Bipod on my PSL

[Holescreek]

I get really geeky when something like this gets my interest.

Do you mean that all PSL barrels are off center bores?

The sectioned barrel is a sample of one and obviously can't represent all barrels. There are bound to be good ones out there just based on various accuracy reports I've read on many different sites.

I did a small sampling of tests using 5 different types of ammo shot from the same rifle and to my surprise, the regular old military silvertip, the same stuff I dissected for the chart above, came out on top even over commercial loadings. Of course that testing was flawed also because of the influence of the shooter. A true test would have the rifle secured in a rest.

All of my tests were documented in the weaponsguild build thread for the heavy barreled PSL shown above. My HB rifle has the worst accuracy flaw of all -me. I can measure and machine with the best of them but age and eyesight are getting the better of me. My best group so far has been 4 shots in 3/4" with a 5th shot 1.5" left of the group (at 100 yards).

According to an old com block book I have, that whip effect is tuned. By that I mean the vibration is controlled throughout the length of the barrel. The article I have is for a Dragunov but it does mention variants do the same thing. It might not come to rest in the same position but the engineering involved allows you to use a pencil barrel (light weight) and still get great accuracy. If you ran a similar barrel length on an AR it would be a nightmare.

I don't doubt what you are saying at all, I believe you read it and the text exists. What I don't believe is that the military rifles have "tuned" barrels. It all sounds too much like "yeah it whips around but we meant for them to do that" to me. The bore machining is too bad to support the theory and the rifles are built to be cheaply mass produced. True "competition" rifles don't have the production and monetary limitations of the military where "minute of man" is good enough.

I'd be interested to see what a "typical" comm-bloc AK barrel would look like if sectioned. Same with a modern AR, etc. Must be my geek side coming out.

I build guns as a hobby but have never bothered with an AK, just not interested in them. If I run across a demilled AK barrel I will section it and find out.

I was more surprised than anyone to find out that AR15 pencil barrels don't whip at all. I tested two rifles with 20" 1:12 barrels fully expecting them to whip but they did not. My theory is they don't whip because the gas travels a long way before it hits the carrier, then is completely exhausted inside the receiver. I would love to film an AR with a piston system installed to see if it whips.

Sorry if I derailed the thread, it's just one of those situations where I get the rare opportunity to pipe in with some data. I'm continuing my experiments, I even bought an NDM86 this week to add another variable and am in the process of building a PSL "space gun" with a lot of non-standard modifications to test some more theories.

[Holescreek]

This is the commie theory in a nutshell: tune the flex or "whip" of the barrel to start as a relatively high level frequency at the early stages of the bullet travel and allow the geometry of the barrel (profile) and any clamped on systems to increase amplitude as the bullet travels forward, creating a "whipping" effect the moves from high frequency (small wave, fast movement) to a low frequency (large wave, slower movement) at the muzzle. Similar to striking a tuning fork.

I was rolling this around in my head trying to make sense of it. It is a very hard concept to grasp due to the speed of the bullet traveling through the bore but if I understand the analogy it's like whipping a garden hose. Move your wrist a little bit up and down (crack the whip) and the further out the length of the hose goes the larger the movement of the hose. I fail to see how a growing sine wave would contribute to accuracy.

The fat barrel theory OTOH has a pretty solid standing based on rigidity. A barrel that is .8" in diameter is 300% more rigid than a barrel .6" in diameter. The more rigid the barrel, the higher the frequency and by default, less whip. I initially thought that the heavy barrel was the "cure" for whip when I started these experiments and in the end -I was wrong. True, the heavy barrel shows little to no signs of whipping, but neither does the pencil barrel when the gas supply is closed. That tells me that the whip is caused by the gas system design.

I've had many theories and per-conceived notions this year and have had all of them shot down in testing. At first I thought the whip was from the off center bores. -Wrong! Then I thought it was from the skinny barrels -Wrong! Then I thought is was from excessive gas pressure -getting closer...At least 54r is still cheap enough to experiment with!

[Discogodfather]

I was more surprised than anyone to find out that AR15 pencil barrels don't whip at all. I tested two rifles with 20" 1:12 barrels fully expecting them to whip but they did not. My theory is they don't whip because the gas travels a long way before it hits the carrier, then is completely exhausted inside the receiver. I would love to film an AR with a piston system installed to see if it whips.

We have some similar interests because I build too and I love pencil profiles. I did this 1:12 20" A1 build with an original NOS colt chrome lined barrel. What I found was as you say, it does not move. I was extremely surprised at this. I took the handguard off and it still did not move.



