The Quarter Norton Development

[miningshawn]

I would like to start this thread to give my experiences in wildcatting a new cartridge. It has been a very rewarding process, but I spent more than I needed to, and it has taken much longer than I wanted to get here. What follows isn't the best way - it is the way that I took and I hope that it can help out others.

I wanted a new cartridge. A cartridge that solved all of my problems. I am primarily a PRS style shooter, but I am also interested in long range benchrest and I wish there was F-class available where I live.

I tried a few different cartridges before:
- 6XC. The problems I experienced with 6XC was inconsistent feeding from an AICS magazine. Every now and then when I was in a hurry, I would end up with a jam - usually on the second-to-last or last cartridge. I tried adjusting feed lips and followers but never had much success. The 6mm bullet was just a little too light for me as well. I live Western Montana where the wind is variable depending on temperature and time of day. Our courses of fire tend to be long distance, the average in 2019 (the last good year before the Corona virus and the components drought) was 600+ yards. I often had courses out to 1200 yards or more. The 6mm just had too much drift for me.

- 260 Remington. The 260 Remington was the closest I got to perfect for me. The biggest problem was recoil. When you are trying to spot your own shots, the recoil was too much for the shorter lanes. At 200 to 300 yards it was tough to use anything resembling free recoil and get back in time to spot the splash. It didn't help that every 260 chamber I have found has had a long distance to the lands, I found myself jumping .100 or greater. With 140 grain projectiles a lot of the bullet was often seated deep in the brass, and getting velocity without pressure while trying to maintain long jumps wasn't working well for me.

- 308 Winchester. I love this cartridge, but in today's competition it just has too much recoil and not enough velocity. I still go back to this cartridge whenever I can. Berger 185 Juggernauts and 200.20X bullets over Varget are are most too easy to develop good loads with.

- 223 Ackley Improved. Cheap to shoot, easy to find components, and no recoil. But again with wind drift. I have never had a problem with these cartridges feeding. I did have a tough time getting low ES/SD with such a small cartridge. I didn't want to spend hours weighing bullets, brass, primers, and beam-scaling every charge.

- 6GT. All the same problems as the 6XTC. Now with fire-forming.

It was time for something new. I also did not like that when I fed through the magazine there was always a jump involved. Often times my best accuracy comes just into the lands, or at a small jump around .020 to .030. Custom chamberings wouldn't solve feeding or recoil issues however. Single feeding on the clock in odd positions wasn't an option either.

About the time I started really getting serious about custom chamberings the 25 Blackjack was introduced, and the "quarter bore" resurgence began. A long, smooth, heavy-for-caliber projectile with a .333 G7 ballistic coefficient? Just what I was looking for! I sat down and made my list:
- Feed from an AICS SA magazine
- Touch the lands at 2.860". The standard AICS magazine is 2.880"
- No bearing surface in the powder chamber
- Low recoil
- Easily available components
- Long brass life
- 2500 round barrel life
- 3000 +/- feet per second

The list was a little daunting. I chewed on it for a while and decided to start with the bullet and work backwards. I wanted to be touching the lands at 2.860", so I ordered 500 bullets from Blackjack. They showed up within a week, and I sat down and started measuring. After I was familiar with the size and shape of the bullet I started working on the brass.

I wanted a long neck, for a couple of reasons. I did not want bullet deflection when feeding from a magazine. I also wanted to preserve the throat of the barrel for as long as I could. Nothing is more annoying than swapping barrels or setting one back mid-to-late season. I settled on a length of 1.33 bullet diameter, 0.310" for this cartridge.

The shoulders were easy - I prefer Ackley style shoulders. I like them because I don't like to trim and they are more consistent for me when sizing. I also tend to get better ES/SD with my Ackley cartridges. In this case they also offered the best powder chamber volume possible. I set the base of the case neck to meet the bullet boattail, leaving all of the bearing surface out of the powder column.

