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    • #34223
      Larry Gibson
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      This was posted over on CBF in response to a question regarding the advisability of using 7.62 ammunition if M95 Chilean Mausers that were converted.

      Here’s the pressure data I’ve taken so far with the Chilean M95 7×57 Mauser using an Oehler M43 PBL. The M95 is in excellent condition, has been “sporterized” with the original milsurp barrel now 22″ long. All measurements are in “psi’s”as to conform to SAAMI and C.I.P. psi MAP and PTc max measured with conformal peizo transducers. All the psi’s listed are not “absolute” as they were measured using the commercial and military grade ammunition made for such arms. As with measuring velocities, measuring the pressure on one day may not be the same as what is measured on another day can vary when tested even the very next day under the same conditions. All testing was done using SAAMI testing procedures including the use of “reference” ammunition to obtain a “standard” psi measurement comparable to the standards set by SAAMI and C.I.P. All pressures shown are with the correction factor obtained through reference ammunition used. All velocities are muzzle velocities not screen velocities and are shown in fps. The psi figures are shown in thousands and hundreds, I. E.; 54,9 would be 54,900 psi.

      All the following loads were tested yesterday. Ambient temperature ran from 70 to 80 degrees but all equipment including ammunition was shaded. Test consisted of 10 shots with the rifles switched after each test to keep the barrels cool. Two “foulers” were fired prior to each test string (as per SAAMI procedure). Yes it was a long 8+ hour day.

      For the 7×57:
      The SAAMI MAP is 51,0
      The C.I.P. PTc maxis 57,0
      Both are with transducer measurement.

      Commercial Factory and hand loads:
      Federal 175 RNSP; 49,9 2400
      Rem-UMC 175 RNFMJ; 57,2 2311
      Remington 175 RNSP; 48,2 2393
      Winchester 175RNSP; 50,2 2376
      My standard load 175 RNSP; 49,2 2334
      Hornady Light Magnum 139 SPBT; 44,5 2624
      My standard “light” hunting load 154 SP; 55,7 2579

      Military Surplus:
      CAVIM (Venezuela) 139 FMJBT; 46,0 2590
      PS 1950 (Spanish) 154 FMJBT; 59,8 2442
      PS 1951 (Spanish) 154 FMJBT; 60,5 2543
      FAMME (Chile) 133 FMJBT; 55,3 2718
      DWM 1918 (German) 172 Cupro RNFMJ; 54,8 2295

      As we see the psi of both commercial and military ammunition made in 7×57 runs from 44,5 psi to 60.5 psi. Note the Chilean made military ammunition made for their own M95 Mauser gave a MAP of 55,3 psi, just under the C.I.P. PTc max of 57,0 psi.

      Now, the original question of this thread was basically if 7.62 NATO ammunition would be safe in the M95s Chilean Mausers converted to “7.62. My response was if the M95s had new barrels most 7.62 NATO would be safe as most or the psi’s of the ammunition over lapped. However, if the M9 5had a sleeved chamber and a rebored barrel then I would not feel it was safe. So now having some actual measured pressures of varied 7×57 ammunition let’s take a look at some actual pressures of varied .308W and 7.62 NATO ammunition actually measured with the same equipment.

      The .308W/7.62 NATO test rifle was a M1909 Argentine M98 Mauser with a 24″heavy sporter contour barrel. The chamber was cut with a match reamer and headspace set to the minimum SAAMI spec for the .308W cartridge. Testing was done with the same Oehler M43 PBL using the same SAAMI testing technique as used testing the 7×57 ammunition. Reference ammunition was used to obtain the correction factor to give the psi as listed in thousands and hundred. The velocity is corrected to the muzzle and given in fps.

      .308W/7.62 NATO:

      SAAMI and C.I.P. MAP and PTc max; 62,000 psi as measured with transducers.

      Commercial ammunition:
      Winchester 150 PP; 61,7 2903
      Remington 150 CL; 54,5 2924
      Federal 150 PS; 57,3 2891
      Winchester 180 PP; 57,7 2574

      Military Ammunition:
      M80 Ball WRA 68; 5 2,8 2790
      M80 Ball LC 87; 61,2 2924
      M80 Ball LC 90; 57,3 2852
      CETME (Spanish) P 7.6 62; 58,7 2694
      M118 SB LC 88; 62,9 2694
      M118 LR (175 MK over 42.2 IMR 4064) LC 07; 59,9 2633
      M852 MATCH LC 89; 59,0 2627
      M852 duplication load (168 MK over 41.5 H4895, WLR, LC Match case); 57,4 2670
      M852 duplication load #2 (168 MK over 42.5 IMR4895, WLR,LC Match case): 61,3 2730

      Thus we see here the psi of commercial .308W and military (U.S.) 7.62 NATO runs from 52,8 psi to 62,9 psi. Comparing the commercial ammunition psi’s to the M80 Ball psi’s we see there’s really not a lot of difference between .308W and 7.62 NATO. We also see that with the exception of 2 loads (one each commercial and M80 Ball) the rest fall within the psi’s the tested 7×57 ammunition psi range.

