Is this load unsafe (according to GRC)?

[marchx]

I am running 30gr of N140 in 6BR shooting 105gr Barts Infinity bullets. I chose Berger Hybrids in GRT because it's ballistically very close. It seems that my load is unsafe. Surprisingly, if I was loading 105gr Scenars, the load becomes safer acccording to GRC. Is anyone running 30gr or more of N140 behind a 105gr bullet?

 

[Bc'z]

I'm 28.9 grain N140 105 hammer Peterson brass cci400, 2780 velocity.
Went to 29.7 sticky bolt lift up there.

 

[ZenArchery]

Start low and work up, you’ll know. I shoot mostly wildcat cartridges and live off GRT. It’s a predictive tool to work off of. Even though it says it’s a hot load. Let your shooting system tell you what’s really happening. Start low, work up.

 

[whatsupdoc]

GRC has max pressure at 58,740 PSI for this cartridge.
The Berger is at 58,760 PSI 20 PSI over max pressure.
The Lapua is at 58,708 PSI 32 PSI under max pressure.

Difference between the two bullets is 52 PSI, very small but GRC is not without
error.

In your rifle the numbers may be similar or they may not, you need to test your components in your gun. Some shooters do push the envelope above what is
believed to be a safe level.

 

[joshb]

My guns are in the 28+ to low 29ish range. The apps can help but real world testing is needed. The mantra of “Start low and work up.” exists for a good reason. Every gun is different.

 

[fkimble@charter.net]

New to 6Br but I run 30.0 N140, CCI 400 and CCI 450 behind Sierra 107's. Nice rounded corners on both primers.

Frank

 

[Fast14riot]

Have you measured your case capacity and bullet length, then adjusted GRT accordingly?

 

[divingin]

I suspect you're at the point where predictions are useless. Go with what your rifle tells you (unless this is all theoretical, in which case work up slowly towards it.)

 

[dellet]

It’s a trick question.

Either both are safe, or both are not.

If 50psi difference means the difference between pieces parts in your face or not, junk the rifle it’s not safe to shoot that cartridge. Rebarrel it to a rimfire.

That said that same pressure swing on even the best loads will happen on cold and hot days, even the same day if the temp swings or not. Maybe even raking 30 seconds difference between shots with a hot barrel. The problem with the comparison is that it’s immeasurable. The 50 psi will be within the margin of error, and no one shoots a match with pressure test barrel. Then the .2 fps velocity spread is what shooters dreams, more likely night mares, are made of. No way to measure that.

Not to encourage bad behavior, but the cartridge was likely proof loaded to around 75,000 psi. And a good bolt action to over 100,000 psi. The brass will be the weak link. Pay attention to where and how much it grows.

 

[6MMsteve]

I have several 6xc barrels and they won't shoot the same loads but then again diff mfg barrels also...work up to max always then back down

 

[joshb]

I have several 6xc barrels and they won't shoot the same loads but then again diff mfg barrels also...work up to max always then back down

Yup! I have 4 different 6br guns. Three of them shoot in the same general charge weight. + or minus 1/2 a grain. The forth needs to be loaded almost 2 grains lower or it blows primers and the bolt gets stuck. I have to be careful when grabbing a box of loads when I go shoot. I keep the boxes clearly marked in BIG letters.

 

[Rat Rifle]

With Your load, no matter what Reloading Software You use, when the temperature approaches 90* You will experience increased pressure and barrel heat. N 140 is temp sensitive.

 

[divingin]

Either both are safe, or both are not.

If 50psi difference means the difference between pieces parts in your face or not, junk the rifle it’s not safe to shoot that cartridge.

I suspect there's a few other steps between a "safe, reliable load" and parts in your face. Pierced primers, enlarged pockets, ejector marked brass, stuck brass, etc.

Also worth noting that the OP said the bullet change resulted in a "safer" load; not "safe".

