Extraction difficulty

[Varmint Hunter]

I am working with a Rem 700 LSS w/ 27" Broughton 5C bbl in 300 RUM. I use Federal Premium brass and Fed GM215M primers. All brass is resized using Redding S type bushing dies. I have the dies set up to push the shoulders back about .002". Reloaded ammo chambers easily.

Here is the problem:

Working with a variety of bullets 190gr - 210gr @ velocities of 2,900--3,000 ft/sec cause slight difficulty in extraction. Bolt lift is a little tight (often with an audible click) and rearward pull starts out tight. Moving up to a 220gr bullet @ 3,000 ft/sec will cause a stuck case that can be lightly tapped out with a cleaning rod. Cases show no signs of excess pressure, primers are normal. I tried Rem brass just as a test but had similar results.

I have used H4831, RE25, H1000, Retumbo & H869, all with similar results. These are all well under a maximum load for the 300 RUM. For whatever it's worth, preferred loads are shooting in the .3's.

What is causing the sticky cases?

 

[AJ Peacock]

Couple questions, are you seating your bullets against the lands (or with a very minimal jump?). This can dramatically raise pressures.

1) Heavy bolt lift is a sign of high pressure.

2) A rough chamber can cause stuck cases.

3000fps for a 220gr bullet is likely too much of a good thing. This is well above pressure limits according to Quickload, unless you have an extraordinarily long barrel.


AJ

 

[boomtube]

"What is causing the sticky cases?"

Excessive pressure. Back off.

Looking at primers is a really lousy way to check for over-pressure. It is a much better indicator of excessive headspace OR improper FL sizing which produces excessive headspace.

But, we can depend on sticky extraction. And you have it.

 

[Varmint Hunter]

Couple questions, are you seating your bullets against the lands (or with a very minimal jump?). This can dramatically raise pressures.
1) Heavy bolt lift is a sign of high pressure.
2) A rough chamber can cause stuck cases.
3000fps for a 220gr bullet is likely too much of a good thing. This is well above pressure limits according to Quickload, unless you have an extraordinarily long barrel.

AJ

RE:

1) I assumed that something other than pressure could be causing the problem. Pressure "should" be well within the normal range.

2) The rifle was just built by a reputable gunsmith so I'd hope this isn't the case. I'll try some new Federal brass and see if this condition happens with factory fresh brass. I had suspected that it was somehow related to the brass.

As to the 220gr bullets and 3,000 ft/sec - I just rechecked my reloading records. I mis-stated the velocity of this particular bullet. The actual velocity of the 220's was 2,900, not 3,000 as posted. However, I took a quick look at a few loading manuals and found several loads that produced 3,000 ft/sec with a 220gr bullet, give or take a few ft/sec.

Boomtube

Is excessive pressure the ONLY thing that can cause sticky extraction?

 

[bailey1474]

Pressure may be the issue but I don't think your velocities seem to high.

Check your fired brass and see if it is round. Maybe the chamber is not perfectly round. I've seen and egged chamber on a factory Savage 22-250 that had the same problems.

 

[Buffalobob]

The rifle was just built by a reputable gunsmith

That's the problem. You paid him to do a good job and he did a good job.

The chamber may be too smooth and the case sidewalls aren't gripping. The case is slamming back against the bolt face harder than it should and then expands out and sticks. Everything is now stuck. Think of it as shooting with some lube in the chamber. Pressure "indicators" may go away as it gets dirty and there is something for the case sidewalls to get a grip on. At least I hope so, being as I have a new chamber giving me the same kind of grief.

 

[Varmint Hunter]

That's the problem. You paid him to do a good job and he did a good job.
The chamber may be too smooth and the case sidewalls aren't gripping. The case is slamming back against the bolt face harder than it should and then expands out and sticks. Everything is now stuck. Think of it as shooting with some lube in the chamber. Pressure "indicators" may go away as it gets dirty and there is something for the case sidewalls to get a grip on. At least I hope so, being as I have a new chamber giving me the same kind of grief.

I'll take extra care in making sure the chamber is clean & dry before I try the same loads in new, unfired brass. I always use a delrin cleaning rod guide (with a tight fitting O ring) and wipe the chamber out when done but who knows?

Fired brass looks and measures fine, at least as best as I can determine. Shoulders move forward .001"-.002" from the dimensions of a new Federal case but I haven't rechecked cases that were fired a few times.

"The more you know - the more you know you don't know"

 

[3006savage]

Inspect the brass and try to determine if the brass has spots that indicate wear or scratching. The chamber may need to be lapped. I had a buddy that had to lap the chamber. He took a case and threaded the primer pocket and attached a variable speed drill. He used a gel lapping compound and "slowly lightly" lapped it in and it fed great after that.

 

[boomtube]

"Boomtube - Is excessive pressure the ONLY thing that can cause sticky extraction?"

IF I understand your problem, yes. The "sticky" only occurs after firing, your new cartridges chamber and extract easily if unfired, right? If so, everything that happened in firing is pressure related, including spitting a bullet out.

When the pressure is too high, the case AND the CHAMBER are both overly expanded. The over expanded brass case springs back less than the steel chamber, so the case gets lightly gripped by the contracting chamber and you get sticky extraction. That takes a LOT of chamber pressure! In my opinion, your action is doing a GOOD job holding together now but don't keep it up or it may give out on you. Violently!

A too smooth chamber and/or residual case lube will certainly increase thrust against the bolt and that may eventually damage the bolt lugs or seats. But, I can see no way that bolt thrust can, of itself, cause sticky case extraction from a mauser type front-locking action.

Some people have stated (on the net) that velocity will, or can, increase suddenly and significantly when pressures reach dangerous levels. THAT'S NOT SO! High chamber pressures usually skyrocket unpredictabily with very little increase, if any, in velocity. Especially with heavy for caliber bullets!

Don't try to understand chamber pressure by any chronograph results, your cases are telling you all you really need to know at this point!