Author Topic: Primers backing out (Read 680 times)

bob helget · « **on:** August 29, 2004, 06:07:30 PM »

I am a new reloader working on some loads for a 7-30 in a 14" G2. Today I was working up with Sierra 130 SSP, CCI primers and 748 powder. At 34.5 grains my primers are starting to back out. Is this a situation of pressure alone or are there other factors that can cause the primers to back out. When I seated the primers they seated with the same pressure as others so I don't think it was an issue of the primer pockets being too large. Also, I have loaded and fired about 150 rounds through this gun with 2520 and 748 powders. I get decent accuracy with the starting loads but my groups open up as I increase the powder charge. This seems contrary to what I would expect. Any suggestions would be appreciated.

Questor · « **Reply #1 on:** August 30, 2004, 03:52:28 AM »

I'd call T/C about that one. I suspect that the gap between the barrel and the receiver is too great.

skb2706 · « **Reply #2 on:** August 30, 2004, 11:04:52 AM »

Even if the gap from frame to barrel is excessive you can remedy this by sizing correctly. My guess is that you are setting the shoulder back too far for this barrel frame combination.

Lancel · « **Reply #3 on:** August 30, 2004, 02:18:43 PM »

Quote

...primers are starting to back out. Is this a situation of pressure alone ...

Oddly enough, too little pressure can cause primers to remain backed out.
When a the primer first goes off it gets pushed back out of the pocket. As the pressure builds, the cartridge then backs up over the primer.

Sometimes you can test this effect by firing an empty cartridge with only a primer and no powder or bullet. (Be sure you still point it in a safe direction.) Odds are that the primer will be backed out since there was no powder burn to push the brass back over the primer.

Note that this is more common in revolvers. My contender barrels don't seem to leave much space for primer movement.
Larry

Somerled · « **Reply #4 on:** August 31, 2004, 01:40:33 PM »

I suspect skb2706 has this one right. I have just started reloading for Contenders. It is critical to get the sizing, and thus the headspace, adjusted right.

bob helget · « **Reply #5 on:** August 31, 2004, 05:42:42 PM »

Problem solved, you guys gave me the right advise with the headspace recommendation. I spent some more time adjusting my die and fitting cases in my gun. I was pushing the shoulder back too far. Shot two five shot groups tonight with the same loads, primers are no longer flat or backing out. It shot a nice group too, first three were within 3\4" then two just outside of 1" Thanks for your help.

Lancel · « **Reply #6 on:** August 31, 2004, 05:52:48 PM »

Interesting comments about the shoulder. Especially since the 7-30 (like it's parent the .30-30) headspaces on the rim. Maybe it's a comment on how T/C makes it's chambers.
Larry

skb2706 · « **Reply #7 on:** September 01, 2004, 03:19:07 AM »

Actually you really don't want to headspace anything off the rim in a Contender or any other break action gun. Even if the case has a rim you will get far superior case life and accuracy headspacing off the shoulder. There is volumes of very good information available to support this. Doesn't really have anything to do with how the chambers are made but more to do with the design of the gun, the way the frame flexs when fired and what is called spring back.

Lancel · « **Reply #8 on:** September 01, 2004, 06:06:49 AM »

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Actually you really don't want to headspace anything off the rim in a Contender ... Even if the case has a rim you will get far superior case life and accuracy headspacing off the shoulder.

How does this apply to straight walled pistol cartridges like .44 magnum, .45 Colt, etc.?

In reference to rimmed bottleneck cartridges (like 7-30), why wouldn't fire formed and neck sized cases give the greatest case life and accuracy?

Quote

There is volumes of very good information available to support this./
Quote

Great, could you list some reference links?

Thanks,
Larry

skb2706 · « **Reply #9 on:** September 01, 2004, 06:33:04 AM »

my error........any bottleneck cartridge. The man is loading a 7-30 Waters and made no mention of any straight wall case with a primer that backed out. Essentially if you use the rim to headspace a bottleneck case you will have pushed the shoulder too far back....each time you load like that you are allowing the case to stretch back to a fireform fit.....greatly reducing case life. For some excellent info. you will need to go to a website associated with an individual who cannot by name be mentioned here.....not my deal.
bexxmtcs.com
or another would be loading info.
specialtypistols.com
there are others.........as well if you would like email me and I will be more than happy to give you specifics.

Lancel · « **Reply #10 on:** September 02, 2004, 06:12:40 PM »

skb2706:
Neither link got me directly to a reference but I was able to decode the bellmxx.com and after a bit of digging found this little nugget:

[re: Contenders]
"Most of the rimmed rounds such has 7-30 Waters above, and .30/30 below, have rim counter-bores cut too deeply to headspace on the case rim without more headspace than suitable for good case life. With new brass, steps should be taken to fire form the shoulders forward before loading for actual use. After fire forming, cases should be correctly sized so that they headspace on the shoulder. Factory ammo will undergo some unnecessary stretching when fired in these chambers."

Interesting,
Larry

skb2706 · « **Reply #11 on:** September 03, 2004, 02:34:23 AM »

Lance at that same website there is an excellent article done by Don Shearer regarding frame springback and loading procedure theory. Also read the article about headspace indicator guage.........good info for the break action shooter.

bob helget · « **Reply #12 on:** September 03, 2004, 09:00:52 AM »

This is definitely the case with my barrel. With factory ammo and before I got my die set correctly, the case was visibly recessed in the barrel.