Problem chambering 300 win

[Mr45auto]

Okay, here's the problem. I am running pulldown MK248 brass. I run it through my size die ( FL Hornady ) It is then loaded with a Sierra 190 SMK. Some of the rounds will not chamber. I measured the cases and they are no longer than the ones that fit. I pulled the bullets on the ones that did not fit and the brass will chamber just fine. I reloaded the round with a different 190 SMK. Same results. If I ridiculously shorten the OAL the round will chamber. I measured the diameter across the case neck with and without a bullet and it's no larger in diameter than ones that do fit.

It acts as if the bullet is being rammed into the rifling. I have not experienced this with the 208 AMAX bullets and the same cases. Is there an inconsistent ogive with the SMKs? Does this have to do with the Hornady seating die? I think my next step will be to pull one of the offending rounds and seat an AMAX and see if it jams up again.

I could use a little help here guys. I'm officially lost.

 

[GIXXER2000]

How far back are you seating the bullet? How many times has the brass been fired?

 

[Mr45auto]

How far back are you seating the bullet? How many times has the brass been fired?

I will check OAL. Virgin pulldown brass. This problem only occurs in about 3 of 50 rounds loaded.

I loaded length to where it was putting out the best groups.

3.450 is where I'm at with most fitting the chamber fine. I know it's in excess of the SAAMI 3.340 but I find it odd that most fit and a few here and there dont.

I am loading this to A191 level and found that seating longer gave the best accuracy. I'm not sure what shortening it up will do to pressures either.

 

[GIXXER2000]

What are you using to get the OAL? I am using the HORNADY lock-n-load O.A.L gauge. In my AI I seat 190 SMK 10 off the lands for a small jump.

 

[Shoottothrill]

Sounds like you may need to bump the shoulder back .002? Have you measured your rifles chamber, and then also measured a 1x fired round, or are you just reloading this brass for the first time and it's never been fired in your rifle before? It's either that or your right you are hitting the lands and if you seat your bullet a few thousand deeper the problem may go away. Sounds like your real close to having them all work.

 

[Mr45auto]

What are you using to get the OAL? I am using the HORNADY lock-n-load O.A.L gauge. In my AI I seat 190 SMK 10 off the lands for a small jump.

Standard dial caliper. I know SMKs are all over on length but I believe the dies seat on the ogive so would they not chamber the same regardless of the OAL of the bullet?

 

[Mr45auto]

Sounds like you may need to bump the shoulder back .002? Have you measured your rifles chamber, and then also measured a 1x fired round, or are you just reloading this brass for the first time and it's never been fired in your rifle before? It's either that or your right you are hitting the lands and if you seat your bullet a few thousand deeper the problem may go away. Sounds like your real close to having them all work.

I've even set the dies to cam over with the same problem. It's just odd that those cases wont chamber even when I put a different bullet in the mix. I suppose it could be coincidence. It just seems odd and it's damned frustrating.

At this point I'm most likely to abandon the most accurate length and seat to SAAMI length and rework for pressure. The whole think kind of sucks.

 

[jrpilot]

How about measuring the necks? Could a few be to tight in the neck dia.

 

[dauntedfuture]

Are you getting any marks on the bullets from the ones that don't want to chamber? Depending on the rifle that you are shooting it could have a quite short throat. If its a new factory rifle that you have not shot before its possible that there is no throat; its happened before when the maker forgets to use the throat reamer when using a two piece reamer. When you are loading a belted magnum case there are five possible "sticking points" Working from easy to ID to harder we could have the bullet seated too long in the case, the neck could be too long and bottom out on the lands, the neck could be too wide, the shoulder can be too far forward and the belt can be too far forward as well. The belt is what can give you fits with belted magnum as that's where the rifle headspaces, not off the shoulder when chambering the rifle.

Provided your bullets are not getting marked up from being too long, I suspect that there is an issue with the shoulder or the belt of the case. Some rifles are picky about the brass that they can use as they are "short belt chambered" If shooting a belted magnum its best to stick with new brass as many normal FL dies will not size the belt down enough or at all. If you are buying pulled down brass where the bullets have been pulled with a kinetic puller the action of all that powder and bullet slamming forward can move the shoulder forward on the case.

I am confident there will be several responses from guys stating something to the effect of "I have a xxx win mag and I have never had problems with....." Its all about eliminating possibilities and these are potential problems.

I think its redding that makes a die especially for sizing the belt.

