Question regarding pressure signs/powder charge

[Bassnbow]

Thanks everyone, I was wondering if the higher temps were going to cause problems. Like most of you, most of my hunting is done in cooler weather, but I want a load I don't have to worry about during summer or early fall hunts.

I do have some RL23 I could try, is shoots great in my 300wm. I was trying to use only powders known to be less temp sensitive. I also live in the comy-Cal, so I'll be working on a non-lead load soon. Not sure which bullet I'm going with yet, I have some Barnes 145lrx and 152 cutting edge, but not sure yet.

 

[memtb]

Thanks everyone, I was wondering if the higher temps were going to cause problems. Like most of you, most of my hunting is done in cooler weather, but I want a load I don't have to worry about during summer or early fall hunts.

I do have some RL23 I could try, is shoots great in my 300wm. I was trying to use only powders known to be less temp sensitive. I also live in the comy-Cal, so I'll be working on a non-lead load soon. Not sure which bullet I'm going with yet, I have some Barnes 145lrx and 152 cutting edge, but not sure yet.

My system may not be the perfect system, and as stated, adds it's own set of things to work through. But, as I tend to "push the envelope" a little, and occasionally shoot on hot days…..I don't want any ugly surprises! memtb

 

[Bassnbow]

My experience with Berger load data is it tends to be very hot. (Same for Alliant load data) In general, I've found Hornady to be more in line with what I end up achieving, even though I might not reach the max velocity they publish. The current manual doesn't have 7 PRC data but their app does. For 7 PRC 175 ELDX they list max loads RE26 67.1/ 3000, H1000 67.1 / 2950, H4831SC 63.9/ 2950. The velocities are for a 24" barrel.
I've been working on load development for a 7 PRC Havak Element with a 22" barrel and a TBAC suppressor. I have been working with 175 ELDX, 175 EH, and 195 EH and Federal Premium 175 ELDX factory ammo. The Garmin Xero C1 makes it so easy, I've chrongraphed everything. I've been using both ADG and Peterson brass and have tried CCI250, F215M, F210M primers. I'm closing in on 250 rounds fired so far but am still working with virgin brass.
As others have pointed out, I suspect your posted loads were likely over pressure. I haven't seen any signs of pressure with my ADG or Peterson brass for the 7 PRC even when I exceeded Hornaday's max (but not nearly as high as you list). I worked up slow with all my powders and generally saw my ES/SD and group size get worse once I passed above Hornady's max loads. My best results for the 175 EH were close to the velocity range @cajun mentioned above 2860-2910 fps, using RL26.

Here are a few of my observations from the data I recorded which may or may not help in your efforts:

• 175 ELDX tended to be about 50 fps faster than 175 EH for the same charge
• F210M and CCI250 gave me similar results while F215M tended to give +30 fps higher
• the factory Federal ammunition gave me 2880 fps on average
• 175 EH, 180 Hybrid and 195 EH all had with-in a few thousand max COAL to the lands in my rifle and jumping them about 0.050 has given me the best results

Good luck with your Tikka and load development efforts.

Thanks this gives me something to compare to. Interesting though the Federal 175 ELDX is running right at 2900 in my 22" barrel and sub 1/2". I've just had such good luck with Bergers that I had to try, and I'm sure I'll find a sub 1/2 with them also

 

[cabelasken]

While I'm not using R26 in my cartridge, potential temperature spikes is the primary reason that I only do load development on hot (90+ F) days.

While not a perfect solution, as the much cooler hunting season temperatures will reduce mv's and alter the group size findings. So now, the velocities/groups must be verified, and re-zero'd on a day replicating expected hunting season temperatures!

It does add a degree of difficulty and lengthens the process….but gives comfort that if shot on a hot day, you won't run into an excessive pressure situation! memtb

A lot of my practicing is done from May thru Sept. and my hunts are all in Oct / Nov. which is why I rezero just before I leave for the hunt. Often i have to adjust the scope 1/4" or so on the week before leaving. I now keep my loads up to 2 or 3 grains under pressure signs to help prolong brass life and to keep from having issues in the field. Usually this ends up being right at book max or maybe a grain above - but not more than that.

 

[HNDLDR]

On the subject of brass being formed to the chamber. Most cartridges I've payed attention to (7mm-08, 25-06 and such) gain about 50fps, with the same load, going from virgin brass to once fired. I would think in your case there would be even less of a change going from once fired to twice fired.

The only part that confuses me is what PddPdd said about the pressure increasing with the same load on fully formed brass. My brass seemed to indicate less pressure not more as the case get fully formed.
I do not have pressure testing equipment and I'm definitely no expert. Maybe someone could explain this to me.

 

[Shane Lindsey]

On the subject of brass being formed to the chamber. Most cartridges I've payed attention to (7mm-08, 25-06 and such) gain about 50fps, with the same load, going from virgin brass to once fired. I would think in your case there would be even less of a change going from once fired to twice fired.

The only part that confuses me is what PddPdd said about the pressure increasing with the same load on fully formed brass. My brass seemed to indicate less pressure not more as the case get fully formed.
I do not have pressure testing equipment and I'm definitely no expert. Maybe someone could explain this to me.

"Open" space/clerance in the chamber due to brass not being fireformed masks the pressure as it forms to chamber dimensions. Once it is tight to the chamber, there is only one place for the pressure to go, backward.

