Bullet seating depth help?

[blazingsaddle]

I have been reloading for a few years now. Up till last week I have seated my bullets to match some factory loads. My accuracy has been fair, but I think it could be better. Instead of changing powder amounts, I though first I would check my OAL for my gun.

I have a Stoney Point OAL gauge. I also followed what it said in one of my reloading manuals about proper seating depth. If I follow either process, I come up with a OAL that is roughly .2756 longer than what I have been shooting. Its more than a quarter inch longer OAL.
Is this normal, to have that much discrepancy? Also with the longer OAL i don't have much bullet seated in the case. I would have .2990 seated in the case for my 7mm stw. (.284") Is this enough? I seated a dummy round at the longer OAL, and it looked very odd.
Or am I not finding the proper OAL to begin with? I found the Stoney Point gauge to be difficult to use and get consistant numbers with.
Can anyone help?

 

[NMlandman]

Have you tried chambering the dummy round and checked to see if it will fit in your magazine? How did you check the OAL for your gun? To the lands?

 

[blazingsaddle]

I did not try it in my magazine, I will when I get home.

I tried to fit it to the lands, I think. I followed the directions on the Stoney Point OAL gauge. Are you familiar with it at all? (cause I'm obviously not) It was very hard to get consistant numbers. How do I tell if it hits the lands? The directions said it takes some practice, to get the "feel" of it.

Correct me if I'm wrong, but isn't the lands the only thing that will stop the bullet, or give enough resistance to push it back into the case?

How do you find an accurate OAL for your guns?

 

[stinkystomper]

take a bullet and cover it with a removable marker. Lightly sit it in the case you wish to reload. Chamber it in the gun you are reloading for. Once chambered remove the bullet by unchambering it. The process of chambering the bullet will have seated the bullet to a certain depth. Now measure this depth. This is the approximate depth to your lands. Usually you can start safely reloading 1/100" off the lands. At this point use a pair of pliers or a bullet puller to remove the tip gently from the case. The process of the bullet being pushed into the case will have removed the marker from the bullet which will let you make a final measurement on just how much bullet depth that particular bullet requires to hit the lands. As far as 1/4" goes every gun and bullet combination is different. For example. My 338/378 can go anywhere from 3.90" COL to 3.50". That's almost half an inch. What I do is play with the powder loads. Once I find the most accurate loads I then seat the bullets in increments of 3/100 of an inch for the most accurate load for that powder until I find the bullet that groups the best. For my 338/378 I found it likes ballistic tips at around 3.61 COL for best groups and that it like a COL of 3.78 for accubond grouping. It prefers all barnes to be a col of about 3.675 COL. Remember that every bullet on the market has a different ogive on their bullet. This ogive will determine where the bullet needs to be seated. This is not the only way to reload, just the way I go about it.

Just my opinion.

 

[NMlandman]

Stinky but pretty much described how I do it as well. The difference is that I have had problems when trying to seat a bullet by chambering it. Sometimes the case will wrinkle a little making it difficult to extract. If this happens you still end up with a starting point for OAL. My preferred method is to seat a bullet more shallow than it will end up. If it wont chamber easily, seat it a little deeper, around .05" until it does. Then adjust depth until you get it where you want it off the lands, about .01-.02 seems to work well in my rifles. I also use the marker trick for this process. When you color the bullet with the marker and adjust the depth in .01" increments my final setting would usually be the first one where the lands dont rub off the color +.01", this leaves the bullet between .01-.02 from the lands. This process takes a while and when you find a depth that works well you need to seat a dummy round and save it for future use.

All of this being said, it does not always work. As stinky said, different bullets have different ogives meaning that OAL does not always mean the bullet will be the same distance from the lands for various loads. I have a load for my .338 win mag that I have to seat much farther from the lands because the rounds will not fit in the magazine if I seat them .01 or even .02 off the lands. You have to have functionality.

 

[NMlandman]

I have no experience with the stoney point guage. I have seen them in the catalogs and such but never used one. Besides, my kids' markers are cheaper.

