why would primers get pushed out 45 colt hs6

[farmbif]

loading and shooting some more 45 colt out of Rossi 92 with 454640 lube sized to .454 with starting load of 9.5 grains hs6 primer was pushed out a bit
all loads are with new Starline brass and cci lg pistol primers. My go to load has been 18 gr 4227 but thought I would try some other loads
19 grains of 4227 also shoots well as does 9.5 grains unique with no primer issues what so ever.
why would the hs6 cause primer issue?

[fredj338]

Possibly not quite enough pressure?

[Neverhome]

Do you mean pushed out beyond flush with rim?
Headspace issue maybe.

[farmbif]

yes pushed out beyond base of shell by just a bit more than it was below shell when loaded. edges were still rounded not flattened and normal looking primer strikes

[Winger Ed.]

Low pressure.
To see a extreme example of the effect-- fire a empty primed case.

[farmbif]

the gun has less than 1000 rounds through it, I just loaded three with hs6 all were the same, but no problem at with the others I shot today with 4227 and unique which are a couple hundred feet per second faster loads. . could powder be bad? it looks and smell normal might be a few years old

[megasupermagnum]

I don't have my books in front of me, but 9.5 gr Unique with a 280 grain bullet is likely well into +p territory, so you wouldn't have any problems there. I can't find any 4227 data on Hodgdon website, but 18 grains looks quite stout to me as well.

9.5 gr HS6 however might be a low pressure load. Hodgdon lists 9 grains as a start for a 300 grain bullet, and only 9,600 CUP. My guess is the pressure is too low.

[BK7saum]

Low pressure load. Primer backs out and not enough chamber pressure to force case back to re-seat the primer. It is normal and an artifact of your light load.

[USSR]

As others have said, low pressure load. You've got to use more powder, and with HS-6 I always use a magnum primer.

Don

[reddog81]

The primer ALWAYS backs out when a round is fired. Most of the time the primer is re-seated when the pressure in chamber/bore pushes the case back against the breech face. If the primer stays backed out that means the pressure form the round was very low.

[Wayne Smith]

Yup, Reddog got it right. In fact this is so reliable that John Garand based his first semiauto design on it. Then the Govt. started crimping primers and we got the M1 Garand.