For the body of the brass I chose .308. I left the original taper in place because it is pretty minimal to begin with. I measured out from the case neck at 40 degrees and chose the dimension to intercept the .308 case. I also chose .308 because I have a half barrel of once-fired brass. I also have never had an issue with .308 (or 260 Rem for that matter) feeding from an AICS magazine. I have had problems with 250 Savage parent-cased cartridges, although length may have been the biggest factor.

I also looked at throat life closely. I wanted to shoot as slow of a powder as possible, and keep the toroid zone inside of the case neck if possible. I could have used a longer neck but I wanted to be able to use lighter bullets without seating the ogive in the case. The Ackley body allowed me to cram as much volume as possible into the length of the cartridge, and the steep shoulders keep the toroid zone as far back in the case neck as possible.

With all of these parameters set I got my wallet ready to start making some expensive phone calls. I drafted the case I designed in AutoCAD and put it into Adobe, Excel, and just about every other format I could think of. I just didn't see how much I would end up spending though... The next thread will be about conversations and costs and loooooong delays.

 

[Nick Caprinolo]

following

 

[miningshawn]

I was working in Alaska at a fly-in/fly-out operation on the North Slope when I started this project. Phone calls were a little tough to handle with the audio delay, but I finally got a hold of the person I wanted to talk to. I have put serious thought into whether I should name the reamer designer or the company into this article, and I have chosen not to. 2020 was a bad year for everyone, and things may have changed, but it was a painful experience for me.

I spoke with the chief reamer designer for the company about my ideas. He was on-board from the beginning and agreed that this would be an excellent project. After talking with him for a few minutes I emailed the dimension files. We talked for almost an hour and after going over a few points ended up not changing a thing. I was transferred over to accounts and made my initial order. I felt really good about the whole process and I ordered a rougher, a finish, and a resizer reamer. I felt good enough to get go and no-go gauges as well. That was my second mistake...

I paid $877.70 for those first reamers. The sad part was that it took almost 9 months to get them. The first order was made 10 April and I finally got reamers and gauges in hand on 29 December.

After I ordered the reamers I got busy building the rifle. Every step of the rifle building process was much better. I ordered:
- A custom Ruckus action from Defiance Machine. I called Defiance and was put in touch with Cody Hart. We talked for over an hour about what I was doing and settled on a Ruckus action with integrated 20MOA rail, a subtly fluted bolt, a heavy tang, faceted bolt shroud, and a flat bolt nose. Since I was investing so much into this project I opted for a custom serial number as well. This all set me back $1250.00 - but the shipping was free because it went across town to....

- I chose McGowen for the barrel. I haven't had anything other than top-notch work from them and every barrel has been nothing less than stellar. I wanted a Remage barrel because I saw myself ordering another and they are so easy to set up. I went with a 7 twist, 32" SS threaded barrel with a #7 McGowen contour. I had the reamers drop shipped directly there to meet up with the action. All told I spent $850ish with McGowen and it was worth every last dime.

- I wanted a chassis rifle, and ARCA rails were just starting to get popular. I looked at all of the options and settled on an XLR Element 3.0 with an ARCA rail attachment. The chassis was finished in less than a month, but the anodizing took quite a while. The chassis was the last piece of the rifle received, and it was months ahead of the reamers. After all of the ordering was done it set me back $920.00.

- To finish it up I chose a TriggerTech Diamond trigger. Unbelievably the only ones in stock were at MidwayUSA at $252.00. I waited for my birthday and took that down 15%.

- I had some Burris Extreme Tactical 34mm rings on the shelf, and a Burris XTRii 8x40-50 in MOA. I picked them up for a previous rifle at $1240 for the scope and $135.00 for the rings. They worked just fine for this project.

- The last piece of the rifle is an EC Tuner Brake. I have yet to "use" it but that day should be coming soon.

By the end of July I had close to $4500.00 worth of rifle parts ready to go. Due to the delays I ended up getting this as a late Christmas present. I finally got it all twisted together and moved on to making brass, which will be explained in the next post.

