Primers are backing out of primer pocket.

[oldhoward]

Hi, perhaps some one has some experience with a Remington 740 3006. I bought a used one recently and shot it for the first time this weekend. First it was a hot day and the ammo was hot from being in the truck. Issue is the primers are backing out of the primer pocket approximately .0015's or so. I shot the rifle the next morning with cool shells and only 3 out of 5 had the primers backed out of the primer pocket. Is this normal for this type of rifle?? or there a problem. These were factory store bought Remington 150 grain bullets. There was no gas leakage around the primers and the struck primers were not puckered like pressure signs. Any suggestions or advice?

Thanks Oldhoward.

 

[rayjay]

You should have a gunsmith check the headspace.

 

[mikecr]

As described, it's not a problem

 

[DRNewcomb]

As described, it's not a problem

I think I agree but it would never hurt to have the headspace checked. When was the last time it was checked?

 

[oldhoward]

I never had the head space checked, as I purchased it used recently.

 

[DRNewcomb]

I never had the head space checked, as I purchased it used recently.

Two ways to do it are with a headspace gauge or checking a fired case with a case gauge or case micrometer.

 

[BoydAllen]

If your loads are not hot, and your chamber is not particularly smooth, having a little primer protrusion is normal and not dangerous. The shoulder angle of the 30-06 is shallow enough that the force of the firing pin and the primer explosion will force the case farther into the chamber. Subsequent pressure from the powder burning makes the case cling to the chamber walls in this position, and the primer is free to move back to the bolt face. If the pressure of the load is moderate, the case will not stretch to the bolt face. As a general rule, semiautomatics require ammunition that has a looser fit in the chamber than would be required by a bolt rifle. When setting your die for shoulder bump, you should use a case that does not have a protruding primer as a reference. Of course, without rifle, ammo, and fired cases in hand, this is just a guess, based on experience, and guesses are only as good as the information that is given.

 

[oldhoward]

Hi, I looked at the fired cases and observed the following. Cases with normal primers seemed a bit shorter at the shoulder and shorter in length, based on 3 normal primers, i.e. no primer set back. Cases with primers which were set back were longer at the shoulder and longer in overall length. The shoulder angle is more clearly defined, sharper shoulder, on the cases with primer setback. I can't measure the angle of the shoulder or the exact length to the shoulder accurately. The necks of all cases are well expanded, more than a bolt gun, and the necks are clean except for a small back mark at the case mouth. So I would say there is no blow by past the neck. (no sign wave)

Thanks for all your replies, I appreciate your efforts.
Oldhoward

 

[jnyfeler]

Two issues
Sounds like a light load -- like Boyd said, it's not pushing the case head back against the bolt face during firing. It also sounds like the shoulder on your brass has been bumped back too far during sizing creating an unnecessarily large amount of head space.

1. Fix the brass
Under these conditions, the next question is how to blow the shoulder forward on your brass so that the case fire-forms to the chamber. Load the bullets long for their next firing. Long enough that they'll jam into the rifling and force the head of the case up against the bolt face when chambered. Make sure your load is indeed on the low end pressure wise as I have assumed here, because jamming the bullet into the rifling will slightly (not greatly, but slightly) raise the pressure of the load. It sounds like your load is light to begin with, but I'm going off of limited information so I'm making a bit of an assumption here. When you fire the round with the bullet "jammed" into the rifling, the shoulder of the cartridge case will blow forward and the cartridge case will become a form-fit to the chamber.

2. Set your sizing die for the correct amount of shoulder bump
Now that you've blown the shoulder forward on your brass, the next step is to measure the fired case with a cartridge case head space gauge. This will tell you the size of the chamber plus any nominal stretching of the cartridge case that took place during extraction. Take one of the newly fired pieces of brass (one that was fired with the bullet jammed into the rifling) and through trial and error, set your sizing die so that it sets the shoulder back on the newly fired brass by 0.002". Then, wipe the lube off of that piece of brass and chamber it in your rifle. Let the bolt slowly slide forward until the cartridge case stops the bolt's forward progress. From there, a slight tap on the bolt should *fully* chamber the cartridge case. If the case doesn't fully chamber, then adjust your sizing die to bump the shoulder back another 0.001" Wipe off the lube and chamber the case again. Repeat this process until the case fully chambers by you slightly bumping forward on the charging handle of the operating rod. Run one or two more cases through the die and make sure they will fully chamber via this process as well.

3. Note the head space measurement on your properly sized brass
After the bolt closes fully on the cartridge case, take your cartridge case head space gauge and measure the case now that it's properly sized. Write down the indicated head space for future reference as you only want to go through this process once!

Jeff

 

[BoydAllen]

I might go a little slow on using the jam the bullet into the rifling to blow the shoulder forward approach for a semiautomatic rifle. It is my understanding that cases for this type of rifle should be sized so that they have more bump from maximum chamber shoulder to bolt face length, so that there will be more clearance to assure reliable lockup. It seems to me that seating bullets into the rifling would be similar to using brass that had no been sized enough for a semiautomatic.

 

[oldhoward]

Hi I just found some further information about this issue. What is happening is the bolt is unlocking while still under peak pressure and the primer is driven back against the bolt face. This information was passed on by a retired service rep from Remington(??). Suggested fixes are to replace the action spring. If that does not work then the gas port is eroded or damaged in some way, but you can drill the gas block deeper approximately. .0090 to .0100 deeper to delay the bolt from opening to early and pressure will remain the same but the peek will occur later in the cycle. The gas port is no longer available but the spring is available for $10.00 so I ordered one. The rifle was discontinued in December of 1959, so a weak action spring would make sense to me. I will let you know the results in a few weeks.
Thanks for your replies.
oldhoward

 

[Old Navy]

Hi I just found some further information about this issue. What is happening is the bolt is unlocking while still under peak pressure and the primer is driven back against the bolt face. This information was passed on by a retired service rep from Remington(??). Suggested fixes are to replace the action spring. If that does not work then the gas port is eroded or damaged in some way, but you can drill the gas block deeper approximately. .0090 to .0100 deeper to delay the bolt from opening to early and pressure will remain the same but the peek will occur later in the cycle. The gas port is no longer available but the spring is available for $10.00 so I ordered one. The rifle was discontinued in December of 1959, so a weak action spring would make sense to me. I will let you know the results in a few weeks.
Thanks for your replies.
oldhoward

I had a 742 for a couple years and let me tell you they are a bitch to load for. Before you start modifying the gun you need to understand that is a gas gun and it will only work in a narrow pressure band. Mine was very fussy even with some factory ammo. Your loads are light. When the bolt opens too soon, before the case contracts, the extractor will rip a piece of the lip on the case. Don't even try to jam bullets into the leads unless you one a locked up gun. There is absolutely no cam action like on a bolt. Better yet, save yourself a lot of grief and just shoot factory ammo. Later! Frank