Can undersized brass cause light primer strikes?

[jimbo88mm]

I took a new rifle out to the range today, a savage 112 in 338 lapua.

Ammo was mid ranged reloads
Brass was unfired peterson brass.

Over the 20 rounds I took out today, 5 failed to fire. Each round that failed to fire had a light primer strike.

Load: 86.5gr of H1000 with a 285gr amax

The way I see it, there could be a number of possibilities:

1) Issue with the trigger itself. I left it how it came from the factory (1.5 LB)
2) Something impeding the firing pin enough to slow it down
3) Firing pin protrusion too short.
4) Bad lot of primers? These were CCI 250 (seems unlikely since the affected rounds had smaller indents than the fired rounds)

I am looking into these possibilities but one possible explanation that I came across on the web is undersized brass.

If the Perterson brass had the shoulder pushed just a tiny bit to far, or if the chamber in the rifle were a slighty out of spec, could that result in light primer strikes?

The rounds that it did fire shot extremely well. My goal today was to just zero the rifle.




Update:

I don't believe the new Peterson brass was undersides. I took measurements of both fired and virgin cases using the hornady comparator. They all had the same measurement.

I took the rifle out yesterday. I had 20 loads with Winchester LRM primers and 15 loads with the same CCI 250s. All of the Winchester loads fired. With the CCIs, I had 3 failed to fire. I'll upload a photo of the primers tonight. What I've been calling a light primer strike may not really be a light primer strike.

At this point I'm suspecting the primers.

 

[Mozella]

New rifle............. new brass. ??? It could be that the brass, or at least some of the brass, is a little short and your head space is a little excessive. That could certainly cause the problem you're observing. If you don't have the tools on hand to set your headspace, chances are very good someone who shoots at your local range does. They're not real expensive and hard to abuse, so it's likely you can borrow them. You can learn everything you need to know about setting Savage headspace on the Internet.

You'll need a barrel nut wrench, a barrel vise, and a go gauge at a minimum. I set my headspace so that the bolt closes without any force on the go gauge. Then I put a layer of clear packing tape on the back of the go gauge and make sure the bolt won't close without forcing it. Take your time.

 

[Homerange]

Over the 20 rounds I took out today, 5 failed to fire. Each round that failed to fire had a light primer strike.



The way I see it, there could be a number of possibilities:


2) Something impeding the firing pin enough to slow it down

Strip and clean any factory gunge from inside the bolt.
Had the same problems with a Tikka recently and cleaning of the bolt fixed it.

 

[dkhunt14]

CCI primers have harder thicker cups. It takes more to get them to go off. If any other problems, like new brass with short headspace or weak firing pin strike will cause this. I would disassemble and clean the bolt like recommended above. Someone should be able to measure your protrusion for you. Did you try hitting them the second time? Another thing that helps with new brass is putting the bullets in the lands a little. Once they are fired the headspace will get longer and when you resize, don't bump them more then a .001. Matt

 

[NorCalMikie]

It could be that the brass, or at least some of the brass, is a little short and your head space is a little excessive.

Pull the bullets out a bit to make the OAL longer and jammed into the lands. That will hold the case head back against the bolt face. If that works, make sure you don't push the shoulders back too far or you'll be in the same situation all over again. If the fired brass will chamber without excessive force needed, size the neck, load it up and go shooting.

 

[hogpatrol]

What Matt posted. ^^^^^^

 

[Drop Port]

Check base to shoulder measurement on a fired case against one with a light hit, the fired case might not be fully formed but it beats speculation every time.

 

[tuttlefarm]

Side pressure on the accu-trigger will give light strikes.....

 

[Bart B.]

Side pressure on the accu-trigger will give light strikes.....

Does Savage know about this problem? I had never heard of this situation with any trigger, but after searching, it does show up.

There's been a generally accepted standard for centerfire rifles' striker pin to stick out past the bolt face at least .055" and .060" to .065" is better. Most large rifle primers need about .020" deep dent to fire, but a bit more to fire uniformly. Yes, primers have extreme spread and standard deviation.

Yes, too much shoulder setback can cause light primer strikes. When you subtract FL sized case headspace from chamber headspace, the answer is head clearance from bolt face to case head when the pin starts denting flush seated primers. Add this to that .020" minimum dent depth and you're on the path to knowledge to understand this conundrum of mechanics.

Note: case heads are not held against the bolt face by the extractor when fired.

 

[260 Ravage]

The same scenario took place on a benchrest gun during a match. Later I discovered that my priming tool developed a glitch. Many loaded rounds had primers that were not seated to their 'dead stop' depth. Replaced my old primer tool and never had it occur since.

 

[retired]

primers should be seated to the bottom of the primer pocket and then given a small crush in place..say about .002.
any primer not seated to the bottom of the primer pocket will likely give irratic ignition.
the firing pin will try to move the primer before firing it.
there is a reason to uniform primer pockets for competition.

