PU mount
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Thread: PU mount

  1. #1

    Default PU mount

    Hello
    I am getting ready to install an Accumount on a refurb laminate stock. Looking for a template or good pics of base placement.

    Thanks in advance
    Paul

    Sent from my SM-N960U using Tapatalk

  2. #2
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    Default

    You mean something like this?
    Attached Thumbnails Attached Thumbnails Backup of our Pictures 592.jpg  

    100_0777[1].JPG  


  3. #3

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    Quote Originally Posted by Montana Bearbait View Post
    You mean something like this?
    So the rear pin is in line with clip slot?

    Sent from my SM-N960U using Tapatalk

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  5. #4
    Join Date
    Jan 2015
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    Be advised that the distance between the holes on sniper receivers varies. Unless whatever mount you have are the same distance between the screw holes on your receiver it will be a no-go. I found that out the hard way. I did find one that worked with my Yugo Mosin sniper - Accumount used to sell bases in 53.5mm and 54.5mm and 55,5. Don't know if that is still the case.

    The pins are not critical to the operation - you may have to dremel one of them off to get everything to fit. It's the screw holes that are critical. And be advised, once you get it together, you may have to do a considerable amount of grinding to get the thing to zero.

    Here are excerpts from an article about restoring my Yugo sniper years ago:

    I’m guessing a lot of people have looked at the Mosin Nagant “ex-sniper” rifles that have been kicking around recently, and thought, “I’ll bet I could cobble a rifle together.” The idea was particularly attractive to me, because I happened to have a PU scope and mount I picked up years ago.

    The first attempt to mount the scope made it clear this was not going to be a quick or simple job. The pins protruding from the receiver did not match up with the pin holes in base plate. I had assumed all of these dimensions would be standard. But Henry Ford's miracle of mass production and interchangeable parts apparently did not completely catch up with the Soviets, at least as far as scope mounts are concerned.

    In looking the situation over carefully, I ascertained that the front pin would line up correctly but not the rear, so I carefully removed the rear pin with a Dremel tool, grinding the remnants of the pin flush with the receiver, so that the base plate would lay flat on the receiver.

    Assuming I was over the worst of it, I prepared to install the two screws which hold the base in place on the receiver. But I quickly discovered that the distance between the screw holes in the receiver was different than the holes in the scope base plate. Again the miracle of mass production and interchangeability apparently didn’t make it to war-torn Russia.

    Some browsing on the web confirmed that original mounts might have a variation of as much as 2 mm between the screw holes. Mine wasn’t ever going to work on that rifle.

    Fortunately, I discovered that ACCUMOUNT (accumounts.com) makes bases with three different distances between centers on the screws. I measured the spacing on my receiver, and ordered closest one from ACCUMOUNT.

    When it arrived, I held my breath as I slid the new base over the remaining pin, and snuggled it down onto the receiver. Although the distance between centers on the screw holes was now correct, the holes in the base did not line up with holes in the receiver. It was clear that the remaining pin was now a problem. So off she came, as had previously been the case with the rear pin.

    Now it was possible to snug the base up to the receiver. Had to do some modifications to the mounting screws, as the inlets for the set-screws did not line up correctly, but that was accomplished without too much trouble. With the base plate now firmly secured on the receiver, it was apparent that the alignment on what had been the front pin was now very close. So I carefully drilled out the remainder of pin, and gently tapped a new pin through the base mount into the receiver, and it all tightened up nicely. Still one pin short of the original configuration, but everything seemed secure.

    I then mated the scope bracket to the base. There is a great article by Paul Oats about this process at http://www.owrpc.co.uk/images/mnpu.pdf.

    Each rifle had to have the scope bracket individually machined to the base in order for the rifle to be set at a true zero. This involves shooting a few rounds, removing the bracket, and filing (presumably very small amounts) from the bracket. Unlike most scopes, the PU scope's field of view is fixed, and the adjustment turrets actually move the entire reticle within the field of view. You first center the pattern by filing the bracket, and then move the reticle to the centered pattern by adjusting the turrets. Then the turrets can be indexed (set for zero windage and correct elevation) and subsequent fine adjustments can then be made using the turrets.

