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  #31  
Old 04-22-2021, 04:12 PM
Larry Gibson Larry Gibson is offline
 
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The problem with considering only the CUP measurement is it only give a static maximum pressure the load achieved. Any CUP measurement does not give a time/pressure trace nor will it give a pressure at the gas port. We can easily have 2 different loads [same bullet but different powders] giving the same CUP measurement. However, one powder may have a much higher gas port pressure because it is slower burning. It also may have enough residual chamber pressure that the cases have not contracted yet. That is really what "bends" oprods. The case is still gripping the chamber walls as the oprod is attempting to cam the bolt open.

The problem is exacerbated as commercial loads with heavier bullets tend to use slower burning powders. Thus the time/pressure curves are not suited to the M1 Rifle.

As an example I have pressure tested 2 different Federal 165 SP 3.0W loads. Both were purchased at the same time in the newer grey boxes. One box was listed as loaded with the Sierra 165 gr GK bullet. The other did not list the make of bullet. The box of rounds with the generic 165 gr SPBT had 42.0 gr of a ball powder in them. That load ran 2702 fps out of the 24" test barrel at 53,100 psi. The box of rounds having the Sierra 165 SPBT GK bullets had 47.3 gr of ball powder in them and they ran 2778 fps at 60,000 psi. Two seemingly similar factory loads except for the bullet and load used. The first would be safe in M1As and M1s converted to 7.62. The second would probably be safe in the M1A but probably not safe in the M1 converted to 7.62. Both would be quite safe in rebarreled (to 7.62/308W) DHT M1903s, M1903sA1s or M1903A3s and M1917s.

BTW; the SAAMI MAP is not the "maximum" psi allowed for cartridges. The MAP is just the Maximum Average Pressure manufacturers should try to keep the production ammunition under. SAAMI uses two other measurements; The MPLM [Maximum Probable Lot Mean] and the MPSM {Maximum Probable Sample Mean]. Just as we find if we chronograph the same load on different days or if the same load is from a different loading time the average velocities will vary thus it is with pressure measurements. They do vary. The MPSM is the maximum allowable pressure of any of the tests of the same lot of ammunition.

Also, again let me reiterate. With some exceptions, most commercial and milsurp ammunition is loaded to a certain velocity level (performance parameters) while maintaining the psi less than the established MAP for the cartridge. Most all commercial 30-06 ammunition is not loaded to the MAP [50,000 CUP or 60,000 psi]

LMG

Last edited by Larry Gibson; 04-22-2021 at 04:37 PM.
  #32  
Old 04-22-2021, 04:17 PM
Jeremy2171 Jeremy2171 is offline
 
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Quote:
Originally Posted by Gewehr43 View Post
Thank for the summary.
What I donít need is your guesses or interpretation of it.

YOU are then use that to make some conclusions that have no basis in truth.
You canít -accurately- then say that they then mean that ALL commercial 3006 ammunition is safe because it meets SAMMI specifications.
Because you have no proof of that, none.
And that is not what they said and itís not your place to then make some goofy conclusion like that.
Stop taking their statement and then attaching your ridiculous conclusions to it.
I pointed out what THEY said...
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  #33  
Old 04-22-2021, 04:18 PM
Jeremy2171 Jeremy2171 is offline
 
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Quote:
Originally Posted by Gewehr43 View Post
Yes, your comments are confusing to say the least.
The 168 smk was made for the 300meter international competitions, it had nothing to do with the Garand.
It was never used by the Military in a 30-06 loading.
What it was used for was the 308 M852 load.

Now a lot of civilian shooters have realized what a great bullet Sierra makes and used ALOT of them, me included.

Please stop with this nonsense, you are making all sorts of statements that have no factual basis.
Please pay attention before posting...

I never said the 168smk...

I said FGMM... pay attention...
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  #34  
Old 04-22-2021, 04:42 PM
Jeremy2171 Jeremy2171 is offline
 
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Quote:
Originally Posted by Fenris_Bane View Post
Partially wrong. The CMP did NOT say "any commercial ammo". You are making an overly broad statement.

The CMP said the following:
"These rifles are at least 70 years old and were not designed for max loads and super heavy bullets." The CMP also warns about bullet weight. Some modern commercial ammo have bullet weights at 180 grains and some have high velocities. This e-mail mirrors the advice given in the InRange video you dismissed.

https://www.youtube.com/watch?v=ZQ_F1riBth8&t=452s

(Adjustable gas plug)
https://www.youtube.com/watch?v=qe3rrlJsEz0

What is the "max load"? Is it 50,000 CUP? Regardless, this second statement clearly states they were NOT designed for max loads. So if 50,000 cup is the "max load", it is by no means the optimal load nor the desired load.

So the Technical Manual may be correct in stating 50,000 psi, which is well below the 60,000+ PSI that 50,000 CUP generates.

Why push the maximum pressures? There is no need to. It also leads to people blowing up firearms when the is a problem with their manufacturing. As I showed before, Herter's brand .308 sold commercially by Cabella's was not safe to shoot and was extremely overpressure.

Just because it is commercial manufacture, does not automatically mean safe.
Posting videos with misinformation in them done by people who don't know the history of the garand doesn't help.

I've said SAAMI spec commercial ammo is fine...and CMP email says anything under 50k cup is fine...did they not? If reread the CMP notice...the weight limit only applies to ammo OVER the 50k cup limit.

You guys are getting all worked up over the 50k cup comment...as if it's the do not cross line...

I wonder if CMP is going to stop selling 308 garands? Why? Because 308 is 52kcup! Obviously dangerous...at least according to the CMP email.

Let's not forget mccann industries .458 garands... 53k cup

Or SA inc .270 win garands... 54k cup.


Now let your brain stem marinate on those numbers a while...
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  #35  
Old 04-22-2021, 05:02 PM
TMB TMB is offline
 
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Something for the brainstem to marinate on, As long as ammo does not exceed SAMMI spec, all the arguing about chamber pressure does not matter as much as the pressure at the gas port in an M1. Garandgear tests that with different factory loads.
  #36  
Old 04-22-2021, 05:59 PM
precision40 precision40 is offline
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Guys it's becoming argumentative at this point. I think the warning CMP put out is pretty straight-forward, if you disagree, we understand but that's the way it is. As with any milsurp, "use with caution" always applies, no matter the weapon.

We're going to close this one down.
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