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Alternative 7.62 brass |
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Shamu ![]() Admin Group ![]() ![]() Logo Designer / Donating Member Joined: April 25 2007 Location: MD, USA. Status: Offline Points: 16839 |
![]() ![]() ![]() ![]() ![]() Posted: November 23 2022 at 1:38pm |
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Good call. be safe & enjoy.
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Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)
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450 Fuller ![]() Groupie ![]() ![]() Joined: June 07 2022 Location: New Mexico-AK-A Status: Offline Points: 40 |
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All of these factors have been considered. 7.62 brass is stronger than commercial .308 indeed.
This $40 -original cost- rifle will be relegated to wall-hanger status. Back to my Garands and pre-64 Model 70 Winchesters, which saw service in WWII and Korea-Vietnam. Life is too short. As a Vietnam combat veteran, and former Federal agent- I have had enough close calls for 3 people. |
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Only the dead have seen the end of war-Plato
Socialism-The equal sharing of misery-Churchill MACVSOG-5th Special Forces Gp |
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Shamu ![]() Admin Group ![]() ![]() Logo Designer / Donating Member Joined: April 25 2007 Location: MD, USA. Status: Offline Points: 16839 |
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OK boys & Girls. ENOUGH! Let it go, please, or I'll be obliged to stop it for the welbeing of other less experienced forum users. It was a serious over pressure event that effectively destroyed a rifle. "It WENT KABOOM & we don't know why" is not a positive path to follow.
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Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)
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The Armourer ![]() Senior Member ![]() Joined: June 23 2019 Location: Y Felinhelli Status: Offline Points: 1246 |
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Had you considered that commercial 308 cases are very different specification to 7,62 NATO spec cases ? Case wall thickness is much thicker on the 7.62 compared to 308 7.62 chambers are 13 thou (0.013") longer than 308 meaning that these thin-walled 308 cases stretch and can split. The case volume on a 308 is greater than a 7,62 leading to different powder burning characteristics Throw in a 'bit of extra powder' and you have an accident waiting to happen. All the problems of stress that you have identified and all you are planning to do is 'replace the bolt head' because it's reasonably priced. The rifle needs gas-axing. Some time in the future a member of your family may not know the rifles history, fire a slightly 'hot' round and end up with an explosion 6" in front of their face. Buy a new rifle - it'll be a lot cheaper than the potential medical bills.
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britrifles ![]() Senior Member ![]() ![]() Joined: February 03 2018 Location: Atlanta, GA Status: Online Points: 5763 |
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So, the base of the bullet was below the neck? I can see that would cause the potential of the GC coming off.
Seems to me that it’s possible the action body is yielded/distorted. It’s surely not just the bolt head that has yielded… |
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450 Fuller ![]() Groupie ![]() ![]() Joined: June 07 2022 Location: New Mexico-AK-A Status: Offline Points: 40 |
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I narrowed the cause of the pressure excursion soon after the event took place.
It was commercial .308 brass. The cause, as best determined, was a moderate loading of 4198 powder behind a 170 gr 30WCF FP bullet with gas check.Used many times with jacketed 150 gr bullets) I had sworn off GC lead cast bullets in ALL bottle neck cases. In violating the rule....these bullets were commercial over 20 years old so both the lube and GC crimping were ancient. Member-never again club. Years ago, a gunsmith explained to me his close calls with bottleneck cases and supposed "crimped" gas checks. If the GC separates and lands on the powder or is stuck in the cartridge neck, it is an obstacle... Numrich offers a stripped Ishapore bolt head. While it may be a possible headspace question, Goosic is correct in that the bolt/bolt head was exposed to excessive pressure. I am going to replace the bolt head. Reasonably priced. I also think the Ishapore 2A1 Indian rifles with their steel history may rank below the 1898 Krag with one locking bolt, which would let go if pushed by excess pressure. |
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Only the dead have seen the end of war-Plato
Socialism-The equal sharing of misery-Churchill MACVSOG-5th Special Forces Gp |
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britrifles ![]() Senior Member ![]() ![]() Joined: February 03 2018 Location: Atlanta, GA Status: Online Points: 5763 |
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I’m afraid it remains a mystery of what went wrong.
