Necking down 300 Saum brass to 7 Saum

[Grapevinedave]

I've searched for a thread about necking down 300 Saum brass to 7 Saum and didn't find much and wondering what others have as a process. The main thing I see is the difference in brass length with the 300 being shorter. I have some 7 saum brass but have a couple hundred 300's. Should I make them all the same length after fire forming. Another question would be is it necessary to neck turn the brass to fit the chamber? Have never necked turned brass, but not opposed to buying the supplies to do that. Any help with this process would be much appreciated.

 

[Harvey_NW]

I've been researching this topic as I may have to do so myself, it depends on the dimension of the neck area in your chamber and the thickness of brass being formed. You should be able to get an idea by the difference between the neck OD of a fired case and a loaded forming round to determine if you need to neck turn. SAAMI specs show a max chamber dimension of .321, and a loaded round dimension of .320", so only .001" of total clearance.

Lots of other other 7/300 wildcats being sized down in a single pass, annealing helps. If I end up going this route I will be setting up the forming loads with a false shoulder and a mild initial charge. You wont know if they need trimmed until they're formed out.

 

[Grapevinedave]

Thank you for the response and the info. Much appreciated. I have fired about 25 rounds through the rifle to get some fire formed brass. Going to make a dummy round and see what neck dimensions come out to be. I have ordered a neck turner and think that will be a good thing to have for this and other cartridges as well if necessary.

My rifle is at the gunsmith getting the barrel threaded, so should have it back in week or two. Will have to wait to get it back to see how the rounds cycle. Will let you know how it turns out.

 

[Harvey_NW]

I have fired about 25 rounds through the rifle to get some fire formed brass.

You will be re-fireforming and blowing the neck/shoulder junction forward about .020" when you initially fire those converted casings so I wouldn't hit them with a stout charge. Since you're stepping down it will be easy to set up a false shoulder so you get a full form on first firing. I'm sure your gunsmith will have some insight on it as well. Very interested to see results, hope it's a smooth ordeal.

 

[Grapevinedave]

The 25 rounds I shot were some 7 SAUM brass that I shot through the gun just to start load development. Will follow that advice and have some 160 sierra's that I have and will use those for fire forming with a light load in the necked down brass. Will see how it goes. Got a note from my gunsmith today that the gun will be ready on Monday. Kinda hot here in Phoenix, so will probably just go to one of the local indoor gun clubs and fire form that brass. Will take a little while and hope it will be worth it in the end. Will share results as the process moves along.

 

[Grapevinedave]

Here is an update on how things are going with necking down the brass.

First, this is not a custom build, it's a Remington Model 7 SS 7 SAUM, 22" barrel, Lil Beast Brake, HS Precision Stock, with a Burris XTR 4-20X50 Scope.

1. Necking down 50 pieces of Remington brass with a RCBS FL sizing die.
2. Lubed body of the cases, also inside and outside the neck. Went very smooth. Came out of the sizing die with .316 neck diameter and same shoulder measurement as the once fired sized Remington 7mm SAUM brass that was shot in the gun.
3. Trimmed all brass to same length 2.010.
4. Used a Forster neck turning tool and turned them down to .314 neck diameter and neck wall thickness of .015. Using 162 ELD-X's the dummy round measured .316 which should leave plenty of room for expansion since a SAAMI chamber dimension is .321. Side note the forster turning pilot is a little undersized from the factory (no sizing mandrel required) to fit the inside diameter of the case but it was a still a little snug with sizing down a bigger case. Chucked it in the drill and a little 600 grit sandpaper polished it right up and it fit nicely.
5. Limited by mag length the 162's had to be seated at 2.855 OAL. That's 10 off mag length and 45 thou off the lands. Going to do a Scott Satterlee ladder test in .2 grain increments and use FED 210 Primers and IMR 7828 as I have quite a bit of it. Hopefully it will get to 2850-2900 FPS or better. Loaded up 15 rounds of once fired 7 SAUM brass and 15 of the 300 necked down brass to do an experiment to see how much difference in velocity there is. If it doesn't work out well, will just use some light loads and fire form the necked down brass with some old components. Trying to save a little barrel life and components since they are so easy to come by and super inexpensive in todays world.
The forest has opened back up here in AZ with the rain we have been getting and will plan a little shooting session in the near future and see how it goes.

 

[Grassymike]

How did that Forster neck turn attachment work for you ? Just going through the same thing forming 7mm-08 from .308 brass.

 

[Grapevinedave]

Grassymike I responded on your post.

 

[wind gypsy]

In the early days of 6.5 SAUM before there was headstamped brass everyone was necking down 7 or 300 SAUM. Most common path was to use a FL bushing die and neck it down in steps. The smaller sizing steps reduced runout induced during the necking down process. It was pretty straight forward - Take a 7 SAUM die and insert bushings in about 0.008" steps to get it to the desired diameter.

