Excess headspace - Win M70 30-06 pre-64

[Stammster]

I purchased a 1961 Winchester Model 70 pre-64 FWT in 30-06 last year off gun broker. The gun is in great shape. However after closer inspection, I came to find out the bolt serial number does not match the gun.

I shot some factory ammo through it, and depending on the brand, it grouped anywhere from 0.8" to 2.5" at 100 yds. Kind of in line with my expectations.

I was going to work up a hand load to see if I could do a little better. I measured my fired cases with a Hornady comparator and realized they were very long. In fact they read 2.055". For reference, my go gauge marked 2.0487" reads 2.0425" with the same 0.375" collet. By my math, that puts me at a chamber length of 2.061", which is over SAAMI max length by 0.0025"-0.003".

I had no soot blow by around any of the neck of the factory ammo I shot (qty approx 30). Each round was individually chambered rather than fed through the mag well, so I don't think the controlled feed had any influence. I measured a few of the unfired remaining shells from the various 20 rd packs, and they came in at 2.040-2.041" on my comparator.

Now the questions I have:
1.) Is it truly unsafe to keep shooting factory ammo in this gun? Personally I don't think so.
2.). If I reload, and only bump the shoulder back 0.002" from 2.055", this to me now brings the tolerance of "case to chamber" well within the acceptable limit of any commercial cartridge. I don't see anything wrong with this approach and will dedicate a string of brass to this gun only. It's a hunting gun, so round count will be <20 per year. Also I see this as no different then those who fire form brass for 30-06 variations like the 30-06 AI or 30 Gibbs, and blow the necks out. Am I wrong here?
Seems to me the previous owner may have inadvertently created a wildcat when they swapped out the bolt. Maybe this will work to my advantage for more powder capacity.

It just doesn't make financial sense for me to have a gunsmith set the barrel back at this time, in order to shorten the headspace. Also I am not very optimistic I could find a replacement bolt to correct the problem.

Another other suggestions?

Thanks.

 

[JMW67]

Sounds like it should work just fine handloading but like you said keep brass dedicated to this rifle

 

[cohunt]

if you want to shoot factory ammo then I would buy a field gauge and check to see if its out of spec-- you can fireform brass, but you should be jamming the bullet in the lands so the front of the case expands to form your "wildcat" chamber and not near the base/web-- you could see case head separations if you fireform the case with too much headspace and not keeping the brass against the bolt face in 1 way or another

 

[Stammster]

if you want to shoot factory ammo then I would buy a field gauge and check to see if its out of spec-- you can fireform brass, but you should be jamming the bullet in the lands so the front of the case expands to form your "wildcat" chamber and not near the base/web-- you could see case head separations if you fireform the case with too much headspace and not keeping the brass against the bolt face in 1 way or another

Can I just "control round feed" each round of a new lot of brass and accomplish the same thing as jamming the bullet in the lands. Shouldn't this accomplish the same thing by holding the case head against the bolt face?

Also based on my measurements, I am quite sure a field gauge would chamber easily. I didn't mention it in the first post, but I used my comparator in conjunction with my laser bore sight to make a "poor man's field gauge" by backing off the battery cap (2.052" comparator length = 2.0587" = max SAAMI chamber length) . I was able to chamber it without any bolt cam over force. When I had it set to 2.056" (comparator length), I felt some major resistance. This was consistent with my once fired brass coming out at 2.055". That's why I'm confident my chamber is 0.003" over SAAMI max spec without an actual field gauge.

FYI, I triple confirmed my comparator readings and offset - with both my go and no-go gauges. I don't have a factory field gauge, as I never saw the need for one.

 

[cohunt]

you can rent gauges just to be sure if you dont want to buy one, or check with a local smith to see if they can check it for you to be sure-- I'm not sure if the crf is good enough to tightly hold the brass back against the bolt face for fireforming--its your gun and its up to you--if you start getting case head separations youll know for sure it didnt work

 

[tobnpr]

Without going through your measurements, if a field gauge chambers easily, the barrel is a tomato stake.

