primers poping

[2osok]

Hi Guys,
Woundering why primers are poping in my .22 b/r barrel ?,
has only fired 7oo rounds , cleaned properly every 50 rounds fired ,
28" barrel 1 in 8 twist using 75 amax,
SAME LOAD as always, no change in loading, which is N150 30 grains half way though 2kilo pot , checked case length at 1.520 seating depth is the same , primers are the same,
using out of same batch of 1000 box federal205 match, which l have been using ,
WHY are they poping ???
Have now started on new pot of Vit N150 dropping load to 29 grains
Has anyone had this ??

 

[fdshuster]

2osok: How about defining "poping"? Are they blanking/ piercing with a small hole in the center, the diameter of the firing pin tip? Are they backing out? Are they cratering? Give us more descripitive information.

Until you are able to provide more information, I will say that when I had a 22BR and working up powder charges, it took only a very small increase in powder ( less than 1/2 grain) to go from completely normal to immediate signs of high pressures. Very hard bolt lift, with some ugly primers. Until you can verify the cause, immediately back-off on your load by as much as 2 grains.

 

[2osok]

Hi, the primers are poping out and are black no firing pin marks or piercing marks, just very hi presures with the same load, i have always used , and the case will not go into shell holder, expanded too much
the load is not too hot ,
have backed off 3.5 grains of a new batch of powder n150 as this i have always used .
and still poped primers

 

[queen_stick]

did you run a couple rounds over the chrono? Maybe the load IS too hot.

Maybe you have a carbon ring in the throat, causing the pressure to increase? (even if you clean every 50rds, carbon rings can develop).

 

[bozo699]

did you run a couple rounds over the chrono? Maybe the load IS too hot.

Maybe you have a carbon ring in the throat, causing the pressure to increase? (even if you clean every 50rds, carbon rings can develop).

Walt ,
I think your probably spot on with the carbon ring!

2osok,
I don't care if the powder charge is the same as it always was if your loosing primers and the base has expanded so badly they wonn't fit into the shell holder your load is WAY TOO HOT!! did this problem develop over time or all at once? I would clean your gun until it's clean then use some carbon solvent or just some Butches,...whatever and a nylon brush and scrub the heck out of your throat, then run another patch through the barrel if it comes out black you have carbon keep working on it until they come clean or at least light gray, then drop another grain or two and fire the rifle and work your way back up until you are where you were or pressure starts again. I have a 22br but haven't had that barrel on the rifle for a while so I don't remember the charges but I never used VV powder in it anyway so I can't help you there, best of luck to you.
Wayne.

 

[fdshuster]

I was too late on my thoughts about a buildup of carbon in the throat, but second the suggestions that it be considered.

This is where a borescope really comes in handy, but without one, give the throat area a real good cleaning. I personally use JB bore paste with a bronze brush, and for the possibility of a ring of carbon at the case mouth, ( guaranteed to raise pressures), I use a pistol cleaning rod with a non-rotating handle ( usually a simple loop) with the brush attached. Run it into the area in front of the case mouth & rotate clockwise. It will remove the ring of carbon in very little time, if that's the cause.

If you never had the problem before, using the same loads & it just started now, then the carbon buildup sounds reasonable as the cause.

As mentioned before though, the 22BR was the only cartridge I've ever had that went from a perfectly normal load to over-pressure without any gradual warning signs. My load was 28.5 grs. of H322 with a 55 gr. bullet. All was well. Increased the powder to 28.9, same bullet & seating depth & things got ugly real fast. Returned to 28.5 & problems immediately went away.

 

[2osok]

Thank you for your kind replys will address and see

 

[bheadboy]

one other consideration, the bullets, are they the same lot?

i have experienced .0005-.0009 diff in dia in some manufacuters and custom bullets, if so the larger will produce higher pressure the first round shot.

Bob

 

[2osok]

Cheers everyone gave the throat a good clean and back on song thanks again for all the advice.