Let’s talk custom M70’s

[nksmfamjp]

I love the M70. It is a classic CRF, but improved from the WWI Mauser lockwork. I realize some may argue that point. It is a bit heavier, but a heavy action is ok to me. Makes for an easier to carry rifle. It has a usable trigger mount, but it seems like most venders prefer the Remington form factor…..that said, everything is better than Savage!

Then there is the stock. To me the M70 stock lines are the best in the business for hunting. Sure there are so many custom stock makers that does this matter??

Going back to the action….does the M70, in your experience, handle pressure worse? I ask because my case growth seems excessive. I have to FL size it -0.003"-0.004" to get it to chamber freely vs 0.002" in my Savage, Hart or Zermatt. Is it just not handling the pressure well? Maybe it is just that it needs tru'd. My gunsmith said he checks them and it didn't need tru'd. Could it be something else?

I think the ultimate question to me here is do I spend money getting this tru'd and rebarrelled to make it a better shooter someday or just live with it as average until I burn this barrel out and then scrap it….

 

[flyguy1]

This was a pretty nice M70, but shot out (.223 Varmint). Came back like this. Go for it. Even with Hornady American shoots great. Handloads in progress. Brux 1:8

 

[nhenry]

This was a pretty nice M70, but shot out (.223 Varmint). Came back like this. Go for it. Even with Hornady American shoots great. Handloads in progress. Brux 1:8
View attachment 587235

God bless Paul.

To the OP's post, the headspace could be ever-so-slightly longer than normal. How does a fired case compare to a fresh, fully sized case?

 

[nwmnbowhunter]

I just had a model 70crf re-barreled to 7prc along with a defiance crf action with same 7prc reamer.

Same brass- powder- bullets

Model 70 pressured out over 1 grain less and 100fps less.

Custom actions are beasts compared to factory from my experience.

 

[HARPERC]

Going back to the action….does the M70, in your experience, handle pressure worse? I ask because my case growth seems excessive. I have to FL size it -0.003"-0.004" to get it to chamber freely vs 0.002" in my Savage, Hart or Zermatt. Is it just not handling the pressure well? Maybe it is just that it needs tru'd. My gunsmith said he checks them and it didn't need tru'd. Could it be something else?

I think the ultimate question to me here is do I spend money getting this tru'd and rebarrelled to make it a better shooter someday or just live with it as average until I burn this barrel out and then scrap it….

I have not seen issues with the several Model 70's I'm familiar with.

The one pictures is on its 3rd barrel (pre-war) 4th stock. .300 H&H, .358 AI, currently .338 RUM. Present stock McMillan Lazzeroni thumb hole. 500 yard chucks never a gimmee, but rifle holds up its end.

If primers are showing premature flattening, perhaps the firing pin hole needs bushing.

 

[MagnumManiac]

The only stock Model 70 I own, and the only wood/blued model, is a Super Grade limited run with really exquisite wood in 300WM. It feeds like butter, just like all of my others, but does feel slicker (as stock).I've only test fired it with 3 rounds.
All of my other Model 70's are blueprinted stainless models and have been made into switch barrels.
I find the coned breech to show excessive pressure as 2 things, first the web will swell and, secondly the primer pockets will loosen and the first sign is cratered primers across the board. I don't see this manifest itself in Remingtons, Kimber or Mauser actions.
I like the stocks shape and form, especially the shadow line cheek piece, but I have wood stocked Kimber 8400/84M that negate the cheek piece but are better feeling because of straight style of the stock and lees drop at heel.
A custom blueprinted model 70 action is one of the slickest actions you can have, the magnum length action is one of the best out there.

Cheers.

 

[nksmfamjp]

God bless Paul.

To the OP's post, the headspace could be ever-so-slightly longer than normal. How does a fired case compare to a fresh, fully sized case?

-0.003 to -0.004"

No idea on fully sized. Whidden dies….the will under size.

 

[nhenry]

-0.003 to -0.004"

Your chamber is probably just a little deeper than typical is what my guess is.

 

[nksmfamjp]

Your chamber is probably just a little deeper than typical is what my guess is.

I guess my point is starting sized to -0.003". Firing it makes it long enough to make the bolt hard to close. Easy closing is accomplished when sizing back 0.003".

On most guns IME, that number is 0.0015-0.002"….just wondering why….why would chamber cut affect that?

 

[nhenry]

I guess my point is starting sized to -0.003". Firing it makes it long enough to make the bolt hard to close. Easy closing is accomplished when sizing back 0.003".

On most guns IME, that number is 0.0015-0.002"….just wondering why….why would chamber cut affect that?

