Primer backing out

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Primer backing out

Post by sdsviper on Wed Dec 01, 2010 12:29 pm

Time to pick your brains. My father in-law had some accuracy problems with his Rem 742 in 30-06 that he has shot for over 30yrs. I looked for the normal stuff (lose scope, barrel fouling etc) and there were a few issues but easy fixes. When we got back to the range to site in all went well till i noticed that every round he fired the primer was backing out this is 180gr federal factory ammo so I fired some through my rifle (Rem 700 30-06) to see what happened and the primers were fine. There was no flatting of the primer or any other pressure signs. That said what should I be looking for or is this no big deal???




Last edited by sdsviper on Wed Dec 01, 2010 5:51 pm; edited 1 time in total
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Re: Primer backing out

Post by Daywalker on Wed Dec 01, 2010 1:18 pm

I would say to recheck your headspace. Seems to me it might be a bit on the long side. Have you tried any handloads? Try some at the same oal as the factory. If the primer is still backing out, test to see how much it is backing out. Seat a bullet a bit longer until you see that the primer is not backing out at all.

I am no gunsmith, but it seems there isn't enough pressure being developed for the case to back up against the bolt to reseat the primer upon firing. My first place to look would be headspace. Hopefully a gunsmith or someone with more expierence will come along and either back me up and or let me know I am way off base here...

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Re: Primer backing out

Post by Reload3006 on Wed Dec 01, 2010 1:20 pm

check the head space ... could be an issue if the primers are backing out and not seating back in. in all guns the primer will back out till it hits the bolt and the gas expands the case to bump up against the shoulder. then the case reseats the primer under pressure. if it is excessive pressure it will flatten the primer out and make it look flush with the primer pocket. If the head space is excessive the primer may not seat and other things could happen ... this may not be the problem but one that is easily checked
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Re: Primer backing out

Post by RemMan700 on Wed Dec 01, 2010 1:27 pm

Usually primers backing out are caused by low pressure. Does there seem to be an excessive amount of powder blowback on the case (which might be hard to tell since it is a semiauto)?

Does anyone think that it could be an excessive headspace problem?

Well I guess everyone posted while I was typing this.
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Re: Primer backing out

Post by hawcer on Wed Dec 01, 2010 1:43 pm

It could be excessive headspace...Compare a case fired from his rifle to one fired from yours....see if the shoulder is higher on the case as compared to yours. You could also try to chamber one of his fired cases in your gun...normally it might be a little stiff to get the bolt closed...but if you cant get the bolt even close to closing I'd assume either his chamber is overly large or he has excessive headspace.

Maybe his barrel is shot-out, causing loss of pressure(blow-by) and poor accuracy.

How does a bullet fit in the muzzle...it doesn't fall all the way in does it?

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Re: Primer backing out

Post by sdsviper on Wed Dec 01, 2010 2:44 pm

Thanks for ideas I will start ckecking. The barrel very well be shot out he has had it for over 30 years and it's never been a tack driver by any means.
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Re: Primer backing out

Post by algunjunkie on Wed Dec 01, 2010 3:28 pm

If I'm not totally nuts you have excessive head-space. If the ammo is fine in one and not the other it is most likely the gun. It's common in older guns that have been used a lot. Not to fear it can be fixed or worked around. To fix it will require the services of a qualified gunsmith. To work around it will require you to partial size the case and not set the shoulder back since it is now case formed.

What generally happens when you are firing a gun is this. You load the ammo in the chamber, most of the time you think that it fits snug but in reality it does not, unless you loaded it that way. Factory specs can have .008" excess diameter of the neck alone and it is considered ok. So the case just sits in there loosely and is held in place by the extractor. When the firing pin is released because you pulled the trigger, it strikes the primer and can move the case forward thereby pulling it off of the bolt face. This allows the primer to back out.

Or once the primer is ignited and the powder begins to burn, it creates a tremendous amount of gas causing the casing to swell and forming a tight fit against the chamber walls. The path of least resistance kicks in, the bullet goes one way and the primer the other.

As far a lite loads, look for the carbon residue on the case neck, now that you know why it is there, .008 excess. If it is low and on the shoulder, the cases are way loose in the chamber and the round is underpowered.

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Re: Primer backing out

Post by Mohunter on Wed Dec 01, 2010 6:13 pm

I have a quick question on this topic while you all are talking about it.
You mentioned carbon residue on the case neck, I don't think I have a single firearm that doesn't leave at least some residue on the case necks? I just thought that was a common thing, because all my rifles will leave some around the case neck??

Or.........is that common with first time fired factory loads only??

Please expand on this if you don't mind......anybody, everybody?
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Re: Primer backing out

Post by RemMan700 on Wed Dec 01, 2010 6:45 pm

Powder on the neck is normal, but powder on the case body means that you have too low a charge or an underpressure issue. The case is not expanding to fill the chamber and gets residue on the body. The only exceptions are semi auto's especially direct impingment guns like the AR since they blow gas directly back into the receiver.
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Re: Primer backing out

Post by dartfreak75 on Wed Dec 01, 2010 9:27 pm

i agree sounds like head spacing to me!
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Re: Primer backing out

Post by Rick459 on Sun May 01, 2011 5:01 pm

In Feb. 1977, date code (LO), on the 742 & 760, the barrel threads were changed from RH to LH, to help stop the problem of the barrel extension (locking lugs) from unscrewing from the barrel during the firing cycle. This date code is shown below in the gunsmithing section. maybe this is what's going on with your 742.
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http://www.wisnersinc.com/additional_info/Remington_7407427400.htm
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