Gunsmithing Bolt lifts hard

[CountryBoy19]

Ok, so long story short.

I have a R700 that at one time had the bolt stuck. It wasn't stuck really bad, just enough that a good tap with a piece of wood broke it free. There is a light marring in the surface of the one bolt lug but it appears to be only visual. I've tried and cannot "feel" the marring. But it could be related so I'm mentioning it.

Anyways, moving on, a friend and I are doing some testing on brass life with different resizing and annealing combinations. We have been doing a lot of shooting, and as the gun heats up the bolt starts to get stiffer and stiffer until at some point you can no longer lift the bolt easily, and it actually has a noticeable "catch" to it.

There is obviously something going on in the bolt lug area, but I can't determine what. Is there any way to determine what is going on without removing the barrel? I don't have a barrel vise and the closest guy I know of that has one is a fellow hide member and smith that lives about an hour away from me. Any recommendations?

Is there a way to lap the lugs smooth without removing the barrel?

 

[ugsly]

Re: Bolt lifts hard

"I have a R700 that at one time had the bolt stuck"

How was it stuck? you couldn't lift the bolt? or did you get the bolt lifted and had to tap the bolt to the rear to get the brass to come out?

 

[CountryBoy19]

Re: Bolt lifts hard

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ugsly</div><div class="ubbcode-body">"I have a R700 that at one time had the bolt stuck"

How was it stuck? you couldn't lift the bolt? or did you get the bolt lifted and had to tap the bolt to the rear to get the brass to come out? </div></div>

Bolt wouldn't lift. Like the lugs were just "friction welded". After a tap with a piece of wood to break the lock, it lifted ok, not grinding but firm. It all resulted from a brain lapse where there was no lubrication applied to the lugs after it had been fully cleaned and degreased. Problem was quickly remedied and nothing ever came of it until now, 2k+ rounds later. Which makes me think it may not be related... but I'm not sure.

 

[former naval person]

Re: Bolt lifts hard

See if you can get a small mirror or such (dental mirrors work) into the bolt lug recess in the rifle. I had a small piece of cleaning rag do that to me. It stuck to the face of the recoil recess and became more and more contaminated as time went on. An AR10 chamber cleaner that has the attached wire brush that cleans the recesses on that action is ideal to clean it out. JMHO

 

[LRI]

Re: Bolt lifts hard

Don't forget to look at your cocking ramp too.

Seen many a M700 that'll start to gall there. Especially if it gets dry.

If you see "rubbage" pull the fire control out, burnish the ramp, and polish it on a soft felt wheel with red rouge.

Works great!

C.

 

[buffybuster]

Re: Bolt lifts hard

Keep the lugs lightly greased, disassemble the bolt body and striker assembly, grease the cocking ramp on the bolt body, lightly lube the striker spring, grease the threads on the striker assembly. Reassemble and dryfire a few dozen times.

 

[ArcticLight]

Re: Bolt lifts hard

I remember SKRanger had this issue - nothing to do with the bolt lugs, everything to do with the bolt cam...if that's what it is called...


What Dixon says:
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: C. Dixon</div><div class="ubbcode-body">Don't forget to look at your cocking ramp too.

Seen many a M700 that'll start to gall there. Especially if it gets dry.

If you see "rubbage" pull the fire control out, burnish the ramp, and polish it on a soft felt wheel with red rouge.

Works great!

C. </div></div>

 

[300sniper]

Re: Bolt lifts hard

how about the obvious, what's your chambering and what are your loads? it could be as simple as pushing things further than they should be pushed.

 

[CountryBoy19]

Re: Bolt lifts hard

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 300sniper</div><div class="ubbcode-body">how about the obvious, what's your chambering and what are your loads? it could be as simple as pushing things further than they should be pushed. </div></div>
.308

41 gr Varget pushing a 165 gr Midway bulk bullet... quite a ways off max...

 

[Bearwalk]

Re: Bolt lifts hard

You said you were experimenting with re-sizing and annealing and this caught my attention.

Check for bulges near the base of the case. I have had this happen to me. Tried eveything until I finally found the problem....the bulging was causing enough friction that opening the bolt was near impossible by hand.

 

[CountryBoy19]

Re: Bolt lifts hard

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bearwalk</div><div class="ubbcode-body">You said you were experimenting with re-sizing and annealing and this caught my attention.

Check for bulges near the base of the case. I have had this happen to me. Tried eveything until I finally found the problem....the bulging was causing enough friction that opening the bolt was near impossible by hand. </div></div>
Hmmm... never thought of that, I'll give it a look when I'm back at the range. I don't think there is any case bulging, but I'll check anything at this point.

One point of clarification on the cocking ramp issue. If it were a cocking ramp issue wouldn't it be present after any time when the firing pin was dropped? I just tried dropping the pin and cocking again, not a problem. The problem only surfaces after the gun is hot (admittedly hotter than it should be if I had a high quality target barrel), and it's only after a shot is fired. The bolt works smoothly up and down all the time up until a shot is fired and there is force back on the bolt from the expanded brass in the chamber.

I'll see if I can get the bolt disassembled. I don't have any tools to do it with.

 

[Greg Langelius *]

Re: Bolt lifts hard

A) Marring of the bolt engagement surfaces is likely a product of galling, which is itself likely a product of overpressure.

B) That galling needs to be polished out. I would get aggressive and apply some valve grinding compound to the rear face of the bolt lugs, then work the bolt handle up and down with a piece of fired brass in the chamber until a clearly noticable improvement appears in the engagement surfaces' finish.

This is probably not the most popular approach, and there is some validity to objections here. The process will (maybe not much, but definitely some) increase headspace. I can accommodate that because I handload; others may stick to factory ammo, and that may not be ideal after this process.

