Stiff opening bolt question

B

Bluefield

Guest
Gun is a Model 70 super grade in 357 H&H. Everything works nice and smooth until it is fired. Factory rounds used of 3 different brands.
Bolt handle is very stiff to open for first 1/4" lift then breaks loose. Not at the caming point were the root of the bolt handle hits the receiver. It is right at the beginning as the bolt starts to turn. Headspace gauges OK. Chamber is clean and polished. No screws intruding into bolt area. Locking lugs even. Only other thing I can think of, but can not see with out pulling barrel, is bolt lug set back into locking shoulders.

Comments?
 
Just had one in the shop the other day, turns out the chamber had a ring in it and the only way I found it was by making a chamber cast. One could not tell it was there without it. Owner also said it was "clean and polished".
 
Bluefield,

It could be the chamber is too polished. Try running some worn 320 grit paper in it or some scotch brite in it so the brass won't grab so hard. All you need is a good cross hatch finish. Hope it helps

Boe
 
OK, you guys have lost me :confused:

I've got several chambers with rings in them...... rings deep enough that brass polishes off on extraction and again upon resizing leaving a bright shiney ring on the case (certainly not hard to see/find) and in no case does the round tend to stick in the chamber from the ring. I've heard this one before but never seen it. It must take a perty steenkin' BIG ring!

And the op says his stickage occurs down at the root, long before the primary extraction cam engages. Long before the EXTRACTOR engages for that matter......

Now, unless the op is shooting very light loads for some reason the casehead should be bearing on the boltface at this point........ there should BE no extraction action going on! I can't imagine any way the M70 extractor could touch the rim in the first 1/4 turn.

So, I'm confused by the answers so far....... maybe someone can set me straight.

Concerning the problem:

Does greasing the lugs change the feel?

How about greasing the cocking ramp?

If greasing these places (separately) changes NOTHING, then we need to move to another area.

please post results...

al
 
Most likely lug set back. Long model 70s suffer from this because there is very little metal left behind the lower lug when they are opened for the H&H cartridges. It will most likely be the bottom lug also since its the one taking to load without sufficient meat behind it. I've fixed two with this very problem, you would have to disassemble and trim the lug seats and re index and head space the barrel. It is also a good idea to have it hardness checked although I've seen good ones have set back that checked out fine. What I did was sleeve the back of the bolt so the top lug stays seated and shares some of the load don't know if it really helps but sure can't hurt.
 
Thank you for the reply's so far. Chamber is not too highly polished. Just tried to make the point that is is not pitted or has major machine marks. I thought about a ring in the chamber and doing a cast. But why the hard lift right at the start? The bolt is only turning behind the case. No primary extraction is taking place. Unless the case is pressing back hard on the bolt and is locked by the ring from springing forward a few thou. I am leaning to the indented lower lug. You are right, ndh78, in that that lower lug does not have much metal behind it. Alinwa, I did grease the lugs and cocking ramp. No change. If I take a fired case and put it back in the chamber it is again hard to lift the bolt. Perplexing.
 
Is the bolt lift hard without firing the live round? Have you checked a fired case for runout? And does the rear of the brass where it meets the bolt face look like the bolt is turning without turning the case?

Boe
 
Just had a 6 BR barrel cut off and rechambered because of hard bolt lift and extraction with any loads. The bolt lifted hard from the very start as well. The smith who did the rechambering said that there was a groove in the original chamber at the body/shoulder junction. The new chamber gives normal bolt lift and extraction.

This chamber may well be okay and the problem being a setback lower lug abutment for the reasons given by others.
 
Could the chamber centerline and bolt centerline be in different planes (offset from one another)? Factory cartridge inserted into loose chamber, bolt cams into battery with no binding because of sufficient clearance in chamber. Cartridge is fired, case expands and centers in chamber. Cartridge casehead now pushes radially (sideways, up, down, etc...) on bolt, binding bolt until extraction cam pulls cartridge back far enough to eliminate the bind.
 