 

[dellet]

I suspect there's a few other steps between a "safe, reliable load" and parts in your face. Pierced primers, enlarged pockets, ejector marked brass, stuck brass, etc.

Also worth noting that the OP said the bullet change resulted in a "safer" load; not "safe".

I am running 30gr of N140 in 6BR shooting 105gr Barts Infinity bullets. I chose Berger Hybrids in GRT because it's ballistically very close. It seems that my load is unsafe. Surprisingly, if I was loading 105gr Scenars, the load becomes safer acccording to GRC. Is anyone running 30gr or more of N140 behind a 105gr bullet?

I read that differently, if the load is unsafe, you can not make it safer. Kind of like being less pregnant. You’re either safe or not, pregnant or not.

I’ll concede A blown primer is often gas and junk in your face vs an action that explodes, so yes there are degrees of catastrophe. Being maimed is technically safer than death.

My original answer stands, if you think a .1% pressure change when dealing with 50,000 + psi will make a load any safer, it’s not thinking clearly. That was the actual question.

The question was not if the pressure difference might cause sticky bolt lift or not. Flatten a primer or not.

The very wise advice of starting low and working up allows you avoid this type of “is it safe” question entirely.

 

[SeabeeKen]

Like any other computer simulation, its only as good as the data you feed it. Everything must be measured to get accurate data. After this, calibrate the powder model by using the OBT tool to match measured velocity. I have a number of calibrated powder models saved. Powders burn differently in different rifles and cartridges. Once calibrated, GRT is quite accurate.
We have locals shooting 3 grains over Vihtavouri max loads in PPC and afraid to back down even though one fella gets only one firing out of his brass and blowing primers. When I ran his data in GRT, he is at 74,000 psi+ and he still wont listen. Hopefully I'm not shooting next to him on a hot day this year.

 

[dstoenner]

Like any other computer simulation, its only as good as the data you feed it. Everything must be measured to get accurate data. After this, calibrate the powder model by using the OBT tool to match measured velocity. I have a number of calibrated powder models saved. Powders burn differently in different rifles and cartridges. Once calibrated, GRT is quite accurate.
We have locals shooting 3 grains over Vihtavouri max loads in PPC and afraid to back down even though one fella gets only one firing out of his brass and blowing primers. When I ran his data in GRT, he is at 74,000 psi+ and he still wont listen. Hopefully I'm not shooting next to him on a hot day this year.

This is the answer. GRT is SWAG until you plug in real data and curve fit by using OBT. My load for my 6br using 105 and Varget is 29 gn.

David

 

[LCazador]

Are you monitoring case head expansion? You'll be more than guessing if you're not doing this. Also have you tried mag primers? In my experience mag primers always give lower pressures. Yeah I always thought the reverse was true.

 

[shoot4fun]

I think there are too many variables for anyone to give you a straight up definitive answer, using GRT or QL or any other reloading tool as to safe or not.
Yes, there are some here that have already clarified responses and that is some great advice.
When I started shooting 6BR my powder was 8208XBR. I bought the rifle from a guy on this forum and he gave me the load it liked. After shooting that load and doing well for months I happened to see load data published and, to my surprise, I was well past the pressure limits they showed in that data.

 

[divingin]

I read that differently, if the load is unsafe, you can not make it safer.

You left out the "according to GRT" part. That is a screen-based judgement, not a physical shooting thing, and will allow you to grade "safe" based on small changes that would likely not apply to real-world scenarios. I understand what you're saying, but you are talking physical, and the discussion was pretty much theoretical.

GRT likes a buffer of 15% under the published max pressure; anything above that (despite being "acceptable" per the published standards) is considered "risky" or "dangerous". So those definitions are GRT-based as well.

In any case, the transition from theoretical, simulated results to real-world physical results is generally iffy, which is why I said the area he's working is better tested by actual results rather than by GRT.

 

[marchx]

This is the primer. Looks like we have our answer.