Pressure signs with factory ammo

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Oct 13, 2019
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Raleigh, NC
I was not complete on the statement about the high vibrations that can occur in vehicles. If the granules in the cartridge is subjected to high vibrations, the micro thin coatings that slow down the burn rate, on the surface could be pulverized off the surface just like cleaning corroded brass. Wash board roads can create high cyclic rates of vibration.
 

WGTX

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He can check his headspace by comparison of his unfired brass to his fired brass.
OP
For what it’s worth. Without knowing the throat and barrel conditions now. You might be going down a rabbit hole and thus causing further unnecessary throat wear.
I’d start there. Just my 2c
2.575- 2.584 ,length is all I can measure
 

WGTX

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May I suggest....Take 5 rounds reduce OAL 10 thousandths, shoot a group , take another 5 rounds reduce another 10 thousandths, total of 20 thousandths. Take a look at the brass.
HTH
I need to order dies, going to start looking.
 

Bob Wright

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Litchfield Park, Az.
The ''ring'' after 15 rounds.
Where is this photo taken in the barrel?
The carbon ring that is discussed is the area where the cartridge neck ends in the chamber and continues to the start of the leade.
What this picture shows is a black ring somewhere down stream from the chamber deep into the rifling.
If it really is this, it looks like a reamer issue as in it picked up a chip and gouged the bore. Not a pressure issue but one issue that might degrade accuracy. Can you clarify?
 

Gcan

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Sep 29, 2017
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Like the title says factory ammo, I do have questions related to reloading though. Little background, very new to reloading, I’ve successfully made a few hundred .223 & .308 lately just tryin to learn the basics. The issue/questions are about a 26 Nosler that I traded for. It supposed has low round count but who knows. Came with 80 rounds of 140 ab and 60 of 142 ablr. I have had it quite a while but had only shot a few rounds through it about a year ago and didn’t think much about it. So forward to now and with the limited knowledge I’ve gained (a lot of it from this site) made me question what I saw yesterday from this factory ammo. First picture is the 142s, second the 140s. The 142s cbto averaged 2.706, the 140s 2.766. I pulled one of the 142s to measure with, I was surprised how scared it was when I did, I’ve only pulled a couple .223s that I’ve loaded,they didn’t look like this (3rd pic), had 71.1gr of whatever Nosler loads. So using the Hornady tool jammed all the way I come up with 2.839 and just touching 2.703. This is where the questions start, I’m unsure of my process measuring, jammed all the way seems simple enough, just touching much harder to be consistent. I started out yesterday with a clean, pretty close to bare, dry bore and chamber. All rounds resulted in stiff bolt lift, not have to death grip or pick up the rifle but definitely stiff. Would it make sense to pull/reseat bullets in the factory ammo for some jump ? Or dump the powder and try something different ? BTW velocity average was 3251 and of the powders listed in the Nosler manual 71.1 should be pretty mild. With a bore scope I can see what maybe a carbon ring starting ? after 15 rounds that wasn’t there when I started. Am I overthinking this ? Couple years ago I’d have looked at the brass and thought that’s weird and kept right on stuffing and shooting, lol. Any advice is appreciated. Hope the pictures load, my sat internet is pretty lame.

Haven’t read all the replies but here are my thoughts.
1. Bad out of spec headspace.
if you have hornady comparator compare growth of fired case mid shoulder to base to a new u fired caee. If you have excessive growth that’s a problem. Is it a barrel nut gun?

2. Custom chamber throated for specific bullet. Custom builds are often throated for a specific bullet ogive to rifling dimension. I’m not clear on how you checked the throat to rifling length. Its a learning process to feel the contact. Small bullets with long noses can be difficult. Do it a bunch of times and write measurements down. You should see a group of similar numbers That gives you an idea. Use the shortest dimension. Then try to feel the lightest contact near that number. You will seldom feel a rock wall.

In some cases with OEM/factory loaded rounds, bullets may be contacting or jamming into the rifling on

guns. This doesn’t allow any jump and can cause serious pressure spikes. Ive seen chambers built for lighter rounds with a shorter throat jam when longer bullets were used.

3. Hv seen chambers that case would not lock up in. This will often give you extractor and even bolt lug marks but not flatten primers.

4. Chamber neck ID might be for turned/tight neck cases and not releasing bullet. To bad you don’t have extreme spread from chrono on strings. Big numbers with factory ammo might suggest the bullet is getting caught up somewhere.


I wouldn’t shoot it till I had some answers. Headspace first. If you don’t have a field or no go gauge, pull the bullet from a new round. Empty powder. Strip the bolt if you can (springs, pin, extractor”.

Put a layer of scotch tape on end of case. (.0015” thick usually) Close the bolt. Keep count of layers and keep adding
until the bolt face hits the tape. If you end up with ten or more layers of tape you have a problem. 8 layers are a problem. Custom guns are usually headspaced Very close on the go gauge. If you have a barrel nut gun it might have just been set up incorrectly.

