Odd Primer Flow with S&B Primers And A .40cal

[jonp]

I've been working with a SW M&P Full Size. My boss gave me most of a pound of Power Pistol and I've been loading it under Nosler 150gr Sporting Pistol HP's. I just loaded up some at 6.9gr and an OAL of 1.1in as the book gave that for a Gold Dot 150gr and the bullets are a similar length. The 6.9gr is well under the max loading for that weight.

I just shot 10 of them and the velocity was well above what I was expecting but below the velocity of the max listed book. What got me was the primer. They looked like a miniature lava flow from the primer hole. Not with raised edges but you can see the flow away from the primer strike. The primer was not pierced and there was no other evidence of over pressure like flattening. All rounds were fine, brass was ejected vigorously but all landed in the same area and the velocity variation was actually quite low with the recoil was nothing I'd consider abnormal.

I can't find any pictures of primers looking like this. Anyone have this happen? Maybe the S&B Primers are soft? I've used them in everything from the 32H&R Mag to 45ACP to 357Mag with no problems.

[jonp]

Marvin, it's not the firing pin strike which is a little odd but doesn't bother me. The primer itself has a little "river" running away from the strike point. You can't feel it but can see it.

[nun2kute]

I can't imagine what that would look like, can you show us ?

[jonp]

Attachment 230239

As you can see, the flow go's from the firing pin strike down towards the 1900-2000 position. The primer is not flattened or cratered. Brass is not cracked, bulged and the primer hole itself is not expanded. Everything but this flow appears normal to me.

[bob208]

it is not the primer. I have some range pickups here that look like that .

[243winxb]

Kahr> "Primer wipe" is a teardrop-shaped firing pin impression, accompanied by a drag mark (scratch or gouge) following the "point" of the teardrop and leading away from the primer, sometimes into the brass. This is because the firing pin does not fully retract after the round has fired and the slide is traveling back during ejection, causing the case to drag across the firing pin as it is thrown clear. It is not in any way harmful, except sometimes to the case if the primer pocket edge is gouged. "

Kahr will tell you it is a normal condition for their pistols, even saying so in the owner's manual.

Happens in other brands also.

[JimB..]

Attachment 230239

As you can see, the flow go's from the firing pin strike down towards the 1900-2000 position. The primer is not flattened or cratered. Brass is not cracked, bulged and the primer hole itself is not expanded. Everything but this flow appears normal to me.

That is odd looking. No suggestions, but is it unique to S&B primers? To a single batch of S&B primers?

[243winxb]

Another reaon. If the pressure is to high or primer soft and there is a gap around the firing pin, the primer metal may flow into the firing pin channel.

When the barrel unlocks, moving down, it wipes the raised metal protruding from the primer. Like in the 45 acp photo.

The pressure was from a short chamber. After a gunsmith corrected the chamber headspace, it no longer happened.

[243winxb]

The OP photo enlarged. So, take you pick as what the problem is.

Its not hurting a thing, keep shooting them.

But since your powder charge is to low, the primer is backing out. Nosler data shows 7 gr starting to 8 grs maximum.

https://load-data.nosler.com/load-data/40-sw/


Alliant data

[jonp]

The 10 I loaded this afternoon had the OAL lengthened from 1.1 to 1.3in. The velocity dropped about 50-75fps but tightened with a variance of 30fps and was in the 1,000 fps range. Still the strange primer flow pattern. All the brass ejected strongly but the recoil was fine. I'll try a different brand of primer as I have Tula, Win, Rem, Fiocchi on hand.

I'm not too concerned about the pressure as the velocity is very good. It's just odd and nothing I've seen from S&B before.

Kahr> "Primer wipe" 243winxb, I have several Kahr's and they are fine pistols. None of the primers look anything like this.

[Mr_Sheesh]

The other thing I've seen on some 9mm self defense pistols are that the top of the firing pin hole has been lightly "filleted" at the top so that a case with a square edge at the base of the case would not hang up on the firing pun hole during feed; Apparently some brass out there can cause that. I haven't seen any but am told it's out there.

[David2011]

Chamfering the firing pin hole in the breechface is a common mod on well prepped 1911s. I’ve had brass shaved on them without the chamfer. It can cause the firing pin to get stuck in the forward position which can cause slam firing.

[nun2kute]

I see what you mean now, but that's a new one on me. You got me headed down to do some closer inspections on my favorite Pistol.

[243winxb]

Chamfering the firing pin hole in the breechface is a common mod on well prepped 1911s. I’ve had brass shaved on them without the chamfer. It can cause the firing pin to get stuck in the forward position which can cause slam firing.

The 1911 has an inertia firing pin. I have never heard or seen the above. But then i am only 74, and still learning.

Found this -

Some gun's firing pins peen the firing pin hole when dry fired and make the peened area protrude from the breach face. Peened firing pin holes are common in break barrel shotguns and some cheaply made pistols. In pistols, this will affect feeding because the case head will stub on the protrusion as a round is being fed and jam. The fix is to hand chamfer the firing pin hole from the front with a slightly larger drill bit to remove the peening. This is not something you would do to a gun "just because" and has nothing to do with dirt or crud accumulation, in fact quite the opposite. If you chamfer a firing pin hole, it would take on the properties of a funnel and direct crud into the hole.

https://rugerforum.net/gunsmithing/1...-pin-hole.html

The inertia firing pin only makes contact with the primer. My Gold Cup 45>

[David2011]

Yes, the 1911 firing pin is an inertia device. If there are brass shavings present the inertia can drive the pin through the hole and it can get stuck on the shavings. All that’s required is to ease the sharp corner of the fp hole; very little metal is removed. I’ve done a fair amount of smithing on 1911s; mostly accuracy, trigger and reliability work.

I prefer a center drill to a bit to make the chamfer.

The occasional shooter that goes through a 50 round box on a trip to the range probably would not benefit from the chamfer but the competitive shooter that burns several hundred per visit may. I built a steel plate gun (predating Steel Challenge) that has proven 100% reliable shooting a 200 SWC boolit at 645 FPS. That makes for a very low recoil impulse and requires an exceptionally smooth action due to the extremely light recoil spring. I did everything I could to smooth both the rearward motion of the slide and the loading motion and the fp hole chamfer was part of that. Some 1911s including many race guns use the smaller .068” firing pin that grabs less of the case head and reduces the likelihood of primer flow.