Of all the things that can cause this magnitude of overpressure, I’d think cases are pretty low on the list. |
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Shamu ![]() Admin Group ![]() ![]() Logo Designer / Donating Member Joined: April 25 2007 Location: MD, USA. Status: Offline Points: 16839 |
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That's a good point its awfully easy to mix one form such a similar batch.
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Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)
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Zed ![]() Special Member ![]() ![]() Donating Member Joined: May 01 2012 Location: France Status: Offline Points: 5351 |
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450 Fuller, I was just wondering if it was one of your modified cases or a standard case that had the over pressure; which unfortunately wrecked your Ishapore?
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It's nice to be important, but it's more important to be nice!
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Shamu ![]() Admin Group ![]() ![]() Logo Designer / Donating Member Joined: April 25 2007 Location: MD, USA. Status: Offline Points: 16839 |
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Just compensate for the decreased internal volume by down loading (2~3 Gr) & then working back up to the same velocity. I've found with several makes & lots of cases the real difference is about 1.5~ 2.0 Gr of IMR 3031 or IMR 4895. This assumes you're using a max load. If you load is Middle of the road you'd do the same but just for the velocity change.
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Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)
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Goosic ![]() Senior Member ![]() ![]() Joined: September 12 2017 Location: Phoenix Arizona Status: Offline Points: 8364 |
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Most current reloading manuals have two separate listings for the .308W and 7.62mm Military and also describe the use of commercial and military brass respectively but, if you are just out to kill paper for the day, load to the starting charge weight and forego any worries...
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Goosic ![]() Senior Member ![]() ![]() Joined: September 12 2017 Location: Phoenix Arizona Status: Offline Points: 8364 |
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I like you will not expound on this but suffice it to say that, Lake City 7.62x51mm LR and Match brass is readily available for reloading through www.diamondkbrass.com
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450 Fuller ![]() Groupie ![]() ![]() Joined: June 07 2022 Location: New Mexico-AK-A Status: Offline Points: 40 |
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You are correct, of course as to the strength and origin steel as to
the Ishapore 2A and 2A1. As much as I like 7.62 U.S. brass, I do look for some available match brass as small quantities have no primer crimp. AMC is the major US Army Command over the small arms ammo plants. RCBS makes a primer pocket swage which removes the crimp. |
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Only the dead have seen the end of war-Plato
Socialism-The equal sharing of misery-Churchill MACVSOG-5th Special Forces Gp |
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The Armourer ![]() Senior Member ![]() Joined: June 23 2019 Location: Y Felinhelli Status: Offline Points: 1246 |
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That is very true - as 7.62 has a thicker case the internal volume is lower than a 308 case, the same weight of powder in a smaller space has quite an effect on burn and pressures.
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Goosic ![]() Senior Member ![]() ![]() Joined: September 12 2017 Location: Phoenix Arizona Status: Offline Points: 8364 |
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Just a FYI here 450 Fuller. The Ishapore 2A and 2A1 rifles are NOT and NEVER were conversions. They are ther own entities and used a different grade of steel during the forging process. They were also proofed to handle and tolerate all offerings of 7.62x51 NATO ammunition by the Birmingham Proof Master and under strict guidance from the British Ministry of Defense prior to and during assembly.
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britrifles ![]() Senior Member ![]() ![]() Joined: February 03 2018 Location: Atlanta, GA Status: Online Points: 5763 |
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I do prefer 7.62 brass to commercial .308 in my No. 4 DCRA conversion, but I also use Lapua .308, it is high quality and on the heavy side for commercial brass, headspace is well under .308 SAMMI No-Go.
You have control of pressures by reloading, although some things are not fully quantified reloading manuals. Pressures can be affected by substituting 7.62 for .308 brass, magnum primers for standard primers, one bullet type for another. This is where you should exercise caution and always err on the side of reduced charges. Especially if you intend on shooting a lot of your custom made load. |
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