25-06 from 270 brass issue

[Oddsix]

I got a new to me m77 in 25-06.
I have a ton of 270 brass so thought I would just resize it in my rcbs 25-06 die.
120 grain hp Hornady interlocks.
I have to force the bolt closed and when I eject the unfired cartridge the bullet has land marks on it and there is a radiused scratch on the neck.
I could see that the the brass would maybe not work out but I loaded the bullets to the coal from the Hornady book.
I have checked the dimensions of the brass that are given in my reloading books and they correct after resizing
Is it me or do I need to take it to a smith?
I have not shot factory 25-06 loads from it

 

[sunray]

The neck likely needs turning due to the difference in diameter. Check the case lengths too. And your OAL is too long.
Trim-to is 2.484". OAL with a 120 is 3.150".

 

[bigedp51]

I see two possibilitys

Your necks are thicker sizing down to a smaller caliber and you do not have enough neck clearance.

You are not bumping the shoulder back far enough.

Try bumping the shoulder back more and pause at the top of the stroke for a few seconds for less brass spring back.

It also looks like you need some gauges to check your cases for your problem.

I do not think you need to see a gunsmith and gauges should fix you problem.

Do you have any case gauges, neck thickness, etc?

 

[bearhunter]

First off, how old is your M77??? The later ones are usually pretty good but some of the rifles made before 1995 can be hit or miss.

Before turning your necks on the brass, try seating your bullets deeper. Just because the manual gives a certain OAL doesn't mean it's correct for your particular rifle. It's quite likely you have a short throat. Another thing, did you chamfer the inside and outside lips of your brass after necking down and resizing your brass?? Tight necks can be a very good situation to have accuracy wise. Also, using a felt marker, smear up the neck and shoulder area on a dummy round that is from your batch of brass but assembled without the primer and powder. This will tell you if you need to set the shoulders back a hair. This may be your real culprit. Also, when necking a case down or up, the brass can increase in length and the case mouth may no longer be square but higher on one side.

By the way, you may want to check out the twist rate in your bore. If it is 1-12 or 1-14, it may not stabilize your long 120 grain bullets.

 

[snoopycda]

I got a new to me m77 in 25-06.
I have a ton of 270 brass so thought I would just resize it in my rcbs 25-06 die.
120 grain hp Hornady interlocks.
I have to force the bolt closed and when I eject the unfired cartridge the bullet has land marks on it and there is a radiused scratch on the neck.
I could see that the the brass would maybe not work out but I loaded the bullets to the coal from the Hornady book.
I have checked the dimensions of the brass that are given in my reloading books and they correct after resizing
Is it me or do I need to take it to a smith?
I have not shot factory 25-06 loads from it

270 should be 2.540 in length before re-sizing, re-sizing down would only cause the brass to grow in length. Did you trim to 2.494 after re-sizing?

 

[Oddsix]

I trimmed to 2.494 after resizing
I believe it is a mid 80's m77 when I looked up the serial number. Red buttpad.
@sunray. My hornady book says 3.240 c.o.l?? But obviously it is too long....
I will get a gauge

 

[H4831]

I trimmed to 2.494 after resizing
I believe it is a mid 80's m77 when I looked up the serial number. Red buttpad.
@sunray. My hornady book says 3.240 c.o.l?? But obviously it is too long....
I will get a gauge

I don't know why you need a gauge? The bullet of your dummy cartridge hit the lands and the bolt wouldn't close. Seat the bullet deep enough so the bolt will close freely and shoot away.

 

[bigedp51]

The OP is case forming and neck thickness will increase along with shoulder location.

He needs gauges to check and see what his neck thickness is after sizing.

And he need a case gauge to check shoulder location.

First you chamber an empty resized case without the bullet and then a dummy round to isolate the cause of the chambering problem.

On top of this the OP has not fired any factory loaded 25-06 ammunition to compare to the case forming he did. And my biggest worry would be neck thickness and having enough room for the neck to expand. And worry about his throat length after these checks have been done.

 

[ATOM]

Sounds like it might be two separate problems. If there are rifling marks on the ogive of the bullet, then your bullet is seated too far out for that particular rifle. The difficulty in closing is, I suspect, a totally different issue as bolts close with a cam action, most of them, and can generally push a bullet in without major difficulty. But solve this problem last.

There are two other possible issues. One is that the shoulder is too far forward or the case too long since you necked it down. I would be tempted to try to chamber an unprimed, empty case. If this is the problem, you should be able to notice it. If there are problems closing the bolt, first check the length and trim if necessary. If that fixes it, great. Otherwise, bump the shoulder back a bit.

The second is, as has been suggested, that the neck is too thick. A too-thick neck wall with a bullet in it will tend to wedge in the neck area of the chamber. You might need a gauge for that. The cure is of course to turn it down.

Once your cases are the right dimensions, an old trick to determine proper bullet seating depth is to take a sized but unprimed case. Using a hacksaw, cut a slot along the length of the neck down to the shoulder. Clean it up and then push a bullet in a bit. Chamber the round and gently close the bolt. Now gently extract it and measure the length, which will be the max length you can have with that bullet and that rifle So you load rounds just a bit short than that - how much is up to you.

 

[Oddsix]

so i got a tapped cartridge for my OAL gauge, and for the 120 grain bullets the hornady listed length is 3.24" and i am touching the lands at 3.15"
this seems strange to me since all the other bullets i have tried in my other rifles had a lot of freebore with what hornady recommended as an OAL and i was able to really push the bullet out.
i thought this might be a typo in their book but i checked my lyman book and it says 3.25"
i also tried some 75 grain v-max ones and it recommends 3.10" and i am touching the lands at 3.124" so it must just not like that bullet??
i might not use this bullet anyways, i got it for deer but the rifle is too bloody heavy to pack anyways so i will stick to the lighter ones for varmints

 

[Johnny G1]

I have all kinds of 270 case's that fit in my 25-06 Mashburn and none of them been neck turned, different story with the Lake City 30 cal brass as it has been turned, the 270 have been shorted to 2490+ and fit the chamber before fire forming with no problem. And the gun will take standard 25-06 also and fire form perfect.