WSnyder said:
Could the chamber centerline and bolt centerline be in different planes (offset from one another)? Factory cartridge inserted into loose chamber, bolt cams into battery with no binding because of sufficient clearance in chamber. Cartridge is fired, case expands and centers in chamber. Cartridge casehead now pushes radially (sideways, up, down, etc...) on bolt, binding bolt until extraction cam pulls cartridge back far enough to eliminate the bind.
Click to expand...

I'm liking where this guy's going....... is this a push-feed or a pre-64?

I don't really like the lug setback idea as the tight 1/4 turn just doesn't work in my mental image and regardless adding/changing lube to the lugs should change the feel. The fact that it doesn't leads me to believe the bind is somewhere other than the lug surfaces.

al
 
Right there with you Al, your questions helped lead me to that line of thinking. I also was thinking of the recent custom action problems that have insufficient bolt to action clearance causing binding.

I suppose I should have said case/casehead instead of cartridge after the cartridge was fired in my above post.
 
Pre '64 push feed. Look like I will be pulling the barrel off this one to take a look.
 
Black marker on the rim diameter or reduce the rim diameter on a fired case by about 5 thou and try it. This will tell you if its an off center issue.
 
Look at the bolt, it's usually easy to see any spots where it is tight. Put bluing on the bolt lugs and see where it rubs off.
If you don't have any bluing a black magic marker will work. It's usually pretty apparent where ever there's a tight spot.
If it's as tight as you say, there will be evidence of it .
 
There's only a max of .150 of case head sticking into the bolt anyhow so why that would expand into the bolt and cause an eccentric situation that is so severe to cause hard bolt lift, I do not understand. I'm not sure where you guys are going with that.

Are the bolt lugs embossed into the receiver lugs? That would cause an engagement that you could feel immediately. Meaning, the receiver lugs shaped in such a way that when you attempt to open the bolt, the bolt actually moves forward toward the barrel before it opens (dropping off the lugs).

And I can't believe nobody has said, is it possible that all the factory ammo is just plain too hot for this gun? Factory ammo is hot anyhow, why would it be hard to imagine 3 diff brands all being hot?
 
When you get the barrel off, set the receiver into a milling machine vise and run a dial indicator up against the bolt face. Pull to the rear on the bolt while you open it and watch for forward movement on the bolt face with the dial indicator. Just a guess, but I'd bet that the bolt is camming forward when it tries to open making it work against the fired case. No case in the chamber, no problem as there's nothing there to push back against the lugs in the receiver. It will probably take setting up the receiver in the lathe and making truing cuts on the receiver lugs and of course reheadspacing the barrel. Set the barrel back a thread and you can clean up the chamber as well if it's needed. I've seen more actions the other way especially where the bolt was lapped in. These will usually show up as the bolt getting tighter and tighter on a go gage as the bolt closes completely.
 
If a lug has set back you can usually feel that with a stripped bolt and a cleaning rod pushed hard against the bolt face while you move the bolt handle up and down 'into' the set back.
 
Interesting developement.
I did the cleaning rod in the bore and pushed back on the bolt. I could feel no "hitch" when moving the bolt lugs against the locking shoulders. Blued both bolt lugs and they are making even contact. On a whim I took a fired case and put it in the chamber. As usual it caused the bolt to stick then pop loose. Took the same fired case and turned .015 off the rim. Case does not stick and bolt lifts normally. There may be misalignment of the chamber to the bolt face. So other than a new barrel, which is not an option since this is a collector super grade. M70, would opening up the bolt face .015 help? What could it hurt?
 
Bluefield said:
Took the same fired case and turned .015 off the rim. Case does not stick and bolt lifts normally. There may be misalignment of the chamber to the bolt face. So other than a new barrel, which is not an option since this is a collector super grade. M70, would opening up the bolt face .015 help? What could it hurt?
Click to expand...

That's what I'm talkin' about :)

I'd do exactly what you're suggesting. Meantime it should be showing some copper or scrubbing marks inside the bf right now.......

BTW, check the rounds to the bf outside the gun.

al
 
Tomorrow I will take a loaded round and cut .015 off the rim and fire it.
 
You must log in or register to reply here.
Back
Top