 

[Whistlepig]

LAST EDITED ON Nov-19-08 AT 12:16PM (MST)[p]Just so I make sure I understand. I've been thinking about this lately also. I reload a .270. I just put a loose bullet in a case, and cycle it through the gun then measure with my calipers. With that measurement I back it off .01 or .02 on my calipers, and reload at that measuerment and keep backing it off .01 intell I get the most accruacy???

 

[blazingsaddle]

I got more accurate numbers from the magic marker trick.

So do I understand this right? It could be common to have big differences in your OAL in "working or functioning" loads? In other words, loads that chamber easily, and shoot, can vary up to a half inch or so?

What is the minimum amount of bullet I need to be seated in the case? I'm close to only having .2990 being seated for my 7mm stw. Would that be enough? (assuming it functions through the chamber) I read once I need at least the diameter of the bullet, to be seated.

I think what I will do is seat them as close to the lands I can, and still get smooth feeding as a starting point.

One more question, what gets you better accuracy? Changing the off lands measurement. or different amounts of powder?

Thanks for all your help!

 

[NMlandman]

>I got more accurate numbers from
>the magic marker trick.
>
>So do I understand this right?
> It could be common
>to have big differences in
>your OAL in "working or
>functioning" loads?
>In other words, loads that
>chamber easily, and shoot, can
>vary up to a half
>inch or so?

They can vary, but I wouldn't try to define it to a certain amount. If you don't feel safe, don't shoot it until you do.
>
>What is the minimum amount of
>bullet I need to be
>seated in the case?
>I'm close to only having
>.2990 being seated for my
>7mm stw. Would that
>be enough? (assuming it functions
>through the chamber) I read
>once I need at least
>the diameter of the bullet,
>to be seated.

I am not sure what the technical "rule" is on this. I will say that I have a load for a 6mm Rem that is seated less than the width of the bullet and shoots really well.
>
>I think what I will do
>is seat them as close
>to the lands I can,
>and still get smooth feeding
>as a starting point.

Just make sure the bullet isn't touching the lands.
>
>One more question, what gets you
>better accuracy? Changing the off
>lands measurement. or different amounts
>of powder?

Seating the bullet closer to the lands will improve your accuracy. Now you can play with the powder, velocity, etc. I think you will be happy with the results after seating your bullets closer to the lands. The one thing that I have noticed that helps a lot is to weigh every powder drop to the .1 grn, especially with the rod shaped powders.
>
>Thanks for all your help!

Above all, always be patient and use care when loading. I reload quite a lot, but I am not a professional and do not claim to be an expert. I am only telling you what I do and what works for me. I have been taught these things from men who have reloaded for a long time and still have all of their appendages and facial features, but that doesn't make them absolutely correct in every situation. Please do not do anything you don't feel comfortable doing.

 

[BuckSnort]

When I measure my rounds with the stoney point guage and bullet comparator I get accurate measurements to .001

Are you using both of these devices?

Most factory rifles have deep throat's (huh huh I said deep throat) that allow a lot of freebore before the bullet hits the rifling with factory rounds..They do this so that all of the factory ammo laded at specs can safely be chambered into the rifle without fear of the bullets being seated to long creating dangerous pressure..

Once you learn how to use the OAL guage AND the camparator you will find it is much faster and more accurate than the felt tip..

.020-.030" seems to be the sweet spot for the factory rifles that I have loaded for..

You should have the bullet seated to at least the depth of the caliber..So if your loading for a 300 mag you want the bullet seated at least .308 into the case..This will give proper neck tension..

 

[NMlandman]

Hmm... This neck tension got me to wondering, so I went and pulled one of the bullets of my 6mm load. It is seated less than .243, but only by a few thousandths. Do you think this would be a problem Bucksnort? I have shot hundreds of 'em with very good results. I haven't chronoed them as I don't have a chrono, but maybe I am losing some velocity??

It is nice to hear from someone using the oal guage and comparator. I will consider buying the two. One (more) question if I may: How does the guage determine the length to the lands? Is it pretty foolproof? It sounds a lot faster than the felt tip method I have been using.

 

[4000fps]

I use the Stoney Point. On most of my rifles, I start load development at .010" off the lands.

My 22-250AI is .005" off.

