Michigan Sportsman Forum banner
1 - 20 of 34 Posts

·
Registered
Joined
·
6,585 Posts
Discussion Starter · #1 ·
I noticed my reloads are hitting pretty hard on the lands at factory spec OAL. I may have to shorten my loads by .05" or so. This is a 300WSM. How much more pressure will there be with the same grain powder charge. Should I start over with min load? Back down a couple of grains?
 

·
Registered
Joined
·
2,295 Posts
This is an interesting and hard to predict tradeoff between reduced case capacity [compressed load/higher pressure] and longer freebore 'jump' to lands [lower peak pressure.]

.050" is too much IMHO to start with. I load my magnums to .025" - .035" off the lands depending on bullet with excellent accuracy. What is your 'jump' now at factory COAL? Unless you are using 'special' bullets you should not need to back off more than .025" total.

You can calculate appx. capacity change by using the bulk powder density and calculating the volume of a .308" cylinder of .025" length, etc. If you are near max load density already you should indeed back off 1-2 grains.

Everything of course depends on the specific powder burn rate, bullet construction, etc. Slower burning powders may be more forgiving.
 

·
Registered
Joined
·
6,585 Posts
Discussion Starter · #3 ·
I'm using a slower burning powder (IMR 4831). Even with the factory ammo, I'm getting a little pressure when I try to close the bolt. The OAL of the bullet is 2.860" and that's where I started. I'm seeing a little scraping of the bullet just ahead of the case. It scapes in the .05"-.11" range. I'm using the Lee Factory Crimp die to give me a little more seating pressure. I found a couple of other reloaders using the shorter load. (from www.handloads.org) .
<165gr SP 69.0 gr IMR 4831 3,175 fps 2.805" Fed LRM guest
The 165 Sierra BT and Fed 215GM primers and Fed Nickle Cases. Great hunting load and very accurate!>
I'm trying to stay away from max loads as much as I can, and I found a load that's pretty accurate.
I think if I shorten .05" it'll still touch the lands. I'm new to this, that's why I'm asking.
 

·
Registered
Joined
·
5,823 Posts
Remind me please.... What are the definitions of: OAL and COL. Thanks!
 

·
Registered
Joined
·
412 Posts
OT,

Make a dummy round and insert inside the chamber closing the bolt, after closing open the bolt ejecting the round slowly. Measure the O.A.L and start from there backing the bullet to the desired jump, at no time should you ever need to use force to open or close a bolt. Another thing you may want to try brass casing and start on the load side working yourself up with the powder.
 

·
Registered
Joined
·
2,714 Posts
if you back it off .05", it will still be on the lands?

no way. something's not right. if that were the case, i don't think you'd be able to close the bolt. are you sure those are lands marks? they'd be evenly spaced, small scuff marks closer to the case mouth on the bullet.

since you're new to it, my apologies if i bring something up that you already are familiar with...
are you aware of the problems with measuring COAL, right? i've sat down and measured bullets before and found up to .02" difference in length, from within the same box. are you aware that you should be measuring with a comparator, so that the reading comes from the datum line on the ogive, instead of the overall length?

this is the compelling reason to seat hunting rounds a minimum of .020 - .025" off the lands.

ideally, you'd find the lands on the ogive, then seat each bullet based on that measurement. that might require adjusting the seating stem often, because bullet lengths can vary, and the seating stem is really making contact on the tip, nowhere near the point on the ogive where your lands make contact. by seating 20 thousandths off, you're safe from hitting the lands even if your overall length varies by several thousandths of an inch.

make sense?

try this. using an uncharged, sized case, seat a bullet long in the case. try to chamber it. when the bolt is cammed, most times it will seat the bullet the remaining depth into the case. that's where i start. then i seat it a little deeper, a few thousandths at a time, to where its just touching the lands, not being jammed in there.. you'll see only a faint mark from the lands. remove the marks with steel wool between chamberings.

save that dummy round for future set-ups of the seating die. then using your comparator, back off loaded rounds by .020-.025". work up a new load from there.

might require a tap from the muzzle end with a cleaning rod the first time you chamber it, cause it will be jammed into the lands.

then again, i have some guns that have so much freebore that i can hang the bullets out on their tippy toes and not touch the lands.
 