C) Galling is a clear indicator of user abuse. No two ways about this.

Bolt lugs should always wear a coat of lubricant grease to reduce this tendency, and hotloads always carry a price. That grease should be periodically removed religiously and replaced, grit is not an ally in this location.

This symptom of galling is one of those prices, but it's mainly also the only noticeable one. Cumulative metal fatigue is the silent issue, and carries a far more dangerous potential. Overpressure <span style="font-style: italic">always</span> adds risk and decreases functional lifespan; there is no free lunch here.

Greg

 

[Bearwalk]

Re: Bolt lifts hard

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: CountryBoy19</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bearwalk</div><div class="ubbcode-body">You said you were experimenting with re-sizing and annealing and this caught my attention.

Check for bulges near the base of the case. I have had this happen to me. Tried eveything until I finally found the problem....the bulging was causing enough friction that opening the bolt was near impossible by hand. </div></div>
Hmmm... never thought of that, I'll give it a look when I'm back at the range. I don't think there is any case bulging, but I'll check anything at this point.</div></div>



FYI, you won't be able to see or feel, you'll have to put a caliper on it, but at least it's a very easy check.

 

[drstieren]

Re: Bolt lifts hard

You have been "doing a lot of shooting...barrel heats up..."

As a suggestion, when your rifle is "room temperature" try chambering a cross section of your reloads. Is there any considerable difference? If so mark those that are rather tight. Shoot and see if it gets tighter.

Next, you mention getting the barrel quite hot...not warm. Was your ammo getting hotter than normal by sitting outside, in the trunk of your car in combination with high ambient temperatures?

Methinks you could be getting the receiver/barrel real hot, feeding it hot (temperature) ammo and with cartridge soak time you have an over pressure condition that is causing your bolt to cease in place.

 

[CountryBoy19]

Re: Bolt lifts hard

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Go Figure</div><div class="ubbcode-body">You have been "doing a lot of shooting...barrel heats up..."

As a suggestion, when your rifle is "room temperature" try chambering a cross section of your reloads. Is there any considerable difference? If so mark those that are rather tight. Shoot and see if it gets tighter.

Next, you mention getting the barrel quite hot...not warm. Was your ammo getting hotter than normal by sitting outside, in the trunk of your car in combination with high ambient temperatures?

Methinks you could be getting the receiver/barrel real hot, feeding it hot (temperature) ammo and with cartridge soak time you have an over pressure condition that is causing your bolt to cease in place. </div></div>

Chambering and firing even "hot" rounds when the gun is cool isn't a problem. I just shot some of my reloads this weekend. My loads right at published max and based upon the ladder test when I developed this load they are near max for this rifle. Not a single problem chambering and firing a few rounds.

But chambering and firing even medium rounds in a hot gun is where the problem surfaces. I don't think these rounds are having any pressure problems because we're loading 41 gr Varget (not temp sensitive) behind a 165 gr. bullet. The rounds are being loaded and fired immediately, and not left to sit in the chamber.

I did check the bolt and it appears fine. There does seem to be a little wear on the cocking ramp, but not anything major that I can see. I did lube it all up really good.

 

[colchester]

Re: Bolt lifts hard

Dont forget to lube the threads on the bolt shroud where they go into the back of the bolt body. You probably did this already just checking, mine felt a little sticky and this was the issue

 

[KHOOKS]

Re: Bolt lifts hard

Could it just be your getting the gun to hot for it's on good? Maybe a little more time between rounds fired with the bolt open to let it cool a bit.

 

[drstieren]

Re: Bolt lifts hard

OK, if there is no FOD in the chamber/lug abutment area and the bolt is functioning properly then I would have to place a bet on the front action screw heating up and interfering with the bolt operation.

Whatever you find out, let us know...this is a good one!

 

[CountryBoy19]

Re: Bolt lifts hard

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Go Figure</div><div class="ubbcode-body">OK, if there is no FOD in the chamber/lug abutment area and the bolt is functioning properly then I would have to place a bet on the front action screw heating up and interfering with the bolt operation.

Whatever you find out, let us know...this is a good one! </div></div>

Good thought, I'll have to check that out. If that is what is happening, the symptoms match exactly to what I would think would happen in that case.

 

[CountryBoy19]

Re: Bolt lifts hard

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: CountryBoy19</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Go Figure</div><div class="ubbcode-body">OK, if there is no FOD in the chamber/lug abutment area and the bolt is functioning properly then I would have to place a bet on the front action screw heating up and interfering with the bolt operation.

Whatever you find out, let us know...this is a good one! </div></div>

Good thought, I'll have to check that out. If that is what is happening, the symptoms match exactly to what I would think would happen in that case. </div></div>

Just to update this to keep everybody in the loop, and guessing WTH is going on.... there is not a single mark on the bolt that would indicate an action screw in interfering with the bolt once it heats up.

I shot a mixed 50 rounds string of handloads (hot) and FGMM this weekend fast enough to get the can hot enough I couldn't touch it for a while. Not a single symptom showed up.

I plan to do more brass testing sometime in the next few weeks before I deploy. I'll bump this and update whether or not I encounter bolt lift problems at that time.

 

[gmbjr]

Re: Bolt lifts hard

I chased this same exact problem for weeks with all kinds of load variations and it turned out to be exactly what Go Figure has suggested. I even stuck the bolt once. When you pull the trigger, the brass expands to fit the chamber and squares up the bolt which can drive the bottom lug into the action screw if the screw is just a hair to long. If the screw is keeping the bolt from properly aligning at ignition, you get a lot of weird stuff going on with the lugs etc. Pressure from the ejector keeps everything a little out of whack up until you pull the trigger. Thats why the BR guys used to pull out the ejectors on their 700 actions. If your front action screw is sticking out at all, file it down and see if you problem isn't gone.