Small pistol primers in 300 Blackout subsonic?

[Elkins45]

I know several longtime members don’t even bother buying small pistol primers and just use rifle primers in everything unless it has a weak hammer spring and won’t ignite them reliably. I’m looking at going the opposite direction because I have a whole bunch more SPP. I didn’t load or shoot much that used SRP until I bought a silencer and got into casting for 300 Blackout. I still have a decent supply of SRP but wouldn’t mind conserving them until the market settles down. Since I will be shooting well below the possible speeds for a normally supersonic round I shouldn’t be getting anywhere near the pressure limit. SAAMI says 300 BLK max is 55K and the highest pressure SPP round I can think of is 357 Sig at 40K, so it seems SPP are rated to withstand the kind of pressures I would be working with.

I know this isn’t an optimal solution and I absolutely plan on starting low and working up. Anybody have any experience going down a similar road?

 

[Elkins45]

Forgot to add: A Google search reveals a number of people claim to have done it successfully. Anyone here?

 

[mcb]

The pressure of subsonic ammo would not be my concern, it would be slam-fires due to the softer cups in pistol primers and the floating firing pin of an AR. If you where shooting it in a non-AR I would be less concerned.

 

[kcofohio]

Since subs run at 22k psi or below, I don't see why not. Only thing I can think of having an adverse effect may be a slamfire.

 

[kcofohio]

I know several longtime members don’t even bother buying small pistol primers and just use rifle primers in everything unless it has a weak hammer spring and won’t ignite them reliably. I’m looking at going the opposite direction because I have a whole bunch more SPP. I didn’t load or shoot much that used SRP until I bought a silencer and got into casting for 300 Blackout. I still have a decent supply of SRP but wouldn’t mind conserving them until the market settles down. Since I will be shooting well below the possible speeds for a normally supersonic round I shouldn’t be getting anywhere near the pressure limit. SAAMI says 300 BLK max is 55K and the highest pressure SPP round I can think of is 357 Sig at 40K, so it seems SPP are rated to withstand the kind of pressures I would be working with.

I know this isn’t an optimal solution and I absolutely plan on starting low and working up. Anybody have any experience going down a similar road?

Okay, I reread your post and you didn't specify subs. Sonics I would avoid for sure, but that's me.

 

[Elkins45]

The pressure of subsonic ammo would not be my concern, it would be slam-fires due to the softer cups in pistol primers and the floating firing pin of an AR. If you where shooting it in a non-AR I would be less concerned.

Do 9mm ARs use a different firing pin setup than the standard rifle BCG does? Are slamfires a concern with them?

 

[mcb]

Do 9mm ARs use a different firing pin setup than the standard rifle BCG does? Are slamfires a concern with them?

That is a good question.

I might have to try this, cause I would love to use small pistol primers (I have lots SPP but not nearly as much SRP) for 300 BO subs just like you but the the slam fire concern came to mind but maybe it is not a real concern.

 

[Elkins45]

That is a good question.

I might have to try this, cause I would love to use small pistol primers (I have lots SPP but not nearly as much SRP) for 300 BO subs just like you but the the slam fire concern came to mind but maybe it is not a real concern.

It’s a reasonable concern on your part. I think I will certainly try proof of concept in my Ruger bolt gun before I try it in an AR.

I’m off to ask the 9mm question in the Rifle forum.

 

[mcb]

I did a little research and it seems that at least some version of the AR-9 use a firing pin spring in their BCG.

ETA: replacing the standard steel firing pin with a titanium firing pin would reduce the chances of a slam fire with pistol primers. I know the DPMS GII used a titanium firing pin to reduce the change of a slam fire.

 

[Walkalong]

I would stick with rifle primers.

 

[Swampman]

I'd try to trade my SPP locally for SRP.

 

[Ohen Cepel]

I have been using small rifle, magnums in my 300BLK sub loads. Very happy with their performance so not going to change up unless forced to do so.

 

[NWcityguy2]

The standard for a firing pin on an AR9 is a spring to restrain it. They are also quite a bit lighter in weight to a standard AR15 firing pin.

 

[FROGO207]

Guess you could try loading a few and try them. I personally would not chance it though. If you do only load 2-3 in the mag at a time for safety sake please. A trade to someone that needs SPP is a much better option IMO.

 

[mcb]

I did a quick experiment and primed six sized-empty case with primers. Left to right: Two with Winchester Small Rifle, two with Winchester Small Pistol, and two with Federal Small Pistol. I then put each one directly into the chamber of my 300 BO without a magazine and dropped the bolt on the cartridges. This seemed the best way to get maximum bolt speed on closing. None of the primers fired. The cartridge in the top left a WSR primer got chambered and additional 5 times (6 total) to see if it would go. Same with the FSP in the upper right corner it got chambered 6 times. Nothing fired. Not that this should be taken at proof it would be safe but an interesting experiment.

 

[film495]

I've never seen it, or tested it, but aside from slam fire, which - seems possible, but unlikely - is pierced primers - which can damage the firearm over time.

 

[greyling22]

out of curiosity, will those 2 heavily dented primers now pop when you pull the trigger?

But I have loaded SPP blackout rounds. I was not using a subsonic load, but a with a 150grn lead bullet moving about 1450fps. worked fine. Now, they were wolf primers, so they may be hard pistol primers.....

 

[mcb]

out of curiosity, will those 2 heavily dented primers now pop when you pull the trigger?

But I have loaded SPP blackout rounds. I was not using a subsonic load, but a with a 150grn lead bullet moving about 1450fps. worked fine. Now, they were wolf primers, so they may be hard pistol primers.....

Yes I actually fired them just to make sure that that much dent had not somehow rendered them non-functional.

Given the pressure of most subsonic rounds the pressure does not bother me at all. My only fear is a slam fire but the above experiment alleviated that slightly but not completely. I would not use the Federal primer being one of, if not the softest, of the pistol primers. But I did my experiment with them for a worst case scenario. I have the Federal primers specifically to feed to my revolvers for lighter double action shooting. I might load a small batch with Winchester or Tula I have since they are noticeable harder.

 

[Elkins45]

Thanks @mcb for the experiment. I only have CCI and Winchester primers. I specifically avoid Federal because they are so sensitive, and because I hate those huge boxes.

 

[mcb]

Thanks @mcb for the experiment. I only have CCI and Winchester primers. I specifically avoid Federal because they are so sensitive, and because I hate those huge boxes.

No problem, I am in a similar situation with a very large stockpile of pistol primers and a smaller stash of rifle primers. If I can use pistol primers in my 300 BO subsonic that would be a big help.

And yes the Federal boxes are rather large. I like Winchester for most of my reloading but for the USPSA revolvers have always gotten a steady diet of Federal.

 

[35 Whelen]

FWIW Accurate Powder data uses Winchester SPP's in their 5.7x28 data at 45-46K psi and their 327 Federal Magnum data at 44K psi.

35W