misfires with Rem 7 1/2 primers

[uncle-buck]

Is this the same rifle you were having misfires with maybe a year ago ?
Have you played with the mainspring at all , meaning trying to lighten the bolt lift ? Just want to eliminate other possibilities besides improper primer seating or excessive shoulder bump .

Good memory. Yes, it is the same rifle.
Haven't adjusted the mainspring yet and will probably switch to CCI small rifle primers if the rifle's head space turns out to be within specs.

 

[NorCalMikie]

More than likely, the head space is off. NOT the head space of the barrel but the size of the cases compared to the chamber. Short brass in chamber, firing pin hits the short case, pushes it forward in the chamber and you get FTF (miss fires). Pull the bullets out a little so you can jam into the lands and increase the OAL of the round. That should hold the case head against the bolt head. Once fired and formed to the chamber, make sure NOT to push the shoulders back too far or you'll be playing the same game again. Reload and go shooting again.

 

[Ggmac]

Good memory. Yes, it is the same rifle.
Haven't adjusted the mainspring yet and will probably switch to CCI small rifle primers if the rifle's head space turns out to be within specs.

I forgot to ask if you changed stocks ? That could also influence the firing pin fall . But I think you have it figured out with primers .
Please keep us posted .
Gary

 

[uncle-buck]

I forgot to ask if you changed stocks ? That could also influence the firing pin fall . But I think you have it figured out with primers .
Please keep us posted .
Gary

Did not change stocks.

I did load another 15 rounds using the Rem 7 1/2 primers and 20 rounds using CCI 400 primers.

Had one misfire with the Remington primers, and none with the CCIs.

FWIW, the Remington primers produced better groups at 100 yds than the CCIs - using the same LC cases, powder charge, hunting bullet, and seating depth. Probably has something to do with the brisance of the primers and the type of powder I was using (N540).

Go, No Go, and Field gauges are scheduled to arrive in a week or so.

 

[Uncle Ed]

CHOOSING THE RIGHT PRIMER - A PRIMER ON PRIMERS
http://www.sksboards.com/smf/index.php?topic=56422.0

CUP THICKNESS

"Different primers have different cup thicknesses. You can see the importance of cup thickness when primers are considered for semiautomatic rifles that have free-floating firing pins. This topic is discussed in greater detail in the post "MILSPEC PRIMERS FOR SEMI-AUTOS FAQ AND INFO" that follows the primer chart.

Handgun primers have thinner cups than rifle primers, making them easier to ignite with the typically weaker firing pin fall of handguns. Small Pistol primer cups are .017" thick, while Large Pistol primer cups are .020" thick. This is the reason using handgun primers in .22 Hornet rifle loads sometimes results in pierced primers in some guns. Obviously their substitution in the high pressure .223 Remington would not be a good idea."

The CCI 400 primers have a cup thickness of .020 and the Remington 7 1/2 have a cup thickness of .025. And the CCI 400 rifle primers are identical to the CCI 550 Small Pistol Magnum and designed for lower pressure cartridges.

I buy bulk once fired Lake City 5.56 cases and use Remington 7 1/2 primers in my Savage 223 and two AR15 rifles and never had a primer fail to fire.

You also were questioned about your firing pin spring in a earlier post by Ggmac. You are not having problems with the CCI 400 primers with a thinner primer cup and this is telling you something.

 

[blvedere]

I have had small rifle primers ftf in cold weather. I have found that temps below 40* acerbate the problem. This is with Lapua brass, brass with larger flash hole do not have this problem.

 

[uncle-buck]

CHOOSING THE RIGHT PRIMER - A PRIMER ON PRIMERS
http://www.sksboards.com/smf/index.php?topic=56422.0

CUP THICKNESS

"Different primers have different cup thicknesses. You can see the importance of cup thickness when primers are considered for semiautomatic rifles that have free-floating firing pins. This topic is discussed in greater detail in the post "MILSPEC PRIMERS FOR SEMI-AUTOS FAQ AND INFO" that follows the primer chart.

Handgun primers have thinner cups than rifle primers, making them easier to ignite with the typically weaker firing pin fall of handguns. Small Pistol primer cups are .017" thick, while Large Pistol primer cups are .020" thick. This is the reason using handgun primers in .22 Hornet rifle loads sometimes results in pierced primers in some guns. Obviously their substitution in the high pressure .223 Remington would not be a good idea."

The CCI 400 primers have a cup thickness of .020 and the Remington 7 1/2 have a cup thickness of .025. And the CCI 400 rifle primers are identical to the CCI 550 Small Pistol Magnum and designed for lower pressure cartridges.

I buy bulk once fired Lake City 5.56 cases and use Remington 7 1/2 primers in my Savage 223 and two AR15 rifles and never had a primer fail to fire.

You also were questioned about your firing pin spring in a earlier post by Ggmac. You are not having problems with the CCI 400 primers with a thinner primer cup and this is telling you something.

Good info., thanks for your reply.
Savage sent a new firing pin assembly two years ago and indicated they were drop-in parts.
Are you suggesting that spring tension or firing pin protrusion adjustment may resolve the issue?

