# High pressure signs



## Elkoholic8 (Jan 15, 2008)

I have been reading up on the signs of high pressure in reloads. I am reloading 7mm Rem Mag. So far I have tried 72 and 75 grains of Magpro, and 140gr Nosler Ballistic Tips, with Winchester Mag primers. 
I am getting just a touch of flattened primers from both powder amounts. (I have also tried 63 grains of IMR4350, and the primers looked the same). The 75 grain loads are getting a little sticky when opening the bolt. I probably need to come down to 74 or so.

If a case is going to crack or start to separate, is it real noticeable? I have looked over my cases, and I don't see any cracks, but I'm just wondering if it's easy to spot or if this is something that can sneak up on you. 

Would it make any difference to try another powder?

Anyone have some extra RL-19 or 22 they want to sell?


----------



## waspocrew (Nov 26, 2011)

I take a paper clip, straighten it out and then bend the last bit at the end to make a really tall "L" with a short foot. I'll insert the foot into the case mouth and rub the edge of the foot along the inside of the case from the bottom to about halfway up. I've been told that if you have an impending case head separation, you should feel a thinned area in the brass. 

I don't FL size my 7mm more than I have too. I'll get new brass, neck size to square up the mouths, load up and fire. Then repeat. After a few firings, I'll start to notice a little more effort to chamber, so then I'll FL size, but just enough to set the shoulder back a tich. Basically, I'll run the brass in the die and make small adjustments until the brass chambers easily again. I'll lock the die in place, then size the rest of the brass.


----------



## Springville Shooter (Oct 15, 2010)

Please reduce your loads by at least 5%. Have you chronographed your loads?-----SS


----------



## Loke (Sep 7, 2007)

Go get a Hornady loading manual. Then actually read the sections before you get to the loading data. They put that information in the front for a reason.


----------



## BPturkeys (Sep 13, 2007)

With the exception of way overloaded rounds, cases don't normally separate until after there has been much lengthening, trimming and improper or lack of annealing. 
Inspect all cases for any signs of cracking/splitting and always check overall case length before reloading. Short of maybe x-ray examination, it is very difficult to really tell if cases are "thinning". Just keep in mind that the metal doesn't just disappear, it can only "disappear" by being trimmed off the neck of the case. Keep your bass soft and malleable by annealing, pay attention to how much bass(metal) you are loosing through trimming.


----------



## Critter (Mar 20, 2010)

I have always wished that the loading manuals would go into a little bit more depth on the signs of excessive pressures. When I first started reloading pistol rounds my primers showed a lot of flattening but I didn't know just how much was too much. I figured that as long as it wasn't flowing all the way to the sides of the primer pocket that I was OK, but was I. When I started loading rifle rounds some of the first ones I could see where the extractor on the bolt and case met so I backed off a little and every thing was fine. I even resorted to measuring cases at the heads, and then just forward of the head to see if I could tell a difference but I never did, but the loads that I was shooting were quite hot. 
Now when you start to get primer cratering that is easy to see, but what is the difference between cratering and flow back and was it caused by a loose fitting firing pin or too much pressure. 

I had so many questions but there were too few answers back when I first started to reload.


----------



## BPturkeys (Sep 13, 2007)

Too high of pressure is an interesting talking point but in all reality with modern firearms and powders it is nearly impossible to create a load that is truly dangerous *IF* you follow the loading manual's instructions and recipes. 
The quest for the "perfect reload" should never be predicated upon reaching the highest attainable velocities. Accuracy should always be your number one directive. Not to say "never", but as far as I have seen, the "perfect reload", based upon accuracy, is always somewhere below the top velocities and never shows any of the classic signs of high pressure.


----------



## Loke (Sep 7, 2007)

You cannot reliably guestimate pressures based on the appearance of the case. Primer cups differ in hardness, as does brass. In a rifle that has a chamber cut to minimum specs, and brass that fits it well (like neck sized for that chamber), you may not see any of the traditional signs of pressure until you are in the 70-75,000 psi range. Those are in the proof load range. Once you get to the maximum load and/or velocity listed in the manual, it is safe to assume that you are at maximum pressure. There is no reason to go beyond that.


----------



## Critter (Mar 20, 2010)

One problem that you will have with the manuals is that when you purchase the X issue of that manual the max load is 90 grains of ABC powder and a 150 grain bullet. Then you purchase the Y issue of the same manual and it says that 85 grains of ABC powder with a 150 grain bullet is max. Then to really throw you for a loop you purchase issue Z of that same manual and now it is back up to 87 grains of ABC powder with the same bullet. 

It kind of makes you wonder just where they get their information from but when you are using different lots of powders in a pressure test barrel they might come up with anything. 

