primer substitution in 223 CB loads for AR

[diyahbeetuz]

Hello folks and I hope y'all are having a good day. We all know that reloaders all over our great nation are hurting for components. Various pro-2A social media influencers are even forecasting an extended scarcity of ammo and reloading components that may last for years, which I dearly hope would not be the case. Some may have been lucky (or diligent enough) to get stocked up over the years, but newer reloaders (like myself) are unfortunately facing tough times.

I know it is generally taboo to discuss "unsupported" configurations of components, but I personally believe in ingenuity and resourcefulness especially during these times. IMO the key is to do it safely and within reason. With that said, I have to ask everyone's opinion on primer substitution, specifically the usage of small magnum pistol primers in cast 223 AR loads.

After doing some research I've found that there are basically two things that render this idea as a big No-No. Slam-fires due to thinner cups, and excessive case pressures that would damage the primer.

People online say that small magnum pistol primers have thicker cups than the regular SPP's, but not as thick as SRP's so there is high risk of slam fires especially when using rifles with mil-spec BCG's. To test this theory, I actually sacrificed a few Federal 200's and Remington 6 1/2's and primed 10 .223 cases each. I loaded 10 of each into two mags, inserted them into the magwell of my competition build AR with an "enhanced" firing pin, dropped the bolt on each primed case, then ejected them without squeezing the trigger. None of the primers popped at all. Then I did the same thing using my bone stock Ruger SR-556, still no popped primers. I will have to test and see if repeated strikes of the floating firing pin would cause an ignition on either rifles, but so far it hasn't done anything to the primers except to leave a slight indentation which is typical in AR platforms. The results of my experiment does not conclude that SMPP's and Rem 6 1/2's are completely safe to use in .223. it did however exhibit that using my current equipment and components, the probability of experiencing a slam fire is low although not impossible.

Typical 223 case pressures using J boolits reside in the 40-50K PSI range depending on the load data. However with .223 CB loads I'm seeing lower recommended powder charge weights resulting in pressures way less than those numbers, granted that those load data are probably for bolt-action platforms and not for semiautos which require a certain amount of gas volume to operate as designed. I understand that reliability in semiauto use is a separate issue, but assuming that I successfully develop a CB load that would cycle my semiauto reliably and produce acceptable accuracy without exceeding the maximum case pressures that small magnum pistol primers are designed for (possibly use an adjustable gas block, or a suppressor which would increase gas to the bolt, or even a lighter action spring), would there be any reason NOT to use small magnum pistol primers in 223 CB loads other than "it is not recommended"? Would the same be true with using Remington 6 1/2 SRP in 223 loads if case pressures are nowhere near jacketed boolit numbers?

This topic may be way over my head to completely understand, but any meaningful and sensible comments or advise is greatly appreciated. I do not mean to stir the pot and cause confusion or misinformation, I am simply trying to make do with what I have on hand to get by during these trying times. Stay safe y'all and God bless.

[farmbif]

you probably don't want to be using Remington 6 1/2's at 5.56 load levels, they are meant for stuff like 22 hornet, 25-20, and other low pressure loads. just like Remington 1 1/2 primers are meant for low pressure pistol loads such as 38 spl they even print warning on package about this
as far as using cci small pistol magnum primers, I have read that they are the same as cci small rifle primers.

[JimB..]

There was a table posted not long ago, appropriated from another forum, that listed the dimensions for each of the primer cups.

[Wolfmanjack]

I fired a few reloads through my ar15 with wolf spp with no ill effects. I think they were around 23 gr h335 and a 55 gr fmj projectile. Take that for what it’s worth.

[Cherokee]

I ran several 100 full power 5.56 loads with CCI small pistol primers and they all worked fine in my AR...no problems.

[Hanzy4200]

I am of the belief that a lot more emphasis is put on primer type than needed. I have personally experimented with all manner of combos and have not once encountered a popped or pierced primer. Accuracy and ignition results were unnoticeable. LP and LR are obviously not safely interchangeable due to dimension variances. Even then, I accidentally loaded 100 .45 acp's with LR primers and had no problems. There are obvious common sense exceptions with free floating firing pins and such. You ask some and they would have you think loading a 9mm with a SR primer would blow your handgun to pieces. All speculation and no real science or experimentation.

[diyahbeetuz]

I am of the belief that a lot more emphasis is put on primer type than needed. I have personally experimented with all manner of combos and have not once encountered a popped or pierced primer. Accuracy and ignition results were unnoticeable. LP and LR are obviously not safely interchangeable due to dimension variances. Even then, I accidentally loaded 100 .45 acp's with LR primers and had no problems. There are obvious common sense exceptions with free floating firing pins and such. You ask some and they would have you think loading a 9mm with a SR primer would blow your handgun to pieces. All speculation and no real science or experimentation.

