Small rifle primers for weak firing pin spring

[Straightshooter1]

Since I'm having a problem finding a replacement firing pin spring for my .308 RPR, other than Ruger insisting I send my rifle to them to have one installed, I decided to run a little experiment first using my palma brass with the 3 different SR primers I've got on hand (CCI400's, CCI450's and Federal 205M's). I'm thinking that with the weak firing pin spring that seems to be producing some inconsistencies (random flyers, larger ES and SD's), maybe the SR primers with their thinner cup thickness, I might not see that kind of inconsistency. I'm loading them up and will fire them this weekend.

Anyone else have any experience doing this kind of thing?

PS: As I got ready to prime my 1X fired Lapua Palma Cases for this experiment, I measured the flash holes with my Accuracy One Precision Primer Gauge. I hadn't measured them before thinking there wasn't anything to be concerned about . . . because these a Lapua brass. . . . right? Well, to my surprise, I found a dozen of the 100 were significantly shallower than the rest by .011 - .013. For example, most of them measure around .1205 in depth and these others measured .108. So I uniformed them the my RCBS Primer Pocket Uniformer to get then to the .120. I'm pretty certain that .013 difference in primer pocket depth would make a difference in ignition . . . huh?

 

[dkhunt14]

I think that weak primer hits doesn't have as much to do with velocity as it has to do with the vibrations in the barrel by difference in the strikes. I do believe they both have an effect on accuracy but I believe the vibrations have more to do with group sizes and fliers. When I used a chronograph at 1000 yards, the velocity didn't agree with the fliers. I also know that weak springs can cause a good rifle not to shoot very well. I saw many rifles over the years that shot terrible and the owner put in a new spring and the rifle came alive. Just my thoughts. Matt

 

[bwoodie]

I was having ignition troubles with CCI 450 primers in my .308 recently. I was concerned that a "weak" firing pin spring was the culprit. That was not the case. I purchased an Accuracy One primer gauge and found that primer pocket depth was variable in the brass I was using- similar to what you found. In addition, the depth that I was seating the primers was variable as well. I purchased a 21st Century precision bench rest hand priming tool and switched to Fed 205M primers and my troubles went away.

 

[rogn]

Might not be a bad idea to strip the bolt and lookm for sandwich wrappers or old shoelaces in the firing pin channel. My guess is Ruger wants to find out if there is some swarf or debris in the channel. "Stuff" can interfereb with the firing pin fall and give the odd results you've seen.

 

[Straightshooter1]

Might not be a bad idea to strip the bolt and lookm for sandwich wrappers or old shoelaces in the firing pin channel. My guess is Ruger wants to find out if there is some swarf or debris in the channel. "Stuff" can interfereb with the firing pin fall and give the odd results you've seen.

I did strip the bolt and and the channel, firing pin and spring . . . all were free of any debri and clean (I keep an eye on that kind of thing as a matter of routine).

 

[Webster]

Since I'm having a problem finding a replacement firing pin spring for my .308 RPR, other than Ruger insisting I send my rifle to them to have one installed, I decided to run a little experiment first using my palma brass with the 3 different SR primers I've got on hand (CCI400's, CCI450's and Federal 205M's). I'm thinking that with the weak firing pin spring that seems to be producing some inconsistencies (random flyers, larger ES and SD's), maybe the SR primers with their thinner cup thickness, I might not see that kind of inconsistency. I'm loading them up and will fire them this weekend.

Anyone else have any experience doing this kind of thing?

PS: As I got ready to prime my 1X fired Lapua Palma Cases for this experiment, I measured the flash holes with my Accuracy One Precision Primer Gauge. I hadn't measured them before thinking there wasn't anything to be concerned about . . . because these a Lapua brass. . . . right? Well, to my surprise, I found a dozen of the 100 were significantly shallower than the rest by .011 - .013. For example, most of them measure around .1205 in depth and these others measured .108. So I uniformed them the my RCBS Primer Pocket Uniformer to get then to the .120. I'm pretty certain that .013 difference in primer pocket depth would make a difference in ignition . . . huh?

