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6 Creedmoor, heavy bolt lift

M

Maverick124

Private
Minuteman
Dec 10, 2018
33
12
So I just did a small ladder test with my AT-X. I'm getting heavy bolt lift on what I believe to be pretty mild loads. I'm also noticing weird markings on some of the case shoulders. No real signs of pressure otherwise (please double check me on this). I'll post some pics.

6mm Creedmoor
107 SMKs
Lapua Brass
CCI BR2 small primers
H4350

Charges were 40.5, 40.8, 41.0, 41.2, and 41.4.

Velocities were under 3100 fps

The brass was new and I sized it with a SAC sizing die prior to loading.
 

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Do you get heavy bolt lift with factory Ammo? Berger 105 should chrono around 2950, Hornady 108 Match in the same neighborhood, what are you getting? For me, 41.3 H4350 and 107SMK out of Gen 2 RPR was right at 3030-3050fps.

I've loaded the same as you in my Ruger Predator, Savage 110 Desert Tactical, Gen2 RPR and Custom Shop RPR. Only rifle that has given me the heavy bolt lift was the Predator. I use both Hornady and Lapua brass 90% of the time. Your brass looks better than mine after a round of testing.

Maybe it's your chamber? How far off the lands are you loading? 41.4 H4350 is at the max in a couple books I have.

Sorry I can't be more help...
 
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Different chambers will have different pressures going on. How far out are you seating it? 41.4 isn't what I'd call mild but not super hot depending on your chamber and how far out you're seating it.
 
You have a piece of something in your chamber shoulder area. See mark on brass shoulder. If you have a bore scope you can probably see it. Clean it out and the issue will go away. I had a similar issue after blowing some primers.

Maybe.
 
I my old barrel 1-7 6 in using ADG brass
41.4 H-4350
105 Berger at 30 off no pressure.

New barrel 1-7.5 I am now running
44.0 N560
105 Berger 30 off and no pressure
 
AllenOne1 said:
You have a piece of something in your chamber shoulder area. See mark on brass shoulder. If you have a bore scope you can probably see it. Clean it out and the issue will go away. I had a similar issue after blowing some primers.

Maybe.
Click to expand...
If that mark wasn't there before you shot the brass then as said here, check it out and see if there's something there.
 
Heretic said:
Do you get heavy bolt lift with factory Ammo? Berger 105 should chrono around 2950, Hornady 108 Match in the same neighborhood, what are you getting? For me, 41.3 H4350 and 107SMK out of Gen 2 RPR was right at 3030-3050fps.

I've loaded the same as you in my Ruger Predator, Savage 110 Desert Tactical, Gen2 RPR and Custom Shop RPR. Only rifle that has given me the heavy bolt lift was the Predator. I use both Hornady and Lapua brass 90% of the time. Your brass looks better than mine after a round of testing.

Maybe it's your chamber? How far off the lands are you loading? 41.4 H4350 is at the max in a couple books I have.

Sorry I can't be more help...
Click to expand...
They're seated about .04 back from the lands
 
Last edited:
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Pressure signs are pressure signs. The presence of even one is reason to take a step back. Only saying this because you mentioned "no other pressure signs." Always put this out because people like to use either no signs at all or only a sign or two as a reason to think they are not over pressure. Even no pressure signs doesn't mean you're not in a danger zone.

That being said....

You said you sized these in a SAC die. Have you checked to make sure you're not actually making the cases longer?

If not, I'd check headspace with virgin unsized and virgin sized and make sure you still have room.
 
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Rio Precision Gunwerks said:
Pressure signs are pressure signs. The presence of even one is reason to take a step back. Only saying this because you mentioned "no other pressure signs." Always put this out because people like to use either no signs at all or only a sign or two as a reason to think they are not over pressure. Even no pressure signs doesn't mean you're not in a danger zone.

That being said....

You said you sized these in a SAC die. Have you checked to make sure you're not actually making the cases longer?

If not, I'd check headspace with virgin unsized and virgin sized and make sure you still have room.
Click to expand...
I'll check that. I just loaded a new ladder with lighter charges. I'm going to see if that makes a difference. I appreciate the tips.
 
