Shoulder bumping-HELP

[bigedp51]

Firing pin is not causing the hard bolt lift. If everything else is OK switching to a harder primer can fix that many times.

The primer flowing around the pin is a sign of high pressure.

3rd full power firing you would be getting max expansion on the case. Measure unfired and fired about .250 above extractor rim to see difference. Especially key on brass hard to extract. Chances are here is your problem.

Then check resized brass and see how much sizing you are getting.

A Remington 700 bolt face isn't a sign of high pressure, because the bevel cut in the firing pin hole allows the primer to flow into it.

And over pressure isn't the problem on my Savage rifles because the firing pin hole in the bolt face is slightly over sized and soft primers flow around the smaller firing pin.

 

[bigedp51]

I shoot a 300 ultra mag that I'm starting to have troubles with. I had a smith do some stuff to it and develop a good load for it. I've followed his load recipe for THIS rifle with exactness. Lately it's been giving me troubles with extraction. I never looked at shoulder bumping and wonder if this is the issue. I got a Hornady headspace/"should bump gauge" and have been measuring cases. They are all over the place. I use Redding dies, so I figured they'd be spot on.
Question now...how does a guy measure them accurately when there is that little ring around the primer sticking up? I understand that between .001-.002 is the happy spot from what I've read and so I want to deprime the case without sizing it so it can be measured correctly.
Any advice would be great. If someone is in the Idaho Falls area, I'd be more than happy to come over and be shown a thing or two.

1. You may not be bumping the shoulders back far enough.
2. When full length resizing pause at the top of the ram stroke for a few seconds. This will reduce brass spring back and make your cartridge headspace more uniform.
3. Lifting the bolt is primary extraction and should break the case free of the chamber walls. And pulling the bolt handle back should be easy.
4. If you are having hard bolt lift it may be a sign of high pressure or soft brass. Meaning Lapua brass has the hardest base of all commercial brass.

Below as a example .223/5.56 rockwell hardness just above the exactor groove.

TEST RESULTS
Using Rockwell hardness standards (.062″x100kg, Rockwell "B"), the brass measured as follows:
LC 2008 = 96
Lapua 223 Match = 86
Winchester 223 = 69
Remington "R-P" = 49

http://bulletin.accurateshooter.com...r-brass-5-56-and-223-rem-base-hardness-tests/


If the problem is pressure related read the link below. Just remember the base expansion is related to how hard the brass is. And Lapua brass would show less expansion than a Remington case at the same chamber pressure.

Simple Trick for Monitoring Pressure of Your Rifle Reloads | Hodgdon Reloading

 

[Stavi300RUM]

1. You may not be bumping the shoulders back far enough.
2. When full length resizing pause at the top of the ram stroke for a few seconds. This will reduce brass spring back and make your cartridge headspace more uniform.
3. Lifting the bolt is primary extraction and should break the case free of the chamber walls. And pulling the bolt handle back should be easy.
4. If you are having hard bolt lift it may be a sign of high pressure or soft brass. Meaning Lapua brass has the hardest base of all commercial brass.

Below as a example .223/5.56 rockwell hardness just above the exactor groove.

TEST RESULTS
Using Rockwell hardness standards (.062″x100kg, Rockwell "B"), the brass measured as follows:
LC 2008 = 96
Lapua 223 Match = 86
Winchester 223 = 69
Remington "R-P" = 49

http://bulletin.accurateshooter.com...r-brass-5-56-and-223-rem-base-hardness-tests/


If the problem is pressure related read the link below. Just remember the base expansion is related to how hard the brass is. And Lapua brass would show less expansion than a Remington case at the same chamber pressure.

Simple Trick for Monitoring Pressure of Your Rifle Reloads | Hodgdon Reloading

I'll have to give both those articles a good read. Thank you for the advice!

 

[ShootnMathews]

How do you clean your brass?

If you media tumble it sometimes a residue can build up inside the case while the outside looks all shiny. This can effectively reduce the case capacity causing a pressure spike. Ultrasonic cleaning or stainless tumbler media are the best ways to clean inside the case.

 

[Stavi300RUM]

How do you clean your brass?

If you media tumble it sometimes a residue can build up inside the case while the outside looks all shiny. This can effectively reduce the case capacity causing a pressure spike. Ultrasonic cleaning or stainless tumbler media are the best ways to clean inside the case.

I use tumbling media. Didn't think about it building a residue. I'll have to get my friend to tumble some for me.

 

[rcoody]

I use tumbling media. Didn't think about it building a residue. I'll have to get my friend to tumble some for me.

are you finding that when you seat your primers that your primer pockets are not as tight as they originally were?

300 rum is very much overbore. could be killing your brass with three loadings? if so I believe I would back off a bit.

 

[ShootnMathews]

I use tumbling media. Didn't think about it building a residue. I'll have to get my friend to tumble some for me.

