Recent content by bill alexander

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    375 Mercenary , the beast unleashed !

    The ability of a polymer case to handle pressure should not be taken in the context of a traditional case design. Nor can polymer be used is the same manner as brass. When applied correctly with a suitable grade, polymers have been used at pressures exceeding those seen with brass without the...
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    Can someone give me guidance on what is happening in this pic?

    If you look at the sheared out surfaces you will note that the surface is bright with minimal rear tearing. This is classical for adiabatic shear which occurs in hard plate when the strain rate (velocity) exceeds a certain limit value. The phenomenon is peculiar in behavior, very digital in...
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    Magnum AR Project

    Be interested to see the results, a good basic experiment. See if you can measure how much weight you applied, the base weapon weight and the BCG weights. Observed that the AR10 (Armalite pattern) has one of the heavier carriers of the 308 class guns and this promotes slower initial...
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    Magnum AR Project

    Momentum! and relative motion of masses Light gun follows the reciprocating mass. Imagine mounting the carrier onto a mass of equal weight. Now drive the system backwards under recoil while trying to accelerate the carrier away from the mass. Gun tries to keep up Heavy gun. Now mount the...
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    Tripods and accuracy

    Use a tripod to shoot 338 Lapua from a variety of field positions. Rifle is heavy, around 21 lbs so recoil is a long heavy push. Currently use a PIG saddle set up on the point of balance and lock lightly on the target. Find dropping the magnification and not chasing the wobble gives better...
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    Best semi auto 308 /dmr

    With bias due to working there. HK MR762 absolutely bomb proof. Advantage of above and running the Test and Prototype dept is that we get to fry, freeze and mix guns with dirt to see what they do. Find one of the older heavy profile barrel units, although the muzzle threading is hinky! Twist...
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    Trigger Tech Diamond

    Run Trigger Tech units in a semi auto 338 Lapua without any problems, multiple 6.5 Grendel rifles and have trial units in several of our 416 and 417 guns. Monkey circus modified to fit and run with the firing pin interrupt in these guns, but no functional problems
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    Angled gas ports?

    Angled gas ports are a method of controlling the erosion such that the area remains constant for higher round counts and the pressure drop across the port is more consistent. The Russians abandoned the complexity of indexing angled ports through the barrel groove during testing of the AK74 as...
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    Grendel-like Belted Magnum Problem

    I must apologize for the delayed response. Work, is at times, most inconvenient. To reply to the question regarding the impulse from the fire control group. To be clear this has little to do with the springs which add only a minor preload. The main input is from the moment of inertia of the...
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    Grendel-like Belted Magnum Problem

    The Grendel chamber geometry and bolt was designed in concert with the Lapua case. The chamber "if" correctly dimensioned and with the correct feed cone geometry will allow chamber pressures well in excess of 68k psi without the case deforming. Obviously this is for Proof loadings only and...
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    Hammer Forged Chamber...?

    The HK hammer forging process includes the chamber. The barrel is manufactured complete with chamber in a single operation. To perform this the forging mandrel includes the chamber form behind the rifling mandrel. The bored and honed blank moves over this during the forging process to create the...
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    MR762 - No Love?

    1 in 11 twist barrels. We accuracy test every rifle out of the facility and it is not unusual to see ragged hole groups (note that these are shot from a massive machine rest that clamps the gun by the barrel nut). They are designed around M80 ball ammunition so do best with projectiles around...
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    Rifling Twist-Rate Effect on Chamber Pressure

    Gain twist became prevalent with the evolution of high velocity cannons. There is a limitation to the shear strength of the driving band when launched over the more energetic propellants at higher pressures. There is a secondary effect of reducing the pressure applied to the leading side of the...
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    Grendel-like Belted Magnum Problem

    My apologies, I note also now that you have a flat wire spring. With the spring rate of this type of spring the initial preload will be too low for the gun to cycle fully or the gun has to have a large gas port to supply enough energy to move the reciprocating parts correctly. This will have the...
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    Grendel-like Belted Magnum Problem

    Brass will move under a residual pressure of only 1600 psi. For a fully plastic movement it will obviously depend upon the composition of the brass but I would use a pressure offset between 5400 psi and 7000 psi while running pressure/velocity measurements. This was derived by static hydraulic...
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