firmer bolt closing with reloads?

[TXbaldhunter]

Here is a post I made on the same problem.It is my understanding that when dies are made,they start with a slightly oversized reamer and use it until it wears down to undersized.If your rifles chamber is tight and the die is oversized,it makes a bad combination.If your die leans toward the undersized,the brass is sized just a little smaller and may give you that perfect fit.I have only had this happen to me one time.I got lucky.The next set of dies gave me that perfect fit.

Tight Chamber
I picked up a 7mag recently in a trade.It has a supposedly a Douglas stainless barrel.I'm fairly certain the barrel never had a round fired through it,if it did ,someone did a darn good job cleaning it.When I chamber a round,I get a lite smear on my head stamp.I readjusted my full length RCBS die down an extra 1/4 turn and it seemed to help a little,but it's still a snug fit.I took the rifle out and fired a dozen test loads through it and it shot very well and I had no problems opening the bolt.I full length sized some of the brass I shot through it.The brass seemed to chamber a little easier,but it already had the lite headstamp smear.What can I do for this?

I just got a new to me older RCBS die set.Set the die up the same way as my other die was set,now the problem is gone.Brass chambers with no problem.I never had any problems with my other 7mag using the other die set,just this rifle.

I set the newly acquired die at 1/4 turn as per directions from RCBS and the brass chambers perfectly.I rechecked my older RCBS die and reset it at a 1/4 turn,resized some brass and it has very lite resistance when resizing the once fired brass.The newly acquired die has noticeably more resistance when resizing the brass even when resizing the brass that was previously run through the older die.The chamber may be tighter on this rifle than my other 7mag,but there definitely is a noticeable difference between the two dies.

Re: Tight Chamber
With Magnums that head space on the belt it does not matter much as far as safety goes if you push the shoulder back a bit as it just blows forward again .
As far as accuracy goes it is better to have minmum blow forward . However one die could be getting closer to the belt than the other or one die is a better match to the chamber diameter or taper than the other . Clean the chamber and leave it dry of any oil . Take a tight case and polish it up with fine steel wool really shinny and then chamber it a few times . Then inspect the surfaces for chambering marks . That may give you an idea of where it is tight .
Marker pen can work also.
Don't forget to re-oil the chamber and bore after .

OK,I shined up a case sized with each die.The older die shows two faint rings around the slope of the shoulder and a tool mark about 1/32 x 1/8 inch down the slope of the shoulder that was most likely caused by the reamer.The newly acquired die appears to be bumping the shoulder back just enough that the two rings around the shoulder are gone but the tool mark is still present.The tool mark does not seem to affect anything,but I was definitely getting too tight of a fit with my older die set.

Re: Tight Chamber
Is the tool mark in the die or the guns chamber ?
Now try a tight unsized and polished case in the guns chamber and see where it is tight in the chamber . Compare that to the cases run through the dies.
Might give you an idea of where it is sticking in the chamber and if the dies are missing that spot.

Yes the tool mark is in the chamber because it appears on the case using either die.The case run through the older die showed rings from the chamber on the shoulder.Shined up the case again,then the same case was run through the newly acquired die,those rings on the shoulder disappeared,but the tool mark was still there.

 

[Oldtrader3]

Reloading dies are 7/8-14 thread pitch. Every 1/4 turn of the die, you are moving the shoulder datum back .018 inches. This is too much forming and working of the case datum in the chamber one direction and in the resizing die another direction. Case life will be shorter. I try to set my FL resizer die to move the shoulder datum back and forth .002/.003 for long case life and not more than that. However, you have to have a gauge to determine and measure that small movement.

 

[kraky]

Oldtrader is on the money ruling out the 1/4 turn...its way too much. Take a marker and make matching marks on the thread of your die right above a matching mark on the lockring...move them about 1/4" apart and you will have made about a. 004" change to head space.
If you like reloading please please please spend $35 on a hornady headspace bushing kit. You won't regret it!

 

[Waldo]

Problem appears to be solved, prepped another 20 rounds today and all fed through the rifle nicely. Only conclusion I can come up with was last time (first time loading a big shouldered round) I must have been a bit inconsistent on the lever as I sized them. This time I focused on consistent heavy pressure on the lever and it seems to have worked
Cheers,
Waldo

 

[cloverleaf]

OT3 sounds like hes on the right track and certainly knows more than I. My eperience tends to confirm the basic premise.
I had a dickens of a time with mt FN mauser and a similar problem. Then one day I took a round that had been difficlt to chamber, dropped it in again, and it slid right in. Tried it a few more times with varying results. Finally marked the barrel of the case as I put it in and then chambered it several more times giving it a quarter turn each time. Eventually was able to deciude that there was a High spot so to speak that made it tight chambering. Lots of trial and error and I finally came up with the therot that the bolt face wasnt flat or square with the chamber.
So the theroy goes like this: When the round is fired the base of the case expands to flat against the bolt. When that same case is re-sized, the base is no longer at a perfect right angle to the wall of the case. The sizing die dosent "straighten" that out. So... as the round chambers, sometimes the case matces up with the bolt and sometimes it is 1/2 turn (more or less) opposed. That measns that the case is too long for that spot on the bolt face and so it is hard to close.
I turned the sizing die down until the case would fit all the time. Thats hard on the brass, so also had the bolt faced "flattened out". If you look at some of the mausers you willl see the bolt face is not flat or level. If you cold accurately measure from the datum line to the bottom of the case all the way around the circumfirance you could get some idea of how "square" the base is to the center line of the case.
Again this was particular to my rifle- and I could be wrong- but the symptoms presented were similar. Some body correct me if I'm way off base here. CL

 

[Oldtrader3]

CL, I absolutely agree that sometimes the bolt face is not machined square to the chamber datum or even the reamer pilot can be off concentrically a little and cause all sorts of issues. That is why I finally bought a gauge so that I can check these things out. We take it for granted that the machinist will setup the action square and check runout but they don't always.