      Those are the actual measured pressures of cartridges used in 7×57 and .308W/7.62 NATO rifles. Obviously the measured psi’s are different, as they should be, than the pressures listed on “data sheets”. All the measured pressures were within the SAAMI MPLM (Maximum Probable Lot Mean), EVPAT 7.62 criteria and the C.I.P. PK (Maximum Individual Statistical Pressure).

      Larry Gibson

    • #34229
      Scharfschuetze
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      I followed that thread Larry. Looks like the acrimony is coming to an end on it. Enjoyed all of the info you posted.

    • #34236
      Larry Gibson
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      Yeah, went back and deleted my last post to the guy, he just doesn’t have a clue and obviously is just a keyboard expert. To paraphrase the movie…..he can’t handle the truth……….

      I’m still posting some suggested other loads to the OP and another there. They understand and want to use what woks well in their own 7x57s.

      Larry Gibson

    • #34250
      Scharfschuetze
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      I followed that thread Larry. Looks like the acrimony is coming to an end on it. Enjoyed all of the info you posted.

      I spoke too soon.

    • #34251
      Larry Gibson
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      10 years ago when I got the M43 and began actually measuring pressues, internal ballistics, actual BC and other things I was very much amazed to find things quite contradictory to what I had always read and believed myself. The more I tested and studied ballistics my concepts changed. There were many ideas we have been told were so that actually weren’t. For example we are now shooting cast bullets upwards of 3000 fps with accuracy out of the .308W, the 30×57 XCB and the 30×60 XCB.

      After posting some of my findings on CBF I thought I would be overwhelmed with requests to test all sorts of loads….that all the supposed experts would really want to know what their loads were doing…..what the truth was…….that we could indeed shoot a ternary cast bullt at 2500 – 3000 fps with accuracy.

      Instead I was met with jealousy, fear, personal insults, rage and even threats. I was also banned from CBF for a year and many of my threads and posts were deleted….the RPM Threshold stickyc s for example. What I’ve learned is most of the experts on CBF didn’t want to learn and they feared the truth, especially when it disputed their own “expertise”, theories and views. Yes they did not want to know the facts as they feared the truth and facts would dispell their “status”. Also there are a large number who are keyboard experts, only “knowing” what they can find on the internet. I was amazed and confounded by the resistence to learning then and now.

      Larry Gibson

    • #34253
      Anonymous
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      Larry
      I read all of your posts and all of your information is Interesting
      CBF did delete some your your posts –Shame on them
      So if your posts if directly Related to what I was doing (ie a cal I reload) I tried to copy to word a copy for referance to refer to when I was off line
      Some of your posts I bookmarked so I could refer to Pictures/ graphs or chrony data (some of the data did vanish):( :(:(

      I have a chrony so that is what I use for velocity when I do test ( but i do not use it all the time)
      Primer appearance is what I use for pressure data so When you post your data I find it very interesting

      I compiled all the data I could find on the 300aac Blackout
      One data source after using it I made note –reduce load data High pressure Highlighted in Pink all Max loads — do not use
      (these were Jacked Loads
      I wish I could do pressure data and send back to this reliable source (a manufacture) to tell them your data is off
      I have 70 pce of converted brass that have enlarged primer pockets — for me normaly primer pockets last several firings
      I did have 5 pcs of 308 that did have enlarged primer pockets when doing a test of max load but I can live with 5/100 — but not 70/100
      I have seen flatter primers in 357 mag factory loads but pistol primers so was not concerned at the time –I now know better

      When I read your RPM thery I used it to to go through Bruce B information on the cast in 308/ M1a where your rpm said cast bullets would fail (increase group size)
      Bruce B through independent testing confirmed the fact
      Not sure of the dates when Bruce published his data and when you first made note of the RPM therey

      Because of your rpm thery I bought a 223 barrel in 12 twist (for cast and jacket) I also have 1/9 twist to be able to shoot lower cost Jacketed 223 ammo
      I very rarlly see 70g 223 ammo and never on sale so I don’t own a 7 twist — cost for jacketed 68g projectiles are .34c each here just to reload
      55g jacketed are .15c each
      so thanks Larry for being able to shoot lower cost ammo

      I know the cost of a pound of powder $$
      My time is Very Valuable — So is your Time
      Time to load
      Cost of componets
      Gas to go to the range
      Day at the range shooting (Fun but it still cost)
      Wear and tear on equipment
      time to do all the posting/ caculating /etc data

      Thanks for Posting your information
      (Hands clapping )

      for
      Larry Gibson 🙂

    • #34254
      Scharfschuetze
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      Well, I spoke too soon again. What I interpreted as sarcasm was just a joke apparently. It’s all good.

    • #34265
      Goodsteel
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      Some folks have a dangerous sense of humor.

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