How low can I go?

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windy

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Good day. I am reloading for a beautiful old Mauser in 7x57. I am using once fired federal brass, 140gn Nosler partitions and reloader 15. Noslers website States 38gn of RL15 as a start load. At the range this morning I had some pressure signs with the starting load, hard bolt lift and some primer flattening. Can I go lower than starting load and if so by how much?
Thanks
Windy
 
38gr is definitely their bottom end load, not showing a load on 7x57 on Alliant's page, last time I encountered a situation like that was with my 7-08 and IMR4320, turned out there was a recall on the powder. There are other things that can cause that with a min load, one may be jamming the bullet into the lands, which you should feel when chambering the round, that may raise pressure enough to cause that. A scale that is whacko, you setting the scale whacko, using wrong or cross contaminated powder that you thought was RL15. If you still have a round, take it apart and check the charge and what the powder look like compared to RL15. I'me not sure what could be haywire with a chamber that would still allow chambering the round. Tight barrel could do it, is it an original or a rebarreled gun? Have you shot factory ammo in it?
 
I have 5 loading manuals on my desk - every one of them has a warning not to use loads different than what they list. You are already doing that - Nosler 7 manual lists 38.0 as start load for RL15 with 140 grain Partition, yes, but they are using Winchester brass and WLR primers for their testing - you are using different brass and not mentioned what primers. As well, their loads were tested with Cartridge Over All Length of 3.065". There are reduced pressure loads, but not likely with RL15 powder. For some burn rates, it is as problematic to go "too low" as it is to go "too high". I have "got away with" using different brass and primers than listed, several times in several cartridge chamberings, but, for some reason, you are "getting caught" by something.
 
windy said:
Good day. I am reloading for a beautiful old Mauser in 7x57. I am using once fired federal brass, 140gn Nosler partitions and reloader 15. Noslers website States 38gn of RL15 as a start load. At the range this morning I had some pressure signs with the starting load, hard bolt lift and some primer flattening. Can I go lower than starting load and if so by how much?
Thanks
Windy
Click to expand...

I don't know about your mauser specifically, but you could probably go as low as 10% of total case capacity before you risk lodging bullets in the barrel.

Once you go below 70% of case capacity you should consider using cotton balls to wad the gunpowder down to the bottom of the case. You aren't packing it tight, but rather as light as possible with as little cotton as possible to get the job done. On a round to round basis, be consistent. If a single cotton ball is too big, cut it into halves. Be consistent on your cotton ball size and your wadding pressure. If you can turn the case upside down without hearing powder tumbling around you are good.

Reason why you do this are twofold:

1) Orientation of powder in the case matters, and you will see very different velocities between a case with the powder leaning towards the base versus powder leaning towards the bullet.
2) There is a lot of folklore about half filled cases blowing up receivers because the primer ignites all of the powder at once rather than having the flame burn through the powder in a linear fashion towards the bullet.

I've done a lot of super low velocity ballistic testing, shooting .308s as low as 75 FPS at the muzzle, and I've never blown up a receiver. ~75% case capacity is where you start to see some unacceptable fluctuations in velocity based on powder orientation inside the case. Your Mauser is a long and skinny case, relatively, so it should be less prone to this. Basically if I can fit half a cotton ball in the case, I'd be wadding.

If you are getting pressure signs at a starting load, I'd say thats weird. and would want to start double checking everything before I proceed further.

How full is your case at 38 Gr?
 
Try some different brass and see if you get the same issue. I have read that old military Mausers were designed for the 173gr RN FMJ. Those that have tried handloading for them have run into the same issues as you. Once they went back to the 173-175gr loads they were fine. So could be your load would be fine in a different rifle but not an older style Mauser.
 
You may not experiencing high pressure loads at all. You may have a sticky chamber (ie needs a polish), or have lug set back. Flattened primers can occur with undersized brass and low power loads. Suggest you try some different ammo, perhaps factory.
 
