AXMC question (pressure signs)

[Unrat3d]

My AXMC 300 win mag shows pressure signs with reloads at very low charges and velocities with 195 eld between 2750-2850 fps. Slight flattened primers and primmer cratering and faint round ejector imprint. Doing a 10 round ladder test some of the higher charges didn’t have pressure signs like lower charges. I notice barrel is pretty slow, it has about 150 rounds.

Peterson brass
H4831
cci250 magnum
195 eld

69.3gr - 2738 (slightly flattened primer, no ther signs)
69.6gr - 2763 (vey slight round ejector imprint)
69.9gr - 2775 (only pressure sign is very slightly flat primer)
70.2gr - 2782 (vey little primer catering, NOT flattened)
70.5gr - 2819 (only pressure sign is very slighty flat primer)
70.8gr - 2815 (slight primer catering but primer is NOT flat and looks good otherwise)
71.1gr - 2821 (very slight flat primer, everything else looks good)
71.4gr - 2873 (barely visible round ejector imprint, slight flat primer)
71.7gr - 2847 (flat primer, very faint ejector mark)
72gr - 2855 (little primer catering, everything else including primer looks good, no marks)

Any input or advice is appreciated.

 

[wade2big]

These aren’t low charges and you are way over pressure. Max loads with H4350 and a 200 class bullet is 67gr according to Hodgons. You started your load work up over book max. I doubt 5-6 grains over book max is a safe load in any rifle.. Your velocity is much faster than book as well with that combo which is another tell tell sign of overpressure. You need to use a different powder such as H1000 to get the speed without blowing yourself up.

 

[Supersubes]

Is H4350 a typo? If not, thats a shit powder for the combination, and your start charge is 2 grans over Hodgdon max with a 190 gr bullet.

 

[Kiba]

What the others have said... H4350 is not an ideal magnum powder and the pressure signs are probably because you're already well over max pressure.

The data on Hodgdons site suggests you're already well over max charge, and they're using Winchester brass-- and while neither you or Hodgdon posted the case capacities I'm guessing the Peterson brass has less case capacity than Winchester, so that increases the pressure even more.

I'd recommend you pick up a powder more appropriate to magnums and your specific combination before continuing...

 

[Unrat3d]

These aren’t low charges and you are way over pressure. Max loads with H4350 and a 200 class bullet is 67gr according to Hodgons. You started your load work up over book max. I doubt 5-6 grains over book max is a safe load in any rifle.. Your velocity is much faster than book as well with that combo which is another tell tell sign of overpressure. You need to use a different powder such as H1000 to get the speed without blowing yourself up.

Sorry my apologies, i meant H4831

 

[Unrat3d]

What the others have said... H4350 is not an ideal magnum powder and the pressure signs are probably because you're already well over max pressure.

The data on Hodgdons site suggests you're already well over max charge, and they're using Winchester brass-- and while neither you or Hodgdon posted the case capacities I'm guessing the Peterson brass has less case capacity than Winchester, so that increases the pressure even more.

I'd recommend you pick up a powder more appropriate to magnums and your specific combination before continuing...

My apologies, I meant H4831. I’m reloading 6.5 right now and had that on my mind while typing

 

[Unrat3d]

Is H4350 a typo? If not, thats a shit powder for the combination, and your start charge is 2 grans over Hodgdon max with a 190 gr bullet.

Yes it is my apology, H4831 I meant.

 

[Supersubes]

Yes it is my apology, H4831 I meant.

Looks like your velocity is right on with Hodgdon’s data. Max listed charge does not mean “you can load to our max and everything is peachy” its just what their pressure test barrel did.

You need a slower powder. h1000 is about perfect.

 

[Unrat3d]

Looks like your velocity is right on with Hodgdon’s data. Max listed charge does not mean “you can load to our max and everything is peachy” its just what their pressure test barrel did.

You need a slower powder. h1000 is about perfect.

Don’t you think 2750 is a little low with a 195 bullet to be hitting pressure? It is it just the rifle, I hear some leave slight pressure signs even though it’s not really pressure. Would you recommend I go until I feel a heavy bolt lift or a piece of brass gets pretty scratched up to where I can feel it? Or just try another powder. Do you think there could be anything fishy with system?

 

[MOUNTIC]

Seems right in line with h4831 and those projectiles. H1k will for sure be an improvement. Or pick up some RL26.

 

[khymiller2]

I have similar same issue before. The issue is totally gone once I convert the large firing pin to be small firing pin.

 

[Kiba]

If you can, post the H2O capacity of a couple of your fired cases as well as your loaded overall length, how far back from the lands it's seated, and barrel length... I can do a quick sanity check in quickload later. It won't tell you if you have a chamber issue, carbon ring, or tight spot in the bore leading to higher than expected pressure, but it's still a decent sanity check.

Also, regarding pressure signs... AXMC's with large firing pins can sometimes show a bit of cratering, so you need to keep an eye on that as well as bolt lift, ejector marks, and case head diameter growth.

 

[Unrat3d]

I have similar same issue before. The issue is totally gone once I convert the large firing pin to be small firing pin.

