Over pressure or excessive headspace

Bush Pirate · August 20, 2010, 09:46 PM

This is the first time I shot this 25-35. The primers are getting pushed back out slightly after firing. This was factory ammo as listed on the box in the picture. If the picture is on here and clear. I also shot 5 rounds of hand loads , at min start load and primers came out about the same amount. Is this more likely a headspace issue than a pressure issue???

wncchester · August 20, 2010, 09:49 PM

"Is this more likely a headspace issue than a pressure issue??? "

Yep, that's exactly what it is and the pressure is quite low.

Do your resizing to not set the shoulder, such as it is, back passed fired location and you won't have primers backing out nor cases stretching.

JMP · August 20, 2010, 10:03 PM

I had primers doing the same thing on the same cartridge very recently. I'm glad you made this thread so I know now also. I went with low starting loads and was worried the pressure was too high but it seemed weird cause the primers were backing out a little but not flattened. The only one they didn't do it on was a 30-30 I reformed just to try it and the shoulder was a little further forward than the 25-35s.

FrankenMauser · August 20, 2010, 11:56 PM

Quote:

Do your resizing to not set the shoulder, such as it is, back passed fired location and you won't have primers backing out nor cases stretching.

The bad part about this situation, though, is that the fired cartridges won't allow for a shoulder head-spacing situation. Since the cases aren't being pushed back against the bolt, they're not reaching the full potential length. Trying to size for the shoulder will give the same results. In this situation, a false shoulder would probably be the better choice.

totaldla · August 21, 2010, 12:02 AM

Why not just neck size?

mehavey · August 21, 2010, 12:15 AM

Commercial 117gr 25-35Win cartridges chrono at ~2,350fps which would put their pressures in the low-mid 30k psi regime. As you see from your own experience, those pressures are insufficient to stretch the case back to the bolt face once driven forward by the firing pin. Hence the primer is left exposed once it backs out into any excess headspace.

(And your pics show a lot of headspace for a rimmed cartridge.)

What rifle/action are you shooting this in?

Bush Pirate · August 21, 2010, 10:06 AM

Shot out of lever gun, model 94 winchester 25-35. I usually have a gun smith check headspace on an older new to me gun, but my uncle said he had fired it about 6 months earlier. I figured it worked for him.

August 20, 2010, 10:03 PM	#3
JMP Senior Member Join Date: June 4, 2010 Location: Wyoming Posts: 118	Thanks! I had primers doing the same thing on the same cartridge very recently. I'm glad you made this thread so I know now also. I went with low starting loads and was worried the pressure was too high but it seemed weird cause the primers were backing out a little but not flattened. The only one they didn't do it on was a 30-30 I reformed just to try it and the shoulder was a little further forward than the 25-35s.

August 21, 2010, 12:02 AM	#5
totaldla Senior Member Join Date: August 10, 2009 Location: SW Idaho Posts: 1,310	Why not just neck size? __________________ Lee Auto Bench Prime Castor Oil Case Lube

August 20, 2010, 09:49 PM	#2
wncchester Senior Member Join Date: December 1, 2002 Posts: 2,832	"Is this more likely a headspace issue than a pressure issue??? " Yep, that's exactly what it is and the pressure is quite low. Do your resizing to not set the shoulder, such as it is, back passed fired location and you won't have primers backing out nor cases stretching.

August 21, 2010, 12:15 AM	#6
mehavey Senior Member Join Date: June 17, 2010 Location: Virginia Posts: 6,919	Commercial 117gr 25-35Win cartridges chrono at ~2,350fps which would put their pressures in the low-mid 30k psi regime. As you see from your own experience, those pressures are insufficient to stretch the case back to the bolt face once driven forward by the firing pin. Hence the primer is left exposed once it backs out into any excess headspace. (And your pics show a lot of headspace for a rimmed cartridge.) What rifle/action are you shooting this in?

August 21, 2010, 10:06 AM	#7
Bush Pirate Member Join Date: June 2, 2009 Location: Michigan Posts: 54	Shot out of lever gun, model 94 winchester 25-35. I usually have a gun smith check headspace on an older new to me gun, but my uncle said he had fired it about 6 months earlier. I figured it worked for him.