[seatleroadwr]

About a year and a half ago William Iorg (Slim) (Beartooth Member) began discussing the possibility of a 308w Improved chambering in the Marlin 336. Our thought was that we would try to reduce bolt thrust in the 336 while approaching 307W velocities. Slim drew up the cartridge. The design used a 308W case with an Ackley Improved profile and a 40 degree shoulder set back to 1.450". I named the cartridge the "30 Lever Maximum" and I sent the rifle to Regan Nonneman to perform the modifications.

The Rifle
The rifle we used was a 336 SS with a 22 inch Douglas barrel chambered in 307W. Due to the shorter shoulder length Regan set the barrel back about an inch to cut the chamber and reposition the forend cap tenon dovetail. He cut the chamber with a 243 AI reamer held back for the shorter shoulder length. He reamed the throat with a 30 caliber reamer. Regan installed a 35 Remington bolt and cut the face to match the diameter of the 308W rim He also supplied C and H 308W AI sizing and seating dies modified by grinding the bottom of the die down to allow proper head spacing. The work took quite a while to complete. I received the rifle back from Regan in late April, 2010.

Of course I had to start testing the rifle right away. The first reports I posted are on Marlin owners at the following link:

http://www.marlinowners.com/forums/index.php/topic,63928.0.html

One thing that bothered me about the rifle was the long free bore Regan cut (about .20"). I was concerned that I'd never be able to tune the loads. Regan offered to reduce the free bore for free so I sent the rifle back to him. I received the rifle back in the middle of August.

Of course the only way to reduce free bore is to set the barrel back and recut the chamber. The rifle barrel is now 20 inches long. The free bore is about .1 from the case mouth which is close enough for me to adjust the COAL to move the bullet close to the lands. One other thing he did was lengthen the distance from the rim the shoulder 1.540". This appears to have been an improvement on the original design.

Below is a picture of the completed rifle.

The Cartridge

I've been working with this load for about 3 months now. I moved to Texas in August and lost reliable access to a range where I could set up a chronograph which has really slowed down load development. I have tried 6 different brass manufacturer's brass and have settled on Lapua although I continue to experiment with other manufacturers. I turn the necks because the brass thickens due to the lengthened neck and set back shoulder. Below is a photo comparing the cartridge to a 30-30 (left) and a 307W (right.)

The range I shoot at let me set up my chronograph this morning and I recorded the following data:

Brass: Lapua Once Fired
Bullet: Speer 170grain
Powder: RE 15
Powder Weight 40.3
Average Velocity: 2417
Standard Deviation: 6 FPS

Brass: Lapua Once Fired
Bullet: Speer 150grain
Powder: RE 15
Powder Weight 42.8
Average Velocity: 2584
Standard Deviation: 9 FPS

Brass: Lapua (New Brass)
Bullet: Sierra 170grain
Powder: RE 15
Powder Weight 40.3
Average Velocity: 2396
Standard Deviation: 3 FPS

Brass: Federal (Fired twice)
Bullet: Speer 150grain
Powder: RE 15
Powder Weight 42.5
Average Velocity: 2599
Standard Deviation: 7 FPS

Brass: Winchester (Fired twice)
Bullet: Speer 150grain
Powder: RE 15
Powder Weight 43.3
Average Velocity: 2575
Standard Deviation: 3 FPS

I hope Speer releases the Deep Curl in 170 FN and 150 FN soon. I'm almost out of the old Hot Cors. Unfortunately the rifle does not like the Hornady FTX bullet.

None of the above loads exhibited any high pressure signs. The cases do not stick and the levers stays shut. I suspect that I can improve those loads a little more but not much.
Accuracy is generally less than 2 inches at 100 yards and sometimes is amazing (I shot a 5 shot .65" group with it this morning with a 163 grain bullet I call "Bubba's FTX" - a Hornady 165 grain Boat Tail Spire Point with the tip cut off)

I still have some bugs to get out of the rifle and reloading system. The sizing dies I'm using are OK but could be better. I use a combination of the C and H die Regan originally modified and a Redding type S die I modified myself. I sent some fired brass to Redding and they are going to make a custom S type die for me. Brass neck thickness varies so much between the various manufacturers that I have to have the ability to adjust the neck diameter of the die. I'm using a Forster 308W bench rest bullet seating die which I've modified to accommodate the shorter shoulder. This die works great and I would recommend that die to anyone for any round it is made for. I use a Lee 308W factory crimp die with a shell holder that I ground some of the top off of to allow for the slightly shorter trim length.

Summary

This round has some great potential for a Marlin 336 with a 20" barrel. The velocities of the loads listed above are very close to the velocities that listed loads for the 307W yield. I will probably make another rifle in the future however I will have a custom reamer made rather than try to jerry rig a reamer using existing reamers. I'd like to reduce the neck diameter of the chamber to about .39" and I'd like to further reduce the free bore. I'll add to this post as I learn more.

