Need technical input: rifle project based on 7LRM cartridge necked to .277

codyadams said:

...BIGNGREEN said. Just get a 7 LRM bushing die...

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Thanks for adding to the discussion! Some very good points. I looked for such a die, but it seemed the only folks that had a die for the 7LRM was Gunwerks...figured because it was a proprietary cartridge. The die is Hornady, and I keep reading how it's crap. Was looking at having a custom die made, but then I'd need a reamer print, and or three fired cases. Finally decided to stop chasing my tail and just ask for some help.
Where do you reckon has one?

3K with the 170's is in line with what I was thinking, and is the goal. Also have 200 or so Matrix 166's, and even about 100 190gr to play with that I bought from a group member some years back! What decided me on going this route with the case was the extra capacity. Figured it would allow reaching 3K at a lope rather than a run...or rather, get there without super high pressure, and have room to spare. That, and the long necks should allow for decent barrel life.

Nothing wrong with the 7LRM. But, neck down a 7LRM to a 277 and you have a barrel roaster. Not nearly as bad as a 7 RUM or 28 Nosler. Necks don't mean squat as to barrel life. It's the flame behind the bullet that determines that.
If there's a 270 WSM, compare those ballistics.
There's an optimal powder charge weight for every caliber, and I think @elkaholic attempts to do that with his Sherman chamberings.
Blowing out the shoulder to 40° should increase capacity and minimize trimmings needed.
You could also take a 6.5 PRC, neck up, Ackley-ize it.
Any way you do it, you'll have fun. Don't mind the drain hole you punched into your bank account in the process - it's a buzzkill.
If you can help it, don't use Hornady brass either.

Magnus777 said:

Thanks for adding to the discussion! Some very good points. I looked for such a die, but it seemed the only folks that had a die for the 7LRM was Gunwerks...figured because it was a proprietary cartridge. The die is Hornady, and I keep reading how it's crap. Was looking at having a custom die made, but then I'd need a reamer print, and or three fired cases. Finally decided to stop chasing my tail and just ask for some help.
Where do you reckon has one?

3K with the 170's is in line with what I was thinking, and is the goal. Also have 200 or so Matrix 166's, and even about 100 190gr to play with that I bought from a group member some years back! What decided me on going this route with the case was the extra capacity. Figured it would allow reaching 3K at a lope rather than a run...or rather, get there without super high pressure, and have room to spare. That, and the long necks should allow for decent barrel life.

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The hornady being crap thing is more about their brass, their dies work fine. If you can't get under half MOA loading ammo with their dies, the problem isn't the dies.

As far as the lope vs run thing, you are correct on the Sherman cartridge, 3000+ with the 170 is running just under pressure signs in most guns, we are actually running 2940 in ours using H1000 and a 24" barrel, but that also tends to be where guns often shoot well in my experience, though there is usually another accurate node 100fps or so lower. So in that case, if you wanted to run at a lower node, you would want something capable of 3100 or maybe more with the 170. Not completely sure if the LRM will do that for you or not, it might, I haven't looked at it's performance in a while, you would definitely want to run the adg brass in that case.

The long neck thing at this point is a theory rather than fact, it may be or it may not be, I have yet to see an actual scientific test conducted to prove either way, but a lot of knowledgeable people have gone both ways on it. That being said, another option that would be pretty neat and certainly get you where you want to be velocity wise, and also have oodles of brass, would be a necked down 300 win mag. This has already been done for a 7mm in a couple of ways, the 7 practical and the 7 BC warrior are two that I know of. Again, just a bushing and you would have a .270 practical or .270 bc warrior. Just some ideas to think on, again I'm not saying to drop your project at all, I think it's doable, and I thought about a 6.5 LRM as well for a laser beam pronghorn rifle. I'm just throwing out some ideas.

P7M13 said:

Nothing wrong with the 7LRM. But, neck down a 7LRM to a 277 and you have a barrel roaster. Not nearly as bad as a 7 RUM or 28 Nosler. Necks don't mean squat as to barrel life. It's the flame behind the bullet that determines that.
If there's a 270 WSM, compare those ballistics.
There's an optimal powder charge weight for every caliber, and I think @elkaholic attempts to do that with his Sherman chamberings.
Blowing out the shoulder to 40° should increase capacity and minimize trimmings needed.
You could also take a 6.5 PRC, neck up, Ackley-ize it.
Any way you do it, you'll have fun. Don't mind the drain hole you punched into your bank account in the process - it's a buzzkill.
If you can help it, don't use Hornady brass either.