My 204, 338, and 6.5 all have long throats, so seating close to the lands is not possible.

One thing I have found though, seating depth is the last thing I play with when trying for tight groups. Bullet choice, powder type, and charge seem to have more of an effect on accuracy than seating depth.

 

[muley210]

One way to check seating depth is to take a empty brass and cut a vertical slit in neck. This allows the bullet to move and not crush the brass. Keep that brass and check with different bullets. With some of my guns, I cannot seat the bullet to the lands because the magazine is not big enough, unless I shoot one at a time.

 

[BuckSnort]

NMlandman,

I doubt a few thousanths would matter...If you have already been shooting the ammo with no problems then I wouldnt worry..

The OAL guage uses a modified caliber specific case that allow the bullet to slide to the lands..then you tighten the setscrew and remove the guage and bullet for measuring with the comparator and caliper..

Most of the time when doing this the bullet will stick to the rifling when you remove the guage from the chamber...Sometimes all it need is to tap the butt of the gun against the table or floor and the bullet pops out..I bought a couple wooden dowles than I can insewrt through the muzzl to push the bullet out..

 

[AZBuckSnort]

The procedures described here to determine seating depth are all sound. That being said, could bullet runout be more important to accuracy than seating depth?

 

[BuckSnort]

>The procedures described here to determine
>seating depth are all sound.
>That being said, could bullet
>runout be more important to
>accuracy than seating depth?

Yes and no...

A bad die will definatly cause bad runout that is much more of a factor than seating depth. I had a bad RCBS die for my 223 that caused some serious runout..I replaced it with a recomended Forster brand die and was really impressed with how the die cradles the brass as the bullet is being seated..In my opinion the Forster mircrometer dies are worth the extra money..

Also some brass manafactures are better than others..As far as the common brands most people feel that winchester has the best brass and Remington has the worst..Having said that unless you have a extreme amount of runout you will most likely not know the difference with a factory bbl/chamber..

 

[blazingsaddle]

Bucksnort-

How hard do I push on the push rod of the Stoney point OAL gauge? I can't seem to quite grasp the wording: "it takes practice to feel the bullet touch the lands"

Also how hard of a push does it take to push the bullet past the lands and into the barrel? Is that even possible?

Can you tell me what runout is?

Sorry for all the questions- I don't really want to live and die behind my reloader, but be just good enough to be safe, save some money and have better than factory accuracy. I don't care to push the speed or pressure limit too much.

 

[mtmuley]

blazingsaddle, With the Stoney Point, I noticed some variation in readings at first also. What I do is lightly tap the rod with my index figer until I feel resistance. I do this 5 or 6 times keeping my procedure as close to the same as I can. Then I take an average. To be honest, I start most of my loads at SAAMI specs and work out from there after a bullet/powder combo shows promising accuracy. As far as bullet runout, with hunting ammo, it is probably of no concern. mtmuley

 

[Triple_BB]

LAST EDITED ON Nov-20-08 AT 09:41PM (MST)[p]Stinky laid out a good way to come up with the best way to measure seating depth for your gun. However, you need to see if the round will fit in your magazine if yer shooting a bolt action. I seated my rounds exactly as he noted years ago in my 300 RUM. When I pulled the round out and tried to fit it in the magazine, it wouldn't fit. The OAL was too much. At that point, I seated my bullets based on the longest round I could fit in the magazine. I didn't experiment with decreased OAL's because the rounds start moving back in forth in the magazine. Over a day of hard hunting, the bullet tips mash or flatten out beyond what I like. So there are some trade offs in my opinion. Maybe I got lucky with the OAL, but my rifle is very accurate and I'm done messing with it. Here's a good thread on bullet seating.

http://www.larrywillis.com/OAL.html

 

[NMlandman]

Sounds like you had the same problem I did with a bullet that has a plastic tip (mine were ballistic silvertips). Have you noticed any loss of accuracy with the mashed tips? In my experience slightly damaged tips don't really hurt performance, at least not noticably.

Nice reference to the article by Larry Willis. He basically said the same things that we did collectively, but more in depth and professionally written. That is a good article for any guy who rolls his own to read.