Pressure signs on 7mm SAUM... is there something else causing this?

[bmorris57]

Hey folks... looking for some input on some pressure signs that have me a bit confused.

If you look at the Norma case you'll see extractor marks... this was at entry level with 60.5 gr of RL26 and a 168 Berger Classic Hunter. My COAL is 2.783 with These bullets to the lands. (CBTO = 2.256 ) I loaded .010 off the lands @ a CBTO of 2.245. I was concerned about early signs of pressure.

This morning I shot some factory Remington 160 gr partitions. See the RP case pic. I am seeing the same extractor marks... my experience with factory ammo has always been that they are conservative... so I am now wondering if this is related to another issue and no necessarily high pressure. Thoughts?

The rifle is a stock Remington 700 in 7mm SAUM.

 

[cohunt]

some times factory loads are waaaay short-- this "induced headspace" can cause "false" pressure signs such as flat primers, ejector marks, etc -- do you have a comparator to measure what the factory rem brass measures before and after firing?

your pics are blurry for me, are those extractor marks or ejector marks? if they are ejector marks are they just marks or are they swipes?

rem 700's are known to have oversize firing pin holes in the bolts which can cause a false "cratering" of the primer also

factory brass is notorious for being under size too

 

[bmorris57]

Looks like the unfired factory is 1.639 and the fired case is 1.648, about .009 growth.

Here is another pic hopefully better quality.

The marks are a bit wider so they look like a swipe. 60.5 is almost 2 grains below where Berger tested with this 168 gr CH bullet.

 

[EddieHarren]

I suspect a "little too long" ejector or a rough ended ejector. Those fired primers are definitely not showing any excess pressure signs.

 

[lancetkenyon]

Did you run them over a chronograph? That is a very valuable tool. A tight bore will increase velocity and pressure even with moderate loads. I have found a few rifles that take 5-6 full grains less powder with all other components being the same (even the same lots) to get similar velocities as most other rifles in the same chambering.

 

[bmorris57]

As a matter of fact I do have speed data... I have a LabRadar unit. The 6 rounds of Factory Remington 160 gr Partitions. Avg Speed was 2986, Hi was 3040, Lo was 2935. In order, 1) 3040 2) 3010 3) 3024 4) 2935 5) 2962 6) 2945. All of these show the ejector marks... ES was a whopping 105 and the SD was 44.1. I see the ejector marks on the RL 26 loads even @ 60.5, with Norma Brass... The H1000 loads, even up to the Berger recommended Max load show no Marks. The H1000 loads were first firing using ADG brass... I am using the BR2 primers, I am planning to switch to Federal Magnum primers...

 

[Flintlock]

I guess I'm just dense but I don't see what you are referring to. My 284, 7-08 and 300 SAUM brass all look like that from my Remington XP 100's. Is this something you just noticed or has it been happening since you got the rifle?
Mike

 

[25WSM]

Those are definatly swipe marks. Take the ejector out and take some fine sandpaper and put a little square piece over the hole and put a pencil with eraser on it and twist it a few times. Should be enough to remove the sharp edge. If you look close with a magnifier before and after you will see the improvement.
I fix this problem all the time.
Shep

 

[Shortmagman]

I had a similar problem with my Rem 700 in 7mm SAUM. I took it to a gunsmith and he found I had a extractor problem. I don't know what he did but he fixed it with no difficulties.25WSM may have the solution.

 

[25WSM]

I'm a 30 yr working Smith and have seen this so many times. Never seen an extractor make this mark. Extractor usually makes marks on the rim. Your problem is definitely ejector. Fix it in less than 5 minutes. Shep

 

[25WSM]

One other cause could be the ejector is not going flush with the bolt face. To check this put bolt in a vise and push the ejector down all the way. Then check if it sits flush or below or above the bolt face. As long as it doesn't sit above its not a length issue. If it is too long remove it and cut the pin slot longer on the top. This will let it sit lower. Very small amount is all that is required.
Shep

 

[bmorris57]

I'm a 30 yr working Smith and have seen this so many times. Never seen an extractor make this mark. Extractor usually makes marks on the rim. Your problem is definitely ejector. Fix it in less than 5 minutes. Shep

Those are definatly swipe marks. Take the ejector out and take some fine sandpaper and put a little square piece over the hole and put a pencil with eraser on it and twist it a few times. Should be enough to remove the sharp edge. If you look close with a magnifier before and after you will see the improvement.
I fix this problem all the time.
Shep

Shep - I mis-spoke in my original post. I said extractor but meant ejector. The marks line up precisely with the ejector. I looked at all of my fires brass with a magnifying glass and on some it is a complete circle. I will do as you described and clean-up the ejector.

Thanks for the input... much appreciated!

 

[bmorris57]

I guess I'm just dense but I don't see what you are referring to. My 284, 7-08 and 300 SAUM brass all look like that from my Remington XP 100's. Is this something you just noticed or has it been happening since you got the rifle?
Mike

It's been happening since I had the rifle. I just noticed it on factory Ammo...

 

[25WSM]

Typically it's just the edge around the hole in the bolt has a sharp edge. Get rid of the sharp edge get rid of the problem.
Shep