Cameron, that "folklore" you speak of is known as SEE, Secondary Explosion Effect and is a real thing. Why do you think there is start charges? Hodgdon only recommends H-4895 and Trailboss for reduced loads for this very reason. Just don't want to see someone get in trouble over this.
 
Thank you for your help everyone. I think I may have a headspace issue and funky chamber as the start of my problems. I tried some factory reloads and they chronographed at 1900fps and the primer was poking out by .018" but not flattened. Then I tried some Federal 140gns that shot at 2500fps, close enough to what the box said it should be. The primers were poking out as well but not flattened. There are wierd serrations on the outside of the brass running from shoulder to case head. ( Cutter chatter marks? ) I was hoping that by neck sizing the fired brass I could make up for the excess headspace. I will find a gunsmith to have a peak as this gun is way to nice to wreck.
Thanks again.
 
back40sniper said:
Cameron, that "folklore" you speak of is known as SEE, Secondary Explosion Effect and is a real thing. Why do you think there is start charges? Hodgdon only recommends H-4895 and Trailboss for reduced loads for this very reason. Just don't want to see someone get in trouble over this.
Click to expand...

Yes thank you. It is 'real' in an existential sense, in that there is a name to it, a theory to it, and a bunch of anecdotal experiences that lend credibility to the theory. Having studied it closely, I like many others have tried to recreate it under laboratory conditions only to fail to conclusively isolate it, and determine causation. If you know of someone or a study that has found a way to reliably create it I'd be very interested to take a look.

When I say folklore, I am not trying to suggest that there is no merit to claims about its existence, certainly I concede that there is something to it. I only mean to indicate that the science on it is less than conclusive.

You are correct to warn others about it, and I can say with high confidence that wadding in the manner I suggest seemingly eliminates any risk of occurrence.

I can't speculate as to why every powder manufacturer lists starting load charges, other than as a generally presumed safe level to start working upwards, in the interest of saving time, resources, and avoiding people from starting excessively high. You will note that they do not claim it to be a minimum safe load, and warnings not to go over minimum or to proceed below starting are written by lawyers trying to limit liability, not technicians.

As with all reloading, you are your own QA department, and you are own Health and Safety department. Proceed with caution.
 
At low loads, the case pressure is inadequate to expand the case, thus causing the protruded primers. So you may not have a headspace issue....
If your reloads were getting 1900 fps, these are definitely low pressure loads. The Federal rounds are also loaded modestly at 2500 fps, review of several loading manuals indicate an achievable velocity of 2700+ fps.
If you dont have a neck sizer, you can use your FL sizing die and partially resize the case to match the chamber. You can do this by trial and error - raise the die from your current position 1/8 of a turn, try for chamber fit. Continue raising the die until your brass doesnt chamber, and back off to the previous setting.
 
7mm Mauser / 7x57mm Mauser (Using 140 GR Nosler Bullets)

Warning .
Notes: Case: Winchester; primer: WLR; barrel length/make: 22" Lilja; twist: 1-9"; bullets: 140 GR Nosler AccuBond Spitzer, Ballistic Tip Spitzer, CT Ballistic Silvertip, Partition Spitzer - OACL: 3.065"; or E-Tip Spitzer
(Due to internal construction differences, always begin with starting loads when using E-Tip products. )
- OACL: 3.015"; maximum OACL: 3.065". WARNING: This load data is intended for use only with new firearms in good condition. If you are using an older military rifle, or question the condition of your firearm, it must be thoroughly inspected by a competent gunsmith before use. Use Maximum Loads with Caution

Be Alert: Publisher cannot be responsible for errors in published load data.

Wt. Bullet Powder Manufacturer Powder Charge Velocity (FPS) Favorite?
140 Nosler Alliant RL-15 42.0 2,693
Remarks: maximum load
140 Nosler Alliant RL-15 40.0 2,597
Remarks: most accurate load tested
140 Nosler Alliant RL-15 38.0 2,498
Remarks:
 
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