This is exactly why I had done those experiments myself and I question those schools of thought that teach otherwise. Like your example of people who are completely against using SRP's in 9mm. Well ever since I started reloading last year I have been using those and small magnum pistol primers in various loads I've worked up for 9mm, and they all go bang every single time with no complications or perceivable difference in performance. I guess they're completely sticking to the thought of "Just because it works, doesn't mean you should do it" - and I completely respect that. My questions and inquiries are mainly due to the scarcity of components, otherwise I would do it the "proper" way.

[diyahbeetuz]

you probably don't want to be using Remington 6 1/2's at 5.56 load levels, they are meant for stuff like 22 hornet, 25-20, and other low pressure loads.

You are correct. So like I mentioned in my initial post, I do not intend to use SMPP's or Rem 6 1/2's in full power .223/5.56 loads. Lyman Cast Boolit Handbook load data shows case pressures for 55gr cast boolit loads maxing out at 26,600CUP using 14.5gr of Accurate 5744. That is well below the usual numbers for 218 Bee, 22 Hornet, etc. So if it fits fine, performs fine, and does not exceed the maximum specs, I do not see a reason why I should not use it for the intended purpose.

[oley55]

There was a table posted not long ago, appropriated from another forum, that listed the dimensions for each of the primer cups.

Is this what you were thinking of? The article is fantastic, IMO.
https://www.sksboards.com/smf/index.php?PHPSESSID=k5b2j5c55uf656fb6135clb3k4&topic=56422.msg646510#msg646510

[tomme boy]

CCI is using the same cup in the spm primer as the srp. They used to be the exact same primer. But CCI just recently stated that they changed the compound in the spm primer. As long as you stay under 42K you should be safe. I use srp in all my 9mm loads. In the AR I use 41's and win srp. I have never had problems with these. My Savage bolt gun would blank cci srp if the load went over 50K.

I also use lp in my Mosin with cast. I don't run them over 40K so they are fine.

[JimB..]

Is this what you were thinking of? The article is fantastic, IMO.
https://www.sksboards.com/smf/index.php?PHPSESSID=k5b2j5c55uf656fb6135clb3k4&topic=56422.msg646510#msg646510

Good article, but not the one I was thinking of. It’s kinda driving me a little nuts.

[diyahbeetuz]

CCI is using the same cup in the spm primer as the srp. They used to be the exact same primer. But CCI just recently stated that they changed the compound in the spm primer. As long as you stay under 42K you should be safe. I use srp in all my 9mm loads. In the AR I use 41's and win srp. I have never had problems with these. My Savage bolt gun would blank cci srp if the load went over 50K.

I also use lp in my Mosin with cast. I don't run them over 40K so they are fine.

Yes, I do not plan on going over 30K for these 223 cast loads. These will be purely for practice and plinking purposes, nothing else.

[Hanzy4200]

This is exactly why I had done those experiments myself and I question those schools of thought that teach otherwise. Like your example of people who are completely against using SRP's in 9mm. Well ever since I started reloading last year I have been using those and small magnum pistol primers in various loads I've worked up for 9mm, and they all go bang every single time with no complications or perceivable difference in performance. I guess they're completely sticking to the thought of "Just because it works, doesn't mean you should do it" - and I completely respect that. My questions and inquiries are mainly due to the scarcity of components, otherwise I would do it the "proper" way.

I agree. I would not encourage someone, especially a new reloader, to just use whatever. I have a problem with the "high and mighty" guys who wag their fingers at anyone who dares go outside rules of the holy book of Speer or Hornady. This topic is going to take on a whole new vigor in the coming months, and already is, with the severe shortage on primers.

[blackthorn]

OK, I get how the pressure produced by any particular load can cause primers to rupture and the associated damage. What I am struggling with is how pressure has anything to do with a "slam-fire" or the damage caused to the primer. Slam-fire damage, (to me) is mechanical, i.e. firing pin pounds through the thin(er) cup base etc.

[diyahbeetuz]

OK, I get how the pressure produced by any particular load can cause primers to rupture and the associated damage. What I am struggling with is how pressure has anything to do with a "slam-fire" or the damage caused to the primer. Slam-fire damage, (to me) is mechanical, i.e. firing pin pounds through the thin(er) cup base etc.

Slam-fires would be a result of using primers with thinner or softer cups, and the issue applies specifically to floating-firing pin platforms like the AR. When charging the firearm (or the bolt grabs the next round and returns to battery) there is a slight possibility of the firing pin applying sufficient force on the cup that it would cause it to detonate without the operator engaging the trigger.

[blackthorn]

Thanks. That is what I thought.

[Lloyd Smale]

i shot full power 556 loads in my ars for a full year in the last shortage with cci mag pistol primers because thats all i had. Never had a problem or even a flattened primer. Started out by reducing loads with all bullets by two grains and working up but found my full power loads with rifle primers didnt act a bit different with mag pistol primers. Non issue if you ask me. 99 percent of slam fires are do not primers not being fully seated not the hardness of the cup and if you have a pierced primer you load is WAY over standard pressure and you need to address your loading not your primers.

[charlie b]

I have been doing the same thing in my .223 bolt rifle. I found no difference in velocity between CCI SRM primers and Rem 7 1/2BR primers. After firing primers looked identical.