 

[farmerjohn]

Tag

 

[miningshawn]

I am no gunsmith. I am a machinist, 7/8 of an engineer, and a surveyor - so numbers don't scare me. I thought "How hard can it be? It's just brass, and I can afford a ton of mistakes.". Yeah, right.

I thought about this for a while. I ended up buying an RCBS standard .308 die and working with my excellent (and patient) local machinist Damon from Nemesis Machine. He removed material the bottom of the die quite a few times until we had the outer shoulder pushed down to the correct length ( You'll see a reamer print in this thread eventually, I promise). Then, just to try it out, we did the same thing with a .257 Roberts AI die and pretty much "Sherman" sized the entire shoulder. Note - dies are extremely hard.

This was just to get a case that we could begin to work with. I should mention that the majority of the brass I have is once-fired Federal GMM. It is definitely easier to work with than most others, but doesn't seem to last as long. After a few hours of in/out and up/down we managed to get a case that fit in the chamber. The neck was paper thin because I had underestimated the neck diameter; but, credit where it's due that was my mistake. To get a fire-form we loaded one pretty much full of H1000 and seated a bullet on top. When we tried to chamber it that was when I found that the first set of reamers had absolutely no free bore. As in none. zero. zilch.

We pulled the bullet and lowered the charge, then walked out back and touched it off at a random sagebrush. Finally I had a case to work with. I summed up all of my shortfalls:

- The neck needed to be thicker. Add 0.006 to the diameter
- I was leaving powder column on the table. After seating the actual bullet and not a drawing I realized that I could extend the powder column (length to the outside shoulder) by a full 0.100"
- Add freebore. A lot of freebore. Hindsight being 20/20 I could have uni-throated, but we weren't there yet and we had to cut a new reamer anyway. Might as well fix that on the next pass.
- I needed a sizer die that worked.

So, I called back to the reamer designer and we talked again for another 1/2 hour. We changed the dimensions and I ended up ordering only a finisher this time. It only took four months for the second order to make it...

A year into this project and it had been fired once. I was really looking forward to what I thought was the final steps. During the wait I found out about Newlon Precision. I have nothing but heaps of praise for his product and expertise. The only thing I have against him is his address. He talked with me and my smith Damon and walked us down the garden path to making what I consider to be the best dies I now own. I ordered a bunch of die bodies from him. (Note - the dies are body dies with a pilot. You drill the dies using the same reamer as the chamber, on the same machine, with the same dimensions. Talk about fit like a glove...)

I get the second set of reamers back and find that they have some freebore but not nearly enough. I was still seating about half of the bearing surface into the case. There was 0.100" added to the shoulder, but they took 0.100" out of the neck. I don't know where the loss in communication happened, but I was not a happy person. I didn't even bother shooting one this time. I just found a new reamer manufacturer.

I called Manson Reamers and was put in touch with Ray, I poured out this entire saga and he listened patiently and completely understood my issues. He asked me to put together a dummy round at the correct OAL in the case that I had and send it. I also had to add another 0.002" to the neck diameter and wanted to reduce the taper of the body ever so slightly. I pulled everything together and based on the conversation ordered another grand's worth of reamers - rougher, finisher, sizer, and this time just a go gauge. I would use scotch tape for the no-go while casting dirty looks at my now useless box of previous purchases. The touch point is exactly 2.860".

I got the reamers within 2 weeks. I gathered everything together and brought it all back to Damon at Nemesis. We rechambered the original McGowen barrel (which sadly put the custom engraving on the barrel under the scope) and chambered up my other project as well - A Falkor 7 action with a Proof no-taper SS 26" 7 twist threaded barrel and a Hart brake, This time on an XLR Envy Pro with a TT Diamond and a Burris XTRiii 5.5-30x56 in SCR MOA. This is the rifle I want to compete with this season.

We cut the dies on the same day with the same reamers. They work perfectly. Now brass is a much easier process:

- Trim the OAL of the parent .308 down to the correct OAL of the 25 Norton
- Push the shoulder back to the correct outer length
- Lube them a lot
- Straight into the Newlon custom die with no internal sizing
- Inner neck sizing with a Wilson mandrel
- Final trim for OAL

I made 100 cases and took them to the range. In the next post I will go over how I selected powder and charge, show you some charts, and maybe get into some results. BTW - I attached the final reamer print.