We all know that slightly excessive headspace can be dealt with simply with die adjustments.

When you get to the point you're at you've got far too much case exposed, read- not just the thickened area of the case head beyond the breech, but now the thin case wall above it. Being unsupported by the chamber wall is a recipe for a casehead separation.

This is basic stuff- field gauges were made for one purpose; to distinguish service rifles that were "marginally" safe.
Fail no-go, but pass field= safe to fire- BUT remove from service as soon as practicable. Fail field gauge- remove from service.

Fail a field gauge= unsafe to fire. Full stop.

 

[Stammster]

The condition of the gun suggests little use, so I don't think the excess head space is due to a sloppy shot out barrel.

My understanding is the late year pre-64 Winchester's suffered from some financial struggles, and rather than control the tolerances of the barrels and bolts, they relied on setting the correct headspace with a variance - in both - by matching things up before they left the factory. This doesn't change the fact the headspace is clearly out of SAAMI spec by my measurements.

However, if I properly fire form "new brass" to correct the excess headspace issue, I don't see the concern. It's just not a standard 30-06 at that point. Please explain to me how this is any different than if the chamber was modified in both angle and increased length like what happens when you bore out longer (I.e. Gibbs). Of course in this case the barrel stamping is incorrect, but as the sole owner/operator - I can live with that.

Plus, after shooting 10 different brands of factory ammo, to didn't "blow my face off".

Any other suggestions other than a $400 gunsmith rework on a $750 gun?

 

[J E Custom]

Head space should be between .0015 and .004 for best function and case life. safety wise you can go as high as .006 to .007 but the brass will suffer and case head separation is a distinct possibility.

If you use it for hunting, the best thing to do if it is less than .006 head space, is to do a minimum sizing when you reload. I don't recommend bumping the shoulder unless chambering is a problem.

The more you size, the shorter the case life and the higher the risk of case head separation.

You can buy a head space gauge for under $50.00 dollars and use added shims to find out what the actual head space is, or just buy a field gauge and if the bolt wont close on it you will be ok, if it does close on the field gauge, i would recommend correcting the head space so it falls within SAMME standards.

again, don't size anymore than necessary and you will be fine. shouldered cases will chamber with many firings with standard loading's.

J E CUSTOM

 

[jdyoung]

The condition of the gun suggests little use, so I don't think the excess head space is due to a sloppy shot out barrel.

My understanding is the late year pre-64 Winchester's suffered from some financial struggles, and rather than control the tolerances of the barrels and bolts, they relied on setting the correct headspace with a variance - in both - by matching things up before they left the factory. This doesn't change the fact the headspace is clearly out of SAAMI spec by my measurements.

However, if I properly fire form "new brass" to correct the excess headspace issue, I don't see the concern. It's just not a standard 30-06 at that point. Please explain to me how this is any different than if the chamber was modified in both angle and increased length like what happens when you bore out longer (I.e. Gibbs). Of course in this case the barrel stamping is incorrect, but as the sole owner/operator - I can live with that.

Plus, after shooting 10 different brands of factory ammo, to didn't "blow my face off".

Any other suggestions other than a $400 gunsmith rework on a $750 gun?

I have a 1917 Enfield that was given to me when I was a teenager, 30-06 spr. It has what is termed " excessive headspace". (field gauge closes very easy), I have always reloaded for it, specifically neck sizing. That was so the cartridge would form to fit the chamber. But as you state, those cases have to be dedicated to that specific rifle. I do that by only using one brand of brass case for it. Lake City Military Brass is what I use for that rifle. Heavier wall and in theory it will take a bit more stretching than thinner commercial.

Over the years I learned how to form cases a little easier than "conventional fire forming".
I.E.: Loading it, driving to the range shooting, going home , reloading , driving back to the range, shooting etc, until the cases fit the chamber. Tended to get expensive when gas prices were way up.

Now, I expand the case neck to the next size caliber , resize to create a false shoulder, shoot it to fireform.

