New Accuracy International AXMC 300 Norma high pressure problems

[EXSOCAL]

I had a pretty rough road to get my 300 Norma to shoot....

A couple things I experienced / learned over the last year that might pertain to your current situation-

Norma brass sucks, its soft and cant take any sort of pressure, Hornady brass is a bit better, Peterson is the best there currently is for the 300 Norma Mag. I experienced pressure signs early on with relatively low speed loads when using Norma brass - I used three different bullets, three different powders and couldn't get anywhere near where it should be. I switched to Hornady and found the brass to be a bit tougher with similar case capacity to the Norma but I still was hovering around 2850 to 2900 with a 230 Hybrid out of a 28" barrel.

When I was experimenting with the Norma brass trying to figure out why the fuck I was having pressure signs at such low velocities, I looked everywhere.... no carbon ring, no excessive fouling, bullet seated .020 off the lands, no excessive neck tension, headspace was correct, chamber was clean and dry... I was so frustrated I almost threw in the towel and re-barreled the rifle to 338 Lapua.

Long story short, I got ahold of some Peterson brass and did a brand new, full load workup... with that brass and the 230 Berger Hybrid, I ended up with a solid load using 85 gr of Retumbo and 2995 FPS average. I have a couple hundred of these loads down range with confirmed dope out to 2k. What I have noticed is when I load new, virgin brass with this recipe I will get flattened primers and ejector marks. After the brass is fired once, no more pressure signs at all. I just attributed this to the smaller internal volume of the new brass before it was fire formed.... I dunno, made sense to me.

Because I can feel your frustration heres what I would recommend.... first stick with Peterson brass, this solved 90% of my issues. Second, make sure your bullet is seated off the lands. Third, do a whole load workup to determine your pressure ceiling and a good, consistent and accurate node, I may have missed it but it sounded like you just jumped to a load that you thought would work instead of starting at the ground floor. Hope that helps bro, good luck, I know how frustrating that can be.

 

[Long Range 338]

Thanks for taking the time to read this and possibly figure out why I'm having increased high pressure issues.
I am condensing the details.

I purchased this AXMC new and loaded 50 rounds that others have used,
Peterson brass
92.6gr RL33
225 Gr Hornady Match
Fed match mag primers

I loaded a few with a few tenths less and more powder and no high pressure issues. Very slight cratering on primer.

Came home from range and cleaned, loaded 50 more all the same with above listed load. No issues and shot great!

Repeated above. Slightly higher pressure signs, little heavier createring of the primer and a few rounds with slightly shinny spot on head stamp.

Repeated above with NEW brass, same lot as first 50. Now holes in primers and bright spots on head stamp.
Pulled out FACTORY loaded Hornady match ammo, hole in primer and bright spot on headstamp.

I ran a new LabRadar on most of the shots and the speeds have increased from around 3000fps to 3040fps.
I understand the bbl is new and expect the speeds to increase.
Pulled a few of my reloads to ensure I didn't accidentally increase the powder charge, didn't. Measured with second scale, confirmed the first scale is accurate or their both off, my luck...

I realize I my need to bush the bolt, however, I didn't 150 rounds ago.

No carbon ring, even bore scoped, all looks clean.

I understand the bbl will speed up, but this mean an increase in pressures to this degree?
Should a factory round show signs of high pressure?
What is changing?

I have been calling the headquarters in VA since Last Saturday, rolls to voice mail.
Called the distributor yesterday, will get back to me.

I would like to know how to start solving this issue. It has been almost a week and would like to continue shooting my new rifle while not voiding my warranty or damaging anything.

Has anyone with a new AI possibly even with the 300 Norma round had this issue?

Thank you for your time,
Steve

It sounds like you've been pretty thorough in going thru the variables here. This may be a stupid question but what are the chances your barrel wasn't seated as tight to the action originally and now you have seated it a couple thousandths tighter? Maybe something was different and now you are jamming the bullets into the lands (even with factory ammo). New Hornady and Norma ammo should be conservative loads and the AXMC action is strong so what else could it be? I would check my COAL and make sure I wasn't jamming into the lands. Easy to do and just might solve the mystery.

 

[HillBilly n TX]

I believe Berger is using Lapua brass in their factory branded ammo. Midway normally has the 215 or 230 gr. in stock. Not sure if it would make a difference or not, but at least you may be able to score some good brass.

 

[Stevo3556]

I had a pretty rough road to get my 300 Norma to shoot....