find a gunsmith.
g
Like the title says factory ammo, I do have questions related to reloading though. Little background, very new to reloading, I’ve successfully made a few hundred .223 & .308 lately just tryin to learn the basics. The issue/questions are about a 26 Nosler that I traded for. It supposed has low round count but who knows. Came with 80 rounds of 140 ab and 60 of 142 ablr. I have had it quite a while but had only shot a few rounds through it about a year ago and didn’t think much about it. So forward to now and with the limited knowledge I’ve gained (a lot of it from this site) made me question what I saw yesterday from this factory ammo. First picture is the 142s, second the 140s. The 142s cbto averaged 2.706, the 140s 2.766. I pulled one of the 142s to measure with, I was surprised how scared it was when I did, I’ve only pulled a couple .223s that I’ve loaded,they didn’t look like this (3rd pic), had 71.1gr of whatever Nosler loads. So using the Hornady tool jammed all the way I come up with 2.839 and just touching 2.703. This is where the questions start, I’m unsure of my process measuring, jammed all the way seems simple enough, just touching much harder to be consistent. I started out yesterday with a clean, pretty close to bare, dry bore and chamber. All rounds resulted in stiff bolt lift, not have to death grip or pick up the rifle but definitely stiff. Would it make sense to pull/reseat bullets in the factory ammo for some jump ? Or dump the powder and try something different ? BTW velocity average was 3251 and of the powders listed in the Nosler manual 71.1 should be pretty mild. With a bore scope I can see what maybe a carbon ring starting ? after 15 rounds that wasn’t there when I started. Am I overthinking this ? Couple years ago I’d have looked at the brass and thought that’s weird and kept right on stuffing and shooting, lol. Any advice is appreciated. Hope the pictures load, my sat internet is pretty lame.
Like the title says factory ammo, I do have questions related to reloading though. Little background, very new to reloading, I’ve successfully made a few hundred .223 & .308 lately just tryin to learn the basics. The issue/questions are about a 26 Nosler that I traded for. It supposed has low round count but who knows. Came with 80 rounds of 140 ab and 60 of 142 ablr. I have had it quite a while but had only shot a few rounds through it about a year ago and didn’t think much about it. So forward to now and with the limited knowledge I’ve gained (a lot of it from this site) made me question what I saw yesterday from this factory ammo. First picture is the 142s, second the 140s. The 142s cbto averaged 2.706, the 140s 2.766. I pulled one of the 142s to measure with, I was surprised how scared it was when I did, I’ve only pulled a couple .223s that I’ve loaded,they didn’t look like this (3rd pic), had 71.1gr of whatever Nosler loads. So using the Hornady tool jammed all the way I come up with 2.839 and just touching 2.703. This is where the questions start, I’m unsure of my process measuring, jammed all the way seems simple enough, just touching much harder to be consistent. I started out yesterday with a clean, pretty close to bare, dry bore and chamber. All rounds resulted in stiff bolt lift, not have to death grip or pick up the rifle but definitely stiff. Would it make sense to pull/reseat bullets in the factory ammo for some jump ? Or dump the powder and try something different ? BTW velocity average was 3251 and of the powders listed in the Nosler manual 71.1 should be pretty mild. With a bore scope I can see what maybe a carbon ring starting ? after 15 rounds that wasn’t there when I started. Am I overthinking this ? Couple years ago I’d have looked at the brass and thought that’s weird and kept right on stuffing and shooting, lol. Any advice is appreciated. Hope the pictures load, my sat internet is pretty lame.
i had a CA rifle in 300RUM. The gun would split cases. Id get the bottom half of the case that looked like a 45 acp and have to dig out the remainder. Had Dave Tooley confirm my check, the headspace was .014” over the Saami max.

So CA screwing up a headspace is not unheard of. Chk the growth on your fired cases compared to the unfired. Mine were growing about .025”. Gun would fire closing the bolt. Id look there first.

id Also chk the depth of throat. Bullets without jump can show pressure with near min loads. I see this in custom guns that were throated for a specific bullet. Often if throated for lighter bullets, longer heavier rounds hit the lands.
if it were a custom chamber Ive seem tight necks show pressure with factory (unturned)cases.
 

WGTX

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Dec 31, 2016
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48
Appears to be the cartridge brass length, where you should also measure to the shoulder datum with a comparator. Both are important initial reloading measurements.
Where is this photo taken in the barrel?
The carbon ring that is discussed is the area where the cartridge neck ends in the chamber and continues to the start of the leade.
What this picture shows is a black ring somewhere down stream from the chamber deep into the rifling.
If it really is this, it looks like a reamer issue as in it picked up a chip and gouged the bore. Not a pressure issue but one issue that might degrade accuracy. Can you clarify?
Yes those are fired and unfired case lengths. I will look into a comparator That ring was 1''-2'' into the rifling, wiped right out so powder I guess. I didn't see anything in the chamber/leade area but I'll look again. Accuracy was decent, 3 shot pic in first post. I'll try to get a better picture of the chamber/bore this evening, still figuring out how to get the best pics with the borescope. Thanks.
 

WGTX

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Joined
Dec 31, 2016
Messages
48
i had a CA rifle in 300RUM. The gun would split cases. Id get the bottom half of the case that looked like a 45 acp and have to dig out the remainder. Had Dave Tooley confirm my check, the headspace was .014” over the Saami max.

So CA screwing up a headspace is not unheard of. Chk the growth on your fired cases compared to the unfired. Mine were growing about .025”. Gun would fire closing the bolt. Id look there first.

id Also chk the depth of throat. Bullets without jump can show pressure with near min loads. I see this in custom guns that were throated for a specific bullet. Often if throated for lighter bullets, longer heavier rounds hit the lands.
if it were a custom chamber Ive seem tight necks show pressure with factory (unturned)cases.
Case growth looks like .009, I don’t know what is normal. That’s just total length of the cases.
 

WGTX

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So I fired a round that was chilled in the fridge, looks the same as the others, cratered primer and swipe. FPS dropped 24, this was with clean, dry bore/chamber. I bought a Hornady headspace comparator, that case grew .005.
 

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