·
Registered
Joined
·
6,585 Posts
Discussion Starter · #8 ·
Makes sense. I knew measuring OAL wasn't reliable, from what I've been reading, but I couldn't find the reason. I'll try that. Thanks.
 

·
Registered
Joined
·
4,023 Posts
0.05" is a fair distance off the lands, Barnes recommends this for their bullets but most others aren't near that far. Some good advice here but a great tool to find your distance to the lands is the Hornady (formerly Stoney Point) OAL gauge. It measures off the ogive, not the tip of specific bullet makes. After finding your max OAL off the ogive of the bullet, you can experiment with seating depths and see what works best for you. I've used it and tinkered with seating depths, varying loads by increments of 0.005" to see what my sweet spot is. Another reason to make sure they're not touching is you don't want to be out hunting and have a bullet stick on them, dumping your powder in the rifle. Also, just off the lands doesn't always give the best accuracy, I have some loads with the Hornady SP's in my 270 that give excellent accuracy and they are seated right up to the cannelure. That's the fun of reloading though is tinkering around.
 

·
Registered
Joined
·
6,585 Posts
Discussion Starter · #10 ·
It just wants to sit .055 less than factory. It's just touching the rifling. I hate to go much less than that. After checking around a little, there are guys running 3 more grains of powder at the same length I'm at. I'll play around with it a little. (oh darn!):) Pressure doesn't seem to be a huge issue. I'll start a little low just to be safe.
 

·
Registered
Joined
·
2,714 Posts
just remember, unless you're using the same bullet as the factory round, you've got no way to know just how they compare to factory rounds.

the profile of the ogive varies by bullet maker. technically, the profile of the ogive can vary a little from box to box, even within the same product line of the same manufacturer. that, imo, is a consideration for purists, cause it can't vary by much... but nevertheless..

anyway, my point is.. if you're shooting, say, a federal fusion factory round, and a sierra hand load, your two comparator readings will be worthless, because the datum line on the ogive changes, given the different profiles of the ogive. you have to be comparing apples to apples for it to be meaningful.

i have the stoney point comparator - not bad, but i think i like this one better..

http://www.sinclairintl.com/cgi-bin/category.cgi?category=RESDTCO&item=09-600&type=store

you might not be noticing pressure signs right now, but be careful to check the inside of your brass for case head separation, and loose primer pockets.. sometimes, as reloaders, we can do things that don't generate enough pressure to be dangerous, but enough to seriously reduce the lifespan of our brass.
 

·
Registered
Joined
·
6,610 Posts
we saw how they test each batch of bullets and if they dont keep the accuracy from the test guns, theyre sold as blems or scrapped. QC with these guys is unbelievable. So many tests. Id have to disagree about the ogive variances. Talking with the engineers and press/QC people was most interesting.
Most of the test groups produced for production runs were all one ragged hole, and if they were out 1 inch or so [5 shots] they were sold as 2nds.
Reloaders are an odd lot for sure, always tinkering with something.
 

·
Registered
Joined
·
2,714 Posts
huntsman - accuracy is one thing. ogive variance is another. some guns shoot factory ammo great. and you can believe that there's plenty of variances.

i'm not saying that a .005 variance on ogive is going to effect accuracy - it may or it may not. i tend to believe it won't have a huge impact. that doesn't mean the variance won't, or doesn't occur.

i spoke with a sierra tech about it a few years ago. sierra's are well known for accuracy. this tech told me that i should get a comparator reading to the lands, each and every time i open a new box, even if they are within the same line. different batches have slight variances, according to him. doesn't mean the variances make them inaccurate to any significance.

again, i'm not advocating that one spend a lot of time measuring bullets of the same brand with a comparator. but they must be bullets of the same brand to come anywhere close to the same reading. his comparator reading from a factory round will be meaningless if he's reloading a different bullet - that's my point.

my philosophy is this: i'll load my rounds .02" off, knowing that a variance of +/- .005 will put all of my bullets no more than .015-.020" off the lands - which will have negligible effect on pressure and not risk getting stuck in the lands while in the field.
 

·
Registered
Joined
·
6,585 Posts
Discussion Starter · #14 ·
I see your point RZ. I'm reloading Sierra GK SBT and they seem to be wider, further towards the point than many others. That may be why I had the issue. I'm ordering your comparator today.
I do have to admit, with 6 different type factory rounds, the best group I could get was 1.255" and after playing with my reloads, I got it down to .65"! The hotter the load, the better it grouped. I got up to 69gr with max load being 70.5.
 