A couple things I experienced / learned over the last year that might pertain to your current situation-

Norma brass sucks, its soft and cant take any sort of pressure, Hornady brass is a bit better, Peterson is the best there currently is for the 300 Norma Mag. I experienced pressure signs early on with relatively low speed loads when using Norma brass - I used three different bullets, three different powders and couldn't get anywhere near where it should be. I switched to Hornady and found the brass to be a bit tougher with similar case capacity to the Norma but I still was hovering around 2850 to 2900 with a 230 Hybrid out of a 28" barrel.

When I was experimenting with the Norma brass trying to figure out why the fuck I was having pressure signs at such low velocities, I looked everywhere.... no carbon ring, no excessive fouling, bullet seated .020 off the lands, no excessive neck tension, headspace was correct, chamber was clean and dry... I was so frustrated I almost threw in the towel and re-barreled the rifle to 338 Lapua.

Long story short, I got ahold of some Peterson brass and did a brand new, full load workup... with that brass and the 230 Berger Hybrid, I ended up with a solid load using 85 gr of Retumbo and 2995 FPS average. I have a couple hundred of these loads down range with confirmed dope out to 2k. What I have noticed is when I load new, virgin brass with this recipe I will get flattened primers and ejector marks. After the brass is fired once, no more pressure signs at all. I just attributed this to the smaller internal volume of the new brass before it was fire formed.... I dunno, made sense to me.

Because I can feel your frustration heres what I would recommend.... first stick with Peterson brass, this solved 90% of my issues. Second, make sure your bullet is seated off the lands. Third, do a whole load workup to determine your pressure ceiling and a good, consistent and accurate node, I may have missed it but it sounded like you just jumped to a load that you thought would work instead of starting at the ground floor. Hope that helps bro, good luck, I know how frustrating that can be.

SoCal,

Thank you very much for the great information and suggestion.

Yes I did start with a load that others had as their "pet" load. It was under published max and I did a short test of a few tenths of a grain up and down. That load worked very well so I stuck with it intending on tweeting the load it to my rifle after the bbl was broken in. Then the pressures steadily increased and you know the rest.

I based my initial seating depth from the factory I believe. I went back when I had pressure issues and actually measured it and I THINK, not by my reloading data right now, that I was loading at 3.5 and I'm touching at 3.6.....

I found that at 88gr I have a little primer flow but no other signs of high pressure. So I started at 88 and am reducing my load looking for my node with a start of .005 off the lands. I believe I was just under 2900FPS at this load.

When I bought the rifle I wanted to order my reloading supplies ASAP so I could start load development and RL33 looked popular by all the threads I read. SO I ordered a couple of pounds of it. When things were initially going well I ordered albs of it...... So I will be shooting a few more with RL33 before I switch..... I was torn during the initial order between RL33, Retumbo, and H1000. I think my distributor was out of the Retumbo and many people stated that the double based powder achieved higher speeds with lower pressures, so I made the decision. If I'm not happy with my results I will be trying the other two popular powders.

I was very frustrated as you noticed. Part of my issue was that I started this the week before Christmas and all the people I need to talk to were off for Christmas week and some the following week as well. I knew I could reduce my load and see lower pressures but I was not aware that the issue could be pressures building up as the bbl broke in. I had never seen this before, well speeds increasing, but not to the point of acceptable pressures then to the point that they reached AND FACTORY ammo having issues.

Thank you again for sharing your knowledge with me on the 300NM. I think I am on the track you suggest, just took me awhile!

Steve

 

[Stevo3556]

It sounds like you've been pretty thorough in going thru the variables here. This may be a stupid question but what are the chances your barrel wasn't seated as tight to the action originally and now you have seated it a couple thousandths tighter? Maybe something was different and now you are jamming the bullets into the lands (even with factory ammo). New Hornady and Norma ammo should be conservative loads and the AXMC action is strong so what else could it be? I would check my COAL and make sure I wasn't jamming into the lands. Easy to do and just might solve the mystery.

LR338,

NOT a stupid question. OK maybe, then we are both stupid cause I asked it as well. I have removed the bbl overtime I cleaned it since I didn't have a bore guide yet. I asked if maybe I wasn't installing correctly and we ran through that process as well as if I could have some debris between the bbl and the mating surface on the action. I was told that I was doing things correctly and that a little something would really not be an issue if I can see that it is touching by the set screw. I did have a look with my borescope and it was clean later when I returned home and had the rifle in front of me.

I had .1 jump if I remember correctly, have to look at my data.

I am surprised as well that factory ammo would be an issue. Had never seen this from factory ammo. That was my benchmark and also I had never had a load that was fine, then wasn't. New to me! So my concerns. When I talked to Scott at AI I learned A LOT about the 300NM. I am going with what I was told since they have much more experience and knowledge than I and certainly nothing else I can find can explain the increased pressures.

