Doug Beach
Silver $$ Contributor
Does the unique shoulder on an RPR barrel serve any purpose? It is not related to barrel / receiver mating, and doesn’t seem to be needed for fore end mounting, either. Am I missing something?
Ruger RPR barrel shoulder?
- Thread starter Doug Beach
- Start date
Doug Beach
Silver $$ Contributor
The barrel is definitely threaded.
Doug Beach
Silver $$ Contributor
I’ve turned down Palma profile barrels to produce the shoulder, for two different RPR’s. The one I’m currently looking at, nothing touches that shoulder, it just exists under the fore end nut & spacer. This gun is 7 years old, I’m told.
I think it may have on the Gen 1 and maybe 2 handguards.
It definitely does not on the Magnum models. I've been boring the handguard lock nut 0.050" on those so I can use standard 1.25" shank blanks.
On my Gen 1 & 2 RPRs, I used a hard shoulder to chamber and then threaded the 1.25" section to AR15 barrel nut specs. Bored the shoulder out of a standard tubular handguard nut to use AR15 handguards.
The primary motivation was using standard barrel blanks.
It definitely does not on the Magnum models. I've been boring the handguard lock nut 0.050" on those so I can use standard 1.25" shank blanks.
On my Gen 1 & 2 RPRs, I used a hard shoulder to chamber and then threaded the 1.25" section to AR15 barrel nut specs. Bored the shoulder out of a standard tubular handguard nut to use AR15 handguards.
The primary motivation was using standard barrel blanks.
ronemus
Gold $$ Contributor
My comments just show how fuzzy memory can be - I just checked the take-off barrel from my Magnum RPR and it is threaded. The flange is only allow the barrel nut to lock headspace; the factory barrel has no shoulder in the conventional sense. It would certainly be possible to make a replacement barrel with a conventional shoulder, but it doesn't appear to be done that way from the factory. The replacement barrel from LRI (Long Rifles Inc., Sturgis MT) was set up the same way.
I dug out my take offs to take a look.
The top bits are the Gen 1. In addition to the barrel nut itself, there was another nut that screwed on it. It is stopped against the sleeve on the barrel. The serrated half shells clipped on that nut and the tube clamped on them.
The bits below the barrel are Gen 2. The tube is a sliding fit on a bushing and held in place with screws. The bushing is held in place with another clamping nut that threaded on the barrel nut. The bushing is trapped between the retaining nut and the barrel nut teeth. The picture doesn't do a great job of showing it, but you can just see the points where the barrel nut teeth contacted the bushing. The sleeve isn't used in this assembly.
The tenon is a nominal 1x16 and the shank ahead of the sleeve is also a nominal 1". The sleeve is 1.175".
The top bits are the Gen 1. In addition to the barrel nut itself, there was another nut that screwed on it. It is stopped against the sleeve on the barrel. The serrated half shells clipped on that nut and the tube clamped on them.
The bits below the barrel are Gen 2. The tube is a sliding fit on a bushing and held in place with screws. The bushing is held in place with another clamping nut that threaded on the barrel nut. The bushing is trapped between the retaining nut and the barrel nut teeth. The picture doesn't do a great job of showing it, but you can just see the points where the barrel nut teeth contacted the bushing. The sleeve isn't used in this assembly.
The tenon is a nominal 1x16 and the shank ahead of the sleeve is also a nominal 1". The sleeve is 1.175".
The conversion to standard 1.25" blanks went like this.
The Ruger forends were not reused.
The completed guns.
One is a 6XC the other is a long throated 223. They originally had Gen 1 Razors on them. Those were robbed for later guns and they now use Gen 2 PSTs.
The Ruger forends were not reused.
The completed guns.
One is a 6XC the other is a long throated 223. They originally had Gen 1 Razors on them. Those were robbed for later guns and they now use Gen 2 PSTs.
Things are scaled up with the magnum versions.
The tenon is 1.125x16 and the shank ahead of the sleeve is 1.2".
The barrel nuts both use the same AR15 pattern wrench, but the wrench will have to be opened up to clear the larger forend mounting threads on the magnum version.
The LRI wrenches are the best I've found. Ruger doesn't sell the nuts to non gunsmiths, so a good wrench could save a lot of trouble.
The barrel sleeves are not used in the Magnum forends.
The tenon is 1.125x16 and the shank ahead of the sleeve is 1.2".
The barrel nuts both use the same AR15 pattern wrench, but the wrench will have to be opened up to clear the larger forend mounting threads on the magnum version.
The LRI wrenches are the best I've found. Ruger doesn't sell the nuts to non gunsmiths, so a good wrench could save a lot of trouble.
The barrel sleeves are not used in the Magnum forends.
Using a 1.25" blank is more straightforward with the Magnum versions. The forend retaining nut is simply bored 50 thou over.
I used a 1.35" blank for this one. I probably won't do another this way because of the additional blank cost. I also fabricated a barrel nut. It wasn't a necessary step to use the standard blank. The nuts are pretty easy to make from 1.625" round bar. The OD/ID threads and one face can be done in the first setup.
