7mm-08 Rem with RCBS 145-284-SIL - Need help

[Camba]

Ok. I decided to load some CB's in 7mm-08 Rem and run into a few problems:
First, the 145gr RCBS boolit comes out to about 157-158gr and after adding the gas check it's just about 161gr. So far, I don't think this is the problem but I thought I should have it out in the open anyway.
1. I decided to use some 308 win cases, sized in my 7mm-08 die and seems simple.
2. I loaded a few recipes to test:
a) 161gr GC-RCBS, 17.0gr Blue dot, WLR primers, OAL = barely touching the lands.
b) 161gr GC-RCBS, 22.0gr 2400, WLR, same OAL.
c) 161gr GC RCBS, 15.0gr Unique, WLR, same OAL
3. Used regular 7mm-08 Rem brass and load the same loads as above plus one other low velocity using regular copper jacketed bullets (2,240 fps, 130gr Speer SP, 24.0gr 2400, WLR).
The velocities I've got from my boolit loads using my Chrony: a) 1,820 fps; b) 2,005 fps; c) 1,730 fps.

To start, none of the loads using the 308 win sized in the 7mm-08 Rem dies even fit the rifle chamber. The round would not go into the chamber completely. For a while I thought perhaps the boolit was too far out (which it also was). I tried the loads using the 7mm-08 brass and other than adjusting the boolit depth, they work just fine.

I need to be schooled on how to make those 308 win cases be useful for my 7mm-08. I am sure I am missing something. I trim all the cases to 2.030 or slightly less.
I will sit back and see the responses from the Cast Boolit experts.

Camba

[1500FPS]

Try chambering a 308 that was sized in the 7mm-08 die. If it doesn't chamber there's a start. If doesn't try screwing your sizer die on the ram enough to get a good tight cam over and size the case again and see if it chambers. If it doesn't there's your problem. If it does chamber then the necks may be too thick. Take one of your cast loads in the sized down 308 cases and mic the neck and compare it to the ones in the 7mm-08 cases. You did not say what size you are sizing the bullets to as that makes a difference in total neck diameter.

What to do if the 7mm-08 die isn't sizing the 308 case down enough to chamber even after you have it set to cam over, take some metal off the top of shell holder. Preferably in lathe. Don't take too much off as it weakens it and it can break trying to pull a tight case out that wasn't lubed good for an example.

Let us know what happens after all this.

[Nickle]

Make sure you set you full length 7mm-08 sizer die so it cams over slightly.

Make sure you trim the cases to the correct length.

And, check the neck diameter of the new cases, as many times you have to ream the necks to the correct thickness.

There's nothing hard here, and we'll help you, if you do some checking and let us know specifics.

[Camba]

My boolit is sized to .285" and gas checked altogether. You may be on to something with the thicker neck/mouth of the 308 win sized down to 7mm. I will check the outside diameter of the sized down 308 w versus the regular 7mm-08 brass. If it is, then it is definitely a factor. If so, how do you take care of that? I know I don't need to mess with the 308 w brass as I have enough 7mm-08 brass. I just wanted to learn how to do it. Any help on that?

[1500FPS]

My boolit is sized to .285" and gas checked altogether. You may be on to something with the thicker neck/mouth of the 308 win sized down to 7mm. I will check the outside diameter of the sized down 308 w versus the regular 7mm-08 brass. If it is, then it is definitely a factor. If so, how do you take care of that? I know I don't need to mess with the 308 w brass as I have enough 7mm-08 brass. I just wanted to learn how to do it. Any help on that?

To insure the thicker neck is the problem load a dummy round with a sized to 7mm-08 308 case and black marker pen up the entire neck and gently chamber to see if the marker is scraped off. If it is you either need to outside neck turn or inside reamer them. Most people go with the outside neck turner like the one for Forester productions.

[Nickle]

You can either outside turn, or inside ream the case necks.

I've done it both ways, and which one I use depends on a few factors.

Cheapest route if you currently have a Forster trimmer is to inside ream. Get a reamer pilot from your source. I was going to say you can find them at Midway, but they don't list the 284 reamer in Forster. They do have RCBS, but I'm not overly fond of the way it looks.

http://www.forsterproducts.com/catal...?prodid=700238

Now, outside turning them is more accurate, IMNSO. I use a Marquart myself for important stuff, but will probably get a Hart, as I'm not sure if I can find Marquart parts. In the mean time, I'll have to inside ream (I've got all those reamers already).