The same scenario took place on a benchrest gun during a match. Later I discovered that my priming tool developed a glitch. Many loaded rounds had primers that were not seated to their 'dead stop' depth. Replaced my old primer tool and never had it occur since.

 

[BoydAllen]

Every single short range benchrest competitor that I know seats primers by feel.
I am always amused when people say that primers need to be seated to a particular depth (dimension). Go to a benchrest match and do two things, pay attention to what they are doing, and how well the best of them shoot. Can you do as well? If you think that you can, shoot a match, and see if you are correct. What ever happens, I predict that you will have a good time.

 

[retired]

go ask bart....go read his post on benchrest central.

just remember not "Every single short range benchrest competitor" wins.
the people with consistency are the consistent winners

Every single short range benchrest competitor that I know seats primers by feel.
I am always amused when people say that primers need to be seated to a particular depth (dimension). Go to a benchrest match and do two things, pay attention to what they are doing, and how well the best of them shoot. Can you do as well? If you think that you can, shoot a match, and see if you are correct. What ever happens, I predict that you will have a good time.

 

[retired]

here is the link

http://benchrest.com/archive/index.php/t-93967.html

Every single short range benchrest competitor that I know seats primers by feel.
I am always amused when people say that primers need to be seated to a particular depth (dimension). Go to a benchrest match and do two things, pay attention to what they are doing, and how well the best of them shoot. Can you do as well? If you think that you can, shoot a match, and see if you are correct. What ever happens, I predict that you will have a good time.

 

[fyrewall]

Here are my experiences with light primer strikes:

Some did fire some did not, probably some of the brass had excessive head space, if so I would be POed since the new Peterson .338 Lapua costs so much and for that cost near perfection should occur.

I have had weak pin hits caused by inadequate spring tension causing variation in pin hits - good spring, adequate protrusion but not enough compression to go bang.

A wild guess might be lots of cold congealed glop caused the inadequate strike - this type of event occurs every year in the frozen north at the start of deer season. I have flushed out numerous stripped bolts with boiling hot soap & water and a pipe cleaner.

A contaminated primer would not go bang but should show a good deep dent if everything else was OK.

The theory that some primers are "harder" than others need more work - this needs more documentation including measurements & actual hardness tests like embedding a small steel ball into the primer. Until I see something like that I will assume that all primers of the same type have equal hardness and equal cup thickness.

 

[BoydAllen]

Information about differences in primer cup thickness has been published many times. All you would have to have done was to look.

 

[retired]

it was about seating to the bottom with a small crush....

Information about differences in primer cup thickness has been published many times. All you would have to have done was to look.

 

[dkhunt14]

The theory that some primers are "harder" than others need more work - this needs more documentation including measurements & actual hardness tests like embedding a small steel ball into the primer. Until I see something like that I will assume that all primers of the same type have equal hardness and equal cup thickness.

The charts have been posted on here many times. Just Google it. Some of the CCI primers have thicker cups. Matt

 

[Webster]

I took a new rifle out to the range today, a savage 112 in 338 lapua. Over the 20 rounds I took out today, 5 failed to fire. Each round that failed to fire had a light primer strike.

Isn't all factory loaded ammo under sized? It always goes off?

 

[fyrewall]

The charts have been posted on here many times. Just Google it. Some of the CCI primers have thicker cups. Matt

**********

Information about differences in primer cup thickness has been published many times. All you would have to have done was to look.

Thank you for your interest in my post - am committed to providing factual information - please allow me to comment

Here are my experiences with light primer strikes:

The theory that some primers are "harder" than others need more work - this needs more documentation including measurements & actual hardness tests like embedding a small steel ball into the primer. Until I see something like that I will assume that all primers of the same type have equal hardness and equal cup thickness.

***********

It would appear the key word in my post was, "type", small words like this can be easily overlooked and might be a reason to create a separate post having a separate heading. Yes, primers of the same manufacturer commonly have different thicknesses. But in this particular thread we are concerned with the mighty high pressure .338 Lapua Magnum.

For Boyd & Matt, to direct this post to a more certain outcome I might ask what kind or type primer might be used in the .338 Lapua magnum. A CCI 300? no! wrong type because this is a pistol primer intended for pistols. The .338 Lapua uses large rifle primers, a different type of primer.

check this out

www.accurateshooter.com/technical-articles/primers-and-pressure-analysis/

I am not a primer expert and apparently my knowledge is open to a general critique on the particular subject being type of primer in this case large rifle then more particularly a CCI 250 primer. I see a common thickness of .027 for all primers of the same type being large rifle.

For Boyd & Matt, actual measurements of the same type of primer used in the .338 Lapua magnum might be offered as a response. In fact I did look and discovered that all large rifle primers, same type, were of the same cup thickness.

All I can say is read stuff real careful.