Pressure signs in 300 Win Mag

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Meph

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I'm loading up a 210gr VLD in my 300 Win Mag.

210gr Matrix VLD
78.0 to 79.8 grains of Retumbo
Hornady brass (once fired 180gr Superformance that printed a hair over an inch with 5 rounds at 200 yards from the rifle)
Winchester large rifle magnum primers
COAL of 3.530"

I started firing them and got pressure signs, mainly a small imprint of the ejector on my brass. No hard extractions though. What worries me is that I got that at two to three grains away from max with load data on a heavier bullet (220 grain bullet) with the bullet farther out of the case. Bullets seated about 0.020" off the lands, if not a little bit more, so they're not jamming against the lands, and I'm not seating them deep at all so they're not overly compressing the powder charge.

Case are all trimmed 0.01 to 0.015 short of max case length, all deburred, chamber is clean of any oil and cases are all tumbled and cleaned of any lube, so it shouldn't be long necks jamming in the throat or bolt thrust due to oily chamber/case.

I used a properly zeroed powder scale and measured every single charge, so it's not improper powder charge.

I'm thinking of backing off the powder load a good like eight grains and working from there or something, I'm not worried too much about under loading 'cause retumbo is really fluffy and fills the case very well.

So what's going on exactly? Roommate thinks it's due to the tight Shilen chamber...

In any case, best group was 1.000" with 5 rounds at 200 yards at 78.2 grains... Not that good.
 
Is Hornady brass on the soft side? I've never used it so don't know but I have run into ejector prints with Federal brass (known for being soft) and heavier loads in my .300 Win Mag.

I don't see how a tight chamber could cause overpressure signs where there wouldn't be the same signs in a normal spec chamber. Perhaps it's a tighter throat/bore that causes more friction on the bullet?
 
LUTNIT said:
Is Hornady brass on the soft side? I've never used it so don't know but I have run into ejector prints with Federal brass (known for being soft) and heavier loads in my .300 Win Mag.

I don't see how a tight chamber could cause overpressure signs where there wouldn't be the same signs in a normal spec chamber. Perhaps it's a tighter throat/bore that causes more friction on the bullet?
Click to expand...

I don't think it's the brass. I'd suspected that the brass could have been soft but then one round kinda had a gas flow make a little hole between the primer and the case, making a tiny black ring on my bolt face, no damage however, just a puff of gas around the action. Definite overpressure leading to case/primer failure...

That was 2 grains away from max on a 220 grain bullet load that seats deeper into the case and 6 grains away from max on a 200 grain bullet load. See why I'm confused?

I'll mike the bullets, but bullets being a few 0.0001" oversize (tenths of a thou, not thou) shouldn't lead to overpressure from what I remember.

I'm thinking of backing it off 8 grains or so as I've said and seating the bullet a little deeper into the case, maybe it's just too close to the lands and it raises the pressure when it engages the rifling.
 
Meph said:
It still fits factory 300 Win Mag brass and is still not under minimum chamber spec for the 300 Win Mag.
Click to expand...

Compair case capacity between a few brands of brass and the Hornady stuff with some fine powder or table salt.

Retumbo can be finicky, some love it and some hate it... I have heard enough that I won't bother playing with it...

Are you sure your COL is correct? Maybe your caliper is having a "bad day".

I have measure my VLD's every way possible... I have found some to be under size but none have ever been over...

Another thing to take into consideration is velocity... I'm not saying some rifles are magic but I have seen a few that have exceeded book velocity at 2gr or more under max charge between 3 load manuals without pressure signs...
 
Hotwheels81 said:
Compair case capacity between a few brands of brass and the Hornady stuff with some fine powder or table salt.

Retumbo can be finicky, some love it and some hate it... I have heard enough that I won't bother playing with it...

Are you sure your COL is correct? Maybe your caliper is having a "bad day".

I have measure my VLD's every way possible... I have found some to be under size but none have ever been over...

