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9/22/2017 12:11:25 AM
Posted: 8/29/2002 12:30:56 AM EDT
I just got a Ruger M77 bolt-action in 7.62X39. I am building a gift custom hunting rifle for my uncle and have everything assembled. However I would like to know If I can shorten the 22" barrel without reducing the velocity much? He reloads and talked about really wanting this caliber, he is conscious of velocity and chronos his rounds. How much barrel, if any, can I cut off without reducing potential velocity gains? At what length is all the powder typically burned up? Any help would be great, thanks.
Link Posted: 8/29/2002 3:06:31 AM EDT
No flame intended but, CampyBob and these fellows will probably be able to better answer your question than us 223 fans. www.ar15.com/forums/forum.html?b=4&f=54

While I own a Hungarian AK and it's barrel is shorter than 22", were I to decide to use a 7.62x39 in hunting situations, personally I'd want all the velocity I could get. Sorry if this hasn't been much help, but Campy will give ya a much better answer as he's the expert on the caliber in question.

Mike

PS - perhaps BTT will get Campys' attention.
Link Posted: 8/29/2002 11:05:42 AM EDT
Link Posted: 8/29/2002 11:46:24 AM EDT
Troy, you say that commercial loads are designed around a 20" barrel. How about surplus loads?
Link Posted: 8/29/2002 3:52:02 PM EDT
Link Posted: 8/29/2002 9:01:25 PM EDT
I thought most 7.62x39 rifles used 16" barrels. All AKs I've seen and a few SKSs had the 16".
Link Posted: 8/30/2002 1:58:19 AM EDT

Originally Posted By mstirton:
I thought most 7.62x39 rifles used 16" barrels. All AKs I've seen and a few SKSs had the 16".



That's been my observation, too.
Link Posted: 8/30/2002 7:35:50 AM EDT
While most SKS have 20" barrels, most of the Military rifles in 7.62x39 are 16" (mostly AKs & AKMs). However the M43 (7.62x39 ball round) was developed prior to the designing of the SKS or AK).

16" SKSs were a comercial item only - military ones have 20" barrels.

Most of the Velociy quotes you see from individuals will be based on 16" barrels. I have no idea what the manufactures use for chrono tests (though I don't doubt they use a 20" or 22" test barrel).
Link Posted: 8/30/2002 9:52:38 AM EDT
Thanks for the responses. He does hand load quite a bit so I guess going down to 18" would be out of the question, but how about 20" would anything at all be gained by leaving the 2" on?
Link Posted: 8/30/2002 1:51:57 PM EDT
Actually its really impossible to say. We don't know what rounds are being used, and how different velocities effect it.

For 7.62x39 FMJ or HP rounds velocity is almost irrelevant because they don't fragment or expand. (with the exception of Yugo FMJ - IIRC it will flatten a bit which helps a bit).

The only softpoint 7.62x39 is a Winchester loading (I've posted the model number before) and It works fine in 16" barrels to CQB distances.

Considering the typical velocity of M43 is 2300-2400fps from a 16" barrel I don't know how much more you can really expect with a few more inches.
Link Posted: 8/31/2002 2:01:04 PM EDT
I have chronoed the Wolf 122gr hp,

in my 16" SKS it does 2400fps, in my 22" Mauser barrel it does 2500fps, and it does expand, quite explosively from the Mauser too.
Link Posted: 8/31/2002 3:13:39 PM EDT
[Last Edit: 8/31/2002 3:24:43 PM EDT by AR15fan]

Originally Posted By Forest:
The only softpoint 7.62x39 is a Winchester loading (I've posted the model number before) and It works fine in 16" barrels to CQB distances.



Winchester, Federal, & Georgia Arms all load a 7.62x39mm soft-point. Corbon has a JHP, and both Magsafe & Glaser offer specialty rounds.

www.natchezss.com/ammo/rifle/ra76239.html

www.georgia-arms.com/rifle3.htm


However, my favorite 7.62X39MM load is the 125Gn Nosler Ballistic tip, as loaded by Georgia Arms.

www.georgia-arms.com/precisio.htm

It's my choice for Deer, Groundhogs, and self defense from my Type 56-S.

Edited to add links...
Link Posted: 9/2/2002 8:36:52 AM EDT

Originally Posted By AR15fan:
Winchester, Federal, & Georgia Arms all load a 7.62x39mm soft-point. Corbon has a JHP, and both Magsafe & Glaser offer specialty rounds.



While that may be true, only the Winchester softpoint load has performed well in Dr. Roberts testings. I do not know if he has tested the ballistics tips.
Link Posted: 9/2/2002 8:42:08 AM EDT
For what its worth I went and looked up the MV values for the AK & RPK:

The 16.3" barrel AK has a MV of 2300 fps (actually if you convert their metric value of 700m/s its 2296.6 fps).

The 23.2" barreld RPK has a MV of 2444 fps (745 m/s).

Source: izhevsk.kalashnikov.guns.ru/models.html

Link Posted: 9/2/2002 6:14:56 PM EDT
Going from 20 to 16 inch expect to lose 100 fps. An animal wont notice that. I advise you to cut the barrel to 16 inches. The velocity loss is not too bad, and the rifle will be a lot handier.
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