Rio Precision Gunwerks said:
Pressure signs are pressure signs. The presence of even one is reason to take a step back. Only saying this because you mentioned "no other pressure signs." Always put this out because people like to use either no signs at all or only a sign or two as a reason to think they are not over pressure. Even no pressure signs doesn't mean you're not in a danger zone.

That being said....

You said you sized these in a SAC die. Have you checked to make sure you're not actually making the cases longer?

If not, I'd check headspace with virgin unsized and virgin sized and make sure you still have room.
Click to expand...

It's two pressure signs though. Higher than expected muzzle velocity is the second. There's no such thing as a fast barrel, just higher pressure.
 
Cascade Hemi said:
It's two pressure signs though. Higher than expected muzzle velocity is the second. There's no such thing as a fast barrel, just higher pressure.
Click to expand...

Of course. But unless you're noticeably higher velocity than verified pressure testing, you won't be able to use that.
 
Rio Precision Gunwerks said:
Of course. But unless you're noticeably higher velocity than verified pressure testing, you won't be able to use that.
Click to expand...
I went down to 39.6 and am still experiencing the heavy bolt lift. Velocity is now well below 3000. I'm inexperienced with the SAC sizing die...I'm thinking maybe I've set it up improperly.
 
Try some loads with virgin brass you did not resize.

Also measure base to shoulder with a comparator on virgin and the virgin sized and see if you are somehow pushing the shoulder fwd.

ZY
 
I was running lapua SRP brass, 41.8gr of h4350 with a 109 hybrid in my old AXSA. 26” 7.7tw bartlein factory barrel. I think I was running them 20k off. Shot great and gave me 3050fps. No pressure with that load.

Anyways, if it’s virgin brass, maybe try with with once fired brass. Load the rest of the virgin brass at like 39gr and see if things improve.

What’s the thought process of sizing virgin brass? You may be accidentally bumping shoulders back when you’re sizing them which will cause false pressure issues. Have you tried non sized virgin cases?
 
I see rub marks on the base of the brass, that make me think the brass is to bog for the chamber in the headspace or shoulder dimension. Base to shoulder. Is it also hard to close the bolt handle on some?
 
Starting to be lots of directions people are sending you in. Don't want to confuse you too much, so I'll post this and leave it alone.

You need to make sure the virgin brass isn't too large for your chamber. This is possible if you're running through a sizing die before first firing.

Stripping your bolt is very easy way. Strip the bolt and use a completely virgin piece of brass. Then use a piece you've sized. If either has resistance, then you know something is too large for the chamber.


If that part is fine, take a measurement of the neck OD for a loaded round and make sure it has enough clearance based on the reamer spec.

Same with loaded round and a stripped bolt. Once you know your brass is sized smaller than your chamber, you can check for resistance with a bullet seated. If there is resistance, then you're into the lands and that could be an issue as well.


And of course, make sure there's nothing in your chamber. Including any moisture or oil.


If you're still having problems after all that, find someone locally who's knowledgeable and have them take a look. If you can't find anyone, PM me and I'll get you on zoom or something.
 
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Rio Precision Gunwerks said:
Starting to be lots of directions people are sending you in. Don't want to confuse you too much, so I'll post this and leave it alone.

You need to make sure the virgin brass isn't too large for your chamber. This is possible if you're running through a sizing die before first firing.

Stripping your bolt is very easy way. Strip the bolt and use a completely virgin piece of brass. Then use a piece you've sized. If either has resistance, then you know something is too large for the chamber.


If that part is fine, take a measurement of the neck OD for a loaded round and make sure it has enough clearance based on the reamer spec.

Same with loaded round and a stripped bolt. Once you know your brass is sized smaller than your chamber, you can check for resistance with a bullet seated. If there is resistance, then you're into the lands and that could be an issue as well.


And of course, make sure there's nothing in your chamber. Including any moisture or oil.