 

[17VLD]

Looking forward to seeing how it shoots. I’ve always liked 25s and really would like them to start stealing some of the 6.5s thunder.Bring on the 134 ELD-M

Matt

 

[Fuj]

Kind of real close to the 25 Creedmoor, and would have been
easier and cheaper..... With the 131 BJ's, Black Jack's load data
will be handy with your case.

 

[miningshawn]

Kind of real close to the 25 Creedmoor, and would have been
easier and cheaper..... With the 131 BJ's, Black Jack's load data
will be handy with your case.

I thought about the 25 Creedmoor but it didn't have everything I was after:
- Short neck of 0.163
- Bullet seated in the powder column (standard of 0.115 freebore)
- OAL of 2.295, longer than an AISC magazine
- More body taper than I would have liked
- Creedmoor............
It just didn't meet all of the parameters I had set for myself.

 

[Evan]

I thought about the 25 Creedmoor but it didn't have everything I was after:
- Short neck of 0.163
- Bullet seated in the powder column (standard of 0.115 freebore)
- OAL of 2.295, longer than an AISC magazine
- More body taper than I would have liked
- Creedmoor............
It just didn't meet all of the parameters I had set for myself.

You landed almost perfectly on a 25x47 ackley improved. Once you burn through your 308 brass, 6.5x47 will be easy to fireform and provide an exceptionally durable case to work with.

 

[miningshawn]

You landed almost perfectly on a 25x47 ackley improved. Once you burn through your 308 brass, 6.5x47 will be easy to fireform and provide an exceptionally durable case to work with.

I agree. I am just a hair shorter than a 25x47 to the shoulder, with a little less body taper. The chance of me using all of my .308 brass in my lifetime is practically zero.
Again with a longer neck. This is the cartridge I almost settled on, but I really wanted all of the boxes checked.

Good catch!

 

[17VLD]

Really looking forward to seeing what velocity this rifle settles into after you fire around 200 rounds through the new barrel.The wheels are spinning in my head and they have told me that my light gun needs a new barrel

Matt

 

[miningshawn]

 

[No manches"]

Isn't this practically a 250 AI?..

 

[NZ_Fclass]

Thanks for an interesting story. I will follow to hear the results of your labour.

 

[miningshawn]

Since this is an all-new caliber there is no load data. I had to do some extrapolation from existing cartridges and run the cartridge through some programs. To start I performed a volumetric sample of the fired case, and again on cases that were formed but not yet fired. The case volume filled to the top of the neck is 49.75 grains of water. Starting there I began looking into similar cartridges.

- 250 Savage Ackley Improved. Load data for this cartridge is pretty variable. I found cartridge capacities from 47.5gr to 51gr (water). I did not have a lot of faith in load data for this one. After scouring the internet, I returned to Sierra Reloading data V6. The biggest problem was the lack of loads for any projectiles above 117gr. Most of the load data centered around Varget-4350, which seemed a little to fast burning for my case.

- 25 Creedmoor. There is a lot of unpublished data for this cartridge. Most of the volumes that I found centered around 52gr (water). Commonly used powders were in the 4350 range. RL16 was also a common mention.

- 25 WSSM. There is much published data for the WSSM. The commonly agreed case capacity is 49.2 grains (water). I took most of my extrapolation from this cartridge, It has a very large range of powders to choose from.

I should mention that during this process Berger introduced the 135 grain Hybrid and the 133 grain Elite Hunter. Too say that I was thrilled would be an understatement! I bought 500 as soon as I could find them and broke out the calipers. The "touch" point was within 0.005" compared to the Blackjack. I have always used Berger where I can and I quickly changed my preferred bullet to the Hybrid. I picked up the phone and had a very long conversation with Phil at the Berger Tech line. He agreed that I was on the right path for this cartridge, which gave me a huge sense of relief.