I guess I understood wrong and I apologize. My bad on that one.

 

[Short Case]

This is my Winchester model 70 short action 6.5/270 WSM, I'm probably go to put it up for sale
on Long Range Hunting. I'm thinking about building a 6.5 LRM on the model 70 long action.

 

[tim_w]

Length growth is typically chamber head space spec to case head clearance unless you have lug setback. Diameter growth with symptoms of stuck cases diameter larger than actual chamber dimension is more indicative of whoop strength of the action at the tenon and the tenon thread diameter with highers pressures as well.

But are you sure the issue is case length to chambering itself? A case not chambering from length should not be from a longer chamber headspace dimension. It would just make the case growth more from virgin. But to grow past the chamber length would require serious pressure or something damaged. This assumes you are FL sizing your cases a spec amount vs the actual zero case head clearance size.

Have you stripped your bolt and setup a zero clearance calibration case? It's the only way to really know what your setting your case clearance relative to the chamber. Then setup a dummy case with a 0.002 clearance to be able to zero any comparator for that chamber.

Then compare that case comparator length to a fresh fired case with primer removed(not run up even partially in any fl/body sizing die as I will squeeze the sides increasing length.

 

[ARlife4me]

having 2 in the same cartridge (264wm) as 1 being a pre and the other being post 64's, the post (haven't measured yet) doesn't have the same throat to handle the pre64 loads i've used for 40 years (140sbt, 61.3gr of imr4831, .5 over sierra #5 manual). could possibly be same pressure, but will require seating and powder adjustments. after more than 2,500 rounds thru the pre i'm sure the throat is way longer than it used to be. no way for me to give chamber info as i never kept any, only shot the same. i could check against old loads (coal differences if any) on what jump would be on the same bullet.

 

[tim_w]

First I would try the coloring the entire case with a sharpie and try to chamber it. See where the wear is. It very well maybe on the side walls near the shoulder joint.

If it is truly length you first need to establish your actual chamber Zero case head clearance measurement.

Take 4 fired cases, to be safe, from the rifle you have issues with. With a sharpie number them 1-4. Deprime them but use a decanting die not your fl die. Do not run it into the fl size die even a little bit. It will squeeze tge walls and lengthen the body. Setup your caliper on your comparator and zero the caliper on the comparator. Measure each 4 fired deprimed cases and record the measurements.

Strip your bolt. You can leave the extractor just slip the case rim under it. If it has a ejector on the bolt you need to pull that. Now unscrew the fl die some so you're sure it will not touch the shoulder of the case to start with.

Start with only case #1. Slowly screw in the die, run case 1 in and test fit the case in the chamber. Continue that sequence screwing the die in a bit at a time and test chamber it, stopping where the bolt handle has any resistance.

As it starts to get close to fully closing only set the die to bump shoulder 0.001 more per time. Continue till the bolt handle will drop freely closed or just at the very bottom the very slightest resistance. Take that measurement of the case with the comparator record that measure. That is your zero case head clearance measurement. Label it as such. For now set that case aside.

Do the same to the #2 case. Check the measurement is the same to the thou and try in the chamber. If they both match up and chamber freely you have your case's zero head clearance measurement. Keep #1 as a dummy zero head clearance case; label it with a sharpie. Set

Take the 2nd sized case and bump the shoulder back exactly 0.002 further. Tighten down the die's the locking ring now. This is your final case size for your reloads. Keep it also as a calibration dummy case you can use with any comparator device to set your fl die for this specific chamber (This does not concerned neck size).

With your #1 case in your comparator zero your caliper. Now measure the fired deprimed cases # 3 & 4. Is the measurement on the zeroed caliper a + or - number? If it's + you are getting case growth exceeding the at rest chamber headspace length. High pressure load or another possibility is a defect like uneven bolt lug to reciever contact can cause this. The normal pressue is enough to get increased contact as the lug flex which would give more head space for the case to expand.

Hopefully it's a - number or it's simply an overpressure if it's a +. Otherwise off to a competent highly rated gunsmith to check out and possibly blueprint the action.

Otherwise if it checks out you now have case #2 as your dummy calibration case to get exactly 0.002 head clearance on your cases. Thus gets you minimum case length growth and sizing yet enough clearance to allow the bullet to self center.

Always keep your cases in the same lots with tge same number of firings and the same loads used. They can effect how the cases size. Never just rely on the die setting expecting the case to size the same. As long as they are jept in lots like that you just need to measure obe ir two to confirm by first zeroing on your dummy case. Adj die accordingly.