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You make a good point with the .270 WSM, that is a factory cartridge with dies easily available. I have loaded for one, 145 ELD-X's just over 3200 fps from a 24", and that is with the stubby SAAMI throat. You throat that WSM how it should be for the 170's, and it will break 3000 with them. It will have to run in a medium/long action for a repeater as OAL will probably be 3.2" or so, but nothing wrong with that.

I don't think a 6.5 prc would do it, as far as performance it is nearly identical to a 6.5x284. However, a 300 PRC necked down would be another option. I know Rich has a 30 and 28 Sherman Magnum, they are insane. The 300 is sending 245's at 3000 fps out of a 28", the 28 is getting 195's over 3200, it is insane. A 170 would be flat out moving! That is a 300 prc with the taper blown out and a 40° shoulder though, simply necked down would still be good, not sure about a .270 bushing is a 300 prc die, you would need to make sure there was plenty of taper in the bushing. All good options, but I think his original idea would be fine too.

Have the rifle made. Get a hornady bushing die for 7 LRM, and get a bushing for .270. Get some ADG brass. That is all you have to do!!

I realize that there is a certain fascination to creating your own cartridge. There are some interesting challenges in creating a 277 cal wildcat.

I have to ask: Why go to all that trouble when the 27 Nosler is available? Additionally the 270 Weatherby is also close to the performance you are interested in creating. You could save money and time going this route. The only expense I would go for is a custom reamer made to your specs. Dies and brass are available.

I know I am a killjoy.....but starting out with a 375 Ruger brass made by Hornady will be an expensive journey and you won't accomplish any performance difference compared to what is already out there. FYI you will have to anneal the brass after such aggressive sizing from 375 to 277

If I were to take on this project, I would start with 300 PRC Brass from ADG. Lapua is supposedly introducing some shortly as well. That gives you 2 excellent sources and you will almost certainly be able to burn out a barrel with 100 pieces with proper care. Straight neck down to 277 could easily be accomplished with a 300 PRC bushing die with 3-4 step downs in bushing size and leave you with a .280ish neck. A Hornady seater die for 270 Weatherby should work as they are based on caliber and length, not individual cartridges. Make 3 dummy cases this way and seat your Preferred bullet with the boat tail junction about .03 above the neck-shoulder junction. Call Manson Reamers and send them the dummy rounds to make a custom reamer for about $200, heck of a deal in my opinion. Then start gathering components. 8 twist barrel finished at at least 26". Action/magazine combo that will accommodate 3.7"+ Coal, and a nice high end stock. When going to the trouble of creating your own wildcat, it's worth it to go all out on your components to have a gun you'll be proud of. Get it all together then the fun part begins with load development and seeing what you can get out of your new cartridge.

Opinions are like @$#holes. Everyone has one but if it were me. I would just get a 27 nosler. Everything standard. Brass and dies available and the same or close to the same performance.

Magnus777 said:

Thanks for adding to the discussion! Some very good points. I looked for such a die, but it seemed the only folks that had a die for the 7LRM was Gunwerks...figured because it was a proprietary cartridge. The die is Hornady, and I keep reading how it's crap. Was looking at having a custom die made, but then I'd need a reamer print, and or three fired cases. Finally decided to stop chasing my tail and just ask for some help.

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The die will be step three, second step is the chamber reamer, first step you can use a 270 WSM sizing die to just get a few cases necked down enough to get an accurate neck diameter for your new reamer, once that is set order the dies from the reamer print and your well on your way to a low frustration high performance wildcat. I've been in on a LOT of wildcats, the KISS principle needs to be in the front of your mind cause it really pays of in the end when you have exactly what you want AND you enjoyed the ENTIRE process!!!
If you desire to make it more interesting, get a sizing reamer also and make your own dies or something other than making the brass the hard way cause that very quickly become not fun!!

