6.5cm large primer or small primer

[Cowcatcher]

So for those of you that load for 6.5 creedmoor, what size primer pocket is king these days. When I was loading for mine I only loaded large pocket brass. Been gonna get back to messing with it. I was using Peterson LRP brass when that rifle and caliber got put on the back burner. I see that srp brass is just as available and read a lil bit about it’ll handle higher pressures better which assume higher pressure would more speed. Any of y’all have actual hands on experience with both? I’m sure I can go spend a day or two sorting through the hide or some other forum but I thought I’d check with the ballsy bunch first. Thanks.

 

[rockchalk06]

I know a big benefit of small primer pockets is they tend to hold tighter with higher pressures. I typically don't reach that level I need to worry about it. My experiences have been better accuracy and lower SD's when not pushing it pas max.

Main reason I went SP was primer availability. Large Rifle Primers are still harder to find whereas Small have not been.

 

[JCann]

If you go to SRP you may need to have something like this done to your bolt.

GUNSMITHING SERVICES: STRIKER PIN BUSHING: M7, M700, M70(PF AND CRF), ACCURACY INTERNATIONAL, BERGARA, HOWA 1500, & RUGER RPR

A relatively frequent complaint with M700 and Accuracy International actions (and others) are cratered primers with factory made ammunition. The root cause of this is from excessive clearance between the striker and the hole through the bolt face. When fired, the primer cup flows into the void...

www.longriflesinc.com

 

[Cowcatcher]

I know a big benefit of small primer pockets is they tend to hold tighter with higher pressures. I typically don't reach that level I need to worry about it. My experiences have been better accuracy and lower SD's when not pushing it pas max.

Main reason I went SP was primer availability. Large Rifle Primers are still harder to find whereas Small have not been.

Yes the availability aspect is another reason I was considering buying some srp brass. Thanks

 

[Cowcatcher]

If you go to SRP you may need to have something like this done to your bolt.

GUNSMITHING SERVICES: STRIKER PIN BUSHING: M7, M700, M70(PF AND CRF), ACCURACY INTERNATIONAL, BERGARA, HOWA 1500, & RUGER RPR

A relatively frequent complaint with M700 and Accuracy International actions (and others) are cratered primers with factory made ammunition. The root cause of this is from excessive clearance between the striker and the hole through the bolt face. When fired, the primer cup flows into the void...

www.longriflesinc.com

I can always count on you to bring something up that wasn’t on my radar. Thanks

 

[conditionzero]

I think you will run in to pressure signs well before you hit that specific benefit of using SRP. I have tested loads over pressure and you will get hit with difficult extractions as the case begins to lock the bolt back.

I would go with whatever you feel comfortable paying for. LRP, especially match grade is simply more cost and can be hard to find (at a reasonable price). I grabbed 5k BR-2 a while back, so I just stuck with LRP. I will burn through 2 barrels at least before I run out.

 

[Cowcatcher]

@JCann reading that I learned that even running the lrp I might should look at getting that service done. I have had some cratered primers that I didn’t think were due to over pressure. Rifle is a Bergara

 

[conditionzero]

Pretty sure @rockchalk06 had that done to his bolt (also a Bergara).

 

[Cowcatcher]

Pretty sure @rockchalk06 had that done to his bolt (also a Bergara).

Yeah I was thinking you or him had posted a picture of the same rifle I have. B14 hmr

 

[JCann]

Yeah I was thinking you or him had posted a picture of the same rifle I have. B14 hmr

I believe he had it done at LRI. Chad and his crew do excellent work. They’re located in South Dakota

 

[rockchalk06]

If you go to SRP you may need to have something like this done to your bolt.

GUNSMITHING SERVICES: STRIKER PIN BUSHING: M7, M700, M70(PF AND CRF), ACCURACY INTERNATIONAL, BERGARA, HOWA 1500, & RUGER RPR

A relatively frequent complaint with M700 and Accuracy International actions (and others) are cratered primers with factory made ammunition. The root cause of this is from excessive clearance between the striker and the hole through the bolt face. When fired, the primer cup flows into the void...

www.longriflesinc.com

Yup!

I found that out the hard way on my HMR in 6.5.

 

[rockchalk06]

I can always count on you to bring something up that wasn’t on my radar. Thanks

I forgot about that.

What rifle you shooting?

Edited: Ya, you're going to have to send that bolt off or stick with Large Primer.

 

[Cowcatcher]

I forgot about that.

What rifle you shooting?

Edited: Ya, you're going to have to send that bolt off or stick with Large Primer.

I’m thinking I need to send it off anyhow because I have gotten some cratering with LRP already. As described on LRI site I noticed no flattened she’s of primers and no ejector marks. Looks like I better call em up and send it of. I think I’ve got 50 rounds back there loaded up to test. Since the headspace may change a little after the bolt work maybe I better go ahead and shoot them. However, I full length resize the brass for that rifle so unless I’m missing something that ammo should chamber after bolt work. Well……yeah that shouldn’t be an issue. Material is being removed so…….. Well shit maybe I better shoot this ammo up, get the bolt work done and then re-evaluate my resizing demensions after that.

 

[JCann]

@JCann reading that I learned that even running the lrp I might should look at getting that service done. I have had some cratered primers that I didn’t think were due to over pressure. Rifle is a Bergara

I don’t think slight cratering would be a problem as long as it’s not pressure related. Now if you start blowing primers due to cratering then you probably should look into bolt bushing.

 

[rockchalk06]

I had a pretty good experience with them. Took a bit, but I'd do it again.

 

[CS Boomis]

Here’s where experience meets theory. According to what I was told… pressure x area = applied force. So in theory a SRP has less resultant “force” against the bolt face than the LRP. Obviously other factors apply. I haven’t pin gauged the ignition holes on the different primer pockets to see if ignition rate or time is the factor that trumps primer flow. It’s some of you more experienced hands can answer that.

This was the very scenario that popped in my head when they were trying to hammer some knowledge into it.

I can easily visualize the rabbit trail you can go down when precision firing pin fit and protrusion, dead nuts head space and case thrust upon fire. Anyone mirror polish the striker channel in their bolt? Maybe have a fluted firing pin to minimize striker drag in the channel? How much effect does case push back have on velocity spread? Paralysis by analysis is real!!!

 

[ClintC]

I’m about to load some SRP brass for my 6.5. I will be posting results when it’s done. Granite it’s a Ruger American so we will see if I’m going to have issues.