I am looking at developing a simple wild-cat based on the 7mmsaum. Remington chambered the model 7 in 7mm saum. However if you want to seat bullets to be close to the lands and feed out of the magazine it is difficult (more or less impossible). You would have to have a chamber reamer with no freebore even then it would be tight -not a good idea apparently.

Unlike the rem 700 short action extended magazine boxes can't be fitted to the model 7 as there is no room to machine material out of the magazine slot at the rear of the action .

I am thinking of building a simple wildcat based on the 7mm saum. The idea is to simply push the 30 degree shoulder back to produce a case that is 0.2 inches shorter. This would reduce the capacity of the case from 73.6 grains to hopefully somewhere around 66 grains (similar to .280 remington and .284 win) according to my very rough calculations/guestimate. I would get a gunsmith to ream a chamber and run the reamer in 0.2 short. I have access to two match reamers which are identical except one has 120thou freebore and the other 160thou freebore.


I would get a form die to work the brass. Hopefully all I would have to do then is trim 0.2 off my sizing die and seater die and I should be good to go. I understand I will have to anneal my cases (I am already annealing every third firing) and also trim and neck turn the cases and possibly inside neck ream them if there are donuts. Obviously loads would have to be worked up carefully..


I have some questions...
Do you think this is a reasonable concept for a wildcat. Would you expect that I would achieve performance approaching that seen in a .280/.284 with 160 grain bullets?


I wonder if you could share any tips or recount any problems you struck through the process? It would be much appreciated. I know that there are some good books on wild catting but if I could find copies I would have to import them as I live In New Zealand. Are there some good online resources?

Lurch, welcome to Shooters Forum! The rules are to play nice with everybody and join in.

I ran some numbers through the QuickLoad software and it looks like the idea of a 7mm RSAUM, trimmed another .200", would put it right into the same groove with the 280 Remington and 284 Winchester. Using ~160gr bullets you should be able to obtain ~2,900fps, with any of the three.

If it was my dime, I would go with the 7WSM, as the parent brass. The entire SAUM line seems headed for complete failure, which will make brass tough to find. With the WSM line, there are enough successful variants that I think you will be able to get "WSM BASIC" brass for a long, long time. Perhaps the SAUM lineup is doing better in Australia and NZ?

In a short-fat design, I like the approach you are taking. I'm not sure that it will be superior to the existing 7 SAUM or WSM, but the beauty of a wildcat cartridge is you get to do it YOUR WAY! As long as you've got the deep pockets it takes to have the work done by a very good gunsmith, I imagine you'll be very happy with the results!

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Ask me about QDMA.

Thanks for that yes 7mm saum is about as popular out here as the WSM. Some people prefer the saum as you can neck down Norma 300 saum brass. Nosler is supposedly bringing out 7mm saum brass later this year.

Good morning.
I got you PM. I am a bit distracted now, sending some things to the Hurricane relief - “In confusion there is profit…”

I believe you will get some good case forming details from Donnelly’s book. Only the cartridge drawings detract from the book.

I do not believe you need any other software than Quick Load. Quick load should handle all of your early predictions. Personally I use single base powders for me initial load work as single base powders deliver a more predictable performance. After I have established what the single base powders will deliver, I move to the ball powders of similar burn rate.
Either way Quick Load will get you close quickly.

The criticism of RCBS Load is based - I believe on the early version. We started with RCBS Load when it was on the large floppy disc - version 2 - and our computer was a 286 Dell. RCBS Load ran slow and many features were spotty. Greg Mushial from GMDR never failed to respond to our questions and his advice was helpful. Greg has modified many of the features and today’s faster computers make a big difference in how RCBS Load functions.
The Cartridge Designer function is now quite easy to use and has many additional features which are “useful” - at least they help pass a the winter evenings…
Designing a new cartridge is easy and modifying your drawings is not difficult. Greg has added color printing and multiple bullet shapes which is a nice feature.
I just put up a cartridge - .25 Souper in this case. When you have the cartridge up on the screen and select “other” at the bottom of the tool list you can bring up cartridge characteristics. This chart will give you a great deal of detail on your cartridge case which helps with reamer and custom die thoughts.
Of interest to the wildcatter is the bolt thrust and pressure max at specific points in the barrel. Radial thrust on the barrel etc. This information is not as detailed as Quick Load but RCBS Load is not intended to provide specific load development information.
As you edit your cartridge estimated pressure you change the characteristics of the case. I assume Quick Load does this but I have very limited experience with Quick Load.