And, it seems I've made 7mm-08 brass from 308 myself, and had to ream them.

[1500FPS]

I like the outside neck turning because it is adjustable where as the reamer is only good for one bullet diameter. With cast you may shoot different bullet diameters with the same caliber. Plus with different calibers you have to buy reamers. With the neck turner all you need are the pilots which are much cheaper then reamers.

[TCLouis]

I formed some 308 cases to 7-08 for a guy and had to size them 3 times.

Finally ended up grinding about 10 - 15 thousandths off of the sizing die.

The hangup seemed to be the junction of the neck/shoulder.

[Camba]

Is these what you are referring to?

https://shop.rcbs.com/WebConnect/ima...ullA/90401.jpg
https://shop.rcbs.com/WebConnect/ima.../HCNTPilot.jpg

[Ben Dover]

Watch it if you think you may have necks that are too thick. Years ago I made 7-br cases from 308 basic cases. I didn't get them reamed fully through the neck/shoulder junction. I almost froze an xp-100 action (that wasn't mine). I quickly re-reamed the necks. Ben

[mroliver77]

If you do a pounded impression of your neck/throat area you would have the dimensions you need.
Jay

[Nickle]

Is these what you are referring to?

https://shop.rcbs.com/WebConnect/ima...ullA/90401.jpg
https://shop.rcbs.com/WebConnect/ima.../HCNTPilot.jpg

Yup! I'll tell you making your necks uniform does help accuracy, if your rifle is up to it, and your skills as well. Assuming you're shooting from a rest too. So, it's not a great loss if you don't need it.

[Camba]

OK. Finally I check the beck thickness. What I did is to size the 308 win brass and measure the outside diameter OD and then I measure the inside diameter ID and subtracted the ID from the OD:
OD - ID = .312" - .280" = 0.032". In some cases I've got 0.034".
Then I check the 7mm-08 Rem brass and did the same:
OD - ID = .309" - .280" = 0.029" to 0.030"

Now, inserting a .284" or .285" diameter bullet/boolit, it adds to the neck OD size by 0.002" to .0025" and that would be: for the 308 win, 0.034 to 0.0345" and for the 7mm08 brass, 0.032" to 0.0325"
That may be enough for the chamber, at the neck area to not allow the round to get in further.

Any other thoughts?
Camba

[lak]

I havent read every response to your problem, so I may have missed something. My problem wasn't the neck. I had the same proble with 7-08 encore that would not chamber once fired 308 brass. Ended up sizing the brass with a 308 small base die first and then sized with the 7-08. Bass worked fine after that.....

[Camba]

How do I find the 308 small base? I use the RCBS Rock chucker single press and Lee's shell holder. I am using a Lee sizer die. I also have the RCBS x-sizer die but I think that will not be necessary at this point until it is resolved the issue of chambering the 7mm/308 brass.

[marshall623]

I had the same issues forming 7-08 from fed 308's , mine was the thick necks turning the necks fixed the chambering problem. this was in in Savage Striker

[Camba]

marshall623,
I think you are right. Any other dimension I checked it is equal for both. The neck thickness, however is different, enough to not fit into the 7mm-08 chamber. I know, I should not mess with the 308 brass and buy the factory 7mm08 brass; but I wanted to know whether it can be done, should we have a shortage of cases for reloading.

Camba

[rockrat]

Fire a j-word load in your gun,using 7-08 brass and measure the fired case neck dia., then compare it to your loaded boolit rounds neck diameter, to see if you have any chamber clearance. I usually just take a little off the base of the die if I need to size a bit more. You could probably use 243 brass necked up for your 7-08

[marshall623]

Another thing also I got some of those 145 RCBS's off a shooter from Md. and they would not chamber with out sizing the nose.

[Camba]

I was not able to chamber the 7mm/308 cases with the Speer 130 gr SP. I could with the regular 7mm08 cases. I tried the 243 brass and had same problem as with the 7mm/308 brass.