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Discussion Starter · #1 · (Edited)
Hello again friends,
Some of you may have noticed that I haven’t emerged from my rabbit hole much lately. It’s been a busy, busy year, and it’s only speeding up as the fall hunting season looms on the horizon. To that end, my efforts lately have been focused on developing some exciting new hunting cartridges for Marlins. We’ve had incredible success with our 1894 pistol caliber short stroke conversions, but that success–and our preoccupation with filling orders–has left me with the feeling that the 336 platform wasn’t getting the love it deserved.

Quite a few of you noticed and commented on my thread regarding development of a couple of 6.5 caliber offerings. They are still in the works, being driven perhaps more by my passion than an expectation of huge commercial success. But in a simultaneous–and more secretive–endeavor I have been working on a new medium bore cartridge, this one inspired by our own @JackTW.

Jack has always admired our .30-30 AX project, but he is a really big fan of .35s, so rather than commission a .30 AX, he started pestering me to work out a .35 AX, or something along those lines. I like the .35 Rem, but I’ve always wished it could offer more, so I was all too happy to indulge Jack. However, as I began studying the .35 Rem more closely, I realized that it had too many limitations, and I was going to have to come up with an entirely new cartridge if there was to be anything worth getting excited about.

So I did, and so it is. It wasn’t in the mission parameters, but I ended up designing one of the most powerful cartridges that can be stuffed into a Marlin lever gun. Oops. Blame it on JackTW.

We’re calling this new cartridge the .36 RPP. Why .36? Well, for one thing it seems silly, given the performance of this thing, to round .358” down to .35 rather than up to .36. For another, there is some Texas Ranger heritage entwined with the .36, and we like that. And, more recently there is a phenomenally good Texas small batch bourbon from Ranger Creek Distillery that bears the .36 moniker, so this will make a triumvirate.

36 RPP.jpg

To address the inevitable question: “if I want a more powerful .35, why wouldn’t I just go to a .356 Win?“ Well, you could, and plenty have, and it is a fine cartridge. But it is severely hobbled by scarcity of brass and ammo. And there are many who feel squeamish about the .356’s chamber pressure of 52kpsi. I was one, but through study and first hand experimentation I’ve become convinced that, while some safety margin may be eroded, the 336 still has adequate safety at those pressures.

Having said that, one nifty aspect of our new .36 RPP is that it can deliver .356 Win performance while operating at comparatively tame .30-30 pressures. But what it can do at 50kpsi is truly impressive.

Without further ado, here’s the skinny:
First, the juicy performance figures. From our test rifle’s 22.5” bbl, safe, accurate loads have achieved the following: 1) with Speer’s 180gr FP, a MV of 2800fps (3133 ft/lbs of energy); 2) with Speer’s 220gr FP, a MV of 2500fps (3052 ft/lbs energy); with Hornady’s 200gr FTX, a MV of 2635fps (3083 ft/lbs energy). Note that we believe the terminal performance of the 200 FTX will likely be compromised by these high velocities.

In short, the .36 RPP can add nearly 400fps to commercial .35 Rem loadings, and well over 100fps to .356 Win loads.

Accuracy in our test rifle’s premium Douglas barrel was stellar, with nearly all test loads shooting sub-MOA before the barrel was even broken in. Some loads shot closer to ½ MOA.


  • Parent case to the .36 RPP is the .35 Whelen. Not ubiquitous by any means, but readily available. Hornady makes quality brass for the palatable price of $.75/ea.
  • .36 RPP brass is formed by trimming and full sizing Whelen brass. No fire forming, reaming, or neck turning is necessary.
  • Max COAL is 2.72”. Case volume is 65gr H2O.
  • Dies are inexpensive and readily available .356/.358 win
  • Appropriate bullets are shared with the .35 Rem
  • Offers more power than any commercial lever gun cartridge except the .450 Marlin. Yes, this includes the mighty .444 and .45-70, as well as the .338 ME and its bolt action analog, the venerable .30-06.
  • Offers more range than any commercial lever gun cartridge except the .338 ME
  • Donor rifles are Marlin 336s chambered in .35 Rem–readily and cheaply available both new and used.
  • Conversions require action stretching, but for the budget minded the factory barrel may be retained, and for those who want the ultimate in range and accuracy a longer Douglas barrel may be fitted.

I’ve kept @JackTW in the development loop, since this is kind of his spawn in a way, and without speaking too much for him, it’s safe to say he’s very excited about this cartridge. I am too. I can already envision it becoming my favorite, for despite the impressive top-end figures, it promises a high degree of flexibility and usefulness on a wide range of game. For those of us who don’t live in grizzly country or feel the need to bring a keg-size bullet to the party, a medium bore like this makes a lot of sense. Like the excellent but virtually unobtainable .338MX, the .36 RPP can bring the lever action out of the woods, and into fields and mountain ranges. It will certainly give you the element of surprise–and probably some braggin’ rights–among your bolt action buddies.
 