I have started at a lower powder charge and am looking for my node. I am not having pressure issues now and I hope to find a load that gives me accuracy and velocity that others with AIs are using. If I find that I am significantly running at lower velocities than others I will continue to investigate.

Thank you for you help.

Steve

 

[Stevo3556]

I believe Berger is using Lapua brass in their factory branded ammo. Midway normally has the 215 or 230 gr. in stock. Not sure if it would make a difference or not, but at least you may be able to score some good brass.

Thank you Hillbilly.

I have 100 Peterson cases right now and have heard good things about it. I would have probably tried Lapua had it been available when I bought reloading components. I run it in one of my 260 Remingtons.

If I still believed that factory ammo was a good benchmark for testing, I would buy some to "test" my rifle for another data point. Tried a few factory loaded Norma cartridges during this pressure increase and they all failed....

Thanks,
Steve

 

[Long Range 338]

LR338,

NOT a stupid question. OK maybe, then we are both stupid cause I asked it as well. I have removed the bbl overtime I cleaned it since I didn't have a bore guide yet. I asked if maybe I wasn't installing correctly and we ran through that process as well as if I could have some debris between the bbl and the mating surface on the action. I was told that I was doing things correctly and that a little something would really not be an issue if I can see that it is touching by the set screw. I did have a look with my borescope and it was clean later when I returned home and had the rifle in front of me.

I had .1 jump if I remember correctly, have to look at my data.

I am surprised as well that factory ammo would be an issue. Had never seen this from factory ammo. That was my benchmark and also I had never had a load that was fine, then wasn't. New to me! So my concerns. When I talked to Scott at AI I learned A LOT about the 300NM. I am going with what I was told since they have much more experience and knowledge than I and certainly nothing else I can find can explain the increased pressures.

I have started at a lower powder charge and am looking for my node. I am not having pressure issues now and I hope to find a load that gives me accuracy and velocity that others with AIs are using. If I find that I am significantly running at lower velocities than others I will continue to investigate.

Thank you for you help.

Steve

For things to spike suddenly it just sounds like something has changed, the question is what. By no means do I claim to have more knowledge than others contributing here, I've just found that usually if I look close enough there is a root cause. Also I'm very interested in this thread as I've got the same setup with a low round count. Good luck sorting this out, and please keep us posted on what you may discover.

 

[Stevo3556]

For things to spike suddenly it just sounds like something has changed, the question is what. By no means do I claim to have more knowledge than others contributing here, I've just found that usually if I look close enough there is a root cause. Also I'm very interested in this thread as I've got the same setup with a low round count. Good luck sorting this out, and please keep us posted on what you may discover.

That was my argument exactly! Although it was not sudden, each 50 I had signs that it increased. It was upon my 151st shot that I punched a primer.

AXMC with 300NM?
What load are you shooting?
Muzzle velocity?
How many rounds have you shot?

 

[redneckbmxer24]

It’s not uncommon at all to see pressure once you get to the point the barrel speeds up. Sounds like you’re running pressure a little high and it’s a combo of that and the weak Norma brass. I dumped my 300 Norma real quick because of the brass but that was years ago when Norma was the only game in town for brass. Now that Lapua and Peterson have brass I kinda want one again.

 

[Long Range 338]

That was my argument exactly! Although it was not sudden, each 50 I had signs that it increased. It was upon my 151st shot that I punched a primer.

AXMC with 300NM?
What load are you shooting?
Muzzle velocity?
How many rounds have you shot?

Yes AXMC 300NM from Mile High. I’ve just been shooting the Hornady factory load. Been getting 2950 FPS with less than 100 rounds down the barrel

 

[Long Range 338]

It’s not uncommon at all to see pressure once you get to the point the barrel speeds up.

Do you have any idea what would cause the increased pressure? I can understand that pressure=velocity so the logic is there. But I thought (perhaps mistakenly) the velocity increase in new barrels would be as tooling marks, etc smoothed. As throats erode velocity decreases so this is a bit of confusion on my part.

 

[Stevo3556]

It’s not uncommon at all to see pressure once you get to the point the barrel speeds up. Sounds like you’re running pressure a little high and it’s a combo of that and the weak Norma brass. I dumped my 300 Norma real quick because of the brass but that was years ago when Norma was the only game in town for brass. Now that Lapua and Peterson have brass I kinda want one again.

Thank you for the confirmation. Nice to hear others that have experienced this.
I was using factory Norma ammo as a benchmark, but I have been reloading Peterson brass from the beginning.
I really like the 300NM and the AXMC.
I am at a safe pressure now and will go out in the next couple days to try to find my node and get my AB programed set for this 300NM and 260 Rem.

