Stiff bolt question

B

bacova

New member
I'm working up a Deer load for my brother's 6mm Rem model 788. Today I was testing loads with 100 gr Sierras and I noticed the bolt was a little stiff when ejecting the spent brass. Nothing terrible, just requires a little more effort than I think it should. This occured with every charge weight, all the way from min to almost max. The rifle was shooting fine, 6 shot groups from 1.223" all the way down to 0.873".

There was absolutely no high pressure signs on any of the brass, which I wouldn't really expect because I noticed the stiffness at even minimum published charge weight. I'm racking my brain trying to figure what's causing this. All I can come up with is that maybe I need to bump the shoulder back a couple .000s. That maybe I have it tight against the chamber and since the brass can't expand forward it's expanding sideways, swelling the case outward and making the brass stick slightly in the chamber. Does this sound reasonable? Or does anyone have another explanation?

Again, I reiterate, the bolt isn't stuck or extremely hard to raise, it's just stiffer than I think it should be. Unfortunately I don't have any factory 6mm ammo to compare it to.

Oh, one other thing, this was only the second firing of the brass. It was new, unfired Win brass last week. I loaded it up and fired it a few days ago and didn't notice any stiffness. Today was it's first time as fireformed brass.

Thanks, Bacova.
 
Good Question
I'm not an expert but if it were the cartridge shoulder, it should be tighter/harder to close the bolt, not open and eject.

I'd, at least, start by cleaning the chamber as best as possible. And I'm hesident to recommend any lubrication after cleaning.
 
The loads are fine. The stiffness is being caused by the cocking action. Dry fire the rifle and see if you get the same results on opening.
 
What cajun said, also check cartridge overall length to make sure the neck isnt too long and going past the throat and into the lands. You may not see any pressure signs on the outside but feel the pressure ring on the inside of the case towards the case head with a feeler gauge and see how deep it is. this is often overlooked by many experienced reloaders and is a sign of pressure, in fact its a sign of case / head seperation!! what brand of brass are you using?
 
Thanks for the input guys. I believe I'll have to go with what Randy says. When I dry fire the gun the bolt is definitely tighter afterwards. I'd never tried that. It's 3 AM here and I have to go to work now, but when I get home I'm going to see if I can figure out why this occurs. It doesn't happen in a Ruger M77 I have here, or in my A-Bolt, but it definitely happens in the 788.

Oops, I believe I'll have to ammend the previous statement. I CAN see a difference in tightness in the A-Bolt after dry firing. Not as noticable as the 788, but it happens.
 
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If your neck is long enough to go "passed the throat and into the lands" you are in deep trouble. Where in the hell does this kind of BS originate?
 
If you are neck sizing, you may need to bump the shoulder back around 2 thousandths to get it to stop. My 6.5-284 does the same thing after only 1 to 2 firings. I dont have any experience with the 6mm but you may want to try it.
 
It's true about the cocking action...

I would also add this: The main issue with the 788's chambering tightly, and with hard bolt lift, is the rear lug design. That causes more bolt compression on firing than you get with forward locking lugs.

When the bolt compresses, the case stretches. The bolt flexes back, but the case does not always.

788's are hard on brass because of this. It is best to use new brass, and fire it no more the a half dozen times MAX. I toss my 788 cases for my .243 after three firings. (Mainly because I've seen accuracy fall off noteably after the third loading). You might get more firings from other chamberings, I don't know... The .308 seems a bit better in this regard.

You'll want to screw the sizing die down an extra 1/16 of a turn, in graduating increments, until you get a setting on the die which allows the empty case to chamber very easily. When you fire the cartridge, if the brass is fairly new, it will spring back and you won't get the hard lift. If the brass is work hardened, that's where the hard bolt lift can come from--especially on the 788 with the rear lug design.

When sizing the cases... you might think that the sizing die is bottomed out against the shell holder, but the press linkage will spring a bit under the load of sizing the case. Put a flashlight behind the die base/shell holder junction (with a case in the sizing die, ram all the way up) and see if there's a gap there. If there is a gap of light, that's showing you that the die can still be screwed in a little more which will give you an extra little bit of shoulder bump.

The next time you hear someone speak of Remington 788 bolt handles being weak and breaking off, remember all of this. These rifles got that reputation not necessarily from any weakness in the bolt handle itself (though they are somewhat weaker than other designs), but rather from improper sizing which causes hard bolt lift on extraction, and even on insertion if the cases are really too long. I've seen guys break into a sweat trying to chamber cartridges insufficiently sized, as they force that bolt closed on the cartridge. This is never a good idea, but with a 788 it's a downright terrible idea. There's where you'll find the broken bolt handles...

I don't neck size cases for 788's. I always just give them the FL sizing and replace them every three firings and all seems to work fine. My Douglas barreled 788 in .243 win is probably the most accurate rifle I own. It'll shoot sub 1/2 MOA day in, day out, oftentimes even when I don't do my part. /ubbthreads/images/graemlins/smile.gif So you can get awesome accuracy from FL sized cases. Winchester and Remington .243 brass is cheap enough...

Dan
 
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Thanks for the input guys. I believe I'll have to go with what Randy says. When I dry fire the gun the bolt is definitely tighter afterwards. I'd never tried that. It's 3 AM here and I have to go to work now, but when I get home I'm going to see if I can figure out why this occurs. It doesn't happen in a Ruger M77 I have here, or in my A-Bolt, but it definitely happens in the 788.

Oops, I believe I'll have to ammend the previous statement. I CAN see a difference in tightness in the A-Bolt after dry firing. Not as noticable as the 788, but it happens.




It is all in the design and the smoothness of the bolt shroud along with the strengh of the firing spring . When you rotate the bolt, the bolt shroud does not rotate. This is what actually re-cocks the firing pin to the firing position. If you remove the bolt and look at the rear of the assembly, you will notice a little cut out V shape. inside this you will see some threads. As you close the bolt, the trigger mechanism will catch the firing pin and keep it held back in the V shaped cut. When the trigger is released, it allows the firing pin to drop into this V shape cutout and the gun goes boom(hopefully). As you lift the bolt, the V shape forces the firing pin back, compressing the spring and re-cocking the gun.

Out of all the bolt guns I have dealt with, the 788's are usually harder to re-[beeep] than others.

Randy


edit: Take a deep breath Eddie, it will be allright. Myths are hard to break /ubbthreads/images/graemlins/confused1.gif
 
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i had the same thing happen on a 7mm08 i had built.was using redding neck die.it was hell getting the bolt back.no pressure sighs what so ever.had to take the gun back to shilen.come to find out the redding die was not forming the shoulder right.they cut my shell holder down a little and it started shooting great.
 
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