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Question, Can it be Fired from a 336 35 rem Rifle?
 
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Discussion Starter · #3 ·
Question, Can it be Fired from a 336 35 rem Rifle?
Nope. The .36 RPP cartridge is fatter and longer than the .35 Rem. While .35 Rem rifles will serve as donors, a conversion involving rechambering and action stretching must be undertaken. But the performance gains are worth it.

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Not much to add to your post other than I like the fact you kept the long neck, so many sacrifice the neck length of a cartridge to gain performance..

edit to add. Would be interesting to compare case capacity of 348 win to your 36 RPP (looked it up 35 whelen 71gr 348 win 75gr "water", first thing I thought of when seeing the cartridge is updated 348 win which is one of my favorite cartridges, but a real handful when loaded to potential to say the least. Not trying to hijack your thread, looks like you have a well thought out cartridge here, I hope this does well for you.
 
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Discussion Starter · #5 ·
In response to a PM regarding the cost of conversion:

The economy conversion, which retains the factory barrel, will run about $480. This involves bumping the barrel shoulder so that the fatter chamber won't weaken at the old extractor cut, refitting mag tube and forearm, and extensive work to the action parts and receiver to accommodate the long cartridge. A set of dies will run you about $35 and we'll add a modified Lee FCD for another $22. A 50pk of Hornady brass is currently on sale at Midway for $34. That puts the total cost to get up and running (not including donor rifle) at around $600.

If one prefers to tap into more of the cartridge's potential, a longer, more precise Douglas barrel can be added for an additional $300. The basic conversion, including donor, would still be cheaper than the going rate for a 338mx, and the upgraded .36 would be cheaper than a .338mxlr. That's assuming you can find either.

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Very interesting ! You started with the mid-bore 30AX, then went on to the 6.5 and now the 36RPP. May I assume( and hope) your next venture will be a 21st century, small bore, 22 caliber varmint levergun or I guess you could go very big bore. In another post I described you guys as " innovative" and that seems like an understatement.
 
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Discussion Starter · #7 ·
Thanks Shawlerbrook. I too think a modern, fast, and accurate .22 lever gun would be fun. I can think of at least one parent case that could be easily converted to lever use, and propel, say, a 45gr Bee bullet upwards of 3500 fps, which would be nothing short of explosive. It's a tough call though. I love my little .218 Bee, and think there is no finer "walking varminter" made, but I think it's a small niche in the shooting community. And while RPP and others have proven that superb, sub MOA accuracy can be wrung from a 336, I'm not sure how many people are willing to adjust their thinking to include lever guns in the class of highly accurate, medium range, shoot-from-station varmint destroyers. Might have to take a poll sometime.

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Well, apparently some good can come from being a pest. :flute:

All I requested to Adam is for a Marlin in 35 cal optimized for increased down range hunting we have out west. Then more than a few emails with Adam discussing whats possible with his AX version and bullets optimized for it, Adam's tinkering genius took over. Some serious kudos for Adam are in order for the results.

While bullets exist for the 36RRP, I'm developing bullets to optimize the fullest potential out of this cartridge. Of course, they will be precision hand crafted bonded bullets developed to the cartridge ballistic performance and we'll be able to squeeze out some impressive BC.

I'm searching for the right donor 35REM and will definitely opt for the Douglas barrel, my 35 Whelen had one and they worth every penny. I have some very specific ideas for my build utilizing some of RRP's custom metal finish work and a custom walnut stock. This custom Marlin will become my go to hunting rifle.

Thanks Adam for making this a reality!

Jack
 
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Discussion Starter · #9 · (Edited)
Jack, I'm definitely looking forward to seeing some RJ bullets for this caliber, and I'm sure lots of .35 Rem shooters will like the new offering(s) too. The only thing keeping the .36 RPP from flat out stomping the .338ME is ballistic coefficient. The 200gr .338 FTX has an enviable one. At .43 it's unmatched in lever gun bullets. By comparison, the .358" 200gr FTX, and Speer's 220 FP both come in around .30. Even though the .36 RPP does more at the muzzle, it's tough to compete with the .338 down range. If a new bullet design will close the gap even half way, the .338's only advantage will disappear at any practical hunting range.

Meanwhile, here are some ballistics for currently available bullets in the .36. All zero distances are 100yds.

Speer 180gr FP MV=2800fps ME=3130 ft/lbs @200yds V=2063, E=1702, Drop=4.5" @400yds V=1465, E=858, drop=42"

Speer 220gr FP MV=2500fps ME=3053 ft/lbs
@200yds V=1942, E=1843 drop=5.6" @400yds V=1475, E=1063, drop=48" (still delivers over 700 ft/lbs @ 550yds)

Hornady 200gr FTX MV=2635, ME=3083 ft/lbs @200yds V=2066, E=1896, drop=4.9" @400yds V=1581, E=1111, drop=42" (still delivers over 700 ft/lbs @570yds)

As you can see, the 200gr FTX looks like a pretty good bullet for this rifle on paper, but I suspect that at ranges less than 200yds it could suffer jacket separation or worse. At greater ranges it could be ideal. The two Speer bullets have a reputation for being tougher, and they could work well for anything from coyotes to moose at varying distances.