I designed the case into Gordon's Reloading Tool and started running scenarios. This was a little daunting at first, but I soon picked up the parameters and worked up some initial loadings. I turned to the forum here for help and Zero333 (thanks! you really clutched up on this one) stepped in with QL numbers that very closely matched what I was doing in GRT. QL was a little bit more aggressive compared to GRT, so I defaulted to GRT.

I did take pressure into consideration. The closest fit of published data (AT THAT TIME) that I could find was 6.5 Creedmoor and of course .308 Winchester. I set my upper pressure limit to 58,500psi to be safe and leave a margin for error.

The powders I have on hand that should be suitable for this cartridge include (from fastest to slowest):
VV N550, RL16, H4350, RL 17, H100V, StaBall 6.5, VV N160, IMR 4831, and H4831. I decided to start with the faster powders - H4350, RL16, and VV N550. In the course of 1 day I formed 75 pieces of Federal GMM once-fired brass and sat down at the press. The initial loads were:

- Federal .308 trimmed to 1.900", necks turned for uniformity to 0.288", L.E. Wilson 0.250" mandrel used, final neck tension of 0.004".
- CCI BR2 primers
- Berger 135gr Long Range Hybrids
- Hodgdon H4350: 38.1 38.3 38.5 38.7 38.9 39.1 39.3 39.5
- Alliant Reloder 16: 38.6 38.8 39 39.2 39.4 39.6 39.8 40
- VihtaVuori N550: 38.1 38.3 38.5 38.7 38.9 39.1 39.3 39.5
- COAL of 2.860" for a "zero" jump

I chose 0.2gr increments to keep an eye on pressure and reduce variability. The next post will cover velocity results.

 

[miningshawn]

Results for the first round of tests.

VV N550
38.1 - 2844 2836 2838 ES-8 SD-4
38.3 - 2840 2863 2871 ES-31 SD-16
38.5 - 2883 2871 2864 ES-19 SD-9
38.7 - 2875 2892 2909 ES-34 SD-17
38.9 - 2906 2893 2898 ES-13 SD-6
39.1 - 2925 2915 2909 ES-16 SD-8
39.3 - 2932 2926 2912 ES-20 SD-10
39.5 - 2984 2953 2947 ES-19 SD-9

RL16
38.6 - 2818 2829 2823 ES-11 SD-5
38.8 - 2832 2832 2837 ES-5 SD-2
39.0 - 2844 2839 2848 ES-9 SD-4
39.2 - 2827 2864 2863 ES-37 SD-21
39.4 - 2881 2874 2884 ES-10 SD-5
39.6 - 2908 2891 2897 ES-17 SD-8
39.8 - 2935 2896 2894 ES-41 SD-23
40.0 - 2942 2906 2934 ES-36 SD-18

H4350
38.1 - 2762 2758 2775 ES-17 SD-6
38.3 - 2778 2774 2776 ES-4 SD-2
38.5 - 2801 2804 2800 ES-4 SD-2
38.7 - 2794 2806 2820 ES-26 SD-13
38.9 - 2809 2824 2810 ES-15 SD-8
39.1 - 2827 2831 2823 ES-8 SD-4
39.3 - 2855 2838 2847 ES-8 SD-17
39.5 - 2868 2863 2888 ES-25 SD-13

All powder measuring was done using an RCBS ChargeMaster 1500. All shots from a 32" 1:7 barrel, shot 1 minute apart. I use a Magnetospeed, so I didn't really shoot for groups but they all came in under 1 inch at 100 yards. testing temperature was 66 degrees. AD was 6220'.

There were no pressure signs at all, at any charge weight. All of the primers look the same, all of the cartridge bases show no signs of wipe or ejector, every bolt lift was 1 finger easy.

At first blush it almost appears that I could use a faster powder... I have Varget, CFE223, and H4895 on hand. However, these were all fire-forming rounds and I should shoot this series again for results.