If you're still having problems after all that, find someone locally who's knowledgeable and have them take a look. If you can't find anyone, PM me and I'll get you on zoom or something.
Click to expand...
Thank you, your responses have been very thoughtful and helpful. I really suspect I don't have the sizing die set up properly...but I'm not good enough at this to diagnose it beyond that. Is it necessary to size virgin lapua brass? I may take some measurements and if nothing jumps out, I'll try loading without sizing.
 
Maverick124 said:
Thank you, your responses have been very thoughtful and helpful. I really suspect I don't have the sizing die set up properly...but I'm not good enough at this to diagnose it beyond that. Is it necessary to size virgin lapua brass? I may take some measurements and if nothing jumps out, I'll try loading without sizing.
Click to expand...

No, most people do not size virgin brass. I will run an expander mandrel to make sure necks are straight and dent free and somewhat consistent before loading and then just load and go. I’m unaware of anyone sizing virgin brass and for what reason.

I would stop sizing that virgin brass and if you have an expander mandrel, use that to set 2-3 thou neck tension and call it good. If your expander mandrel is built into your die, then I would screw the die out a bit so you’re not touching the shoulder but getting the expander into the case mouth. Still use lube before running them through the die and make sure the cases are free of lube before firing them.

You can set your sizing die once you’re ready to reload the 1x fired brass.
 
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To be clear, everyone is guessing. Most people that size new brass are only sizing the necks. Generally, sizing dies don't size the body of new brass. It's pretty challenging to push back the shoulders of new brass too. Can it be done? Anything is possible with enough effort. I have a die that will size down new brass case bodies...it's in my junk drawer. If your die is sizing the case bodies of your new brass you may want to consider a different die.

Can you drop a bullet freely into a fired case?
 
Maverick124 said:
Thank you, your responses have been very thoughtful and helpful. I really suspect I don't have the sizing die set up properly...but I'm not good enough at this to diagnose it beyond that. Is it necessary to size virgin lapua brass? I may take some measurements and if nothing jumps out, I'll try loading without sizing.
Click to expand...

It's generally not necessary. Especially on rifles where you're not trying to squeeze everything out of even the first firing.

Personally, if I decide to size virgin brass I take measurements and setup the die just like I would for fired brass. I just set the die up where it's sizing the neck as far down as the die or bushing will allow without pushing the shoulders back.

If the die is new I'll also take measurements and make sure it's not changing anything on the body. Every once in a while you'll run into a bad die.
 
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I will repeat this....no guessing required....

"Also measure base to shoulder with a comparator on virgin and the virgin sized and see if you are somehow pushing the shoulder fwd."

ZY
 
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People size virgin lapua for a saami chamber?

I’d bet that’s your problem.

I’d delve into when and why to size, learn about comparing brass with a comparator, which is something you should have. I’d guess you’re seeing this due to brass growing excessively unless there is actually something wrong with the rifle.

I’d start by grabbing a box of factory ammo and seeing how that runs. If that’s fine you know the problem lies with you.
 
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Rio Precision Gunwerks said:
It's generally not necessary. Especially on rifles where you're not trying to squeeze everything out of even the first firing.

Personally, if I decide to size virgin brass I take measurements and setup the die just like I would for fired brass. I just set the die up where it's sizing the neck as far down as the die or bushing will allow without pushing the shoulders back.

If the die is new I'll also take measurements and make sure it's not changing anything on the body. Every once in a while you'll run into a bad die.
Click to expand...
I'm loading for a PRS match. I just made the switch from factory to handloads...not sure if the virgin brass
Lawnboi said:
People size virgin lapua for a saami chamber?

I’d bet that’s your problem.

I’d delve into when and why to size, learn about comparing brass with a comparator, which is something you should have. I’d guess you’re seeing this due to brass growing excessively unless there is actually something wrong with the rifle.

I’d start by grabbing a box of factory ammo and seeing how that runs. If that’s fine you know the problem lies with you.
Click to expand...
Factory runs fine through it. I think you may be right
 
Maverick124 said:
I'm loading for a PRS match. I just made the switch from factory to handloads...not sure if the virgin brass

Factory runs fine through it. I think you may be right
Click to expand...