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Adam, no doubt the 36RRP has the potential for unseating the 338ME. Once I have the once fired case and max room to stretch a bullet before running into the lands, I'll be all over this. If the AX affords the room then their is no reason why the 35 cal can't run a .400 BC. Possibly more but that would be enough to stomp the 338ME.

Jack
 

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Well, apparently some good can come from being a pest. :flute:

All I requested to Adam is for a Marlin in 35 cal optimized for increased down range hunting we have out west. Then more than a few emails with Adam discussing whats possible with his AX version and bullets optimized for it, Adam's tinkering genius took over. Some serious kudos for Adam are in order for the results.

While bullets exist for the 36RRP, I'm developing bullets to optimize the fullest potential out of this cartridge. Of course, they will be precision hand crafted bonded bullets developed to the cartridge ballistic performance and we'll be able to squeeze out some impressive BC.

I'm searching for the right donor 35REM and will definitely opt for the Douglas barrel, my 35 Whelen had one and they worth every penny. I have some very specific ideas for my build utilizing some of RRP's custom metal finish work and a custom walnut stock. This custom Marlin will become my go to hunting rifle.

Thanks Adam for making this a reality!

Jack
I am sure your .358 inch bullets will be fantastic Jack! I have heard that your .308 inch offerings are pretty outstanding too! :flute:
 

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I am sure your .358 inch bullets will be fantastic Jack! I have heard that your .308 inch offerings are pretty outstanding too! :flute:
LMAO, I wonder where you heard that? Since you're assisting on load development and all. LOL

jack
 
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Discussion Starter · #13 ·
LMAO, I wonder where you heard that? Since you're assisting on load development and all. LOL

jack
Like they say, sometimes you just need your friends. 🏻
 

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Any reason this couldn't be done in a .338 as well? It'd be great to have someone like Adam take the wheel for Marlin, but if he did, then we wouldn't have innovations like this and the others he's doing being developed. DP
 
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Discussion Starter · #16 ·
Maybe it's time for RPP to change its business name to Lever AX Men! Still getting used to my 3030AX, but I do like it alot!

Sure wish RPP could buy out the Marlin brand so it could once again be a maker of quality firarms!
Heck, we made 'em a good offer, but apparently Freedom group won't take Texas bourbon in trade. Fools.

Here's a sneak peak at our test rifle, just reassembled today after a long session in the paint booth. There will be more pics on our website soon.

AD .36 RPP detail 1.jpg
 
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Discussion Starter · #17 ·
Any reason this couldn't be done in a .338 as well? It'd be great to have someone like Adam take the wheel for Marlin, but if he did, then we wouldn't have innovations like this and the others he's doing being developed. DP
Here's an idea, let's all (MO members) pool our funds and buy Marlin. Then we can all get the Marlins we want, at the level of quality we expect. I've got at least $100 or so in folding cash, and I think there's a bucket of change around here somewhere. Anyone else got something for the kitty?

A .338 could be done, but there are a couple of ways to tackle it. The .338 ME can only be built on an M platform, as these have the stronger chambers and barrel/receiver junctions required for the souped up half inch diameter case body. Unfortunately M receivers aren't a dime a dozen, and by the time you convert one to .338, you're well north of $1000.

The other option is to neck down the .36 RPP and give a 366 similar treatment with a .338 barrel. Much like the .36 uses .358 dies, the .338 RPP could use .338 Federal dies. Dangit DPE, not ya got me thinking again...
 

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Adam you are truly a genius when it comes to what the world needs out of lever guns. With you and Jack teamed up you two seriously have me craving more guns!
 
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Discussion Starter · #19 ·
Well, I don't know if need has much to do with it. We just want what we wants. And yes, Jack is a bad influence. Does CA have extradition laws? We gotta get him outta there so he can realize his potential.
 

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Here's an idea, let's all (MO members) pool our funds and buy Marlin. Then we can all get the Marlins we want, at the level of quality we expect. I've got at least $100 or so in folding cash, and I think there's a bucket of change around here somewhere. Anyone else got something for the kitty?

A .338 could be done, but there are a couple of ways to tackle it. The .338 ME can only be built on an M platform, as these have the stronger chambers and barrel/receiver junctions required for the souped up half inch diameter case body. Unfortunately M receivers aren't a dime a dozen, and by the time you convert one to .338, you're well north of $1000.

The other option is to neck down the .36 RPP and give a 366 similar treatment with a .338 barrel. Much like the .36 uses .358 dies, the .338 RPP could use .338 Federal dies. Dangit DPE, not ya got me thinking again...
Necking the 36 down was what I had floating around in my head. Solves the bullet issue, Hornady has the FTX and it's stouter than the 35 caliber FTX. AND, I'm waiting for Jack to get his .338 bullet out, made for levers. DP
 
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