 

[broom_jm]

Seatleroadwr,

That's a cool project and I'm glad it's worked out fairly well for you, but I just have to ask the obvious question: Why did you go this route instead of the 308 Marlin Express?

 

[seatleroadwr]

I started working on high performance 30 caliber leverguns just as the 308 ME was released. At the time of the release I was concerned about longevity of the cartridge as well as the fact that the components and reloading supplies would be limited. I thought staying in the 308 family was the safest route as well as having the most potential. The 30 LM is a bit faster than the 308 ME when one compares barrel length and reload data. It is not faster than a 22 - 24 inch barrel with a factory Hornady LE round. If a person were to compare the economics to the performance, the 308 ME would be the best decision. Still, this has been a great journey and it is not over. With the release of the Hornady's Leverevolution powder, I should be able to equal or exceed the 308 ME's 24 " barrel factory ballistics with a 20" barrel. The difference is not great but still intriguing. Below is a picture of a bullet I've been working on for the rifle, It is a Hornady 165 grain Boat Tail Spire Point. It weighs a little over 160 grains modified. For some reason it is extreamly accurate in my rifle. I call it the Bubba FTX.

 

[Old Shatterhand]

Interesting project!

BTW - How do you cut the spire point into a flat nose to get it that flat and nice as on the picture?

Pete

 

[seatleroadwr]

I chuck the bullet up in my drill press and press the tip onto sandpaper while the bullet is rotating.

 

[William Iorg]

Eric,



The die situation is always difficult with unique wildcats.

It appears it is requiring two loads to fully form your cases? That is to say to sharply define the shoulders.

As we expect to see the new brass gave slightly lower velocities as it assumed the shape of the chamber.



For initial load development you are moving along fine. You are within 100 fps of the factory 308 Marlin Express load fired from a 22” barrel using what amounts to your initial starting loads. Lots of room for development work using Hodgdon Varget, Alliant Reloder 15 and IMR 8208. It will be interesting to see what the performance levels will be with the new Lever-gun powders from Hodgdon.



I believe the improved case shape with a new barrel of high tensile strength steel is the route to take for any cartridge conversion process involving higher pressure loading. The reduced back thrust from the Improved cartridge case shape on the bolt is one factor of consideration for the lever action rifle to safely digest high pressure loads but not the most important factor. P.O. Ackley regularly mentioned the requirement for the use of high tensile strength barrel steel when re-barreling a rifle for one of his wildcat cartridges. Most of us overlook this issue. For many bolt action rifles this is not necessary because the rifle was barreled by the manufacturer using high quality steels intended for high pressure. For lever action rifles which were not originally intended to be fired with high pressure loading this is not the case. This is evidenced by the number of Marlin receivers pictured on the internet which have failed in the barrel thread area. I believe I have pictures of three 45-70’s and one 30-30 which I have gleaned from internet posting over the years.

We do not know the type of barrel steel used in the 308MX rifles but it would be understandable if Marlin chose to upgrade the barrel steel for the higher pressure 308ME cartridge.

Examination of my Marlin 308MX indicates Marlin took some effort in fitting the locking bolt to the sliding bolt. The locking bolt fits the recess in the sliding bolt much more closely than in my Marlin 336 chambered for the 30-30AI cartridge.

The change of the barrel threads is another are where Marlin has taken steps to increase the safety margin in the critical barrel thread area.



By increasing the rim to shoulder length of your cartridge you have equaled the case capacity of the 308 Marlin Express by my estimates. The way I rough figure it the 307 Winchester has a total water capacity of 56.3 grs. The 308 Marlin Express 52.8 grains and the 30 Lever Maximum has 53.2 grains of water.



When a bullet is seated .308” deep the 307 Winchester has a water capacity of 50.5 grains and the 308 Marlin Express has a capacity of 47.2 grains of water. The 30 Lever Maximum has a water capacity of 47.3 grains by my model.

This puts you back even with the 308ME cartridge. By using the Improved cartridge case shape you should be able to increase your loads to at least equal the 24” barrel velocities from your 20” barrel.



Looking at the drawings it is interesting to note the shorter neck of the 308ME cartridge and to see a bullet seated .308” deep protruding slightly below the neck shoulder junction. Your 30 Lever Maximum has a neck length long enough to preclude this.



Future load development with this cartridge should be very interesting.

 

[seatleroadwr]

Dang, I just lost a very long post I wrote about the sizing dies when I tried the spell check function. Anway, I have been struggling with the sizing quite a bit. Bullet runout is about .003. I have a custom Redding S type die on order but I won't see it for a while.

That Bubba FTX I show above shot a remarkable group last Sunday. Cut down as shown in the picture the bullet weighs 160.5 grains. I suspect that the ballistic coeficient is greater than the Speer 170. I'll run some ballistic tests with it if it continues to produce good groups.

