Psl barrel

[Richard Erichsen]

Twist rate for the .308 Win. is 305MM
Twist rate for the 7.62X54R is 320MM

I hope this info helps!

Richard

Yep, for most of the early PSLs and maybe later civilian models, it's the 12.6" you indicate, intended for ball ammo no heavier than about 170 grain lead core jobbies 1.76" in length or thereabouts. Since bullets of this mass are getting into heavy ball territory, costs more and requires upgrades and careful planning to use in a PSL without worry, the 150 grain(ish) ordinary ball ammo falls well within the required twist rates and may (should?) improve accuracy with this type of ammo relative to the fast 1:9.5" and 1:10" twists more common in this caliber.

R

[Holescreek]

If you haven't seen the slo-mo footage of a PSL being fired check this out and pay attention to the barrel whip: http://www.youtube.com/watch?v=ozyw84Swmb4

I'm not sure I'd be able to use the term "barrel harmonics" with a straight face, more like barrel accordian. Everyone tends to think that barrels return to the exact same place around the bore axis between shots, I don't think anything that moves that much could. People have written over the years that they achieved better accuracy just by shortening the barrel down to 20". If true, increasing the diameter alone should bridge the gap. I'm willing to go through several barrels if need be to find out so starting with an affordable one is a good start.

The Romanians had a great idea in upsizing the AK to the 54r but they did it on the cheap with the stamped receiver and longger barrel. Is it reasonable to hang that much whip on the end of a sheet metal "U" and expect it to repeat? I'm betting that a heavy barrel and stiffened receiver will be enough to make it a respectable shooter. If nothing else the journey will be fun.

[Richard Erichsen]

If you haven't seen the slo-mo footage of a PSL being fired check this out and pay attention to the barrel whip: http://www.youtube.com/watch?v=ozyw84Swmb4

You should have warned me - I had on my 3D emulator glasses and ducked as the first spent case that seemed to be flying straight into my forehead twirled at me!

People have written over the years that they achieved better accuracy just by shortening the barrel down to 20". If true, increasing the diameter alone should bridge the gap. I'm willing to go through several barrels if need be to find out so starting with an affordable one is a good start.

All things equal, the shorter barrel is the stiffer barrel. A shorter and fatter barrel is stiffer still as anyone who has tried to apply a load to a rod of a given diameter can attest. Yes, 25" barrels "look" mean, but since you are limited to how large in diameter you can go, it might make sense to trim it a bit. 21-22" long but 15% thicker might be worth contemplating.

I don't see much velocity gain from a more truncated 20-22" to the 25-27" barrel lengths for most loads (looks like less than 150 FPS), so that extra 5" of noodle thin barrel looks like a real liability if the goal is consistency as opposed to velocity. Since you don't plan to handload, shorter probably gets you closer and is like adding more barrel diameter without adding weight. For example, the M38 and M44 carbines with 20.4" barrels had an MV of 2650 FPS (avg) while the M91/30 with 28.75" barrel has an MV of 2850 FPS (avg). If over 8" of barrel equates only to 200 FPS or so, it hardly seems worth it to go much beyond the carbine length. It may also make for a rifle that is a bit lighter if you wanted to do something a bit more dynamic than from the bench.

The Romanians had a great idea in upsizing the AK to the 54r but they did it on the cheap with the stamped receiver and longger barrel. Is it reasonable to hang that much whip on the end of a sheet metal "U" and expect it to repeat? I'm betting that a heavy barrel and stiffened receiver will be enough to make it a respectable shooter. If nothing else the journey will be fun.

I'm not sure the stamped receiver in an of itself is a liability. I suppose it comes down to the actual thickness, alloy, and method of attachment. Further stiffening of the fixture between front/rear trunnions and receiver may prevent fracture, not sure if it will do beans for accuracy. Overgassed PSLs using light ball have been known to crack in the same spot under the trunnion as the PSLs being used for heavy ball do, so there is a known weak point or two that should be considered.

R

[Dan FS71]

Excellant info, always wanted to do a barrel from a blank.

[Richard Erichsen]

Excellant info, always wanted to do a barrel from a blank.

If you are set up to cut a barrel from a blank, plenty of members here and elsewhere would be interested in talking to you about it.

R

[Dan FS71]

Likely I'll have a go, not setup for production though. If it turns out favorably I'd likely do a few extra for fun

[Richard Erichsen]

Likely I'll have a go, not setup for production though. If it turns out favorably I'd likely do a few extra for fun

Which blanks were you planning on using? Do you have the cutters and reamers already?

R

[Dan FS71]

Not entirely decided, a fair bit of tooling but still a piece or two to make it a fun job.

Will update once I get close.