In that case, hopefully you have not sized all the virgin lapua.

You need a comparator to go on your calipers. I like the SAC comparator but a cheap Hornady will do. Measure a virgin case with it, write that down. Measure one of your sized cases, write that down, then measure a once fired case and write that down. Tell us those measurements and I’d bet we can make something meaningful of it. Likely if you have sized, and sometimes with using virgin brass it can take a couple firings to match your chamber.I write down my base to shoulder measurements with a comparator every time, what I see is after two firings I have made sense of what my brass is doing as far as growth when being fired.

FWIW I have shot a lot of virgin lapua and never sized it. I run a mandrel through it with some kind of wet lube, tumble it, chamfer/debut and load.
 
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Maverick124 said:
I'm loading for a PRS match. I just made the switch from factory to handloads...not sure if the virgin brass

Factory runs fine through it. I think you may be right
Click to expand...

You can literally just drop a consistent powder charge, do seating depth test, and then just load straight virgin brass with no prep work and be way good for prs.
 
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Lawnboi said:
In that case, hopefully you have not sized all the virgin lapua.

You need a comparator to go on your calipers. I like the SAC comparator but a cheap Hornady will do. Measure a virgin case with it, write that down. Measure one of your sized cases, write that down, then measure a once fired case and write that down. Tell us those measurements and I’d bet we can make something meaningful of it. Likely if you have sized, and sometimes with using virgin brass it can take a couple firings to match your chamber.I write down my base to shoulder measurements with a comparator every time, what I see is after two firings I have made sense of what my brass is doing as far as growth when being fired.

FWIW I have shot a lot of virgin lapua and never sized it. I run a mandrel through it with some kind of wet lube, tumble it, chamfer/debut and load.
Click to expand...
The SAC comparator should be here tomorrow. I'll update with the measurements
 
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Rio Precision Gunworks said:
You can literally just drop a consistent powder charge, do seating depth test, and then just load straight virgin brass with no prep work and be way good for prs.
Click to expand...
I'm really thinking I need to just keep backing down my charge. At 39.6 I still had heavy bolt lift on most and my velocities were around 2960. Dunno whats going on...
 

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Maverick124 said:
I'm really thinking I need to just keep backing down my charge. At 39.6 I still had heavy bolt lift on most and my velocities were around 2960. Dunno whats going on...
Click to expand...

Doesn't seem to be the sizing of the virgin brass based on those pics.

Move to the next thing on the list. Make sure that brass isn't too tight for your chamber. Then make sure you're not seating into the lands.
 
Rio Precision Gunworks said:
Doesn't seem to be the sizing of the virgin brass based on those pics.

Move to the next thing on the list. Make sure that brass isn't too tight for your chamber. Then make sure you're not seating into the lands.
Click to expand...
So there's this ring around my primer. I'm not sure what to make of it. It is NOT present on my factory ammo
 

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Measure a fired case as well, see how much it’s growing.

Agree next I’d check your not in the rifling with your bullet.

Next I’d insider last time you cleaned and how well it went.
 
Another thought im having is this: I'm using Hornady case lube and only wiping it off with a paper towel. Would any residue from that be causing this?
 
Maverick124 said:
Another thought im having is this: I'm using Hornady case lube and only wiping it off with a paper towel. Would any residue from that be causing this?
Click to expand...

Lube on the case can prevent case wall from gripping chamber. This increases thrust on the bolt face. Brass can expand too much and have heavy lift.

So, yes, this could be the culprit.
 
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If your necks are .273 all the way (no lip on the mouth, etc), then you should be fine there. Saami for 6cm is .276. I prefer a bit more than .003, but .003 is fine.

If your chamber is tighter than that for some reason, that could be an issue. But if it's Saami, the neck isn't the issue.
 
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Rio Precision Gunworks said:
Lube on the case can prevent case wall from gripping chamber. This increases thrust on the bolt face. Brass can expand too much and have heavy lift.

So, yes, this could be the culprit.
Click to expand...
I'll try just loading it straight from the box and report back on how that goes. It feels dry to the touch though...
 
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