Look inside a few cases with a flashlight. In my overbore cartridges I've found that tumbling media can build up a residue with some types of powder. In fact I just went through this with one. I used an ultrasonic cleaner to clean them and was blown away at how thick the residue layer had became. The powder I was using is known to be a little dirtier powder. Still didn't expect it to do that. Anyways, peek inside with a light.

 

[rcoody]

Look inside a few cases with a flashlight. In my overbore cartridges I've found that tumbling media can build up a residue with some types of powder. In fact I just went through this with one. I used an ultrasonic cleaner to clean them and was blown away at how thick the residue layer had became. The powder I was using is known to be a little dirtier powder. Still didn't expect it to do that. Anyways, peek inside with a light.

yep

I started using an ultrasonic after I started seeing big flakes of powder residue coming out of my cases in the tumbler. Figured it couldn't hurt to have them clean inside and out.

but with just 3 firings I wouldn't expect that to be the problem.

 

[Stavi300RUM]

yep

I started using an ultrasonic after I started seeing big flakes of powder residue coming out of my cases in the tumbler. Figured it couldn't hurt to have them clean inside and out.

but with just 3 firings I wouldn't expect that to be the problem.

I'll give that a try today and see what turns up. Thanks all for the input!

 

[DogDown1994]

Hello stavi. If you havnt solved your issue yet, you may try coating the casings that are hard to eject with a black sharpee untill it is completely black. Then chamber the case and eject like you normally would. This process may be able to show you exactly where your case is binding. Ive used this process when i first started loading for 257wby and 338Lm. I came to find that i wasnt rezing the case down far enough and had to really crank down on the dies. It worked for my 257 but when i had my 338 dies completely bottomed and still had a hard time chambering i had to file down the the shell holder ever so slightly in order to get a tick more of the case resized. It worked well for me and i havnt had an issue since. Best of luck to you.

_dogdown

 

[philipbrousseau]

are you seeing any indication of brass flow on the face of the cartridge head. on a rem 700 the brass will flow into the ejector hole and when you lift the bolt there will be a round shiny spot where the bolt shaved off the brass that protruded into ejector hole.

 

[Stavi300RUM]

are you seeing any indication of brass flow on the face of the cartridge head. on a rem 700 the brass will flow into the ejector hole and when you lift the bolt there will be a round shiny spot where the bolt shaved off the brass that protruded into ejector hole.

I have the ever so slightly hint of an ejector mark, but that was present even when the gunsmith was doing load development. He said it will be normal. And when I say slight hint, I mean it is extremely hard to see it. I measured some fired rounds and found it was setting them back more than .001-.002. More like .015. That could be the issue. I haven't been able to shoot or prep some brass and load up a few to see if I've found the problem yet. Classes started up again, and I have a heavy credit semester if I want to graduate and get to Chiropractic school by July.

 

[bigedp51]

If you have a hint of ejector mark it means you have brass flow witch means the base of the case may have expanded. You need to measure a new unfired case and one of the problem cases.

Simple Trick for Monitoring Pressure of Your Rifle Reloads
Simple Trick for Monitoring Pressure of Your Rifle Reloads | Hodgdon Reloading


Hard bolt lift indicates the brass is not springing back from the chamber walls, indicating high chamber pressure, and this varies with brass hardness.


We also live in a plus and minus manufacturing world and you may have a small diameter chamber or a large diameter die, or both.


On a semi-auto rifle it is recommended the fired case be .003 to .005 smaller in diameter after full length resizing as an example for reliable extraction. Meaning your die may not be sizing the case small enough in diameter.


You could try pausing at the top of the ram stroke for a few seconds and this will reduce brass spring back after sizing. Or try another resizing die, "BUT" you would be surprised how much dies vary in internal dimensions. I have a Lee .223 full length die that sizes the case smaller in diameter than my RCBS small base die does.

 

[Stavi300RUM]

If you have a hint of ejector mark it means you have brass flow witch means the base of the case may have expanded. You need to measure a new unfired case and one of the problem cases.

Simple Trick for Monitoring Pressure of Your Rifle Reloads
Simple Trick for Monitoring Pressure of Your Rifle Reloads | Hodgdon Reloading


Hard bolt lift indicates the brass is not springing back from the chamber walls, indicating high chamber pressure, and this varies with brass hardness.


We also live in a plus and minus manufacturing world and you may have a small diameter chamber or a large diameter die, or both.


On a semi-auto rifle it is recommended the fired case be .003 to .005 smaller in diameter after full length resizing as an example for reliable extraction. Meaning your die may not be sizing the case small enough in diameter.


You could try pausing at the top of the ram stroke for a few seconds and this will reduce brass spring back after sizing. Or try another resizing die, "BUT" you would be surprised how much dies vary in internal dimensions. I have a Lee .223 full length die that sizes the case smaller in diameter than my RCBS small base die does.

I'll have to give it a go this weekend and see what I come up with. I'll try what you were saying by measuring a new unfired case to the ones I have fired and see what's up. May just have to toss the ones that cause me issues.