I have small firing pin for my short action bolt. So they have small firing pin magnum bolt bodies? The short actions come with small pin, if it was a problem why not have them come with the magnum bolts.
But even still, I wouldn’t think you should need a small pin for For a standard to light 300 win load.

 

[Supersubes]

Don’t you think 2750 is a little low with a 195 bullet to be hitting pressure? It is it just the rifle, I hear some leave slight pressure signs even though it’s not really pressure. Would you recommend I go until I feel a heavy bolt lift or a piece of brass gets pretty scratched up to where I can feel it? Or just try another powder. Do you think there could be anything fishy with system?

Yes, switch powders.

 

[Kiba]

I have small firing pin for my short action bolt. So they have small firing pin magnum bolt bodies? The short actions come with small pin, if it was a problem why not have them come with the magnum bolts.
But even still, I wouldn’t think you should need a small pin for For a standard to light 300 win load.

You can now get small firing pin AXMC bolt bodies for the low price of $750/ea and they can use the same small firing pin assembly that AI provides with the small firing pin AXMC 308 bolts.

Or you can have LRI bush your existing large firing pin AXMC bolts for $175/ea, but their bushing job means that it isn't compatible with a factory AI small firing pin, so you have to use a factory AI small firing pin assembly with your factory small firing pin 308 AXMC bolt and the LRI modified firing pin assembly with your bushed AXMC bolts.

The large firing pin is typically not an issue with large primer magnum cases, it's usually only an issue with the 308 bolts when shooting 260/6cm/6.5cm or similar or using small primer cases. Since you are also getting some ejector marks, this isn't just a primer / large firing pin issue.

 

[Unrat3d]

If you can, post the H2O capacity of a couple of your fired cases as well as your loaded overall length, how far back from the lands it's seated, and barrel length... I can do a quick sanity check in quickload later. It won't tell you if you have a chamber issue, carbon ring, or tight spot in the bore leading to higher than expected pressure, but it's still a decent sanity check.

Also, regarding pressure signs... AXMC's with large firing pins can sometimes show a bit of cratering, so you need to keep an eye on that as well as bolt lift, ejector marks, and case head diameter growth.

do I tumble the fired brass with primer in and then do the H2O, or no?

 

[Kiba]

If you want you can tumble first, just make sure there's no media left in the flash hole. Then zero the scale and carefully fill the case with water until it's full to the top of the neck. This is just a sanity check for your load and brass combo, Peterson brass might have more or less case capacity than the case that was measured for quickload's database.

 

[Bacarrat]

What barrel are you using? From my brief experience if you are using a factory AI barrel you won't run into pressure issues as fast as you would as a Proof barrel. Just had a fellow hide member have 2, 300WM prefits, 1 from Proof and 1 from AI(Bartlien) and both Proof barrels would show pressures way faster than that of the factory AI barrel. I had the exact same issue as well on my Proof 300NM barrel until I had the freebore recut.

Also if you are not getting good case fill, you can and will get pressure issues. high 60s and low 70gr charge weight is pretty low for that weight bullet and powder.

 

[Unrat3d]

What barrel are you using? From my brief experience if you are using a factory AI barrel you won't run into pressure issues as fast as you would as a Proof barrel. Just had a fellow hide member have 2, 300WM prefits, 1 from Proof and 1 from AI(Bartlien) and both Proof barrels would show pressures way faster than that of the factory AI barrel. I had the exact same issue as well on my Proof 300NM barrel until I had the freebore recut.

Also if you are not getting good case fill, you can and will get pressure issues. high 60s and low 70gr charge weight is pretty low for that weight bullet and powder.

It’s a barrel directly from England. So Lothar Walther I believe. Yea there is definitely a lot of space left, but when I went higher the day before, like 73 ish, the mark on the bottom of the brass we more pronounced

 

[Unrat3d]

If you can, post the H2O capacity of a couple of your fired cases as well as your loaded overall length, how far back from the lands it's seated, and barrel length... I can do a quick sanity check in quickload later. It won't tell you if you have a chamber issue, carbon ring, or tight spot in the bore leading to higher than expected pressure, but it's still a decent sanity check.

Also, regarding pressure signs... AXMC's with large firing pins can sometimes show a bit of cratering, so you need to keep an eye on that as well as bolt lift, ejector marks, and case head diameter growth.

H2O 89.8
OAL 2.8700 to base to ogive
20 Thou off lans
26 inch barrel

 

[Kiba]

H2O 89.8
OAL 2.8700 to base to ogive
20 Thou off lans
26 inch barrel

I'll run it through quickload when I get home.

 

[Unrat3d]

I'll run it through quickload when I get home.

Appreciate it thanks.

 

[vh20]

I have small firing pin for my short action bolt. So they have small firing pin magnum bolt bodies? The short actions come with small pin, if it was a problem why not have them come with the magnum bolts.
But even still, I wouldn’t think you should need a small pin for For a standard to light 300 win load.