I like the forend on the Magnums and wanted to retain it. This requires the threads on the Ruger barrel nut. On the Magnum version, they're too large to just cut into the barrel. I was also after a more rigid connection than the 1.125" tennon would provide, so the barrel nut was set up trapped like a recoil lug. The connection to the front of the 1.25" blank seemed a little light, so I tried the 1.35". After assembling it, the 1.35" looks like overkill. The 1.25" looks like this;
Boring the retaining nut does not prevent it's use with the original Ruger barrel.
RPR Magnum set up for hobby level ELR.
The buttplate is fabricated from 1" steel bar stock and adds 3# to the back of the gun. The weight and shift in balance help with the tracking. Cartridge is 300 Lapua.
I used a 1.35" blank for this one. I probably won't do another this way because of the additional blank cost. I also fabricated a barrel nut. It wasn't a necessary step to use the standard blank. The nuts are pretty easy to make from 1.625" round bar. The OD/ID threads and one face can be done in the first setup.
I like the forend on the Magnums and wanted to retain it. This requires the threads on the Ruger barrel nut. On the Magnum version, they're too large to just cut into the barrel. I was also after a more rigid connection than the 1.125" tennon would provide, so the barrel nut was set up trapped like a recoil lug. The connection to the front of the 1.25" blank seemed a little light, so I tried the 1.35". After assembling it, the 1.35" looks like overkill. The 1.25" looks like this;
Boring the retaining nut does not prevent it's use with the original Ruger barrel.
RPR Magnum set up for hobby level ELR.
The buttplate is fabricated from 1" steel bar stock and adds 3# to the back of the gun. The weight and shift in balance help with the tracking. Cartridge is 300 Lapua.
@ShaunBrady
Sorry to resurrect an old thread, but it seems like you might be able to answer a question of mine. I came across an American Rifleman review of the magnum RPR that suggested the handguard was replaceable with AR-10 handguards....which is the very first I've heard of this. From what research I've done in the past, I didn't think there were any aftermarket options available.
However, I haven't been able to confirm the specs for the fore-end mounting threads on the outside of the barrel nut. Do you happen to know what they are?
https://www.americanrifleman.org/content/tested-magnum-length-ruger-precision-rifle/
The threads on the OD of the Magnum RPR barrel nut are DPMS 308 pattern 1-7/16 x 16.
I haven't tried other handguards on the Magnum RPRs, so I'm speculating, but it appears a standard AR308 handguard would have the same problems AR15 handguards did with the first RPRs. Those included the flange on the RPR barrel nut stopping the handguard nut and the ID shoulder in the handguard nut being in the wrong position relative to the RPR barrel flange in front of the RPR barrel nut. The teeth on the RPR barrel nut would still be exposed after the installation of the AR Handguard.
My first cut at fitting a DPMS 308 handguard to a Magnum RPR would be to bore out the internal shoulder in the handguard nut as I do on the short action RPRs and then bore a relief into the handguard nut threaded section to allow it to cover the flange on the RPR nut and stop flush with the receiver. The handguard nut would bottom internally on the front face of the RPR barrel nut.
It's not apparent from section views, but once you've disassembled one, it becomes obvious that the RPR barrel nut system does not retain the barrel in the receiver like an AR despite the flange on the barrel. The RPR barrel nut works the same as a Savage 110.
The flange pattern on the Magnum RPR is AR15, but most AR15 barrel nut wrenches will have to be bored to fit over the larger threads.
I haven't tried other handguards on the Magnum RPRs, so I'm speculating, but it appears a standard AR308 handguard would have the same problems AR15 handguards did with the first RPRs. Those included the flange on the RPR barrel nut stopping the handguard nut and the ID shoulder in the handguard nut being in the wrong position relative to the RPR barrel flange in front of the RPR barrel nut. The teeth on the RPR barrel nut would still be exposed after the installation of the AR Handguard.
My first cut at fitting a DPMS 308 handguard to a Magnum RPR would be to bore out the internal shoulder in the handguard nut as I do on the short action RPRs and then bore a relief into the handguard nut threaded section to allow it to cover the flange on the RPR nut and stop flush with the receiver. The handguard nut would bottom internally on the front face of the RPR barrel nut.
It's not apparent from section views, but once you've disassembled one, it becomes obvious that the RPR barrel nut system does not retain the barrel in the receiver like an AR despite the flange on the barrel. The RPR barrel nut works the same as a Savage 110.
The flange pattern on the Magnum RPR is AR15, but most AR15 barrel nut wrenches will have to be bored to fit over the larger threads.
The flange is there for mounting the handguard so I shoot mine for Highpower and wear out barrels so I always set back my barrels so when I put the first barrel on mine I did not put a flange on the barrel and instead made a little spacer that sets against the barrel nut and the nut the handguard fits on. I made 5 or 6 of these in different thicknesses by .003 because that how I time the handguard by switching one of these washers. I also thread the barrels long enough to allow for cutting off an inch or so to set the barrel back otherwise you would have to chase threads on the original threading job if you wanted to set it back just one inch and that bothered me so I thread them 2 1/2 inches long from the start and when I set the barrels back I just cut off an inch and stick the reamer in and job all done. I've taken the 6.5 creedmore barrels and stuck in a 6.5x284 reamer and they shot well and my hunting rifle is a rpr I put a 30x284 barrel on and it shoots well, right now I'm going out to the shop to finish my next across the course rifle, a rpr in 6 dasher. none of these have that flange on the barrel
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