A friend of mine has a Winchester M70 chambered for the .264 Winchester which is a belted casing.

I sized them with a set of Lyman dies, trimmed them to 2.500 length and checked them for proper function in the rifle....so far all is good. They chamber effortlessly.

The problem surfaces when I seat a bullet at 3.30 OAL (which is less than the SAAMI spec), The round will not chamber.
I smoked the casing to see if I can find a rub spot that would let me know where the problem is.....NO MARKS...darn it!

I measured the thickness of the exterior of the case mouth, right where it needs to be.....maybe inside case neck problem? Calipers say they are spot on.

Bullets are Sierra Game King 140 grn and they are right on at .264, Casings are Remingtons.

Again, sized casings chamber perfectly, the problem shows up in the seating of a projectile.

What am I missing?

Randy

Some rifles are not sword swallowers......................

You may have a "Short action" from how the company taped and drilled.......
no big thing, just that you need to be careful with the OAL and bullets Ogive shapes, used.

I have friends with a Rem .270 and another with a Win 30-06,
both bolt actions, that will not accept my "Long accuracy" hunting loads.

You have the option to take it to the "Doctor" to remove its tonsils.......... only if you can't find a load that makes you happy.

I really love the 140gr bullet in this rifle but the lighter 120gr is nothing to sneeze at.

I loaded for a 264 Newton, non-belted. One heck of a round but it had a long free bore and loved the Sierra bullets.

Good loading.

I no longer have a .264, but based on my loading for two, a Winchester and a Sako, most bullets must be seated pretty deeply, probably more than what you are doing. I've used five bullets ranging in weight from 125 to 140 grains, but have not used the Sierra 140 that you have.

You don't need to smoke or mark anything; seat the bullet to where you have slight bullet engraving after chambering a complete dummy round. Then seat a little deeper and experiment with OAL from there. If you're not using a loading manual, do so. It should have all this information in greater detail. Good luck-

if you are really set on using the 140gr. bullets, get a hornady COL. measuring tool and the corresponding 264 win mag cartridge case. it will prolly cost you 30 bucks, but then you can find out the COL to the lands w/any bullet you choose to load in that gun. or you can just return it after you check out your max COL. w/the bullet thats giving you problems.

When sized brass chambers and a loaded round will not, it is either because the neck has bulged during crimping or the bullet is jamming into the rifling.

I thought .264 WM brass was like unicorn horn. Was this brass formed from 7mm Rem Mag brass? If it was, it's possible that the neck diameter is too large and neck turning is required.

Update....

Brass is .264 Winchester Mag brass, not necked down 7mm brass. Winchester and Remington.

Did another test this morning where I loaded a WW piece of brass and it to will not chamber, I pulled the bullet and tried that exact same round and without a bullet it DOES chamber which seems to eliminate having a shoulder issue during seating.

The bolt will not go far enough forward to allow the bolt to go downward.

So, there is something amiss in the seating of the Sierra Game King bullets. They mic out at exactly .264, the neck mics out at .285-286 and the SAMMI spec. is .290 so there is no reason for the round to not chamber.

I seated a bullet deeply into the casing to see if the bullet itself is touching the lands of the rifling (3.25 OAL and it isn't touching)....still won't chamber.

Still baffled in Montana!

Randy

The bullet at 3.25"... I wouldn't think so, but you may now have it seated too deep. Try it a little longer and see if it engraves; you could be be very close.

Is you loaded cartridge diameter measurement taken at the very top of the cartridge case neck rather than below the neck? You are removing all possible neck flare when seating the bullet, right? Are you measuring loaded diameter with a caliper or micrometer? Micrometer is better but you can get by with a caliper.

With some Sierra bullets, because of their design/ogive, they have to be seated somewhat deeper than other bullets of the same weight. Some 7mms and .30s come to mind , but there may be others.

Make up a dummy round-no primer or powder, making sure the case chamber first. Then seat a bullet and SMOKE it. Should show your problem!

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Good shooting.

Push just a bullet into the chamber with a dowel pin, put a cleaning rod in from the muzzle until it touches the bullet and mark at the muzzle. Then close the bolt and push the rod in until it touches the bolt face and mark at the muzzle again. the distance between the marks is your max OAL. Your rod must have a flat end so the tip of the bullet does not enter the female threaded section.

ARE YOU USING NEW BRASS? If you are using brass that has been fired several times, the brass will flow back toward the belt and full length sizing will NOT size all the way down to the belt. I have had this happen to me, making the bolt hard to close on loaded rounds. There are special collet dies made for sizing to the belt.

Solution found!

I did the old start a bullet in the case mouth, close the bolt even if it is a bit resistant, remove the cartridge, measure the OAL, set the seating die to that length and ........the Sierra Game King ogive is significantly different than the factory round I was using as a template.

The correct OAL for the GK is 3.139..... Just needed to seat the bullet quite a bit deeper and it chambers effortlessly now! YEAH!!!!

Thanks to everyone for you help....I was getting a bit bewildered on this one!

Randy

Line 3 in post, #2.

Glad you fixed the problem.

All "FREE" solutions aside, if you're going to reload for several different rifles, this is THE WAY to go.

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Good shooting.

Groo here
The original 264 bullet was a two diameter design.
The part out of the case was like a bore rider where the base was normal.
Watch the twist, I have a Douglas XXX target barrel.
Flat base factory 140gr shoots inside 5/8th for five
100gr hp shoot near 1/4in for five [100yds]
140gr Sierra matchkings keyhole!!!!!!!!!!
If so try the 120gr matchkings.