The AXMC was originally designed for the military and the three common NATO sniper rounds (308, 300WM, 338LM). Large firing pin (LFP) bolts were not a problem with any of these chamberings. Primer piercing didn’t become a problem until other chamberings became available, particularly higher pressure ones, or cases using small primers. I first experienced it with a fairly hot factory Berger load in 6.5CM with small primers (Lapua brass). I did not have problems with either 338LM or 338NM. However, when I went to 300NM (which used the same 338 bolt) I started seeing it again. So I had to get the SFP bolts for 308 and 338 bolt faces, along with a SFP assembly. This cured the problems.
I believe the decision to use the LFP in the AXMC was to try and make it as indestructible as possible for the military. And it worked just fine for those cartridges while making the possibility of a broken firing pin while deployed in remote locations very small. I will say that slight primer cratering seems to be common with even the NATO cartridges when using a LFP bolt. I can see it on my 338LM and 338NM primers on factory loads, so it’s not a great indicator of pressure when using a LFP bolt. As was said above, your ejector marks/swipes are not because of LFP though, so that is a better indicator of getting too hot with that load.

 

[Baron23]

I guess the OP just doesn’t want to change to a slower powder. Lol

 

[Unrat3d]

The AXMC was originally designed for the military and the three common NATO sniper rounds (308, 300WM, 338LM). Large firing pin (LFP) bolts were not a problem with any of these chamberings. Primer piercing didn’t become a problem until other chamberings became available, particularly higher pressure ones, or cases using small primers. I first experienced it with a fairly hot factory Berger load in 6.5CM with small primers (Lapua brass). I did not have problems with either 338LM or 338NM. However, when I went to 300NM (which used the same 338 bolt) I started seeing it again. So I had to get the SFP bolts for 308 and 338 bolt faces, along with a SFP assembly. This cured the problems.
I believe the decision to use the LFP in the AXMC was to try and make it as indestructible as possible for the military. And it worked just fine for those cartridges while making the possibility of a broken firing pin while deployed in remote locations very small. I will say that slight primer cratering seems to be common with even the NATO cartridges when using a LFP bolt. I can see it on my 338LM and 338NM primers on factory loads, so it’s not a great indicator of pressure when using a LFP bolt. As was said above, your ejector marks/swipes are not because of LFP though, so that is a better indicator of getting too hot with that load.

Good info, thanks. I’m just curious though and like experienced opinions, do you think it’s weird or there is is something wrong with my rifle if there is brass pressure indicators at those velocities with that bullet? I take advice and am currently working in doing all the advice all the experienced people have been giving, and changing powder and looking for powder, but ive had problems with this rifle as I’ve posted in previous posts, so I’m just curious if something was off with this situation I’m having and if my rifle is out of sort, or if it’s kind of normal with the axmc

 

[Kiba]

H2O 89.8
OAL 2.8700 to base to ogive
20 Thou off lans
26 inch barrel

Wish I had noticed earlier, but I need the COAL to the bullet tip, not to the ogive.

Also just realized my version of QL doesn't have the 195 ELDM, but I can use the 200 ELDX which should be very close for a sanity check.

 

[vh20]

Good info, thanks. I’m just curious though and like experienced opinions, do you think it’s weird or there is is something wrong with my rifle if there is brass pressure indicators at those velocities with that bullet? I take advice and am currently working in doing all the advice all the experienced people have been giving, and changing powder and looking for powder, but ive had problems with this rifle as I’ve posted in previous posts, so I’m just curious if something was off with this situation I’m having and if my rifle is out of sort, or if it’s kind of normal with the axmc

I have no experience with 300WM, but agree with others you need to try a different powder, H1000 being the suggestion of many. Other than the issues caused by AI's decision to use the LFP in the AXMC (which aren't related to your issues, and haven't really been reported for the 300WM), the AXMC in general doesn't have any other "normal" issues. I'm not familiar with the problems you refer to in previous posts, as I have not seen those posts. I doubt you really "need" a SFP bolt assembly for 300WM unless you start experiencing pierced primers with loads of normal pressure. The rest of the pressure signs you mention will likely be solved with choosing a better powder for your cartridge/bullet combination. Slower powder for heavy bullets can give higher velocity with less pressure.

 

[Unrat3d]

Wish I had noticed earlier, but I need the COAL to the bullet tip, not to the ogive.

Also just realized my version of QL doesn't have the 195 ELDM, but I can use the 200 ELDX which should be very close for a sanity check.

My bad bro, 2.535

 

[Kiba]

My bad bro, 2.535

I'm going to guess you meant 3.535...

Anyways, here's a charge increment table using a 200 ELDX and the Ba of the powder trued to your lot of H4831 as a rough estimate what's going on. Again, a tight chamber, short throat, tight bore, carbon ring, etc, can all cause pressure to be higher than this.

And here's a table of velocities of various powders if you loaded to a 57.5ksi target pressure or a max fill of 110% (whichever is hit first) to see how different powders would perform.

As you can see H4831 isn't ideal for your case/bullet combo. N560, N570, RL33, RL25, RL26, Retumbo, H1000, and quite a few others would provide a lot more velocity at the same pressure.

Hope that helps.

 

[Kohl604]

H1000 would be better suited for your purposes.