I would like to hear your thoughts on the next steps. As of now I am loading this series again and adding three more powder steps to the upper charge for a total of 33 rounds per test instead of 24 (i.e. H4350 will be 38.1 to 40.1). I will again be shooting for pressure and velocity - so no groups yet. After the next series I am planning to perform a 600 yard ladder, a seating test, and finishing with a 3 round OCW. Then I will move on to different powders.

 

[357Mag]

Miningshawn -

Howdy !

Great wildcatting post !

IHMO - I think 6.5 Stabal will give you more vel than H100V, should you get chance to do a run-off. Would be interesting to see.

FWIW -
I DK whose burn rate chart you believe, but will say that VV160 has often been placed at varying positions on individual " burn rate " charts.....IMHO more often than some other powders in the immediate burn rate span have been. I had top-end charges of VV160 gave me more vel than max charges of WW760 in a 24" 1-14 " .22-35 Remington " wildcat; with both loads still giving safe pressure. I was a bit surprised by that result.
But yeh....that was a .224" cal and you are talking a .250" cal.

I'm not sure H4831 or I4831 will " get you there ", even having 27" to work with ?
Hmm....

Please keep us updated on your progress.


With regards,
357Mag

 

[357Mag]

I agree. I am just a hair shorter than a 25x47 to the shoulder, with a little less body taper. The chance of me using all of my .308 brass in my lifetime is practically zero.
Again with a longer neck. This is the cartridge I almost settled on, but I really wanted all of the boxes checked.

Good catch!

Miningshawn -

Howdy, again.

I've sent along a pic of my " DEEP 6 wildcat. Please see below.

*Case capacities arrived @ by using H2O filled to the case mouth can be a bit deceiving.

When you end-up operating w/ the case' neck completely occupied w/ the bullet body;
" practical " case capacity could be determined by taking an inert case w/ the bullet seated to the desired depth.... and filling w/ H2O through the primer pocket flash hole. Case wt would be measured both before and after H2O fill. Subtracting the smaller number from the larger number would tell you the " practical " case capacity. This would give a more realistic idea of the powder space truly available.

L-o-n-g case necks can give one a somewhat bogus capacity figure, when the
" fill to case mouth " method is utilized.


With regards,
357Mag

 

[miningshawn]

I am sitting on top of Homestake Pass waiting on the sand trucks, so I have a few minutes. Attached to this post is a graph of the results of the first velocity test. Check the graph out and I will attempt to explain what I am thinking in what follows. EDIT - VV N550, RL16, H4350 top-to-bottom.

I like to produce these to give a visual perspective of trends. My initial thoughts after making the graph is that the best stability for VVN550 is near the maximum loaf. The pressure is probably picking up, I don't think more N550 is going to be possible.

RL16 is a little wild, but there is a workable window in there. I haven't tried seating depths yet so there is at least one opportunity to reduce ES/SD for this powder.

H4350 for the win. I am definitely going to run this powder out a little farther. It appears that there is another smooth curve coming. Pressure appears to be very linear and there should be room for a little more velocity.

There is still a lot of volume left in the case for these first few powders, there haven't been any compressed loads yet. I will shoot this series again using the fully fire-formed cases and compare results, and bump up the H4350 three more 0.2gr steps. Then it is on to new powders. I am working loads for StaBall 6.5, VV N160, and IMR 4831 for the series following the re-test.

 

[SweaterDood]

Your cat is essentially splitting hairs with the 25x47L. Nothing wrong with that, as I did a very similar project and ended up within 0.004” in all dimensions to a .257 Rob AI, except for freebore and neck length. Those 2 areas making a drastic difference in performance (3100+ fps w/ Berger 135 LRHT).

I mainly shoot the 25x47L now. H4350 or 6.5 Staball will likely be the sweet spot for powder. You will probably start to crunch kernels with H4350 before 41gr. I was using IMR 4451 which is a little bulkier, and had less energy density but was very happy with ~2840fps from my 1-7.5t 27” barrel. 32” should be roughly 75-100fps higher, all else equal.