Nick and others on the board have experience and can provide a more in-depth comparison of the programs.

A feature of RCBS Load which I believe Quick Load shares is the estimate of uncompressed cartridge case capacity for various powders. As you vary your case design - body taper, shoulder angle, bullet seating depth etc. RCBS Load will adjust the case capacity measurements in grains of water and by specific powders by full case, capacity without the neck and capacity with the bullet seated to whatever depth you desire. RCBS Load has a database of at least 105 different powders.
Greg and I have discussed his method for determining and confirming powder density and he spends quite a bit of time ensuring his powder density figures are correct.
This information is not load data but is intended to assist the wildcatter in establishing his case capacity. The wildcatter often designs his cartridge for a specific performance goal - often with the use of one specific bullet in mind. The ability of these programs to estimate cartridge capacity for several different powders - instantly - as you vary case shape/volume is very useful.

This brings up the advantage of Quick Load as you are able to quickly estimate optimum powder charges and estimated pressure. I still use the Powley Computer for Handloaders as I primarily use single base powder for initial load development. I am an older guy and I think better in CUP than I do PSI. I have a spread sheet which works a lot of the Powley math quickly and I can estimate chamber pressure, muzzle pressure, velocity etc quickly and while I would enjoy Quick Load it is not a pressing priority for me.
As you can imagine, I am in the stone-age compared to most of the wildcatters on the board. Marrontoad (Snow) and I have compared some Load From A Disc information and I find the information very useful - for use with my preferred single base powders.

I’ll draw a few pictures for you. I am attaching the picture of your cartridge with the shoulder, the bottom of the neck and the case length cut by .2". Leaving the neck long looksodd. I'll draw that one later. I am not a 7mm guy so I don’t have many 7mm component bullets in my collection so if you are to post the overall bullet length it will help to estimate seating depth.
In general terms it is hard to predict the effect of different throat angles on internal pressure. For the best thoughts on internal ballistics which are understandable to a “simple” mind such as mine I recommend Lloyd Brownells Firearms Pressure Factors which is available on CD from Wolfe Publishing. I have the book and the CD and I believe the CD is more useful to those who will actually use the math. Even if you don’t intend to spend your evenings working your calculator overtime the book answers many questions about internal ballistics and will give you a better idea of what you are able to predict.
I believe Denton is posting on the Beartooth Forum and he could probably add some thoughts as to how throat angle and free bore affect pressure.

I drew your cartridge with the point of the shoulder pushed back .2”.
This puts the shoulder at 1.3383” and I shortened the overall case length to 1.835”. The bottom of the neck is at 1.5242”.” deep, to the bottom of the neck, I estimate the water capacity at 56.6 grains of water.
With the bullet seated to the bottom of the neck your estimated case capacity for IMR 7828 would be 49.94 grains of powder.
You have enough room for 51.0 grains of Alliant Reloder 19. Gain this is not load data simply capacity.

The maximum loads listed for the 7mm Remington Saum with 160-grain bullets and these powders is 63.0 grains of IMR 7828 and 60.0 grains of Reloder 19. These are shown as uncompressed loads.

I would run some side by side models of the 7mm-08 to look for optimum powders and to compare muzzle pressure with your intended barrel length.


I had a reason for drawing the case with the neck shortened first and I'll get up the drawing of the case you ension as quick as I am able.

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slim

Well, I posted the picture of your cartridge first! I'll eedit the body of the post.
I believe your idea of running the reamer in short will work fine - has for many years.
Your idea for dies works well. My Dad has modified dies for many years. Dad made his own 300 Whisper dies many years ago and they work fine.

I just saw the picture posting thread and will change the picture later today.

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slim

Thanks so much for your help. The volumes you give with the powder are helpful, I would guess that this case has slightly less capacity than the .280/.284?

