Bulged 209 Primers

[ElDiablo]

So I tried a modified (deeper) OEM plug yesterday with an o-ring. Thanks @ronlaughlin!

TC Omega X7/300 gr Nosler Partition/120 grV BH209. 80-85 degrees (Using a cooling rod to bring the barrel temp down to 73-83 between shots - yes, still pretty warm). Accuracy was good.

The 209s are clean on the front half but still getting bulging with the F209As (and primer cup leakage). Tried Cheddites as well and they are better but signs of pressure (cup leak).

So I backed down to 110 grV BH209. Much better. Only very slight bulge and primer cup leakage. Maybe this slight bulging is something that had been happening in warm weather and I hadn’t noticed it before

I’m starting to think it’s the heat combined with the heavy charges.

Need an adjustable head space plug that more fully supports the 209.

Photos of the Fed209A and Cheddite with 120 grV:




Fed 209A with 110 grV:

 

[alternate]

So I tried a modified (deeper) OEM plug yesterday with an o-ring. Thanks @ronlaughlin!

TC Omega X7/300 gr Nosler Partition/120 grV BH209. 80-85 degrees (Using a cooling rod to bring the barrel temp down to 73-83 between shots - yes, still pretty warm). Accuracy was good.

The 209s are clean on the front half but still getting bulging with the F209As (and primer cup leakage). Tried Cheddites as well and they are better but signs of pressure (cup leak).

So I backed down to 110 grV BH209. Much better. Only very slight bulge and primer cup leakage. Maybe this slight bulging is something that had been happening in warm weather and I hadn’t noticed it before

I’m starting to think it’s the heat combined with the heavy charges.

Need an adjustable head space plug that more fully supports the 209.

Photos of the Fed209A and Cheddite with 120 grV:

View attachment 35027
View attachment 35025

Fed 209A with 110 grV:

View attachment 35026

Make sure your flash channel has been reamed to get all the carbon out. The carbon is glass hard and sometimes you think its the steel of the plug. The flash channel acts like a delayed blowback mechanism. Upon firing the high pressure gas leaks thru the flash hole building pressure in the flash channel. By the time the pressure builds to the point of bulging the primer the bullet leaves the barrel and the pressure drops to zero. For this to work the flash channel volume is critical. Carbon buildup reduces the flash channel volume and pressure increases too high while the bullet is still in the barrel.

 

[ElDiablo]

Yeah, that was the first thing I double-checked. All my OEM Omega plugs get a 1/8” drill bit reaming every time I clean them.

 

[ronlaughlin]

Well it would have been simple for me to drill out the flame channel to 5/32" when the primer socket was milled 0.015" deeper. This as mentioned in a previous post would have reduced the pressure on the primer. Most of my shooting is done at 4700', and near first light so it is plenty cool. Also, the powder charge is normally 90g to 105g; the pressure issues experienced by ElDiablo were never experienced by me, when shooting the same exact breech plug.

 

[ElDiablo]

Great minds think alike Ron. I opened up the flash channel to .127” earlier today. Going to see if that helps any before going larger.

 

[billyboy*]

Were you able to Test the OEM Modified Breech Plug with the 5/32" Flame Channel?

 

[ElDiablo]

Were you able to Test the OEM Modified Breech Plug with the 5/32" Flame Channel?

No - was not able to do any more shooting yet. I’m in AK now, so I wont be shooting for a while.

 

[jsteurrys]

No - was not able to do any more shooting yet. I’m in AK now, so I wont be shooting for a while.

Get that bear.