    The articles I read suggested the grinding process would amount to removing small amounts of metal. In the case of my mount, it turned out to be a lot of grinding. The pattern started off way to the left in the scope’s field of view (which is where you want it to begin with). I fired a few rounds to warm the barrel up, then three rounds at 100 yards to get a pattern. Then I removed the bracket, filed the bracket to adjust the point of impact, and reassembled it to fire again.

    You want to keep the barrel at a fairly constant temperature or the point of impact wanders around. Which means you can only work on it for a relatively short time at a stretch. If you get the barrel too hot, the patterns aren’t good. You can sit around at the range and let the thing cool off, or you can go do something else. Easier for a busy person to go do something else, so I made numerous trips to the range over many days. Fire, file, fire file. I went slow, because if you grind too much, the pattern will end up to the right of center, and then you’ve got a problem which can only be resolved by shimming. Didn’t want to go there.

    Once the pattern was very nearly centered, I made the fine adjustments with the turrets and indexed them at 100 yards. At this point I was getting consistent MOA groups at 100 yards.

    Then the acid test. I moved the targets out to 200+ yards and prayed that the point of impact wouldn’t shift left or right. If you've done the grinding correctly the scope should be dead center over the barrel, and windage should remain constant at all ranges. If not, the problem shows up right away at 200 yards. Bingo! I was lucky - everything was perfect. First two shot straddled the vertical center line on my target. Last thing I did was cold-blue the places I had filed and ground.

    Believe me, after having spent at least 20 hours on this job, I have a lot more respect for the guys who were setting these rifles up while the enemy was at the gates. Crude process by modern standards, but nonetheless effective. I'm sure the learning curve improves with experience, but there was still a lot of work to bring each individual rifle up to sniper standard. It’s a far cry from modern weapon systems.

    I realize that I now have a rifle that is not completely “original”, and thus strictly speaking, not very collectable. But it’s my favorite of the three Mosin Nagant snipers I own. Why? The others will always be there – one in pristine condition. They have their own histories. Mine is a bit of a mutt – well in fact they all are – but this one was put together far from its home long after the battles it was originally meant to fight. But this one has given me a deep appreciation of what was going on in midst of a desperate war many decades ago. And there is a lot of me invested in this particular rifle. So when rounds go down range, I know what was involved during Великая Отечественная война - the Great Patriotic War. And even when I’m shooting my original sniper, the work I have done on this restoration helps me feel a tiny connection to the craftsmen who helped keep the Nazi hordes at bay more than half a century ago.

  6. #5

    Default

    Chcusnr, thank you.

    Mine was never a sniper so I shouldn't have the pin/hole alignment issues that you did....but the final fitting info I will need to go through is great.

    Since my 91/30 has never been drilled, does the rear pin center with the clip slot & where the stock meets the receiver.....approximately?

    Sent from my SM-N960U using Tapatalk

  7. #6
    Join Date
    Jan 2015
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    265

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    Short of taking mine apart, I could not tell you. Good luck with the conversion!

  8. #7
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    Quote Originally Posted by 63cagedfalcon View Post
    So the rear pin is in line with clip slot?

    Sent from my SM-N960U using Tapatalk
    I took a picture of my son's original matching Classic Arms '43 PU.

    I hope you can see what you need to see.Click image for larger version. 

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  9. #8

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    Quote Originally Posted by Montana Bearbait View Post
    I took a picture of my son's original matching Classic Arms '43 PU.

    I hope you can see what you need to see.Click image for larger version. 

Name:	100_1219[1].JPG 
Views:	5 
Size:	957.5 KB 
ID:	3644731Click image for larger version. 

Name:	100_1218[1].JPG 
Views:	4 
Size:	792.2 KB 
ID:	3644737
    Thanks, using the rough elevation screw as a constant, the rear pin is located in the slot.

    Thank you all who replied.

    Sent from my SM-N960U using Tapatalk

  10. #9
    Join Date
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    Quote Originally Posted by 63cagedfalcon View Post
    Hello
    I am getting ready to install an Accumount on a refurb laminate stock. Looking for a template or good pics of base placement.

    Thanks in advance
    Paul

    Sent from my SM-N960U using Tapatalk
    It is typically cheaper to buy an already built than to make one. An original refurbed PU can occasionally be found at a good price. I would go that way if it were, and it has been, me. I had three already made replicas. All shot OK, one very well. All are replaced now with refurbed PUs and Samcos.

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