To do this, I use a Sinclair Expander Body and a Sinclair Expander Mandrel of the next size caliber. That would be .338". (some might say 8mm, but .338" always worked well )

Prep the cases and expand the necks to .338" with the Sinclair Expander Mandrel in the Sinclair Expander Body. (I deprime and de-crimp in a beginning step of case prep)

Then I apply a light coat of Redding/Imperial Sizing die wax to the case neck.

I prefer to follow that coating with some Powdered Mica, it is white and provides a visual check as the die is adjusted and case is sized.

Back your sizing die out a turn or so. To start, you only want to size 2/3 of the neck length, maybe a little more. Run the waxed/coated neck case through a sizing die, BUT don't do a complete stroke till you are confident how much of the neck is being sized. Like I said, you only want to size 2/3 of the neck back to .30 caliber as a start. The powdered mica is white and you can see the line on the neck "walk " toward the shoulder as you size the case and adjust the die.

Remove the cocking piece/firing pin assembly from the bolt.

Put the partially sized case under the extractor and gently chamber it.
You want feel just a slight bit of drag as the bolt handle closes.

Keep adjusting the sizing die to size the neck closer to the shoulder, chambering the case as you go to get the right feel as the bolt handle closes.. (If you get too much buildup of sizing wax/mica, wipe excess off so it doesn't dent the shoulder, but you still want some lube on the case. Run a patch into the chamber every now and then to eliminate the wax/mica buildup.)

You are creating a "false shoulder" between the case neck and shoulder that will fill the chamber.

When that is done, you can "COW" them or charge the cases with a beginning load and fire . This eliminates the "false shoulder" and gives a fireformed case without the bullet touching the lands.

Also, you might want to make note of the water weight your newly formed cases hold . You are creating a sort of a "wild cat" and if you have a computer program such as QuickLOAD, you can be a bit more precise indicating the water weight.

 

[tobnpr]

However, if I properly fire form "new brass" to correct the excess headspace issue, I don't see the concern.

The concern is internal ballistics "101".

"Fireforming" has it's LIMITS. You're beyond the thickened walls of the casehead that are designed to handle 60KPSI.
You're into the very thin walls of the case, that are completely incapable of containing that pressure.

On ignition, the case expands....to grip the chamber walls, and the case stretches at the rear in the area of the casehead until it smacks up against the boltface, reseating the primer.

The clearance provided/measured by a field gauge is considered the maximum safe clearance for a case to stretch.

You think you can push it further? Good luck, and wear your safety glasses.

Frankly, anyone that suggests that it's perfectly fine to fire such a rifle is providing downright dangerous "advice".

 

[Privi457]

A few corrections here. A CRF model 70 has a coned breech that does not support the case head. Worked fine on 03's, M54 and M70s to name a few.

To correctly fireform brass for that chamber DON"T shoot factory ammo.

Get some new brass, run a .33 neck expander in to make it a 338-06. Then start running it into a 30-06 FL die a bit at a time until you can close the bolt with some effort. This is the "false shoulder method" that has been around forever.

Then load the case with std 30-06 loads and fire them. You now cases dedicated for this rifle.
NEVER run the all the way into a FL die. I'd only neck size them. As long as you're using reasonable loads FL sizing may never be needed. Who would want to hotrod a 30-06 FW ? It will loosen your fillings.

 

[beretzs]

I agree with the others, if you are using new brass, bump them up in neck size then resize them down for a crush fit and you'll never worry about CHS. Brass will be perfectly fireformed for your chamber.

I wouldn't worry about factory ammo myself, it would be the subsequent firings of fully resized brass. As long as you know this, it isn't any big deal. I do this for quite a few cartridges to keep growth to a minimum anyhow, as chambers vary enough, along with brass sizes it makes sense for me to do it to keep brass lasting as long as possible.

 

[Tim Sharp]

I purchased a 1961 Winchester Model 70 pre-64 FWT in 30-06 last year off gun broker. The gun is in great shape. However after closer inspection, I came to find out the bolt serial number does not match the gun.

I shot some factory ammo through it, and depending on the brand, it grouped anywhere from 0.8" to 2.5" at 100 yds. Kind of in line with my expectations.