 

[Stevo3556]

Yes AXMC 300NM from Mile High. I’ve just been shooting the Hornady factory load. Been getting 2950 FPS with less than 100 rounds down the barrel

WOW! I am very interested in shots 101 through 200. My bbl really saw the pressure go from OK to over through these rounds and I used a few Norma factory Match rounds to see if extra cleaning seating of the bbl, ect made any difference. They punctured the primers on all of them. If you plan on reloading for your AI I might have a good starting place for you...

I appreciate your help and would certainly share all my data with you if you want/need it.

Steve

 

[Stevo3556]

Do you have any idea what would cause the increased pressure? I can understand that pressure=velocity so the logic is there. But I thought (perhaps mistakenly) the velocity increase in new barrels would be as tooling marks, etc smoothed. As throats erode velocity decreases so this is a bit of confusion on my part.

ME TOO!
So as I was looking for an answer to this problem with my AXMC in 300NM I was told that the bbl could speed up and I noticed the second 50 rounds were consistently hitting about .6-.8 mils higher. I assumed that I had different conditions, not been as careful as I should have been in the original sighting in of the scope, and just that the first few rounds would be different due to a new bbl as well as fouling. I was also trying to learn my new LabRadar and had other shooters ect. So I was not able to log all my shots and also got a few of others shots on the LR. Next time out I had the LR working properly and started noticing the increased speed of the bbl.

I had asked if the bbls sped up do to less friction as you stated or because they "sealed" better behind the bullet. The first two hypothesis that came to mind. Really could not find an answer. I was able to talk directly with Scott at AI, GREAT guy learned a lot, he told me that velocities only speed up with increased pressure.

So I understand that I was at high pressure when I started shooting the new 300NM then as the bbl sped up I became over pressured with the same loads. I had started at 92.6 gr of RL33 where several people found their load, which was below published max load, after my issues, I am not running from 88 grs and decreasing looking for my node....

Please let me know what your 300NM does as you get more down the tube. Hope you don't have the issues I had, but don't know why it should be different with the same rifle and cal.

Steve

 

[richthe1]

ME TOO!
So as I was looking for an answer to this problem with my AXMC in 300NM I was told that the bbl could speed up and I noticed the second 50 rounds were consistently hitting about .6-.8 mils higher. I assumed that I had different conditions, not been as careful as I should have been in the original sighting in of the scope, and just that the first few rounds would be different due to a new bbl as well as fouling. I was also trying to learn my new LabRadar and had other shooters ect. So I was not able to log all my shots and also got a few of others shots on the LR. Next time out I had the LR working properly and started noticing the increased speed of the bbl.

I had asked if the bbls sped up do to less friction as you stated or because they "sealed" better behind the bullet. The first two hypothesis that came to mind. Really could not find an answer. I was able to talk directly with Scott at AI, GREAT guy learned a lot, he told me that velocities only speed up with increased pressure.

So I understand that I was at high pressure when I started shooting the new 300NM then as the bbl sped up I became over pressured with the same loads. I had started at 92.6 gr of RL33 where several people found their load, which was below published max load, after my issues, I am not running from 88 grs and decreasing looking for my node....

Please let me know what your 300NM does as you get more down the tube. Hope you don't have the issues I had, but don't know why it should be different with the same rifle and cal.

Steve

Were you ever able to figure out a solution to the issue you were having? Sorry to hear about it all!

 

[Stevo3556]

I don't know! I have reduced my load and have not had the issues. I actually was thinking that I would go back to the old load and give it a try.

I really thought I had the bbl was free from carbon as well as copper. If I HAD to say what I think it is now, I would have to guess that Barney was correct, carbon ring. I have no explanation why it was suddenly an issue. Going back to the higher load and not experiencing the issues would make me believe that was indeed the issue.

 

[richthe1]

I don't know! I have reduced my load and have not had the issues. I actually was thinking that I would go back to the old load and give it a try.

I really thought I had the bbl was free from carbon as well as copper. If I HAD to say what I think it is now, I would have to guess that Barney was correct, carbon ring. I have no explanation why it was suddenly an issue. Going back to the higher load and not experiencing the issues would make me believe that was indeed the issue.

Keep us updated if you choose to try that. Glad it works now, though!

 

[Defiance]

So Axmc bolts also need to be bushed in large rifle calibers like 300norma if one wants to run normal loads?

 

[918v]

No this round is problematic in multiple platforms.

 

[Fixr]

So Axmc bolts also need to be bushed in large rifle calibers like 300norma if one wants to run normal loads?

I had my 2018 AXMC 338LM and 300 WinMag bolts bushed to stop some significant cratering.