Here is a modified reamer print that shows the actual dimensions if the reamer is run in 200 thou short. This is the actual reamer I will go with. The 1 degree 30 throat apparently suits the higher BC bullets I will use such as the 162 amax, the 160 accubond and the 154 sst.

I corresponded with a shooter who had developed several wildcats by running the reamer in short. He cautioned that when ever he reduced the cartridge base diameter he ended up with a click at the top of the bolt lift.

In my situation it would be 2 thou according to the reamer print (shortening the case by 200 thou) base dimension changes from .551 to 0.549. I have a couple of bags of new remington 7mm saum brass on hand and when I measure a few of them them 200 thou up from the base they are 0.541-0.544. Brass fired in my factory chamber is about 0.546. The measurements are not flash they are taken with set of digital calipers it should really be done with a blade mic and some kind of jig to hold the case and ensure measurement at the same point for consistency.

My thoughts were if I these measurements provide enough clearance and I got my shortened redding body die honed by someone like JLC precision with some fired brass then I might get away with it. What do you think? Will this be a problem? I really want to avoid the bolt click issue if possible. Would I be best to design a new reamer with a .551 base dimension?

The AOL tip to toe with a 160 accubond measured in a chamber reamed with the full length version of the shortened 7mm saum reamer print shown below is 2.995 touching the lands. So I estimate the OAL of the wildcat version would be 2.795.

My model says the 284 Winchester with a bullet seated to the bottom of the neck - .294” - has a water capacity of 61.9 grains of water.
The 280 Remington with a bullet seated to the bottom of the neck - .344” - has a water capacity of 64.4 grains.

The problem with the 284 Winchester for the Model 7 is the short COAL of 2.800”. I estimate your bullet is 1.160” and it will require deep seating for the 284 to fit the short magazine. I estimate your bullet would have to be seated .530” deep leaving you with a water capacity of 58.1 grains.
I am a bit distracted and don’t know what COAL the estimate of 2,900 fps is based on or how long your barrel will be. With Quick Load I would run a few models using your desired COAL with your barrel length with the bullet deep seated for your short magazine box. You might find a slower powder will give you a moderate velocity with good down range ballistics as some of the older short rifles and cartridges did.

I thought a bit on your two reamers and with the short magazine box you might as well go with the shorter throat.
Case taper does cause problems when running a reamer in short. George Nonte wrote of this and I think Donnaley repeats some of his words.
.002” does not appear to be a significant taper and the new brass being under size at the base - a common situation with new brass, you may get away with this wildcat cartridge without difficulty.
It is a roll of the dice whether to start with a new reamer. I would contact C-H 4D tools, they make custom reamers and dies. C-H has quite a bit of experience in this area and I have run a couple of odd ideas past them. C-H seems receptive to discussing “dumb ideas” with wild-eyed wildcatters! You will find the price on special order dies expensive but still within reason at C-H. If you keep the rifle five to seven years and shoot it 300 rounds per year the cost of custom dies amortizes out reasonably well.
One of the reamer rental places could have a worn 7mm SAUM reamer or with its lack of interest at this point, an extra reamer that could be re-ground to your short case. I would ask 4D if this is an option.

Back to these load models, you have Quick Load and I would run a few comparisons on the 7mm-08 and possibly the 284 Winchester against your wildcat based on your anticipated barrel length. With cost a consideration, you may find performance quite similar.
With a rough 12.0 grains of water difference between the 7mm-08 Remington and the 284 Winchester the difference in performance from a short barrel may not be a great as we envision.
I’m not trying to be negative, I enjoy wildcats. When looking at cartridges I run the numbers with various powders - I am “stuck with single base powders” - and establish my COAL and desired barrel length before running the numbers. I have nothing against single bullet hunting or target cartridges. I like to compare cartridge efficiency - fps per grain of powder and look at the muzzle pressure with various powders. I am not against high intensity cartridges but sometimes we can achieve the same goals with less fuss.
I hope this long thing makes sence!

