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Discussion Starter #1
I am still amazed that this round is not out there somewhere. If we elininate the extreme taper would it not solve the magazine feeding problems in the ARs? The PPCs do fine, and its the same case. At 50,000 CUP it will easily get 2330 FP from a 125 PSP @ 2900 fps. Increase the COL and shoot 150 gr 308s and we still top 2600 fps.

Tell me why this is not a GREAT round for deer, or even battle, for that matter.

So, where is this ctg? Any ideas?
 

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Loader,

If I understand you are proposing essentially a 7.62 with the same profile as a PPC. If it does 2600 with a 150 .308 I have to cocur that it would be a solid deer round. What COL are you using?

I looked into a 7.62X45 with the same taper as a PPC, but limited it to 45k for comfort in the little CZ527. At this pressure I gave up on it as not really making the performance to justify the trouble.

Fireplug
 

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Discussion Starter #3
Fireplug -

I got curious when I took the standard 7.62X39 case up to 50,000 CUP and topped 2600 fps with 124 gr .310 bullets in the CZ 527. Speer says the SAAMI specs are 50,000 CUP but the pressure is held down in deference to the AK and SKS types out there. I am currently trying to fit the round into a mil spec AR magazine, or about 2.280 COL...too long for the CZ, I think. We need the case to hold 35 grs of powder to the base of the neck...is that possible in an improved version?
 

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Loader,

I do not know what the 7.62x39 would hold in an improved version, since my research was on the 7.62x45. I was looking for something with a bit more capacity, and due to the rarity of actual Czech. cases I modeled a 7.62x45 formed from 6.5 Carcano. The Carcano (found the Carcano from advice received here) is also rare but at least available and the nearest head diameter in a longer case.

The capacities in grains of water for this round modeled on QuickDesign are: 38.8 to the base of the neck, and 35.4 with a Hornady 174gr .303 bullet seated to COL 2.350. The .303 was to allow a simple rechamber of the Euro. barrels. The COL was an EWAG. My software says 2210-2330fps for this combo at 45-50k cup. Essentially a bolt copy of the old .32 Special.

Please, measure the magazine and magazine recepticle length for your CZ527. I would be very interested.

Fireplug
 

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Discussion Starter #5
Foreplug -

Magazine interior length is 2.285 and the well is 2.44. Hope that helps.

I really have 2 goals for the 7.62X39. The first, and most important, is to decrease the case taper so it will feed any AR magazine reliably. the taper resilts and a curved magazine you see in the SKS and AK rifles out there, but it does not work in the AR mil spec rifles. A curved mag does not fit.

A steeper shoulder of larger diameter will prevent the round from being used in 7.62X39 chambers, and we can take the round up to 50,000 cup to match the SAAMI spces. So, we call the new round the 310 AR.

The second goal is to make it into a legitimate deer cartridge, defining that as a 150 gr .308 to .311 bullet with a 2600 fps MV. This will take about 35 grs H2O of useful case capacity. I'm not sure the 310 AR will have that much.
 

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Loader,

Thanks for the measurements. I have been asked if a .35 Rem. could work in the CZ527, but didn't have one around to measure. Given the measurements, I will answer maybe with a lot of work---converting the well to a fixed magazine.

Even if you do not hit your deer hunting performance limit your .310 AR could be the best thing to ever happen to an AR. I have no love for the .223, after finding that I could not even trust mine as a pest rifle.

Fireplug
 

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The Hog Whisperer (Administrator)
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I ran across an article in an old Handloader's Digest (or perhaps Gun Digest) where the 7.62x39 was necked up to .35 cal and the shoulder blown out. A Ruger Mini-30 was bored/rifled and rechambered to what they dubbed a "Mini-35". They got close to .35 Rem ballistics, if memory serves.

Struck me as a good idea, but obviously it hasn't made it as a commercial success.

I'm wondering if this wasn't one of Ed Harris' projects. He does a lot of articles on the 7.62x39, and he's creative enough for this to be his brainchild. Heck I'd buy one.
 

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Discussion Starter #8
I did a little case forming and found that a .440 base tapered to a .430 shoulder @ 30 degrees will yeild a case capacity of 33 grains H2O to the shoulder. This is good for 2772 and 2530 fps with 125 and 150 gr bullets, respectively (50,000 CUP).

Seating would be to the base of the neck in both cases, so we need a slightly longer COL for the 150 grainer. They line up nice and straight in my AR 20 round magazine, which will take a COL of 2.28, so it all works out on paper. Cases could be fire formed from factory 7.62X39 brass ammo.

I have worked with the factory case and .308/224 sabots, getting 3450 fps with 55 gr .224s, and it is very accurate in the CZ, while improving the accuracy of my SKS. The AR 310 should easily do 3600 fps with the .224 sabots and 55 gr bullets. It also shoots .312 pistol bullets with devastating terminal effects.

So, what's not to like?

I think I can make this exact chamber by running a 6MM PPC reamer .044 inches deeper than spec into my CZ chamber to move the shoulder of the PPC forward to match the current location of the 7.62X39. The throat would remain untouched, except for polishing.

Can a good gunsmith do this?

If its risky, I might be better off getting a 7.62X39 Encore bbl for test work...
 
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