I was going to work up a hand load to see if I could do a little better. I measured my fired cases with a Hornady comparator and realized they were very long. In fact they read 2.055". For reference, my go gauge marked 2.0487" reads 2.0425" with the same 0.375" collet. By my math, that puts me at a chamber length of 2.061", which is over SAAMI max length by 0.0025"-0.003".

I had no soot blow by around any of the neck of the factory ammo I shot (qty approx 30). Each round was individually chambered rather than fed through the mag well, so I don't think the controlled feed had any influence. I measured a few of the unfired remaining shells from the various 20 rd packs, and they came in at 2.040-2.041" on my comparator.

Now the questions I have:
1.) Is it truly unsafe to keep shooting factory ammo in this gun? Personally I don't think so.
2.). If I reload, and only bump the shoulder back 0.002" from 2.055", this to me now brings the tolerance of "case to chamber" well within the acceptable limit of any commercial cartridge. I don't see anything wrong with this approach and will dedicate a string of brass to this gun only. It's a hunting gun, so round count will be <20 per year. Also I see this as no different then those who fire form brass for 30-06 variations like the 30-06 AI or 30 Gibbs, and blow the necks out. Am I wrong here?
Seems to me the previous owner may have inadvertently created a wildcat when they swapped out the bolt. Maybe this will work to my advantage for more powder capacity.

It just doesn't make financial sense for me to have a gunsmith set the barrel back at this time, in order to shorten the headspace. Also I am not very optimistic I could find a replacement bolt to correct the problem.

Another other suggestions?

Thanks.

These guys do work on Pre-64 M70's only. They may offer a solution and/or give you an idea of the costs to bring the rifle back in spec.

Pre-64 Winchester Model 70 Rifles and Rifle Parts

Your first stop for pre 64 Winchester model 70 rifles & gun parts. pre64win.com is a dedicated site for collectors and shooters of the the Rifleman's Rifle.

pre64win.com

 

[ronstone09]

I purchased a 1961 Winchester Model 70 pre-64 FWT in 30-06 last year off gun broker. The gun is in great shape. However after closer inspection, I came to find out the bolt serial number does not match the gun.

I shot some factory ammo through it, and depending on the brand, it grouped anywhere from 0.8" to 2.5" at 100 yds. Kind of in line with my expectations.

I was going to work up a hand load to see if I could do a little better. I measured my fired cases with a Hornady comparator and realized they were very long. In fact they read 2.055". For reference, my go gauge marked 2.0487" reads 2.0425" with the same 0.375" collet. By my math, that puts me at a chamber length of 2.061", which is over SAAMI max length by 0.0025"-0.003".

I had no soot blow by around any of the neck of the factory ammo I shot (qty approx 30). Each round was individually chambered rather than fed through the mag well, so I don't think the controlled feed had any influence. I measured a few of the unfired remaining shells from the various 20 rd packs, and they came in at 2.040-2.041" on my comparator.

Now the questions I have:
1.) Is it truly unsafe to keep shooting factory ammo in this gun? Personally I don't think so.
2.). If I reload, and only bump the shoulder back 0.002" from 2.055", this to me now brings the tolerance of "case to chamber" well within the acceptable limit of any commercial cartridge. I don't see anything wrong with this approach and will dedicate a string of brass to this gun only. It's a hunting gun, so round count will be <20 per year. Also I see this as no different then those who fire form brass for 30-06 variations like the 30-06 AI or 30 Gibbs, and blow the necks out. Am I wrong here?
Seems to me the previous owner may have inadvertently created a wildcat when they swapped out the bolt. Maybe this will work to my advantage for more powder capacity.

It just doesn't make financial sense for me to have a gunsmith set the barrel back at this time, in order to shorten the headspace. Also I am not very optimistic I could find a replacement bolt to correct the problem.

Another other suggestions?

Thanks.

I had the same problem when I bumped the shoulder too much ! Complete separation due to incorrect headspace! You only need to bump the thickness of a dollar bill !