Another thing to take into consideration is velocity... I'm not saying some rifles are magic but I have seen a few that have exceeded book velocity at 2gr or more under max charge between 3 load manuals without pressure signs...
Click to expand...

Yeah case length is correct. Using Mitutoyo Absolute caliper that I check against a grade B gage block every so often. To this day I've set various bore gages (measures bore dia down to 0.0001) and it's never been off more than 0.0003" - less error than the screen can even display as the caliper screen displays in increments of 0.0005. It's not a cheap caliper and I'll trust it to a thou or two, even if I know it's more accurate than that.

Of course I fine tune the bore gage with a mike after, but the caliper gets close. Closer than it should, to be honest.

After that I got a set of Mitutoyo mikes, 0 to 4", with the zeroing rods and certs from the factory as well as my work's quality control stamp every six months.

Velocity was chronographed with an Alpha chrony at 2900 to 3040 until I stopped. Barrel length is 30" so it's getting a bit more speed than usual.

Seating depth is constant with the Forster micrometer seating die.
 
It still fits factory 300 Win Mag brass and is still not under minimum chamber spec for the 300 Win Mag.
Click to expand...

Factory brass tends to be quite small.

I started firing them and got pressure signs, mainly a small imprint of the ejector on my brass.
Click to expand...

I'd suspected that the brass could have been soft but then one round kinda had a gas flow make a little hole between the primer and the case, making a tiny black ring on my bolt face, no damage however, just a puff of gas around the action.
Click to expand...

Velocity was chronographed with an Alpha chrony at 2900 to 3040 until I stopped. Barrel length is 30" so it's getting a bit more speed than usual.
Click to expand...


With the symptoms above, there is not much doubt, as to there being excessive pressure. A smallish chamber, and perhaps a fast lot of Retumbo, and you can reach maximum pressure with less powder than that listed as a maximum load in a manual.
 
Welcome to the wonderful world of reloading, where jacket material, bearing surface, chamber and bore dimensions, and lot to lot differences in brass, powder and primers can equal excessive pressure.

Deal with it.
Since that's what happens in your rifle, not your neighbors, or the uber custom chambered pressure gun the factory used..

Back off your load.
 
You seem over pressure.

I've had a couple of rifles that developed clear pressure signs at textbook medium level powder charges. I don't have them anymore.

I shoot Reloader-17 in my 300 winmag. You may want to give it a try.
 
I have run very simmilar loadings in my 110BA with the 208 AMAX, and have had comparble results in win cases and CCI LRM primers.

Weigh the case, then fill level to the top with water and weigh again. Do 5 cases and you will have an idea as to the water capacity of the fired cases. If you are over 89gn water capacity then Quickload says you are JUST at max at 79.8gn of retumbo. Speed matches your findings at 3040fps.

Hope this helps.
 
Meph said:
I'm loading up a 210gr VLD in my 300 Win Mag.

210gr Matrix VLD
78.0 to 79.8 grains of Retumbo
Hornady brass (once fired 180gr Superformance that printed a hair over an inch with 5 rounds at 200 yards from the rifle)
Winchester large rifle magnum primers
COAL of 3.530"

I started firing them and got pressure signs, mainly a small imprint of the ejector on my brass. No hard extractions though. What worries me is that I got that at two to three grains away from max with load data on a heavier bullet (220 grain bullet) with the bullet farther out of the case. Bullets seated about 0.020" off the lands, if not a little bit more, so they're not jamming against the lands, and I'm not seating them deep at all so they're not overly compressing the powder charge.

Case are all trimmed 0.01 to 0.015 short of max case length, all deburred, chamber is clean of any oil and cases are all tumbled and cleaned of any lube, so it shouldn't be long necks jamming in the throat or bolt thrust due to oily chamber/case.

I used a properly zeroed powder scale and measured every single charge, so it's not improper powder charge.

I'm thinking of backing off the powder load a good like eight grains and working from there or something, I'm not worried too much about under loading 'cause retumbo is really fluffy and fills the case very well.