If you work up to max and beyond with virgin brass, you will often see this. If you are well under max pressure, you may not need to back off with subsequent firings.

Added, a good sign of this at least for me, is very hard to size once fired brass. It usually will, but the brass doesn't last long.

I trashed a few ADG cases a few years back working up loads in a 300 win mag. Belted cases really give you a false sense as they seem to have crazy space to the shoulder.

 

[PddPdd]

On the subject of brass being formed to the chamber. Most cartridges I've payed attention to (7mm-08, 25-06 and such) gain about 50fps, with the same load, going from virgin brass to once fired. I would think in your case there would be even less of a change going from once fired to twice fired.

The only part that confuses me is what PddPdd said about the pressure increasing with the same load on fully formed brass. My brass seemed to indicate less pressure not more as the case get fully formed.
I do not have pressure testing equipment and I'm definitely no expert. Maybe someone could explain this to me.

Hi HNDLDR,

I'll try to explain my earlier post.

There are two things going on when fire forming brass. 1) the brass absorbs energy in the process of being permanently deformed to a new, different shape, 2) the fire formed brass has a new larger volume then the unformed brass so the pressure energy is being contained momentarily in a larger volume than the unformed brass.

These two processes offset each other to some degree and their magnitudes depend on the amount of energy required to deform brass versus the volume increase of the brass.

I would recommend, based on my experience, to error on the side of caution and realize there could be a pressure increase when transitioning from un-formed to fire formed brass. I have seen this with fire forming new brass to my rifle chambers for 7-08 & 28 Nosler Peterson & ADG brass.

 

[HNDLDR]

Hi HNDLDR,

I'll try to explain my earlier post.

There are two things going on when fire forming brass. 1) the brass absorbs energy in the process of being permanently deformed to a new, different shape, 2) the fire formed brass has a new larger volume then the unformed brass so the pressure energy is being contained momentarily in a larger volume than the unformed brass.

These two processes offset each other to some degree and their magnitudes depend on the amount of energy required to deform brass versus the volume increase of the brass.

I would recommend, based on my experience, to error on the side of caution and realize there could be a pressure increase when transitioning from un-formed to fire formed brass. I have seen this with fire forming new brass to my rifle chambers for 7-08 & 28 Nosler Peterson & ADG brass.

So no one has information for a study or something that has plotted this with pressure equipment. I'm not saying it's wrong as I have no way to test it. I was just trying to understand why my brass seemed to show less pressure sign the second time.

 

[cajun]

Fire formed brass has a little more case capacity.

 

[cajun]

You guys have to keep in mind... just because you don't see pressure signs on the brass or heavy bolt lift etc... doesn't mean that your ammo isn't over pressure!

Ammo can easily go over pressure and you not see the signs any where.

I won't say the caliber but this is a good example. I was able to get brass and build a rifle in a spec caliber where it wasn't production made available yet to the public.

I worked up loads and did my testing like normal.

Because and only because we make the ammunition test barrels for different manufacturers I asked the one place that if I sent them some of my ammo and the next time at they're convenience when they have the p&v barrel set up again for this caliber would they run some of my ammo thru the test barrel for me? They said yes sure. Send it in and will all the load data and lot numbers of the components.

Per they're data and actual released loading data which came out about the same time... my one load at a .5gr over they're max load they recommended in the book my pressure was 5k psi over maximum recommended. My next load was 2gr more of a heavier powder charge and that bumped the pressure another 10psi but in my gun I had no pressure signs at all. So again just because you don't see any pressure signs doesn't mean that you have not exceeded the max pressure.

Later, Frank
Bartlein Barrels

I try and tell folks this all the time. Glad to see Frank chiming in. I ran a ladder with R 26 in a creedmore before there was any real data. I got a 140 to 3025 fps in a 26" barrel with no signs of pressure.
I cant tell you how many loads
I've seen on the net and I'm
Like hello. Brass doesnt show pressure till 70k. Reading primers is voodoo especially if your firing pin is not bushed. When your bolt gets sticky your way over.

 

[Okanogan]

OP, FYI Hornady app lists max RL23 as 61.2 / 2900 fps with 24" barrel. I like RL23 for mid weight bullets in my 300WM but haven't tried it in my 7 PRC.

 

[Bob Wright]

Thanks everyone, I was wondering if the higher temps were going to cause problems. Like most of you, most of my hunting is done in cooler weather, but I want a load I don't have to worry about during summer or early fall hunts.

I do have some RL23 I could try, is shoots great in my 300wm. I was trying to use only powders known to be less temp sensitive. I also live in the comy-Cal, so I'll be working on a non-lead load soon. Not sure which bullet I'm going with yet, I have some Barnes 145lrx and 152 cutting edge, but not sure yet.

This would be a great combo with RE23. Trick is finding RE anything. Since you have some, try it. I'm running a 143 Hammer Hunter and RE23 in my 7RM for no lead hunts here. Case capacity is pretty close by your numbers on the 7PRC. Worth a 10 shot ladder.

 

[Shane Lindsey]

This would be a great combo with RE23. Trick is finding RE anything. Since you have some, try it. I'm running a 143 Hammer Hunter and RE23 in my 7RM for no lead hunts here. Case capacity is pretty close by your numbers on the 7PRC. Worth a 10 shot ladder.

RL23 and the 131 Hammer was da bomb in my 7RM.