A standard FL sizing die might be even smoother and induce less runout but never done it to confirm. I definitely prefer a FL sizing die if you are necking down something that will be neck turned because it actually sizes all the way to the shoulder so it helps you turn a neck of consistent thickness to the neck/shoulder junction.

I'd be curious @Grapevinedave if you have and difference in total runout between the 7 saum headstamp ammo vs with the newly necked down 300 SAUM brass. If you've got a bit more runout with the necked down brass a lot of that should get straightened out after being fired.

 

[Grapevinedave]

Hey @wind gypsy I've read a lot of your posts on other topics and always like what you have to say. Don't really measure runout anymore because it doesn't seem to effect my groups. Have you found different results? I went to the indoor range yesterday to do a .2 grain ladder test with 162 ELD-X's using H-1000 and IMR 7828. Started with 63.6 of H-1000 and hit pressure at 64.8 and FPS was right at 2893 which is good enough for me. Glad I didn't go to the high end of the Hogdon data at 67.00. Starting at 58.2 of 7828 I hit pressure at 60.4 and 2875 FPS. Loaded the same ladder with once fired 7 SAUM Remington Brass and the 300 SAUM Remington necked down brass. Had similar results in speed but the 300 brass hit pressure faster. Was hoping I didn't have to fire form them, but looks like that will be necessary.
To answer your question on runout made me curious since I haven't measured it in quite some time. Got out the Hornady Concentricity Gauge and measured both 7 Saum and 300 necked down brass over 8-10 cartridges had less than .002 of runout and most were .001 so I guess the process that I'm using is working for that.
Question, do you know of a good way to fire form brass with out wasting a bunch of components and powder?

 

[amassi]

Hey @wind gypsy I've read a lot of your posts on other topics and always like what you have to say. Don't really measure runout anymore because it doesn't seem to effect my groups. Have you found different results? I went to the indoor range yesterday to do a .2 grain ladder test with 162 ELD-X's using H-1000 and IMR 7828. Started with 63.6 of H-1000 and hit pressure at 64.8 and FPS was right at 2893 which is good enough for me. Glad I didn't go to the high end of the Hogdon data at 67.00. Starting at 58.2 of 7828 I hit pressure at 60.4 and 2875 FPS. Loaded the same ladder with once fired 7 SAUM Remington Brass and the 300 SAUM Remington necked down brass. Had similar results in speed but the 300 brass hit pressure faster. Was hoping I didn't have to fire form them, but looks like that will be necessary.
To answer your question on runout made me curious since I haven't measured it in quite some time. Got out the Hornady Concentricity Gauge and measured both 7 Saum and 300 necked down brass over 8-10 cartridges had less than .002 of runout and most were .001 so I guess the process that I'm using is working for that.
Question, do you know of a good way to fire form brass with out wasting a bunch of components and powder?

Cream of wheat or cow method if you have some pistol or shotgun powder laying around.

Sent from my SM-G991U using Tapatalk

 

[wind gypsy]

Hey @wind gypsy I've read a lot of your posts on other topics and always like what you have to say. Don't really measure runout anymore because it doesn't seem to effect my groups. Have you found different results? I went to the indoor range yesterday to do a .2 grain ladder test with 162 ELD-X's using H-1000 and IMR 7828. Started with 63.6 of H-1000 and hit pressure at 64.8 and FPS was right at 2893 which is good enough for me. Glad I didn't go to the high end of the Hogdon data at 67.00. Starting at 58.2 of 7828 I hit pressure at 60.4 and 2875 FPS. Loaded the same ladder with once fired 7 SAUM Remington Brass and the 300 SAUM Remington necked down brass. Had similar results in speed but the 300 brass hit pressure faster. Was hoping I didn't have to fire form them, but looks like that will be necessary.
To answer your question on runout made me curious since I haven't measured it in quite some time. Got out the Hornady Concentricity Gauge and measured both 7 Saum and 300 necked down brass over 8-10 cartridges had less than .002 of runout and most were .001 so I guess the process that I'm using is working for that.
Question, do you know of a good way to fire form brass with out wasting a bunch of components and powder?

I don't measure runout anymore either if using good components, i just know that my process with the bushing dies going from 7 saum to 6.5 induced some runout and accuracy was a little less consistent on first firing with my brass that resulted in loaded rounds with over 0.004" of runout. It sounds like a standard FL die is doing better for you though which makes sense to me.

I'm curious what you are hoping fire forming will achieve if you already have straight brass? Just spitballin here but there may be other differences between the brass such that you will not get the same results with the 300 headstamp as the 7mm headstamp cases even after fire forming. If the cases are straight and the shoulder isn't moving forward much at first firing, I'm not sure that fire forming is notably different than just the standard virgin vs fired case differences.

There are lots of rabbit holes to go down in relation to this but just some things to consider:
-Did you anneal after necking down? that much sizing is working the necks quite a bit and can harden them
-If quite a bit is turned off the neck, beware of the possibility of donuts forming at neck shoulder junction from thicker brass flowing from the shoulder into the neck after firing/sizing. You might not see this if it's inside the neck as I don't believe the forster neck turner cuts on the inside.