View attachment 1255932

Your assuming it's a weak FP spring. Could be? Ask Ruger if they use carbon steel music wire for springs or the Chrome Silicon alloy wire. The Cr/Si wire retains tension almost indefinetly. I have seen charts showing how fast the cheap wire looses tension. The test comparison is with both wire alloys and the number of cycles VS tension loss. Are you seating the primers to the bottom of the pocket? Why would you buy an expensive guage when you can just uniform the pockets.

Check with Whidden and Tubbs for new springs. I bought one for a Remington. Don't know if they carry Ruger. I bought the entire FP assembly. Don't forget to put some oil on the FP assembly where it comes out of the shroud. Lube inside and out side with the bolt removed. This is the only area of friction to restrict fp movement. Most people never lube this area. With the bolt cocked you can see the rub marks on the part that protrudes out of the shroud.

 

[Straightshooter1]

Your assuming it's a weak FP spring. Could be? Ask Ruger if they use carbon steel music wire for springs or the Chrome Silicon alloy wire. The Cr/Si wire retains tension almost indefinetly. I have seen charts showing how fast the cheap wire looses tension. The test comparison is with both wire alloys and the number of cycles VS tension loss.

Yes, I'm only "assuming" a weak FP spring. If I had a way to measure the tension I'd do so and compare mine with my shooting buddy's RPR FP spring. Good idea about asking Ruger about the spring. I'll do that and see what they say.

Are you seating the primers to the bottom of the pocket?

Yes, for my LR primers.

After measuring the SR primer pockets and seating the primers, it doesn't seem like I'm getting any kind of crush, given the chart dimensions I have and they're only seated .0035 - .004 below the case head surface. For the first firing for fire forming, these SR primers performed just fine at that depth.

Why would you buy an expensive guage when you can just uniform the pockets.

Because I can?

I got tired of trying to get somewhat accurate measurements with my caliper and wanted to have an easier/faster way to measure not just the pocket depths, but also the seating depths.

Check with Whidden and Tubbs for new springs. I bought one for a Remington. Don't know if they carry Ruger. I bought the entire FP assembly. Don't forget to put some oil on the FP assembly where it comes out of the shroud. Lube inside and out side with the bolt removed. This is the only area of friction to restrict fp movement. Most people never lube this area. With the bolt

I'll check Whidden and Tubbs, but I have a feeling the RPR is just not prolific enough to warrant having any made or to keep in stock . . .???

That's good advice about lubing. And I actually do that, just as you've described.

 

[Alex Wheeler]

Im not familiar with those rifles, what does the spring measure and how much fall does it have? Fed 205s would be my first pick for weaker ignitions. I have a bunch of springs around here if you measure it up I may have one that will work.

 

[Straightshooter1]

I think that weak primer hits doesn't have as much to do with velocity as it has to do with the vibrations in the barrel by difference in the strikes. I do believe they both have an effect on accuracy but I believe the vibrations have more to do with group sizes and fliers. When I used a chronograph at 1000 yards, the velocity didn't agree with the fliers. I also know that weak springs can cause a good rifle not to shoot very well. I saw many rifles over the years that shot terrible and the owner put in a new spring and the rifle came alive. Just my thoughts. Matt

Good thoughts! I wonder though. . . if it's a vibration issue, I'd think a barrel tuner could be easily adjusted to compensate. Huh?

Is it you're thinking that the vibration that's imparted is done solely by the force of the strike?

It seems to me that a difference in ignition would also impart a difference in vibration . . .???

 

[NZ_Fclass]

Go talk to Wolff gunsprings. They may be able to help.

https://www.gunsprings.com/index.php

 

[Webster]

Since I'm having a problem finding a replacement firing pin spring for my .308 RPR, other than Ruger insisting I send my rifle to them to have one installed, I decided to run a little experiment first using my palma brass with the 3 different SR primers I've got on hand (CCI400's, CCI450's and Federal 205M's). I'm thinking that with the weak firing pin spring that seems to be producing some inconsistencies (random flyers, larger ES and SD's), maybe the SR primers with their thinner cup thickness, I might not see that kind of inconsistency. I'm loading them up and will fire them this weekend.