That is where it is up to the reloaded to make sure that their loads are safe in their rifle no matter what the manual says.


----------



## Elkoholic8 (Jan 15, 2008)

I do have a Hornady manual, and I have read through the first couple sections on reloading. I have been measuring my cases, trimming, full length sizing, and re-measuring. I seated the bullets a shade below the COL in the book trying to minimize the pressure. The thing I don't get, is that I am seeing the same primer marks on a near max load versus the minimum load (with exception of that 75gr load, where the bolt was a little harder to open). I will reduce that load to 73 or 73.5 grains and try it again.

I'll try and check to see if there is a groove developing on the inside, by the belt. 
Other than that, I just can't see where I am doing anything wrong, but I'm getting some minor signs of pressure. I don't think it's a problem with my process. I am being careful with everything, measuring powder on each load, checking primed case one by one, measuring each finished load. Don't know what I am missing.


----------



## Loke (Sep 7, 2007)

Sticky bolt lift is a sign of pressure. But there could also be other factors at play. A rough or dirty chamber can cause sticky bolt lift. Are you getting a shiny spot where the ejector passes through the bolt? That is a sign of high pressures.

See the shiny ring about 1/2" from the extractor groove? That is a sign that case head separation is about to happen.


----------



## BPturkeys (Sep 13, 2007)

Perhaps you are over reacting to what you believe are signs of high pressure. Marks on the base of the case can be caused be mill marks on the bolt face. Your concern about case separation, although something to pay attention to, sounds to be way overkill. Case separation due to high pressure only happens in conjunction with and after many other high pressure sign will be present. It is one of the last things to happen.
Are these or any other signs of high pressure apparent when you fire factory loads?


----------



## fishreaper (Jan 2, 2014)

winchester primers seem to show signs of cratering even on factory rounds, at least in my .243 and whatever primers are being used in PPU 7.62x54r. with that said, sever cratering and noticeable blow-back residue on the bolt is a different story. the primer will naturally flatten a little bit as a result of displacement, however there should be a noticeable amount of curvature left.


----------



## Huge29 (Sep 17, 2007)

You are within the specs according to http://www.nosler.com/7mm-remington-magnum
Do you have access to a chronograph? That is one tool that puts all of the speculating and guessing aside. Here is a great post from Frisco Pete on the topic from this thread http://utahwildlife.net/forum/18-firearms-reloading/39170-chronograph.html


----------



## BPturkeys (Sep 13, 2007)

Huge29 said:


> You are within the specs according to http://www.nosler.com/7mm-remington-magnum
> Do you have access to a chronograph? That is one tool that puts all of the speculating and guessing aside. Here is a great post from Frisco Pete on the topic from this thread http://utahwildlife.net/forum/18-firearms-reloading/39170-chronograph.html


How is a chronograph used in measuring, or for that matter, even estimating chamber pressure???
I suppose given all data i.e., bullet weight, power type and charge weight, temperature, elevation, humidity, caliber, etc, one could possibly back door a estimate of chamber pressure given the chronographed velocity, but the math would certainly be way beyond me.


----------



## El Matador (Dec 21, 2007)

A sticky bolt is a pretty reliable sign that pressure is getting up there. True it could be caused by other factors but most of the time it's pressure. A bit more powder, a little closer to the lands, or a hotter day at the range could give you a very sticky bolt or a very flat primer. Pay attention to the signs. Also, I'd recommend working up loads in smaller increments. 3 grains is a huge jump and could be the difference between no pressure signs and a bulged chamber. 1 grain is the biggest increment I'll use for a rifle.


----------



## Huge29 (Sep 17, 2007)

BPturkeys said:


> How is a chronograph used in measuring, or for that matter, even estimating chamber pressure???
> I suppose given all data i.e., bullet weight, power type and charge weight, temperature, elevation, humidity, caliber, etc, one could possibly back door a estimate of chamber pressure given the chronographed velocity, but the math would certainly be way beyond me.


Go to that thread Frisco Pete answers that; essentially just like in the PV=nRT pressure calculation that I recall from Chem 101 is that velocity is directly related to pressure; there certainly are some variants, but Pete hits that one too, here is his quote:


Frisco Pete said:


> Well there is a lot more to using a chronograph that that bit of misconception.
> And BTW, the very best chronograph of all is available again for a short time - The Oehler 35P. Oehler is the leader in chronographs and in the past most data you saw was chronographed using them. They have a 3rd screen that helps detect bogus errors.
> I would also look at the RCBS chronograph before the Chrony. But any chronograph is better than no chronograph.
> 
> ...


----------

