Margin for error??

[VikingsGuy]

All good engineering projects provide some margin for error even at "max tolerances". In the hand-loading world, I assume this is the case as well. So, if I work up a load that is at the published "max" load from a credible book (nosler, hornady, lyman, etc) and I do not see over pressure signs when shooting this "max load", how much room for error (safety-related error, not accuracy issues) is there in powder measurement? 2%, 5%, 10%? I have got to believe, in modern rifles, that manufactures give us some breathing room above the SAMMI numbers -- but maybe that is not the case. What is the collective wisdom of HT? I am not trying to push my loads above book, I am a "safety-first" guy, just trying to get a feel for whether I am on a tightrope or a 4x4.

 

[TimeOnTarget]

Really depends on your particular rifle. I had a 300wsm that I could go well over published max and still not see any signs of pressure. On the other hand, I've got a .223 that leaves extractor marks and beyond flat primers at less than middle of the range published loads. I've no doubt if I loaded a published max load in this rifle, Id be using a hammer to get the bolt open.

All rifles are different.

 

[Deleted member 28227]

I think there is quite a bit of breathing room from my experience with my .264... but that just might be that specific caliber. I have an old lyman book that has a max load 300fps faster than the exact same powder, bullet weight, etc. in the new nosler book. I think in our litigious era books have backed way down, I wouldn't be surprised if it's more than 15% in some instances.

 

[Gunner46]

Take a tour over on the Nosler Reloading forum. If you can't get an answer there, then I can't help you any further. It's an amazing free resource of technical knowledge. It's like being on a Masters level research team.

 

[VikingsGuy]

Really depends on your particular rifle. I had a 300wsm that I could go well over published max and still not see any signs of pressure. On the other hand, I've got a .223 that leaves extractor marks and beyond flat primers at less than middle of the range published loads. I've no doubt if I loaded a published max load in this rifle, Id be using a hammer to get the bolt open.

All rifles are different.

Good input. To narrow my question a little, I am looking for failure tolerances where the health and well being of the shooters and bystanders are at risk. There of course is a place short of this where you may fubar your action.

 

[MThuntr]

Good input. To narrow my question a little, I am looking for failure tolerances where the health and well being of the shooters and bystanders are at risk. There of course is a place short of this where you may fubar your action.

You need to read the brass to get that answer. Once you start getting signs of pressure you probably aren't going to want to go any higher because you are approaching the safe limits of your components. Your primers will probably fail before your rifle explodes however do you really want hot gasses flying toward your face. In some cases, you couldn't cram enough powder in to get to failure and in other you could only be a few grains off.

Read this...https://www.primalrights.com/library/articles/understanding-pressure

I would suggest loading for accuracy over velocity.

 

[Doublecluck]

Good input. To narrow my question a little, I am looking for failure tolerances where the health and well being of the shooters and bystanders are at risk. There of course is a place short of this where you may fubar your action.

Not likely to blow yourself up working up in increments beyond book specs if the load is safe at max. From what I have seen cases split, primers blow it etc before it goes really bad. Usually when people get hurt it's case length, coal, starting max with extended coal/wrong powder entirely. I have a 30-06 that shoots 168 gr bergers 2.0 grains over berger book max charge. It has zero pressure signs.. I have probably shot over a 1000 rounds at that charge and have some brass that has been loaded 5+ times with that charge.

 

[Tradewind]

Not likely to blow yourself up working up in increments beyond book specs if the load is safe at max. From what I have seen cases split, primers blow it etc before it goes really bad. Usually when people get hurt it's case length, coal, starting max with extended coal/wrong powder entirely. I have a 30-06 that shoots 168 gr bergers 2.0 grains over berger book max charge. It has zero pressure signs.. I have probably shot over a 1000 rounds at that charge and have some brass that has been loaded 5+ times with that charge.

Exactly. I was working my way forward with the coal but kept the load in the middle of the range. Then started working up on the powder. Nothing new here. I was just following along what others were already doing with the same cal. bullet and load. They were all loading beyond the max suggested. Whence I got there, no signs of any problem with the case or primer in a new rifle. But I am still very careful about it. I am on my 3rd loading.
On the other hand, went out shooting with a buddy and took an old nagant along. Fed it some of the old military ammo i had. funny stuff started happening. Cases started splitting (3 out of abt 15). getting a poof of blowback my way.
weak case obviously but the rifle handled it.

 

[mtmuley]

A chronograph is a great tool. Sometimes a spike in velocity tells a story before any other pressure signs. mtmuley

 

[ol_spark]

Mthuntr has it right, read the brass. Work up in small increments .3 or .5gr at a time load each cartridge the same and only change powder charge. Hard bolt lift with a bolt action is a sign of high pressure. Also look at brass if you start to see little smiley faces you are approaching max, back off this load. A lot of guns of same make and caliber are different. Max in one gun does not mean max load in another. I find loads for all my rifles by running a ladder test. Google works great.

 

[VikingsGuy]

Thanks for all the helpful posts, but for clarity's sake, I am not working loads past book max, I was wondering about leeway in light of a one off error, such as erroneously overloading a single cartridge or not fully seating a cartridge so that it was a little long, but bolt would still close. For example, if my scale was off by a grain (2-3%) once is there some leeway built into the actions specs and the loading book info.

 

[cahunter805]

1 grain you will be fine. May lose the brass to pressure if anything but that's probably it.
Rifle actions are designed to hold much more pressure than that. Seating a bullet a little long won't harm anything either. The brass can take some over pressure also.
Now if you loaded the wrong powder that's a whole different situation.

 

[tom338]

I have loaded a 7mm that 3 grains under max its showing lots of pressure signs and another 7mm that will go 3 grains over. Every barrel is different and needs to be worked up carefully.

 

[ol_spark]

If your not loading past book max and you have a current book using current powder, I would say not to worry. There’s leeway built in.

 

[375H&H]

One thing I have found with a load that I recently backed off by 2gr because of flattened primers is that the precision was not affected nor was point of impact. Just nice to know that if I back a load off I don't have to go through the whole process again.

 

[mtmuley]

One thing I have found with a load that I recently backed off by 2gr because of flattened primers is that the precision was not affected nor was point of impact. Just nice to know that if I back a load off I don't have to go through the whole process again.

How far out did you check the point of impact with a 2 grain change in charge, and what cartridge? mtmuley

 

[375H&H]

How far out did you check the point of impact with a 2 grain change in charge, and what cartridge? mtmuley

I don't shoot long range so we shot 2 more groups at 100 yards and they didn't move at all, couldn't tell which were which. This was for a 25.06 with 115r Barnes TSX. That gun killed both an antelope and deer this year and hit where we aimed so we did not notice a difference.

We were originally 4 gr over max and dropped it down to 2 gr over max published load by Barnes. I would like to drop it down a couple more next year as I don't see a need to have the higher load and sometimes the bolt is a bit hard to work.

 

[std7mag]

There is reading the casing for pressure, kinda like reading tea leaves..

Or you can get a Pressure Trace and know what is going on.