Anyone else have any experience doing this kind of thing?

PS: As I got ready to prime my 1X fired Lapua Palma Cases for this experiment, I measured the flash holes with my Accuracy One Precision Primer Gauge. I hadn't measured them before thinking there wasn't anything to be concerned about . . . because these a Lapua brass. . . . right? Well, to my surprise, I found a dozen of the 100 were significantly shallower than the rest by .011 - .013. For example, most of them measure around .1205 in depth and these others measured .108. So I uniformed them the my RCBS Primer Pocket Uniformer to get then to the .120. I'm pretty certain that .013 difference in primer pocket depth would make a difference in ignition . . . huh?

View attachment 1255932

There are many variables that could cause fliers including the shooter. Without any proof you are assuming it's a weak FP spring. How big are the fliers? Are they related to wind direction. Quality of bullets. How is the rifle supported. Just changing how you hold the rifle a little can change the POI.

 

[Straightshooter1]

There are many variables that could cause fliers including the shooter. Without any proof you are assuming it's a weak FP spring.

With over 10,000 cycles (over 9,200 rounds fired), it's probably a pretty good guess . . . don't you think?

How big are the fliers?

I'll have pretty decent 5 round groups (like high .2's to mid .3's going and suddenly there's one round of the 5 that ends up where the group is at or just over .5" at 100 yards and pretty much the same kind of results (in terms of MOA) at longer distances.

Are they related to wind direction.

Definitely not.

Quality of bullets.

Mostly SMK's and sometimes Bergers.

How is the rifle supported.

Just changing how you hold the rifle a little can change the POI.

Understood. Trigger is at 10oz. and I shoot pretty much free recoil. . . where when I'm ready to break the shot the only thing touching the rifle is my thumb on the thumb rest (same side as trigger finger) and finger on the trigger.

 

[searcher]

I'm sure you are on top of this - but I'd be sure to eliminate any excessive headspace slop in your shoulder-to-chamber. That is probably the number one reason a lot of folks complain about the Russian primers. If the case isn't properly supported in the chamber, it merely moved forward, rather than allowing the primer to receive the full striking force of the firing pin.

 

[Forum Boss]

How many rounds through that Barrel? Is it aftermarket?

Have you inspected the forward tip of the firing pin?

Do you have any Factory .308 ammo to test?

Are your “flyers” showing abnormal velocity?

Is the hand guard piece tight?

Frankly if an honest 0.5” is your ”bad” 5-shot group I’m not sure you can expect much more from that rifle/platform.

Have you shot it without the tuner brake?

 

[Straightshooter1]

How many rounds through that Barrel? Is it aftermarket?

Have you inspected the forward tip of the firing pin?

Do you have any Factory .308 ammo to test?

Are your “flyers” showing abnormal velocity?

Is the hand guard piece tight?

Frankly if an honest 0.5” is your ”bad” 5-shot group I’m not sure you can expect much more from that rifle/platform.

Have you shot it without the tuner brake?

How many rounds through that Barrel? Is it aftermarket?
5,512 rounds to date. It's a 24" Krieger heavy sporter barrel.

Have you inspected the forward tip of the firing pin?
Yes. I've compared it with my shooting buddy's RPR firing pin today, which has the same specs (even use his in my bolt), and could find no anomalies. Except, when compressing the two difference springs, mine definitely felt easier to compress than his. His bolt and spring has less than 1,000 rounds.

Do you have any Factory .308 ammo to test?
Nope. Not any more. It's been 2,000 rounds since I lasts fired any factory ammo.

Are your “flyers” showing abnormal velocity?
Typically, they tend to be the slower ones resulting in the higher ES's.

