7MM Magnum Question

R

reomack

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I have been reloading the 7MM mag for years and have always wondered whether the stated max loads for most powders is what causes the round to, according to a number of sources, experience unpredictable pressure spikes. What I have observed is that most powders don't come very close to filling the case when using max or close to max loads. I was wondering whether using a powder that comes closer to filling the case at near max load levels might help with this problem. And if anyone here knows of such a powder. Also has anyone here done any actual research using said powder. I think use of a powder that gives a slightly compressed load at max might solve the unpredictable pressure spike problem. If this supposition is ridiculous on its face, don't be afraid of embarrassing me by saying so, since this is all guesswork on my part and I have a thick skin anyway.:ninja:
 
Check this out, it may help...

RSI Barrel Harmonics said:
In every instance when secondary pressures are detected they can be eliminated by using a faster power, heavier bullet or a bullet with more bore contact area. Normal "tweaking" of loads may change the peak of secondary pressures but will not eliminate the problem. Below is the list of factors we now know can cause secondary pressures.

1. Powder burn rate too slow for the bullet.
2. Bullet weight too light for the powder's burn rate.
3. Bullet bore contact area less then normal for the bullet weight
4. Barrel longer then normal
5. Bore severely worn or incorrectly lapped (loose/worn toward the muzzle)
6. Moly in bore or moly coated bullets that reduce bore friction
Click to expand...

http://www.shootingsoftware.com/tech.htm

http://www.shootingsoftware.com/barrel.htm

SL
 
How do you know you're getting unpredictable pressure spikes? Are you trying to describe sudden appearances of pressure signs or wild, excessive velocities when working up through increasing charges during load development? This can happen - charges 1, 2, 3, & 4 are whistling along quite nicely, not showing pressure signs on the cases and then charge #5 all of a sudden shows a flat primer or sticky bolt. No biggie, you just found your max (or possibly a bit more)!

What powder are you using? What charge increments? Do you weigh each of your development charges? What bullet? Seated how far from / into the rifling? Is your bullet seating consistent? Are you using mixed lots of brass? Do you drink beer when you reload? Do you stand on your head and scratch your nutz when you throw a charge? Lots of variables.

There are several manuals that show general powder volume percentage with the given charge. Yes, powders with enough bulk to fill the case to near 100% is usually desireable for conistency and should give you more stable results and theoretical numbers.

Rooster
 
I have learnt over the years to ignore the filling percentage of any powder for any given load. Yes, a lot of the loads don't come close to filling the case, BUT, everything is based on the pressures that that amount of powder will create with your combination due to all the different burn rates. I have found over the years, loading for my 7mm Rem Mag, that the listed loads tend to be on the soft side, but they are safe. If you want more powder percentage in your case you must very carefully work up that load and watch for pressure signs. Every gun is different to every load and any listed load tends to be a strong averaging of pressures tested. Any load in the 7mm close or at 3000 FPS is a monster load, you don't need anything more. If you do, you need a different larger gun and theres nothing wrong with that at all.
 
I find like HIGHRPM pointed out, published 7mm. remington mag data is on the light side.
Have never done all that much experimenting with my 700 7mm Rem Mag as I found what it liked pretty quick.
An honest charge of IMR 7828 under a 150gr. Nosler Ballistic Tip clocking in at 3200fps....And yes it is a compressed load but safe and predictable for over 2 decades in my 700. Groups under an inch and hits very hard.
I think you are on the right track when trying to have the case filled or even compressed when at or near a max load. In my mind it's got to help by taking out a variable at ignition.
Only ever tried H4831 and IMR7828 and don't recall anything that I would call unpredictable like pressure spikes...Pressure and velocity progressed evenly as charge was increased...The IMR7828 reached a much higher velocity with what I would call same pressure as the H4831 did at a lower velocity...Plus the IMR7828 filled the case and shot more accurately.
From what I have read, back in the day 7mm mag chamber dimensions varied greatly from one rifle manufacturer to another which made it difficult for load data to be safely published at max levels for the public...Hence the conservative load data.
 
Thank you all for the responses. For some reason, I have never tried 7828 but rest assured that I soon will. Having the case full without exceeding max load recommendations is what I was aiming at with this question. I understand that there are many variables at play in the reloading game but the fact is that the issue of pressure spikes in the 7MM Mag is one that pops up with some frequency and it seemed to me that a partially filled case could be one reason. I normally load 140 gr and 175 gr bullets and have used a variety of them. Have also used a number of different powders but never found one that filled the case completely while not exceeding max load recommendations. Will buy some 7828 and give it a go.
 
I have done a bit of load developing in 7mm rem with imr4350,H1000, imr7828, and hybrid 100v. Never noticed any unusual pressure spikes with any powder, any different than all cartridges I reload for. I reload for or have reloaded for at least 15 different calibers. I had a huge amount of 145 speers that I loaded with those powders and all had great results up to 3300fps in a 26" tube with minimal pressure signs and over book loads. I even made a rookie mistake and skipped development with H1000 and used info I had incorrectly wrote in my log. I luckily had the chrony going at the time to record velocities in the 3500fps range and a sticky bolt that required some persuasion to open. I shot three of these(stupid I know) but there ES was within 15 fps and they grouped well. The only pressure spikes that I have noticed in any caliber is guns with tight chambers. Also I reloaded for 4 different rifles in 7mm that all had predictable results. FYI Hybrid 100v is awesome in 7mmrem.
 
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