 

[Uncle Ed]

Good info., thanks for your reply.
Savage sent a new firing pin assembly two years ago and indicated they were drop-in parts.
Are you suggesting that spring tension or firing pin protrusion adjustment may resolve the issue?

Its one of the first things I would check, some people forget and store their rifles with them cocked and the firing pin spring can become weakened. I have replace many firing pins and springs on my old milsurp rifles and also checked the protrusion.

It could also be as simple as a small piece of brass, dirt, etc inside the bolt causing the problem. The Savage bolt is simple to take apart and all you need is the correct size allen wrench.

As you can see from the video below you might need a left handed allen wrench.

 

[uncle-buck]

Its one of the first things I would check, some people forget and store their rifles with them cocked and the firing pin spring can become weakened. I have replace many firing pins and springs on my old milsurp rifles and also checked the protrusion.

It could also be as simple as a small piece of brass, dirt, etc inside the bolt causing the problem. The Savage bolt is simple to take apart and all you need is the correct size allen wrench.

As you can see from the video below you might need a left handed allen wrench.

I just disassembled the bolt and cleaned the firing pin channel. Did not find any debris. May have to take it to my local gunsmith for further diagnosis and repair.

Thanks for your help.

 

[wkdickinson]

I forgot to ask if you changed stocks ? That could also influence the firing pin fall . But I think you have it figured out with primers .
Please keep us posted .
Gary

Not trying to obtuse or argumentative, but how could changing stocks affect firing pin fall?

 

[tomswede]

Did not change stocks.

I did load another 15 rounds using the Rem 7 1/2 primers and 20 rounds using CCI 400 primers.

Had one misfire with the Remington primers, and none with the CCIs.

FWIW, the Remington primers produced better groups at 100 yds than the CCIs - using the same LC cases, powder charge, hunting bullet, and seating depth. Probably has something to do with the brisance of the primers and the type of powder I was using (N540).

Go, No Go, and Field gauges are scheduled to arrive in a week or so.

Really don’t need those gages, can use shim stock behind the go gage.
I have fired something like 10k plus Remington 7 1/2 BR primers without a single issue.

 

[Ggmac]

Not trying to obtuse or argumentative, but how could changing stocks affect firing pin fall?

On some ( savages ) makes the stock could hit the bolt side bolt release and interfere, slow the fall or stop it completely. Others could bind the trigger and do the same .

 

[D-4297]

Sorry to hear you're having a issue with the 7 1/2 BR primers . When my "comp" primer became no longer available , thanks to King Barack the 1st , I had to find a new one , and the 7 1/2 was recommended . Over 1,500 rounds later , I have not had a single failure-to-fire from a Kelby FTR .308 ...Just a thought , but is your firing pin bushing tight , and concentric ? That can cause issues , especially with small diameter cases . Something else to check ......

 

[uncle-buck]

Update: Received head space gages today. Removed striker pin assembly from bolt and checked the rifle's head space.

Bolt closed on Go Gage and did not close on No Go gage. So the issue is apparently not related to head space.

Upon reassembly of the bolt with the striker pin assembly, I did notice that the pin would slide easily inside the bolt one way, but not when it was rotated 180 degrees.

 

[D-4297]

Think it may be time to consult with a knowledgeable gun-smith regarding my earlier suggestion to have your firing pin checked and F/P bore checked for concentricity . Something is definitely not in alignment someplace in there .
Had similar issues with a competition bolt gun , and had the F/P bushing replaced with a smaller diameter , and two firing pins turned down to match the smaller bushing . Have not had a single hang-fire , misfire , or FTF since . And the primer idents are beautifully symmetrical , too .

Edit : I just went back and looked at the photo's you posted , enlarged to get a clean look . I saw one commonality in all the photos . The strike is "off-center" in almost every , if not all the photos . Same exact thing my one rifle was doing till I had the bolt re-bushed . Now it strikes center every time . Thinking you have some excess clearance in your bolt bushing . It doesn't take much . Just a couple extra thousandths .

 

[uncle-buck]

Final update: I installed a Rifle Basix trigger in the rifle and a 36 lb. Wolff striker spring in the firing pin assembly. Took it to the range today and shot 35 rounds loaded using the Rem 7 1/2 primers. Had zero misfires. I think the heavier spring made the difference.

Thanks for all of the helpful ideas and suggestions.

 

[BenPerfected]

How do you clean your brass?
Ben

 

[uncle-buck]

How do you clean your brass?
Ben

With Flitz in corncob media in a vibratory tumbler.

Why do you ask?

 

[BenPerfected]

Using a tumble washer on all my brass, I recently found a a few cases that were not 100% bone dry & ended up with wet powder at the base of a few cases. It takes very water to kill a primer. Now after washing cases, I double check that all the brass is bone dry. I have a small oven, but prefer using the sun on the driveway.
Ben

 

[uncle-buck]

Gotcha. I place cases in the oven at 250F to make sure they get dry.

The misfires in my rifle were almost certainly due to light primer strikes. A heavier striker spring fixed it and all is well.