So what's going on exactly? Roommate thinks it's due to the tight Shilen chamber...

In any case, best group was 1.000" with 5 rounds at 200 yards at 78.2 grains... Not that good.
Click to expand...

A 5 shot group that measures an inch at 200 yards not that good!!?? What are you expecting? If you want a measure of how the load will perform at long range, you'll have to shoot it at long range, but if you can maintain a half minute at a half mile, I doubt you have much to complain about.

Given the length of the 210 Matrix, if your rifle has a SAAMI chamber and you aren't jamming the bullets, you are almost certainly compressing your powder charges. It appears to me that the base of the bullet is just slightly below the junction of the shoulder and the body of the case. IMHO, compressed charges of Retumbo are bad news, and seeing extractor marks on Hornady brass might be the last warning you get to back off. I assume your brass is within the specified trim length. If you work up your load with a chronograph, when you see the maximum velocity listed in your manual pop up on the display, you'll know you're close to maximum pressure, regardless of your powder charge.
 
I have a Sako with a custom Hart barrel. I almost always max out 2-4 grains below what is listed in the various reloading manuals. My velocity also usually equals the reloading manuals velocity but with 2-4 grains less powder.
 
Thanks for the replies everyone, I'll be cooking up more handloads with a starting load of 71.5 grains and a max load of 76.5 grains of Retumbo or so.

I think that using magnum primers might be increasing the pressure of the load so I'll start low. With the 210VLDs and the 30" barrel, it's not like they need to be screaming out of there that bloody fast to get to a mile or a bit more (depending of how poor my shooting is).

Retumbo has a lot of volume so unless I'm wrong, I shouldn't be risking any problems arising from underloading it. Even at 71 grains, it fills the case to the shoulder easily.

Boomer said:
A 5 shot group that measures an inch at 200 yards not that good!!?? What are you expecting? If you want a measure of how the load will perform at long range, you'll have to shoot it at long range, but if you can maintain a half minute at a half mile, I doubt you have much to complain about.

Given the length of the 210 Matrix, if your rifle has a SAAMI chamber and you aren't jamming the bullets, you are almost certainly compressing your powder charges. It appears to me that the base of the bullet is just slightly below the junction of the shoulder and the body of the case. IMHO, compressed charges of Retumbo are bad news, and seeing extractor marks on Hornady brass might be the last warning you get to back off. I assume your brass is within the specified trim length. If you work up your load with a chronograph, when you see the maximum velocity listed in your manual pop up on the display, you'll know you're close to maximum pressure, regardless of your powder charge.
Click to expand...

Well first it's a 400$ match barrel on a savage action and I've seen builds like that shoot half MOA or better with proper high quality handloads. I know the rifle can shoot better than that as it's shot 1" groups with five rounds using the Hornady Superformance 180gr rounds - tuning handloads with bullets matched to the 1/10 twist in the barrel and brass that's perfectly formed to the chamber should really bring out the good groups.

Retumbo is listed in the Lee and Hodgdons books (amongst others) and is almost ALWAYS compressed when at near max or max powder charge...

None of my loads were compressed actually, you could still hear the powder rattle around in the case with a shake.


CanuckWR said:
I have run very simmilar loadings in my 110BA with the 208 AMAX, and have had comparble results in win cases and CCI LRM primers.

Weigh the case, then fill level to the top with water and weigh again. Do 5 cases and you will have an idea as to the water capacity of the fired cases. If you are over 89gn water capacity then Quickload says you are JUST at max at 79.8gn of retumbo. Speed matches your findings at 3040fps.

Hope this helps.
Click to expand...

That was pretty damn helpful actually! Reminds me how much I need quickload...

Cases came out at 90.2 grains of capacity, and if I look closely, my 78.0 grain loads had tiny but perceptible ejector imprints, so even that seemed to be over pressure, hence why I backed it off as seen above in the post.
 
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