What is you channel called mate? I will have a look.
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Re: Small Rifle v Small Rifle Magnum

Post by wanneroo » 04 Apr 2022, 9:21 am

JimTom wrote:What is you channel called mate? I will have a look.


Same user name on Youtube.

https://www.youtube.com/channel/UCWy4y9 ... ljJBHD-8Eg
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Re: Small Rifle v Small Rifle Magnum

Post by JimTom » 04 Apr 2022, 10:50 am

Legend thanks mate. As an avid 300 Blackout reloaded / hunter it looks like there is a fair bit of content in your channel to keep me entertained mate.
:thumbsup:
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Re: Small Rifle v Small Rifle Magnum

Post by wanneroo » 05 Apr 2022, 12:59 am

JimTom wrote:Legend thanks mate. As an avid 300 Blackout reloaded / hunter it looks like there is a fair bit of content in your channel to keep me entertained mate.
:thumbsup:


Yes sir, just getting started. Have already done a few projects for 300 BO and there are more to come. I'm working on finishing up the 110g Hornady VMax and once done will start on 125g Speer TNT bullets. Plans over the next few years include some rifle builds, short barrel 300 BO, suppressors, experimentation with different bullets and powders, etc. It's not a 300 Blackout exclusive channel but I do plenty with the cartridge on the channel.
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Re: Small Rifle v Small Rifle Magnum

Post by JimTom » 05 Apr 2022, 5:05 am

Sounds great mate.
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Re: Small Rifle v Small Rifle Magnum

Post by Oldgunfan » 06 Aug 2022, 4:48 pm

Just got back from the range and my results for my 300blk seem ok. 230gn lead black widow bullets 10.0 grains ar2207, coal 2.225. Shot from Remington model 7 16.5 barrel was average of 941fps with SD of 10 and ES of 25fps. That’s using cci small rifle primers. Since adi data shows small rifle magnum I’m guessing that’s why velocity was less than their predicted 1050fps ? Not that I’m bothered it’s for slapping steel and having fun not hunting.
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Re: Small Rifle v Small Rifle Magnum

Post by dnedative » 06 Aug 2022, 5:12 pm

rc42 wrote:There are numerous test videos on Youtube, some using high end pressure test equipment, comparing different primers and they all find that the explosive force from the primer is insignificant compared to the propellant powder so changing primers does not affect load data, despite all the nay-sayers that will warn you to work up loads again.



Eh, changing primers will change pressures but generally its not really worth worrying about.
The only exception is substituting magnum for regular primers and running low end or reduced charges of slower powders in large cases, you start getting really erratic ignition and pressure while drifting towards a window of opportunity where a secondary explosive effect becomes a possibility.
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