Almost forgot, some rifles are more selective about rim height then others, if your rifle is on the tight side and there is mixed lots of brass, some could be smaller then others and those will fit.

 

[bax]

When you are loading a belted magnum case there are five possible "sticking points" Working from easy to ID to harder we could have the bullet seated too long in the case, the neck could be too long and bottom out on the lands, the neck could be too wide, the shoulder can be too far forward and the belt can be too far forward as well.

I agree on those five places. You can also have interference in other places if your chamber is tighter than your full-length die. For example, when I neck sized, I sometimes had trouble with the case body just above the belt.

Also keep in mind, that Sierra bullets are not the same shape as a 208 amax or berger or others. Sierras are not as pointy so the bullet ogive may contact the rifling at a shorter COL.

The "identify" technique. Identify a round that doesn't fit. Take a black magic marker and blacken the entire round - base, rim, belt, case body, shoulder, neck, and bullet. Remove the firing pin from your bolt - the firing pin spring tends to mess up this technique. Try to chamber the round. Wherever the marker is scraped off is the first issue - there may be more than one. If no brass or copper shows then try again and move the bolt from open until you get bolt-closing-interference several times - 5 or 10. That should scrape something off. If nothing seems to be scraped off, check the outer corner of the shoulder. Again, whatever is scraped off is the interference issue.

The "change something" technique. Identify a round that doesn't fit. Immediately check belt height with your caliper, the spec is 0.220. Also check the rim diameter and the belt diameter, they should be 0.532 or less. If you shoot your rounds hot, the base can expand to the point that the rim doesn't fit into the bolt face. Next, seat the bullet 0.010 deeper. Check it. If it now fits then the bullet seating depth might be the issue. If that didn't work, disassemble the round and verify that the bolt still doesn't close. If the bolt closes on the disassembled case then it was something about the bullet. If the bolt still won't close then bump the shoulder back in 0.002 increments until the bolt closes. If you have an RCBS case measuring micrometer or similar device, before you bump the shoulder check to see if this case is in spec. If this turns out to be the issue, consider using dies that do not drag an expander plug through the neck -- that can stretch the neck and move the shoulder. If it isn't the shoulder then it has to be the body -- outer shoulder or just above the belt indicate that you need a different full-length die.



There is no magic. Something is hitting something else so you need to figure it out and fix it. Be methodical and thorough, you will find it.

 

[SWRichmond]

I also had this problem, and for me it was the belt. Cases fired in one rifle would not chamber in the other rifle, no matter how far the shoulder was set back. I suspected the belt was "growing" in one of the chambers, radially, and confirmed this with a caliper.

Brute force solution for me was to mark cases as to rifle fired in. Since you are using once fired brass from "others", you have no idea which case was fired in which chamber.

 

[delfuego]

Measure the shoulder. I had a similar problem with some cases shot in my semi that wouldn't chamber in my bolt gun. I measure the should and they were .004 out from the correct should length. I bumped them back to match the fire bolt gun cases and then they chambered fine.

 

[former naval person]

The interesting part is that when he pulls the bullet the rounds chamber without difficulty. Doesn't compute that the belt is at fault. JMHO

 

[FCS]

Standard dial caliper. I know SMKs are all over on length but I believe the dies seat on the ogive so would they not chamber the same regardless of the OAL of the bullet?

Seating stem does not push on bullet at the ogive / bearing surface junction but at some point on the ogive. If you have some variation on ogive from bullet to bullet, and you will have variation, attempting to seat bullet close to lands then this could lead to some bullets being into the lands. SMKs will take 0.040" jump, or more, w/o affecting accuracy. I have seen some lot#s of SMKs vary by 0.035" on base to ogive/bearing surface junction, I've also seen some lot#s of SMKs vary by 0.002" (which is pretty much at/below resolution of the measuring tools tolerance stack).

Do you have a comparator? If yes, then measure rd that will chamber and compare against rd that will not chamber.

Another test is to take rd that will not chamber, cover bullet with black sharpie. Chamber rd, or as close to chambering as you can w/o excessive pressure applied to bolt, and then extract rd. Make sure to reach in as soon as possible to hold case head against bolt face so you don't get a bunch of marks on bullet from where it drags against bolt race way. Look for rifling marks on the bullet.

3rd way to address the offending rds is to seat bullet deeper by 0.005" and attempt to chamber round. Find out how much deeper you need to seat bullet for it to chamber w/o requiring additional force on bolt.

300WM, seating bullet 0.020" deeper in case is going to have no appreciable affect on pressure for same powder charge.