Magnus777 said:

Hello all! Long time member, lurker...posted a few comments and questions over the years. But this will be my first shot at initiating a real technical discussion. I'm a dry sponge, and intend to soak up every particle of knowledge offered by willing experts. Hopefully build something together that will contribute to the overall knowledge base for the group.
OK, so I finally dove in to reloading early last year, after gathering equipment for some time. Pleased overall with the results for the handful of cartridges I load for. But for a long time now I've had a burning desire to start a special (to me) project, and build a rifle. My full intention is actually to create a cartridge, and then build the rifle for it. But first things first...
The 7LRM intrigued me as a concept since it's introduction. I understand and appreciate what those guys did. But never had any affinity for a 7mm, myself. So the plan is to carry forward with the work they put in, and utilize the nifty, high-speed/low drag projectiles finally coming available in .277.
When asked, there was no plan from Gunwerks to enter such a project. A missed opportunity, I says! And apparently still no interest, even after Nosler fired first with their 27! And although there is occasional mutterings from the shooting community about the subject, it never goes anywhere! There is no follow through, or at least no published accounts that I have been able to dig up.
Apologies for the long winded introduction. Just trying to lay out the tape for the starting line. Now to get right to it, I'm open to any any all technical input carrying forward, starting with forming brass. And it's my understanding the first step is going to be trimming a 375 Ruger die to relocate the shoulder? If so, it can be chucked in the lathe most ricky-tick. But what brand of die to buy?

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I've never adventured to where you are going with this project, however............I would suspect that the first thing you have to do if come up with a design, on paper, then have a reamer made. From there you will have to find a gunsmith to have the barrel reamed and fitted to a barrel, ensuring that the cartridge will cycle through the action meaning the magazine box and then feed rails. After that I set of custom dies are going to have to be in the makings, hopefully the dimensions of the parent brass will allow you to fire form your brass so three fire formed cases can be shipped to the company making the custom dies for samples, but I "think" that the die company can make your dies from the reamer?? I'm sure there are others on the forum who can comment on that.

Then.....my original thoughts were, how come he wants to reinvent the wheel????? There's plenty of wildcat cartridges that will meet or surpass just about anything anyone can come up with in the design of a .277 wildcat. There's just so my casing and so much powder that can be burned and pushed down that barrel, and after that the gain is not worth the effort. I'm thinking that Nosler is just about pushing the envelope with their new 27 Nosler. I have a .270 Ackley Improved that is shooting just about the same vicinity as the 27 Nosler, using about 3/4 quarters of the powder. Something that you might want to look into. Also elcoholic on the forum, Sherman Wildcat cartridges might also be able to help you out, I'm not sure if he has a .277. I would also check in with J E Customs (on the forum) he's very knowledgeable and I would certainly check in with him before I started a project such as the one you've described here. One last thing is that presently there is not a real great selection of bullets out there to select from. But......that's in today's market, who knows tomorrow the shooting industry and the gun magazines may start to tout the .277 caliber/cartridge to be the greatest and latest, 1000 yard, T Rex, anti-tank, Zombie killer and that's all you will read about for a year, then you might find a better selection of bullets out there.

One more last thing......I didn't read anywhere about what you intend to do with this wildcat, what are you intending to hunt with or distances to shoot?? Also.......might want to reconsider the .284 caliber, there's a whole lot more versatility with this caliber then the .270. I like the .270 Ackley Improved because I built the rifle specifically for whitetail deer hunting, and perhaps a coyote hunt if I can find a place to hunt that doesn't break the bank. The 130gr and the 150gr bullets, and there's a good selection of this weight bullets, are what these rifles were built for; 1-10 twist. Hope my two-cents has given you some insight, and good luck with your new project.

Just a quick plug for the 7LRM...
I had Dallas Lane build a 7LRM for me and it shoots 180 grain Berger's lights out. I'm not running it too hot, only 3000 FPS with H1000 to conserve some barrel life but it didn't show pressure up to 3140 FPS so you could run it pretty quick if one wanted.
Interested to know why some folks are down on this cartridge, is it accuracy issues, brass life?.... I anneal each reload and have 7 rounds on my current brass with no issues, primer pockets are fine, brass looks good. What are the issues?

Mine is the same, shoots little tiny holes with 180's going 2950-3000. I think the bad press came from people not being able to get 180's to 3100, which was the original claim from Gunwerks. The crappy Hornady brass was probably the culprit. It will be interesting now that ADG is making Gunwerks brass, should give the round new life.

P7M13 said:

...Don't mind the drain hole you punched into your bank account in the process...

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My bank account has more than one hole. What, between fishing, hunting, and things with wheels...now this...kind of looks like one of those garden sprinkler buckets! Lol! But it is some small comfort to know I'm not alone in my troubles.