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slim

Thanks again William. Looking into it further based on your numbers the cartridge with the closes capacity would be the 7x57AI still a useful gain with heavier bullet sin a 24 inch barrel over a 7mm-08 as far as I can tell.

Regarding the cartridge case clearance versus the chamber at the base this is what clymer has to say about it

Any idea what degree of clearance is reasonable?

I began thinking if I did have to design a reamer then I might be better to go with a 35 degree shoulder essentially switching to a short 7mm wsm with the same neck length as a saum this might give me a slight increase in case volume with better neck length (one of the criticisms of the 7mm wsm is short neck length hence the popularity of 7/300 wsm). Is there a program or spreadsheet set up out there that allows you to play with cartridge dimensions in reamer print format?

If it keeps a few idiots from blowing themsleves up, then it was probably worth it, in Winchester's defense.

Well I made some progress on this. I decided to go with a 7mm saum shortened 200 thou.

First I had Mark Spencer of Spencer tool and gauge in Michigan build me a form die and go and no go gauges and send them out to me in New Zealand. Mark was excellent to deal with and I thought his prices were very reasonable. http://spencertoolandgrind.wordpress.com/

The die has a series of 4 inserts to bump the shoulder sequentially they have 15, 20, 25 and 30 degree shoulders. Bumping new remington brass is fairly straight forward. Here are some pics of Marks handiwork and some brass I formed and neck turned (roughly!) versus the parent factory brass



After forming I checked the neck versus body runout on a Wilson concentricity guage and it was around 1 thou TIR, the same as the factory brass, so I was pleased with that

One minor issue I struck was that after forming I had trouble with the expander mandrel when trying to expand the necks prior to neck turning. I annealed the necks and this seemed to solve the issue. I am concerned about the possibility of donuts forming. I deliberately ran the neck turner into the shoulder just slightly in an effort to reduce this problem. I have a mandrel with a donut cutter on it for my K&M neck turner so will keep an eye out for therm after firing. The case capacity measured with water to the brim comes out at 62.5, about the same as a 7x57AI.

Next step will be to get the saum chamber in the barrel cut down 200 thou and the headspace set. The gunsmith will also polish the rear of the chamber to avoid clearance issues and the dreaded click at top of bolt lift. Sizing and seating dies (Redding body die, Wilson seater and Lee collet neck die) will also be adjusted to suit. Still a few challenges yet but so far so good, largely thanks to Mark's excellent form die.....

Hi Lurch, and welcome.
Now that you have the hardware, how well does this shorty cartridge of yours, feed from the magazines of several different rifles? My question is also geared to how it compares to the WSSM's. I'm playing with a .270 caliber, 1.75" long 300 RCM, wildcat. Your wildcat has quite a bit more capacity. My trial cases only have about 48.5 grs. of H2O to their mouths. So, with the longer bullets and quick twist barrels, they are only equal to the old 277 Titus. This was the 300 Sav. necked down to .270 caliber. It looks to me that you have put together a 300 Sav. length case, on Steroids, whereas I have only built a bush veld class cartridge. IMO, you, using a Rem circlip extractor, will center your cases in the chamber, and that will alibi a slightly oversize one. And since your WSM cases were already a rebated design from the start, it should work out fine, regardless how much you polish out your short chambered barrel.

So far I have only quickly tried some dummy rounds and they seem to feed OK. I went with a saum case as I already had all the dies to modify and a chambered rifle to shorten the chamber on. If I was starting from scratch I might have done this with a wsm case as it would give a slightly larger capacity.

Real interesting wildcat. I've shorten the 6br case also the 7-08 got some form dies from Skip Otto using bushing pretty close to your form die. Wilson sells blank neck and bullet seater gunsmith used chamber reamer so had a set. Neil Jones will make good set of shoulder bumping die and seater using bushing Neil Jones Custom Products.

Precision Shooting did a article on the short 7-08 and Redding used my 6br short change the name to 6brShortenTalldog.

I've got 3 custom WSM calibers and at times I wish I'd done something on the Remington case. Well good luck

I had thought of sending some dies to JLC precision in the US for honing if I have any issues with dies, a bit cheaper than the Jones Dies as I am on a tight budget and have t6o pay freight on everything to NZ. I use a redding body die to bump shoulders and a lee collet neck die to neck size with the saum. I rarely FL length size. Found a nice way of modifying LEE collet neck dies for shortened wildcats Here.

