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Thread: Getting a PSG1 barrel put on a PTR91

  1. #1

    Default Getting a PSG1 barrel put on a PTR91

    Does anyone know a gun smith that can put this barrel - https://www.hkparts.net/shop/pc/RCM-...m#.Ux69NP-YZaQ

    On to a PTR91 that currently has a standard 18" barrel. If so how much would it cost and most importantly how leveraging is a 25.5" barrel vs an 18" barrel for a 0.308 cal anyways. The barrel is over 900 after shipping and if there is a place that can install it I cant imagine its cheap so im guessing 500 for the install do you really get 1500 worth of accuracy out of the extra length?

  2. #2
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    I know nothing about this, but since no one else is answering, the only thing that changes with barrel length is speed of the projectile. Which only means range really. Think physics. As long as the powder is burning in the barrel, the gases are expanding and in turn pushing the bullet out. As soon as the powder stops burning (or VERY shortly after) the gases stop expanding and are no longer pushing. So, if you are burning up all your powder in 18" of barrel, adding an additional 7" means you are traveling against friction for 7" without expanding gases pushing. In that case, you might actually see decreased velocity. BUT, if your powder is still burning at 18", then adding length will allow more expanding gases to push longer. So if you theoretically have a load that burns exactly 100% of the powder at just before point that the bullet exits the crown, you have a perfect powder charge. If that's 25.5", perfect. Or even if you have powder still burning, it's better than burning all the powder up and having the gases slow down to the point that the friction of the barrel is slowing the bullet down.

    None of which "improves" accuracy. Only how fast the bullet is traveling when it exits the barrel. Fast bullet means flatter trajectory and longer range before having to adjust for bullet drop. But all bullets essentially drop at the same rate, question is where is that point? Is it 500 yds away or 550 yds away? Faster exit speed means that pushes back.

    There are other things about the barrel that will affect accuracy. Mainly it's how the bullet exits the barrel. A good even crown will mean the gases vent evenly and don't destabilize the bullet as it exits. etc, etc.

    After that, it depends on what you want. If you gain 1/10 of a MOA, does that justify the cost? If so, good. If not, there you go.

    But bottom line, all you gain with this is the length. So to really take advantage you might have to work up a custom load that matches the longer barrel.

    Anyway, that's my 2 cents. Take it or ignore it, just thought someone should give some answer.

  3. #3

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    That is a good point, are there tables that equate powder load to barrel length. I also know there is a maximum powder load for a given brass cartridge otherwise you can rupture the cartridge. So if the .308 will reach rupture powder load before the new lenght can be exploited then it would be a waste.

    Do you know where a barrel like this could be put on?

    Is the money better spent on upgrading rifles to say a .338 lupula or even a .50 bmg barrett M82?

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    Quote Originally Posted by rppearso View Post
    That is a good point, are there tables that equate powder load to barrel length. I also know there is a maximum powder load for a given brass cartridge otherwise you can rupture the cartridge. So if the .308 will reach rupture powder load before the new lenght can be exploited then it would be a waste.

    Do you know where a barrel like this could be put on?

    Is the money better spent on upgrading rifles to say a .338 lupula or even a .50 bmg barrett M82?
    Not really barrel length, but there are burn rate tables that show which powders burn faster or slower. It's pretty much up to you to find the right combo. Start with a commonly used powder and move up or down the chart to find where your muzzle velocity peaks. It's a time consuming and potentially expensive process to buy all the powders.

    I guess it all depends on what your goal is. If you're looking to go hunting, no, it's not worth it cause a cheap $400 rifle will take a moose. If you're looking to set a distance and accuracy record, maybe it is worth it. If you want to have the longest shot ever made from a PTR91, it might be worth the time. It all depends on what you want to do.

    As for the guy, are you local to AK? Andy "ADfields" is a smith, he might know what to do or at least point you in the right direction.

    Oh here's that burn rate chart:

    http://www.hodgdon.com/burn-rate.html

    It's not quantitative. But it gives you a range to work with. Moving down the chart means slower burn rates. Say you start with Varget as a mean. Try some loads with RL-15 (faster) and some with Winchester 748 (slower). See what happens to the velocities. Essentially watch your velocities until they start dropping back down. Then back up a touch. If the velocities don't drop back down at the max recommended charge, switch to a different powder and start over. Maybe you need something slower burning. If they drop before you hit the max charge, it's burning too fast. Eventually you'll find a sweet spot. You'll be playing with a TON of variables including primers and even the bullet you choose. It might take a while, but if you're serious you might find the perfect load for you. Again, depending on what you goal really is in the end.

  5. #5
    Moderator Paul H's Avatar
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    Accuracy has almost nothing to do with barrel length, and if anything shorter barrels are potentially more accuracy because they are stiffer than longer barrels. A barrel that has a good chamber, good bore and good crown will shoot accurately, or more correctly the only thing that can happen to a perfect bore is for the accuracy to negatively affected by the gunsmith or manufacturer who chambers and crowns the barrel.

    If my goal was the utmost in accuracy than my approach would be to select a well respected accuracy oriented custom smith and have him fit his preferred brand of barrel to your rifle. I would not purchase another factory barrel if the current barrel didn't meet my expectations.
    Those that are successful in Alaska are those who are flexible, and allow the reality of life in Alaska to shape their dreams, vs. trying to force their dreams on the reality of Alaska.

    If you have a tenuous grasp of reality, Alaska is not for you.

  6. #6
    Sponsor ADfields's Avatar
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    I can install that but you seem a bit cart before horse here. I got to ask why, what is it you are trying to get from the rifle? Bench rest accuracy? Velocity? Greater range? What is it you are looking to do with the rifle?

    IMO 18" is too short for a 308, I'd not go under 20" and 22" is about right for it. But you don't need a $900 barrel to fix that. Anyway, the first step is defining what it is you want the rifle to do.
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    Member The Kid's Avatar
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    I would be skeptical about spending that kind of dough on one of those barrels. I at one time had easy access to one of only around a dozen real live PSG1 rifles in the US. It was NIB when I got my mitts on it complete with case, 5 mags, H&K scope, bipod, yadda yadda. After extensive shooting with multiple brands and weights of ammo, myself and several other shooters were never able to get any better than 1.5" accuracy at 100yds and more often it was on the order of 2.5" groups. Lots of hype for not much peformance IMO.

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    Member winibezold's Avatar
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    i'm sure you've researched the PSG1 thoroughly, but in case you haven't.... They were state of the art long range tools of their day. They were plenty more accurate than any other semi auto rifle in their class. But now, for the $1500 or so you would spend, yuo can get an off the shelf AR10 that will outshoot an original PSG1 with good ammo. And spend a bit more for a high quality AR10.... REPR, SASS or the like, and you'll have a lights out longisg range precision rifle that Still costs way less than a real PSG1. but if you want a clone thats a sweet look alike and is fun to shoot, buy the barrel and let the lead fly.

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