Sinclair sent me an email and recommended a Meplet Trimmer from Whiden Guworks for trimming the nose of the Horndady spire points. The link is below:

http://whiddengunworks.net/meplattrimmerbuynow.html

 

[seatleroadwr]

That LVR (Leverevolution) powder is no joke. I chronographed two strings today with 160 grain bullets in the 30 LM. 42.5 grains of LVR powder in a Federal case clocked at an average of 2558 fps with 5 FPS standard deviation (20" barrel.) There were no signs of high pressure. I'll move the load up .3 grains and try again next week. Accuracy was good (Less than 1.25" at 100 yards.) I tried the LVR Powder in my 307W last week. Accuracy was poor. It seems as though the 307W case may be a little to large for the LVR powder to function in efficiently.

 

[cj307]

I would be interested still in hearing about your 307 testing with the LVR powder....I've been waiting for someone with more experience crafting non-book loads to try it with the 307...and 7-30 Waters for that matters. I can't wait to buy some of the powder, but don't currently have any recipes to try.
thanks
cj

 

[broom_jm]

On the Hodgdon website, they have LVR loads for the following cartridges:

25-35
30-30
308ME
338ME
338Fed
35Rem

Not sure why they are only listing those rounds and not others based on the same parent brass, but it is my understanding that this powder is not appropriate for every cartridge. My guess is, data for the 7-30 Waters, 307Win and others will be published, at some point in the future.

 

[Flat Top]

Geeze, I just love this stuff!!!!!

 

[broom_jm]

You like what it's doing for your 35 Remmy, Flat Top?

I think it shows the 200gr FTX at a MV of 2100fps. That should be pretty nice out to around 200 yards; sighting in 3" high at 100, you'll be 3" low at 200, with almost 1600fps and 1200 ft/lbs remaining. An extra 50 yards of smack-down for an old lever classic!

 

[zb338]

Seatleroadwr,

You have done a really fine job on the building and designing of this rifle. You have
done an even better job of reporting the results to us. All I can say, is well done! Nice job!

Zeke

 

[seatleroadwr]

Thanks Zeke. there is still a lot more exploration to do with this cartridge. It may be a year or two before I feel I really understand it.

Regarding the use of the LVR powder in the 307W, my sense is that the case may be two large for the powder to work efficiently. I could be wrong but my accuracy was terrible. Normally my 307W keeps a 160 grain FTX bullet in a 1.25 inch group with a velocity around 2450 FPS. Since I didn't have a chronograph when I shot the LVR loads, I don't know how fast the bullet was traveling but the accuracy was about the worst I've experienced from that rifle. I'll still try some other loads to see if I can figured out what is going on.

 

[sawbuck]

Thanks Zeke. there is still a lot more exploration to do with this cartridge. It may be a year or two before I feel I really understand it.
That's the fun of it , if you could really get it sorted out in six months the fun would then be over .
Really have enjoyed your project over at MO ,
THANK YOU

 

[seatleroadwr]

Thank you Sawbuck. This rifle experiment has been great. I was able to set up the chronograph at the range today. 43 grains of LVR powder behind a 160 grain bullet with a Lapua case averaged 2595 fps with 9 fps standard deviation. The group measured 1.25" Cases and gun are still behaving well. The cases are not sticking to the chamber and are not stretching appreciably. The gun stays locked up and the lever stays in position. I'm not sure if I have the nerve to push this cartridge much more though. Maybe 43.3 grains of LVR powder just to see?

I'll have to think about it.

 

[William Iorg]

I would load for a solid 2,600 fps based n my 22” 308 Marlin Express delivering this performance with the 22” barrel. If you load for 2,610 fps you will have this velocity on cold days and on the hot days you will not have enough increased pressure to give you cause for concern.
Before we had pressure tested load data I was loading the 308ME above 2,580 fps with no indications of distress.
I believe a solid 2,600 fps from your 22” rifle is good performance. Over time, you may look to experiment further but this is good performance.
My top loads from the 20” 307 Winchester are about 2,560 fps and I prefer to keep them in the 2,500 fps range for maximum loads to use in any temperature. You accuracy is better than my rifle will now deliver. I have a new 307 Winchester barrel and need to get it mounted to compare with my old rifle. I now plan to use the Timber carbine as a donor.
We are have a beautiful day and I am working on the water system, getting ready for spring. May get to shoot tomorrow, I hope to look at some 800X loads for the 375 Winchester. I have shot Unique and Little gun but have not thought of 800X until I saw the inquiry.

 

[seatleroadwr]

Keep in mind, Slim, the rifle now has a 20" barrel. I had to shorten it to adjust the free bore.

Still though, I should be able to get 2610.

 

[William Iorg]

I did forget that! You are already exceeding my 20” barrel 307. Goes without saying you have met your goals.

 

[cj307]

Seatleroadwr,
Do you (or anyone else) have any concerns about point to primer issues with your Bubba FTX in a tubular magazine??
I just cut down some 7mm's for my 7-30 Waters similar to your bubba and am just a little nervous. I haven't shot them yet, but am curious as to whether I need to be concerned. After all, the point is flat, but the copper jacket extends all the way to the end.
All thoughts are welcome, thanks
CJ