Interesting that you have shortened the 7mm-08. I also have a 7mm-08 in a remington model 7 and if I ever rebarrel I wondered about going to a shorter calibre with similar specs possibly a 7mm IHMSA or 7mm wssm. Aside from the 7mm wssm are there any other cases that duplicate the .308 case volume in a shorter case that feeds OK?

[QUOTE=lurch;590979]I had thought of sending some dies to JLC precision in the US for honing if I have any issues with dies, a bit cheaper than the Jones Dies as I am on a tight budget and have t6o pay freight on everything to NZ. I use a redding body die to bump shoulders and a lee collet neck die to neck size with the saum. I rarely FL length size. Found a nice way of modifying LEE collet neck dies for shortened wildcats Here.

Interesting that you have shortened the 7mm-08. I also have a 7mm-08 in a remington model 7 and if I ever rebarrel I wondered about going to a shorter calibre with similar specs possibly a 7mm IHMSA or 7mm wssm. Aside from the 7mm wssm are there any other cases that duplicate the .308 case volume in a shorter case that feeds OK?[/QUOTE

I've shot the 30 IHMSA in the Hunter BR match. I know they done the 270,6.5,7mm and 338 IHMSA Hodgdon manual 26 has loading data. It's an older manual and I'm sure someone with QL give you up to date loading data.

One reason I like the Wilson/Jones dies is hang over from my BR days I like to use dies for the arbor press as I load at the range. With Jones neck bushing die if it's for the 222 you just change bushing and it work for my 222AI,223,223AI,222mag and if I do the 222magAI. With his bushing seater you get perfect alignment on seat bullets very little run-out.

I think the time is good for the 7mm get on 6br site lot of interest in the SAUM in 7mm.

A couple of quick notes on the IHMSA cases, versus the 308 family. The 300 Savage (parent brass for the IHMSA cartridges) is limited to ~53,000psi, while the 308 is 60,000psi. Also, the IHMSA cases were created with the express intent of pushing the shoulder back to give a longer neck than the parent. As such, the case capacity and operating pressure would make a 7mm IHMSA quite a bit less potent than a 7wssm, for the same general case length.

Gates also made a 35 IHMSA, which is within about .080" of legal for a deer-hunting rifle in Indiana...which is how I became acquainted with the details of the IHMSA line of cartridges.

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Ask me about QDMA.

One problem I am having at the moment is with the trimming of the shortened Saum cases.

I have ordered a redding form and trim die but it hasn't arrived yet after 2 months.

What I have been doing is placing a nut on the neck and then using a dremel tool to slice the excess neck off. I get sandblasted with brass filings and it is pretty rough. I finish up on a Wilson trimmer

I had wondered about another option, using a Lee trimmer, but I figured that this would be pretty hard on it and it might be blunted pretty quick.

Another option I had though about was one of These

The possum hollow kwik trim also looks very good and has a carbide cutter

I'd be interested to hear peoples thoughts on trimming options

for some that may not know what IHMSA stand for here is is "International Handgun Metallic Silhouette Association. the loading data in Hodgdon manual 26 is for a 14" handgun and Wichita made the pistol and the Rem 7br XP pistol was another one.

The IHMSA cases were formed from 300 Savage case and IHMSA made case also and they were always a low pressure. 168gr 30IHMSA top velocity 2100fps if you used a long barrel might get 300 Savage velocity. the reason we used that case in Hunter BR was small case capaity as required also Rem made BR cases with small Primer pocket and you could use that case to form the 30x47,30x44. We also shot the 30 AARVARK
OT - .30 Aardvark [Archive] - Saubier.com
I got out of match shooting just before the 30BR which pretty much wins everything in the BR score matches.

the 7-08 case I shorten was for Silhouette. And here is something on E. Gates "Elgin also founded the International Handgun Metallic Silhouette Association (IHMSA) and helped develop many of the Dan Wesson Super Mag cartridges."