Accuracy was not great, I only did 50 yards on the irons and got a 1.75" group on a rest. I'd like to set it up with some optics and see if I can do better. I was shooting the M193 Vietnam ball ammo, which is supposed to be the best for 1:12. I know they tumbled like crazy after 150 yards. I'll take a high speed video next time I am at the range.

I would love to get a VEPR 54 and compare to the PSL. I have to think the added quality would produce better results.

[Holescreek]

Accuracy was not great, I only did 50 yards on the irons and got a 1.75" group on a rest. I'd like to set it up with some optics and see if I can do better. I was shooting the M193 Vietnam ball ammo, which is supposed to be the best for 1:12. I know they tumbled like crazy after 150 yards. I'll take a high speed video next time I am at the range.

I would love to get a VEPR 54 and compare to the PSL. I have to think the added quality would produce better results.

I'm very surprised to hear that your bullets tumbled at all! The 1:12 was made to stabilize the 55gr BT bullet. I was issued the same model in your pic in the Marines from '77 to '81 and we qualified with them at 200,300 and 500 yards every year. I saw a lot of bullet holes while pulling butts and never one keyhole. Gotta be something else going on!

High speed cameras are addictive. If they didn't require massive amounts of light I'd be recording everything.

This was recorded by a member over on the militaryfirearm.com site. Jump to 1:26 and watch the end of the barrel. http://www.youtube.com/watch?v=oEaty...eature=mh_lolz

[desert dog]

That's nice. Now tell me how I could possibly benefit from lying about that.

IDK, I see it all the time. Have even seen guys shoot groups at 50 and write "100 yards" on the target. After all, this is the internet. Most folks give BS internet group sizes by only shooting 3 rounds or by calling their flyers. I have been shooting for 30 years in competition, hunting, plinking, and training and BS accuracy claims are very common. Its like penis size or how much you can bench press - always embellished behind the keyboard.

Please forgive me if I find it hard to believe that you are shooting 3/4 MOA out of one of the crappiest-built rifles of all time with 50 year-old ****ty Russian surplus ammo that varies in MV by almost 200fps per round, using one of the worst optics ever invented to shoot tiny groups at almost 200 yards. And to make matters worse, your rifle was put together by the wizards at Century. Buuut, stranger things have happened.

I own 5 PSLs and have worked on dozens of them. I saw one that shot 1MOA years ago by a guy building a PSL with Jim Fuller. It would only do it with 7N1 ammo - and not consistently. That gun had the barrel chopped and recrowned, a TWS rail with a Leupold scope, and a modified/clearanced handguard. Variation and quality control was so bad in the manufacture of PSLs, that the mags are individually ground to fit each rifle receiver.

[gwgn02]

I'm very surprised to hear that your bullets tumbled at all! The 1:12 was made to stabilize the 55gr BT bullet. I was issued the same model in your pic in the Marines from '77 to '81 and we qualified with them at 200,300 and 500 yards every year. I saw a lot of bullet holes while pulling butts and never one keyhole. Gotta be something else going on!

High speed cameras are addictive. If they didn't require massive amounts of light I'd be recording everything.

This was recorded by a member over on the militaryfirearm.com site. Jump to 1:26 and watch the end of the barrel. http://www.youtube.com/watch?v=oEaty...eature=mh_lolz

Curious if the added weight of a muzzle device exacerbate the whippping?

[viper37]

Please forgive me if I find it hard to believe that you are shooting 3/4 MOA out of one of the crappiest-built rifles of all time with 50 year-old ****ty Russian surplus ammo

I forgive you. It's Ukrainian ammo by the way.

[Holescreek]

Curious if the added weight of a muzzle device exacerbate the whippping?

I'm not sure how far off topic we can get here, but it stands to reason that the more length and weight you put in front of a whipping barrel it is bound to exaggerate it.

One thing to remember is that it isn't the whipping itself that creates accuracy issues, the bullet is gone long before it's visible. The problem lies with where the heated barrel returns to between shots. PSL's are famous for vertical stringing as they heat up but again, it's inconsistent between rifles. None of mine string vertically even after 80 rounds. I've read where shooters state their guns start stringing after 10 quick shots.

[desert dog]

It's Ukrainian ammo by the way.

The "Ukrainian Surplus" that Palmeto State and others are selling is 70s vintage Soviet surplus that was stocked in Ukraine for decades and released for sale as it was deemed unusable by current military standards. After the break-up of the USSR, Ukraine was left with a MASSIVE amount of Soviet hardware, including ICBMs!.