Thanks once again to everyone for adding to the discussion! Lots of excellent info and varied opinions! It kept me up late last night running down leads, and didn't mind it a bit.
Now I'll take the opportunity to address some concerns, and add some clarity if possible. Firstly, as Aaron Davis said in his excellent write-ups of the 7LRM; "The first question you have to ask when designing a new cartridge is, 'WHY?'". And; "Why reinvent the wheel?", was asked a couple times. I often ask myself the same thing whenever reading about the latest and greatest whiz-bang in the shooting rags.
Certainly, from a hunting standpoint there is already a plethora of cartridges to choose from with near same or better performance then this project is likely to yield, out to most any sane range. And personally, I'm not of an age, shape, or capability to entertain any contest of skill. Nor am I attempting to bring a new product to market. So, " WHY?!"
Well...to be totally honest, I guess because I'm a fiercely independent, stubborn sumbitch that doesn't care to follow along, or settle for what everyone else has. Likely, if I was born two or three hundred years ago the crowded cities and towns would drive me nuts, just like they do now. I'd be out on the frontier, taking the last trails out as far as they'd go, and then blazing new ones...just to see what was there.
These days there aren't many places left that haven't been seen. Not much room for trail blazing. So I was born too late. Or, being as star ships haven't been invented yet, maybe I was born to early? "To boldly go...", so on, and so forth!
So...I've picked my battle. I'm doing what I want, where I can, while I can. In this instance, I like to shoot...like to build things...am pretty resourceful. So why not take a whack at trying something a little different...creating something unique, and then wringing it out for all it's worth?
Now, why this particular cartridge variation? Well, firstly, .270 doesn't get enough love. It's been neglected. And for that very reason there's still room for "improvement"!
But many will say, and have said; " The distance between .277 and .284 is so close...there's nothing you can do with a 270 that hasn't already been done with 7mm!", or "6.5 and 270 are so close, and there are already so many excellent projectiles for 6.5, yet hardly any for 270!". Admittedly, those viewpoints are true. I'm big enough to admit it. But rather then see it as an obstacle....rather than throw up my hands, and just follow along with what everybody else is doing, I see it as an opportunity! Between .284" and .264" there's exactly .020" of wiggle room! In this arena, that's all the frontier that's left...about 20-thousandths of an inch!
Since 1925 there's only been a handful of attempts at improving the caliber. The original 270 Winchester was, and is very good for it's intended purpose, and few have bothered. With so little interest in tinkering with it, not much energy or resources has been devoted to developing a greater selection of components... until recently.
The same was true for the 6.5 caliber in this country. Nobody took an interest, until somebody else did. But the spark finally caught, and a few brave and inquisitive individuals fanned the flames, new and better components started hitting the market in a flood.
Now the 7mm and 6.5mm trails have been explored extensively. Not a whole lot left to see down those well trampled roads. And in recent years there has been more interest in developing the 270 then in the last century! With only .020" of room left, and Nosler hot on the trail, I figure it's high time I get started!
My vehicle of choice for this journey is a non-belted case with near same OAL as the 7mmRM, which has a standard magnum case head. The body diameter, however, is larger with no belt. The case neck is longer and the shoulder angle is 30 degrees. The case should fit and feed from a standard magazine box. This is all pretty much verbatum from the work Gunwerks did for the 7LRM...work greatly appreciated, which I will build on.
The project is not about ultimate velocity. Kirby Allen has already tested those limits with his 270 AM. And the 27 Nozler is not dragging ***, by any means! But as with the stated development goal of the 7LRM, this is about balance.
I want to take the most advanced, lowest drag, readily available projectile...which I believe is currently the Berger 170gr EOL, and be able to SEND IT between 2950fps-3200fps. It is my belief that the case capacity and design of a cartridge like the 7LRM, necked down for .277, will allow the 170gr. EOL to comfortably reach 3050fps without excessive pressure. I believe it can do this in a rig that is both portable, and comfortable to shoot without a muzzle break, or with a muzzle break for extended sessions.
It is my sincere hope that this project may serve to further fan the flames of enthusiasm for the 270. May others take what I learn, and ad to it for their own use. And maybe, just maybe, manufacturers may eventually take notice of all the fuss, and start to produce more and varied high-speed/low-drag projectiles in this caliber...and bring to market factory rifle barrels with twist rates faster than 1:10!

I think your right on about where it will perform, the 270 WSM runs right at those numbers when built correctly and on a long action with a 170 EOL and it's phenomenal. I've spent many hours petitioning for heavy for cal bullet in 277 and it's paid of slowly but surly, the first 165 Matrix that we brought in opened the door which I have up to 180 gr then we got EOL on board with the 270 WSM and then the 170 EOL got traction, now with some others like the 27 Nosler and their bullet we really have the choices we need without a bunch of redundancy to have some amazing times with the 270 cal.