Just a question about possible overpressure

[std7mag]

Ummmm, i don't believe so...

When firing the pressure acts equally in all directions. The only place for the brass to flow (under normal circumstances) is towards the case mouth, while in the chamber.
If it got shorter from head of case to mouth there would never be a need to trim.

Only way i know for the case to actually get shorter is for greater space than normal around the case body in the chamber, or moving the shoulder forward.
Or both.

Sure we aren't dealing with an Ackley Improved?

 

[cw308]

Bart B
I'm getting to feel this is more of a test . When I measure a case in my mic. it's base to shoulder . Like I posted before , I have my trimmer set to trim my cases to.2.010 so I stopped measuring base to mouth . I feel I covered all the bases by now and answered your questions to the of my ability .

Chris

 

[cw308]

std7
When I sent my rifle out for rebarrel it came with a card listing the reamer , 308 Match Tactical , Headspace .0015 The rifle has shot very well for me ,

 

[Bart B.]

Std7mag,

All of my bottleneck case lengths shorten a couple thousandths when fired. Their body and neck diameters increase almost the same. When fired, their head is a couple thousandths off the bolt face and shoulder is hard against the chamber shoulder.

When full length sized, they lengthen about three thousandths and the diameters go down a couple thousandths. 308 Win case lengths grow about 8 thousandths across 10 such cycles.

Anyone ever measure case length and diameters after sizing then again after shooting before resizing? What's the cartridge and numbers?

Ever measure how much more case length is while full into a bottleneck FL die compared to after it's out? FL die chambers are smaller than barrel chambers, both diameters and headspace.

What's the normal clearance from case to chamber?

 

[Don Fischer]

Well did you back off the powder from where this hard bolt lift came from? What then? How about when you chamber a loaded round, any drag closing the bolt? If so my though would be your seating the bullet's into the lands and jacking up pressure. Chamber a round and take it back out and inspect around the ogive carefully. If the bullet is touching there will be small scratch's around the ogive. And that will jump pressure on you. Do you get any extractor mark on the case's?

 

[44 AMP]

Nube,
If this happens again, be sure to separate the fired cases with hard bolt lift from the rest of the brass. Then you can measure them and see if there is anything significantly different about them (length, or case head expansion, or case neck thickness, etc) that would account for the hard bolt lift.

if you are seating the bullets so the round is at or below SAAMI listed max length, you won't be into the rifling.

 

[HiBC]

Just to confuse the thread.... Temperature can have an effect on pressure.
Dwell time in a warm/hot chamber,maybe?

Just something to think about. Any difference in how the case head,primer,etc looks after the hard bolt lift?
Next time,sort the hard lift brass out. Make note of temp,dwell time in chamber,etc to ID "What was different?"

If you have a chronograph,shoot 20 rds or so through t,and compare velocity.

It might indeed be some length issue,but I'd not go tunnel vision

 

[cw308]

Nube
It seems after asking you a few questions your post got hi jacked , sorry for that . It sounds you may have a tight chamber , not that bad . You may have to clean more often . Years back a shooting friend had a Remington M24 the chamber was so tight he had to give a quick pass with his cleaning rod and patch after 5 shots or the fouling caused a hard lift but it was a tack driver . You may have a chamber like that , does the hard lift happen after it has been fired a number of rounds.

 

[GeauxTide]

Mixed Brass

Every manufacturer is a little different. I suspect that the bolt lift is caused by long cases. I NEVER mix cases in load development. The 22-250 is a tack driver with proper loads. My friend regularly dispatches Prairie Dogs at 300+, so his 100 yard groups are less than 1/2".

 

[Nube]

I think that I have found the problem, I trimmed the cases to 1.912 and after further examination I found that some of the cases had “stretched” a little more than some of the others. I think that this was the problem with the heavy bolt lift. I have loaded some with the cases all being just a little shorter and they all worked fine. I do appreciate all of the replies, even the replies that are too involved for this new reloader! I think that I can always learn something from almost any discussion.

 

[jetinteriorguy]

Do you trim before sizing? If so, size first then trim.

 

[cw308]

Nube
On a 22-250 the maximum trim length is 1.912 to 1.892 so a good safe trim to keep your case length after sizing would be 1.902 . I shoot only one rifle a Rem 700 308 , I have my trimmer set at a certain measurement and after my cases are cleaned an sized , every case is trimmed on every firing , most of the time it's more of a cleanup then a trim . Just one thing I don't worry about cases getting too long . No short cuts in reloading . I wet tumble so I'll go through my way of prepping my fired cases .
First I pop the primers in a Universal decapper die , wet tumble , after the cases are dry I lube and size , wet tumble to remove any lube . Trim all my cases to a set measurement , chamfer inside and out on the case mouth and prim the case . To make seating the bullet smoother I have a smaller cleaning brush wrapped with 0000 steel wool locked in my drill press , a few up and down passes in the neck to polish not ot remove any brass , clean out any dust and when seating the bullet I dip the base of the bullet in Redding Imperial Dry Lube , comes in a little jar with beads that are coated with the dry lube . Makes seating as smooth as silk without decreasing neck tension . I only load 30 at a time for benchrest shooting , if your loading quantity it's a different story , maybe too time consuming but worth a try. Hope I Helped in some way

Chris

 

[zeke]

Reloading manuals are always a good place to look for the max and trim to brass length. Rarely are trimmers accurate/consistent to .001, so maybe good idea to trim to the minimum/trim to length. Hornady manual lists 1.912 as max case lenght, and 1.902 as the case trim length.

Good to trim your cases after resizing, especially if using the expanding plug in sizing die.