·
Registered
Joined
·
6,610 Posts
rzdrmh said:
huntsman - accuracy is one thing. ogive variance is another. some guns shoot factory ammo great. and you can believe that there's plenty of variances.

i'm not saying that a .005 variance on ogive is going to effect accuracy - it may or it may not. i tend to believe it won't have a huge impact. that doesn't mean the variance won't, or doesn't occur.

i spoke with a sierra tech about it a few years ago. sierra's are well known for accuracy. this tech told me that i should get a comparator reading to the lands, each and every time i open a new box, even if they are within the same line. different batches have slight variances, according to him. doesn't mean the variances make them inaccurate to any significance.

again, i'm not advocating that one spend a lot of time measuring bullets of the same brand with a comparator. but they must be bullets of the same brand to come anywhere close to the same reading. his comparator reading from a factory round will be meaningless if he's reloading a different bullet - that's my point.

my philosophy is this: i'll load my rounds .02" off, knowing that a variance of +/- .005 will put all of my bullets no more than .015-.020" off the lands - which will have negligible effect on pressure and not risk getting stuck in the lands while in the field.
Youve said yourself you dont shoot matches and make all these "extra" steps for varmint shooting? I dont do it and still have groups one ragged hole. As I said some folks will go to the ends of the earth, but as long as your happy thats all thats needed. Never seen a need for all the extras.
 

·
Registered
Joined
·
4,023 Posts
Huntsman27 said:
Youve said yourself you dont shoot matches and make all these "extra" steps for varmint shooting? I dont do it and still have groups one ragged hole. As I said some folks will go to the ends of the earth, but as long as your happy thats all thats needed. Never seen a need for all the extras.
Isn't that the truth...I have loads that are far above what I need for hunting but seems I'm always tinkering with something. You'd think I was shooting benchrest or something..:lol:

I'll have to check out that Sinclair tool, for $17 what the heck.
 

·
Registered
Joined
·
6,610 Posts
M1Garand said:
Isn't that the truth...I have loads that are far above what I need for hunting but seems I'm always tinkering with something. You'd think I was shooting benchrest or something..:lol:

I'll have to check out that Sinclair tool, for $17 what the heck.
Like I need more reloading manuals or the latest gizmos for case trimming. Its as technical as you want to make it. And to think, I hated math in school!:lol:
 

·
Registered
Joined
·
2,714 Posts
huntsman -

in this particular case, i want to know where i am on the lands. its more of a safety (pressure) issue than accuracy issue, though, consistency does equal accuracy. and while some guns shoot the same no matter what distance from the lands, i've definitely encountered other guns that like to be a certain distance away.

furthermore, for one so inclined, a dummy round, seated to the lands, can be re-checked at later dates to see if throat erosion is occuring.

outside of that, i simply try to have a repeatable, consistent process.

i don't trim meplats, i don't weigh cases, don't sort bullets by length or weight, don't check for run-out (though i do square my dies); i don't ream necks or primer pockets, don't debur flash holes, etc. these types of things might improve accuracy a little, but what's the point in a hunting rifle that shoots MOA?

but.. for pragmatic reasons, we have to measure our seating depth in some fashion. and given that COAL is not the best method, it only makes sense to use a comparator. the added (and certainly not insignificant) benefit is that we know to a pretty high degree how far away from the lands that bullet is.

couple this knowledge with temp sensitive powders, or higher pressure loads, or powder variances from lot to lot, etc, and its clear to me that its another piece of the puzzle in terms of safety, not an extra step.
 

·
Registered
Joined
·
6,610 Posts
However, simply measuring my 243s and setting the bullet seating in the comp dies at an OAL of -.010 under max OAL gives one hole groups without the extra gizmos and seating out farther than may work with the magazine feed. The pressure problem may arise when someone tries to stick a bullet into the lands....not something I do to be worried about. Of course, the manufaturers use different ogives and the seating is different. But, if it works for you [comparator] thats great.
Throat erosion? Think Hawkeye borescopes.
Safety is always a concern with reloading. Not being cautious can be disasterous.
 
1 - 20 of 34 Posts
Top