Like some I had from today's shoot:



Is the hand guard piece tight?
Yes.

Frankly if an honest 0.5” is your ”bad” 5-shot group I’m not sure you can expect much more from that rifle/platform.
It's the random flyers that's happening more lately that I can't explain. I've been analyzing everything and had been thinking it may be time for a new barrel . . . except I hadn't considered a weak firing pin spring. In comparing Federal and CCI primers in both LR and SR sizes, the Federal primers have been giving me better results on paper as well and more consistent chrono numbers, which seems to support the idea that the weaker spring on the thinner/softer primers may be producing more consistent ignition than on the harder/thicker CCI primers.

Here's what what my targets look like today (note the 1st page on the left are the LR primers, the second and fourth set being Federal primers; the bottom page with shooting with magnetospeed attached):


Have you shot it without the tuner brake?
Not for a long time. . . like ~ 2,500 rounds ago.

 

[Forum Boss]

You have 5500+ rounds through your barrel!!

Stop. Do not pass go.

Get a new barrel.

Your second target, with the Fed primers is fine. You only have one shot (left-most group, target 2) that looks suspciously high, but that was probably shooter because the preceding three groups (left-most target) do not have any big vertical.

Ignore the groups with the magnetospeed.

Anyway, I honestly think it is completely pointless to analyze this any further. Get a new barrel.

I honestly think it is a total waste of time to worry about the spring and primer variations.

And this is only an RPR. This is not a benchrest rifle or even a $3000 fancy PRS rig.

The tuner/brake could be fouled, or your crown could have some damage that you can't see. But honestly, get a new barrel.

 

[Straightshooter1]

You have 5500+ rounds through your barrel!!

Stop. Do not pass go.

Get a new barrel.

Your second target, with the Fed primers is fine. You only have one shot (left-most group, target 2) that looks suspciously high, but that was probably shooter because the preceding three groups (left-most target) doesn't have any big vertical.

Ignore the groups with the magnetospeed.

Anyway, I honestly think it is completely pointless to analyze this any further. Get a new barrel.

I honestly think it is a total waste of time to worry about the spring and primer variations.

And this is only an RPR. This is not a benchrest rifle or even a $3000 fancy PRS rig.

The tuner/brake could be fouled, or your crown could have some damage that you can't see. But honestly, get a new barrel.

LOL . . . would you believe that for a long time now I've had a new Krieger barrel sitting in my closet in wait for the right time to make the swap? And I feel you're right . . . it's time. After feeling the difference between the two firing pin assemblies, I'll be installing a new firing pin spring as well. Then I should be good to go. . .
. . . maybe for another 5,000 rounds.

As far as the tuner/break and crown, that's a good thought. . . . but I clean them every time I clean the bore, which was done, just before this shoot, a couple day ago.

To be sure, I don't expect my RPR to be at the same level as those high level rigs. But, I like to see how close I can come with my relatively small budget.

 

[JSH]

Not to derail the thread by any means.
So many get hung up on BR type case and ammo prep with off the rack rifles. I have found the return to be a moot point for all the time spent.
I am not a BR shooter, but when those that are speaking I listen.

If primer pockets have not been uniformed, how is using a dial type seater doing any good?

To those using a dial type seater. I was always told to seat solid to the bottom of the pocket in order to get reliable ignition, making the anvil and the cup work properly.

I seat mine solid into the pocket. My groups may suffer? But it has been a longgggg time since any misfires.

I had issues a year ago, I thought were pressure. Ended up being firing pin length.

 

[Straightshooter1]

OK. I just want to thank everyone here for their input. It's all very much appreciated.

So, I've gone and mounted my new barrel (though a longer and heavier one) and am getting much improved results. I haven't yet determined if the spring has been the issue at all, but will see as I do a little more testing with this new barrel.

 

[clowdis]

The new barrel should help for sure. As to your firing pin spring, I have had misfires with CCI450 primers in 3 different actions, Barnard, Remington, and RPA. All other primers are fine.