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Jim,
Thanks for posting that thread, Mule Deer gives a relevant summary that makes sense.
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Campfire Ranger
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Campfire Ranger
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From another thread, this relevant comment on the current question by Mule Deer:
"Some comments on the latest batch of comments:
1) Actually the .243 Win. and 7mm Rem. Magnum do not exhibit pressure "spikes," at least not often. What they do generally show in pressure labs is wider pressure variations--both high and low from average--than most other cartridges. These might amount to a total of 12,000 psi, or plus-or-minus 6000 from average, rather plus or minus 3000 in some other rounds.
And I agree with that--but I didn't mean to suggest that spikes only occur higher. But it's the higher spikes we are concerned with from a safety standpoint. It still doesn't change the evidence that some cartridges exhibit a wider range of pressures than others. The question remains why some cartridges exhibit larger spikes than other cartridges based on the same case. But it does explain why SAAMI limits are different for different cartridges based on the same case. Casey
Casey
Not being married to any particular political party sure makes it a lot easier to look at the world more objectively...
Having said that, MAGA.
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Campfire Ranger
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After reading the thread regarding Charlie Sisk's testing that was posted on this thread by Teal, I think you are right about it not likely having anything to do with caliber.
Charlie was getting secondary spikes with various calibers by using small for caliber bullets with slow case filling powders.
I am still not clear on one point, given that spikes can occur in many calibers, are they more likely in the 7 RM or was the 7 RM perhaps the caliber some lab technician was using when they first started discovering these spikes?
I'm having the impression that the 7 RM would be spike free using a 160 bullet.
Does anyone know or remember who or what was the source of the original rumor in regards to the 7 RM pressure spikes? My original info came from the family friend who supplied tools and dies to Remington, and more info from an engineer who worked for Dupont. Since then I have read more stuff on the subject. Of course, over time that info may have changed as more and better testing has been done. Undoubtedly the 7mmRM has been tested quite a bit more than some of the other less common cartridges that come from companies that don't have the same ability to test as Remington. Again, it's likely that different powders, charges, bullet wieghts and bullet styles will have an effect on spikes/variations in the pressure curve, but my understanding is that some cartridges are more apt to show the spikes than others regardless. But one peice of anecdotal evidence is Remington's advertised muzzle velocity with their factory 150gr Corelokts decreased during the same time periods as when they allegedly reduced the powder charges in the 7mmRM. Until the late 70's that load was advertised at 3300fps. I know the subject of the thread is the 7mmRM, but I want to emphasize I'm not picking on the 7mm, because there are other cartridges out their that also exhibit these relatively large spikes/variations. As JB has written, ALL cartridges exhibit spikes to varying degrees. Casey
Casey
Not being married to any particular political party sure makes it a lot easier to look at the world more objectively...
Having said that, MAGA.
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So, it seems like Remington themselves may have been the first to have concerns over this round.
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Campfire Kahuna
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Campfire Kahuna
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There was a WHOLE lot more to his equation than just case design and pressure spikes. The brake DEFINITELY had something do do with it, since that is what blew off. I would say the unburnt powder or part of it was acting like a bomb in the recessed brake area. Perhaps copper was shearing off the bullet in the break area. Too tough to call, since I wasn't there, but the test was too simple and basic to quantify good data. If it were simply physics of case design, no Mfg. would be loading such a dangerous round. 30,000 PSI would cause a lot or rifles to "nuke". I take his findings with a grain of salt. That isnt' to say he didn't know what he was doing, but there isn't enough data to work off of. Flinch Had a break blow off a 7stw once, purely coincidental though IMHO, it was a metal issue, wonder if the annealing of cutting the holes wasn't right in your instance... I know it made a really weird noise and blew the brake right off the end, weak spot amongst all the holes that started it, and the bullet caught the edge and pop.... Replaced free of course...
We can keep Larry Root and all his idiotic blabber and user names on here, but we can't get Ralph back..... Whiskey Tango Foxtrot, over....
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Funny: I fired a 7mm Rem Mag -- ADL with open sights -- in the late 70s with lighter, faster bullets.  I got my cheek whacked hard.  Hated that round ever since.  I bet today loads would be more pleasant.  BMT
"The Church can and should help modern society by tirelessly insisting that the work of women in the home be recognized and respected by all in its irreplaceable value." Apostolic Exhortation On The Family, Pope John Paul II
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Campfire 'Bwana
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I think some might be confusing a sudden increase in velocity or large deviation from average speed as a "pressure spike".
What Charlie was talking about and most others I believe when discussing the 7mm is a measurable change in internal pressure exerted on the walls of the barrel.
That "pressure" spike is a "repeat" of chamber pressure - only several inches down the tube. Charlie was testing via strain gauge.
Me
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Flinch
I'll be the first to say I dont know what I'm doing, but I do know a test of one means nothing. So I did another test with a factory Remington 338 with a blued barrel....blew that one off at exactly the same length with the same load. Then another test with a stainless Winchester 338...blew off at the same length, all within .125 of each other. May not mean anything.
Charlie
The data and opinions contained in these posts are the results of experiences with my equipment. NO CONCLUSIONS SHOULD BE DRAWN FROM ANY DATA PRESENTED, DO NOT, UNDER ANY CIRCUMSTANCES, ATTEMPT TO REPLICATE THESE RESULTSj
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Campfire Ranger
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Glad to hear from you again Charlie!
I hope all is well.
BMT
"The Church can and should help modern society by tirelessly insisting that the work of women in the home be recognized and respected by all in its irreplaceable value." Apostolic Exhortation On The Family, Pope John Paul II
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Flinch,
I agree with most of the things you said in your post. However, I would disagree with your first sentence that it was NOT the design of the 7mm case or caliber that was causing the pressure spikes. I think it�s because of the design that makes it more susceptible to changes in cases, primers, powder, bullets, ect...Seems like no one seems to know what it is. One only has to look at the load data for the big 7 and see wide variation in charges by the bullet and powder makers ..I believe that Ken Waters in his �Pet Loads� recommended when loading for the 7 pick one type of case and primer and work your loads from that. I have loaded for two 7�s and never had a problem that I was aware of...but then, I don�t work on the �ragged edge� either..
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There was a question asked a few months ago if anyone had ever figured what caused blow ups when using a reduced charge of slow burning powder.
I might be wrong, but I think Dr. Howell said he knew the cause, and could duplicate it.
Does anyone know if he ever published what was causeing this.
If anyone knows the why of this, it could help explain the pressure spikes in certain calibers.
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