Switching/changing primers on a established load ?

M

Metal god

New member
I've always just picked a primer for a specific load combo and stuck with it with both rifle and handgun . I how ever recently bought new primers for my handgun loads ( 9mm & 45acp ) .

Can I just switch primers out with out tweaking/reducing the load ? I know the rule is to always reduce and work back up but I can't tell you how many times I've read . Once you get a good load you can adjust seating depth OR try different primers to see what if anything works better .

Here are some specifics as to what I'll be changing .

45acp - WLP to CCI LP . I'm thinking this change can be done with out reducing or changing the load . My thinking is the Winchester LP primers are good for both standard and magnum cartridges . That would seem to indicate they have a little more pop/flash then a standard LP primer like CCI so the CCI likely will not produce higher pressures ????????

On the other hand I'll likely also be changing in 45acp - Fed LP to CCI LP . Both of these are more of a standard primer only , unlike the WLP primers . So reducing the load and working back up may be a good idea here ????

Then there's the 9mm and the higher pressures of that cartridge . Is switching primers in 9mm a no no with out reducing period ???

FWIW I'll be changing from WLR to CCI LR as well but will just rework those loads but any comments on switching rifle primers with out changing charge weight is welcome .

I did a search on here but the results were quite low so I started this thread .
Thanks Metal
 
Primer changes sometimes do and sometimes don't affect peak pressure. The rule of thumb Rocky Raab worked out some time back was to knock your old load down 5% when you change a single component brand. 10% is for new loads or multiple component changes.

That rule seems to be about right for primers. In 2006 in Handloader, Charles Petty found about 5% velocity difference produced by different primers working with a fixed powder charge and bullet and case headstamp in .223 Remington. That's about the most difference I've seen from a primer change, so I think 5% is a good number to go with. Powder charge and velocity change by about the same percentage when you are inside the normal load range (-10% to maximum) in most cartridges. Since you are using the same bullet and powder, if you still have some of your old loads and you have a chronograph, compare the average chronograph velocity of the reduced load with new primers to the chronograph velocity of the old loads. If the new primer behaves the same as the old with this powder, expect about a 5% velocity loss. Take an average for 25 rounds if you can, to cut down on the standard error (how much the mean moves around).

If the new primers produce, say, 3% lower average velocity, look at increasing the charge 3% rather than going all the way back up to the original, then test side-by-side with some of the original load again. If they are more than 5% lower velocity, you should be able to increase the charge by the amount lower that they are, but I would first go back to your original charge and see that you get only a 5% velocity increase just in case some other dynamic is flumoxing expected behavior. Short powder space pistol cartridges sometimes get unexpected shifts due to the primer starting to unseat the bullet before the powder burn gets fully underway, and you want to allow for that sort of confusion to come about.

The side-by-side testing is to eliminate a percent difference in performance due to lighting or ambient conditions affecting either the chronograph or the performance of the ammunition.
 
I've tested Win LP, Remington 2 1/2's, and CCI 300 primers in 45 ACP with the same charges and cases. My tests show RP 2 1/2 and Win LP gives highest velocities with CCI 300 the mildest. Some charges RP 2 1/2 showed highest velocity and some charges showed Win LP and RP 2 1/2 to be nearly the same velocity. Haven't done any tests in 9MM as the only primer I've used ever in 9MM has been CCI 500's. I believe you'll find CCI 300 to be milder in your loads but as mentioned already, best to back off your charges and work up. Wouldn't spend a lot of time with work-ups but it is the safe thing to do. Velocity doesn't show pressure but a chronograph is useful comparing primers and loads. One thing to note, while CCI 300's showed less velocity in the range of 50 fps less than RP and Win primers, they did often show less extreme velocity spread.
 
Accepted theory is if you change any one component you need/should to work up the load again. Never noticed any difference myself. Entirely with cast bullets and target loads though.
Just going from a cast to a jacketed bullet will increase pressures. Hodgdon shows max loads for cast 124 is 27,300 PSI, while the same weight jacketed is 32,700 psi. Mind you, the cast max load is the jacketed start load too.
Anyway, it's more about accuracy than pressure.
 
Yes. It's the safe thing to do. The chronograph does not show pressure, but as long as you are using the same lot of powder, it is a useful method of matching one lot of primers to another. What is unsafe with the chronograph is trying to match velocities with different powders as the burn rates and curve shapes don't match. A slow powder typically produces the same velocity with a lower peak pressure than a faster powder does, so if you try to match slow powder velocity with a fast powder the peak pressure can get well above normal limits.
 
As mentioned it is the safe thing to do. That being said, if it is a low to mid range load with a powder that does not have a tight tolerance between minimum and maximum I just change the primer and shoot. I try to avoid tight range powders and this would be for casual shooting / target loads. If I am loading hot or for best accuracy I would start over.
 
That would seem to indicate they have a little more pop/flash then a standard LP primer like CCI so the CCI likely will not produce higher pressures ????????
Click to expand...
I recall reading years ago that milder primers can produce higher velocities in some handgun loads because they produce less bullet jump as the primer goes off. IIRC fast powders like Bullseye produced higher velocities with standard primers, but it's just the opposite with magnum powders like H110.
 
When I started handloading 16 years ago I had been designing electronic power supplies. I disconnected my over current protection, over loaded the output, and blew up my design. I then beefed up what ever failed did it again until I had a strong design. Lots of firecracker explosions were part of the process.

As my first handloading project, I tried to work up every bullet and powder to failure in 9mm. When the primer pierced, I switched to a magnum primer with thicker cup, reduced the load and resumed the work up. The difference in work up to the threshold of failure in the brass was ~ 0.7 gr AA#5.

If the average bullet and powder combination in the average case support 9mm will show brass failure at ~~ 5.0 grains more powder than max published, then a magnum primer change is not dangerous, unless one is already on the edge of trouble due to overloads.
 
Unclenicks suggestion is a good common sense approach. If the only thing changed is the primer, and the load was safe before, 3% will be safe and you can work up.

Fwiw, I usually use CCI primers. But sometimes I'll get a brick of another if that's all they have or just for experiments. I have found more brand variation when using standard primers vs magnum. Eg CCI 450 and Win SRM or wolf SRM didn't show any remarkable difference. However CCI 400, win SR, wolf SR had 5.56 velocity difference of nearly 30 fps. It isn't a big deal as you can compensate by using more powder. But if you were on the ragged edge of over pressure to begin with, the pressure needed to generate an additional 30 fps could cause an issue.
 
Speaking of standard and magnum primer differences . I did a duplicate load development using CCI 400 & 450 in 223/5.56 . The 400's not only had slightly higher velocities through out the entire load spectrum . They also produced the better ES/SD . Maybe that had to do with the mag primers unseating the bullet early ?
 
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