Thread: Rabbit holeing with primers

I went out to the range yesterday and shot a bunch of rounds through a chrony, I was testing the speed and characteristics of 3 types of primer.

CCI 250 ( Magnum large primer ) MLRP
CCI 200 ( Standard large primer ) LRP
CCI 450 ( Magnum small primer ) MSRP

I had read a lot about them being different and not different so I was going to make my own conclusions.

In my rifle I found there to be a change in velocity from Large to Small primer of about 40 fps. So that is to say that the LRP's went faster than the SRP's

To drive the SRP's to the same speed requires seating deeper, for every 20 thou deeper they were seated I gained 20 fps.

Or you could achieve it by adding more powder ...but thats a different warren on another farm.


With the two LRP's I found the difference in speed to be negligable, but by using the Magnum primer the ES (Extreme Spread) was much lower.

I imagine results would be different for different powder types ( I was burning ball powder under the test of LRP and MLRP ) so that may be why the spread was so low, but it leads me to the conclusion that the only difference between the two CCI primers is cup thickness not compound heat/amount.

Between the LRP and the SRP there is a small advantage in Extreme Spread with the small primer and that is traded off against the seating deepth or increase in powder charge (which ever way you go).

Let me know what your results have been.

How about accuracy, we're you using your tried and true load? Have considered doing something similar.

I wasn't really going for accuracy, as the thingy on the barrel dosent help, but most groups went to the same place. Was tried and tested loads but new barrel and various seating depths .. I put a cheap scope on just for the test, normally open sighted but my drugs are playing with me, so went to a scope....bluury little outdoorsman, most groups went about an inch but thats as good as I can hold at the moment.....mainly just a velocity test.

I reduced my ES a lot by shifting from CCI 200 to Federal GM215M magnum with RL26 in a 260. One 3 shot group had an ES of 1. I'm also pretty anal about neck tension, annealing & bushing size too

Greetings @johnd,
What was the cartridge and load? You mentioned that the extreme spread was lower with the magnum primers and ball powder which is what I would expect. Ball powder has a hard shell and Winchester or magnum primers are often recommended. The same test with a different powder or the same powder in a different case could change things about.
Regards Grandpamac.

@grandpamac
Yes I agree the results for another powder would change it up a bit. I will repeat the test with stick powder, next time out. I want to use the Ball powder up in large primer cases and save the small primer brass for the hotties. I dont know when Belmont will sell their popwder again and if it will be cheap anymore either.
Loads tested were in .308 with 155 projo Lapua large and small cases.

48 grains SMP763 for vel of 2950 fps With MLRP's and LRP's

47.6 grains 763 vel 2920 as above

44.4 grains BM8208 vel 3033fps with LRP's and SRP's

The above is averaged out speeds.

Originally Posted by johnd

@grandpamac
Yes I agree the results for another powder would change it up a bit. I will repeat the test with stick powder, next time out. I want to use the Ball powder up in large primer cases and save the small primer brass for the hotties. I dont know when Belmont will sell their popwder again and if it will be cheap anymore either.
Loads tested were in .308 with 155 projo Lapua large and small cases.

48 grains SMP763 for vel of 2950 fps With MLRP's and LRP's

47.6 grains 763 vel 2920 as above

44.4 grains BM8208 vel 3033fps with LRP's and SRP's

The above is averaged out speeds.

Greetings again,
Thanks for that. That is clearly not an 18 inch barrel. I am finding that testing is even more habit forming than hand loading. I have been doing some testing with powder lots and with different powders with all other components the same. I found a big step in the speed of AR2209 about 20 years ago and a change in velocity due to a change in ogive shape in Hornady soft points. I wrote some of this and other tinkering in NZ Guns on line mag a while back before they closed down. One word of caution, it might be better to keep the 763 powder only for use in the large rifle primed cases. The 40 fps drop in velocity for the small rifle primers versus the large rifle primers tells me that the ignition of even the easy to ignite BM8208 is marginal. With 763 you would run the risk of a misfire, hang fire or worse still a squib load that leaves a projectile in the barrel. This would be worse in cold conditions as others have discovered. The thing that really got me into handloading was a subscription to Handloader in 1980. While more cautious than some of the early articles it is still the best in class for handloaders and they do an on line subscription.
Regards Grandpamac.

Thanks for the insights @grandpamac, I got onto the small primer jig when I ran a 6.5 Creedmore that came with small primer brass.......I had ignition problems then with W760, hang fires and the like, all cured when I changed over to the 450 primer. Since I had a good supply of 450's I went with palma cases in the 308, but as things go I ended up with a mix of both. Which I actually enjoy, (being able to keep loads seperated by primer type) knowing the Palma brass can take a lot more pressure helps when chasing high velocity and I can run the large primer brass for practice. and its good to know the number of reloads is significantly higher with the palma brass.
And yes definitely not an 18 inch barrel!

The LRP and SRP cases might be different capacity which would explain the difference in velocity.