 

[Grapevinedave]

Thanks for sharing the info and no I don't have an annealer. I know it is helpful but haven't gone down that path in my reloading process as I'm a hunter not a competitive shooter. Thought about investing in an annealer many times, but just haven't pulled the trigger.
To share results of necking down the 300 brass was all trimmed to 2.010 and the 7mm brass was trimmed to sammi spec 2.025. Should I trim the 7mm brass down to .210 as well to make everything consistent? The sized brass came out with a neck diameter of .316 and would cycle in my chamber with a bullet seated at .318. Just skimmed the brass as didn't want to take too much off since it cycled without issue, so don't think a donut issue is in play.
Maybe it's just best to use the 300 SAUM brass for development since I have 200 pieces of that and go forward with the results that I'm getting since I only have 50 pieces of the 7mm. The shoulder measurement is the same as the 7mm brass using the comparitor.
Think I will do a ladder test with just the 300 brass with H-1000 and see if it gets consistent results.
@wind gypsy , Thanks again for your insight.

 

[wind gypsy]

I wouldn’t worry about trying to make the 7 brass the same as the 300 brass. I would treat them as 2 separate loads. They might shoot the same or close enough if you find a charge in both that gets the same velocity.

 

[Grapevinedave]

@wind gypsy Decided to follow your advice and just concentrate on the necked down 300 brass because I have 200 of them. Set up an annealing process that turned out with pretty good results by the looks of things. Annealed 50 pieces then sized them and turned the necks down .001 to .315.
Loaded a ladder test and found a node with H-1000 at 62.8, 63.0, 63.2 grains. Question, what is the best charge of powder to do the seating depth test. I'm limited by mag box so max length will be 2.865 and work my way down from there.
Will head out to the desert and shoot some groups .003 apart and see how it goes.

 

[wind gypsy]

I at one point thought eric cortina’s method (very small seating depth adjustments) of seating depth tests made a lot of sense but don’t think I’ve got the patience anymore and it seems way overkill for a hunting rifle.

Lately I just set stuff to 0.040-.050” off the lands or mag length and let er buck. If that shoots well I might then test + and - 0.015” to make sure it’s not finicky around that depth and then call it good. All my rifles/ammo that shoot acceptably to me will do so with a nice range of seating depths so I don’t waste time chasing perfection.

There are some interesting articles about bullet jump studies on the precision rifle blog.

 

[Grapevinedave]

Thanks for the insight. Always trying to simplify the process, so that sounds like a good place to start. Try to get a hunting rifle to shoot under an inch with a 5 shot group and have been pretty successful doing so. Think everything that you mentioned is going to narrow the process. Mag length is .065 of the lands so will see if it likes that length and go from there. Will head out to the desert next weekend to shoot and share what happens with the development.

 

[Grapevinedave]

Just read the precision rifle blog. Interesting how the most consistent loads were in the .060 to .075 off the lands. Kind of blows the getting it close to the lands theory out the window. As you say many ways to go about it. Hope that holds true with my rifle being limited by mag length at .065 off. Looking forward to seeing how it shoots this weekend.

 

[Grapevinedave]

Went out to the desert this morning and shot a few groups to see how the process worked. Looks like I found a decent seating depth just under mag length. All groups were shot at a 100 yards.
Remington 300 SAUM necked down brass and neck turned. 162gr ELD-X, 63.0 gr of H-1000, 2860 FPS average, Fed 210 primer.
Results are in the picture and will load up some more rounds with a seating depth of 2.205. All measurements are CBTO not CAOL. Only have about .005 to .008 of mag length left to play with so will load 6 more at 2.208 and see how it shoots along with another set at 2.205. . If this holds up as a good load and seating depth, I will call it done and go hunting.

 

[Grapevinedave]

Feel like this process has come to a close and the Rifle shoots good enough for hunting purposes and for a gun with a 22" lightweight barrel. The goal was to neck down some brass and learn that process and hope it works well in this rifle with the powder and bullets I have for it. Think that has been accomplished.
Went shooting this morning and these are the results.

Final load for this rifle is Remington 300 SAUM brass annealed, necked down to 7 SAUM and neck turned. 63 grains of H-1000, Fed 210 primer and 162 grain ELD-X.

Shot 4 shot groups. All measured CBTO. All shot at 100 yds, 75 degrees. 3500' elevation.

1st - 2.205 not sure what happened to shot number 2
2nd - wanted to get closer sight in above target and chrono the load. (Magnetospeed Sporter) ES of 12 over 4 shots. The chrono moves point of impact quite a bit. Moved right a little much but got back to center.
3rd - 2.208 measured .76 but the first 3 were .58
4th - 2.210 measured .78 but the first 3 were .50

Looks like 2.210 is the winner and will load up 50 rounds and site it in and go try and kill a coues deer this November.

Hope this helps someone else looking to go through this process. It worked out for this rifle.