O.A.L. Advice

[MDslammer]

Hi Guys,

I'm very new to reloading so please excuse the newbie question(s).

I used a Hornady O.A.L. gauge on my Remington 700 5R Milspec .308 and the measurement came in at 2.317" to the lands.

I was told I should seat my bullet at least .003" to .005" shorter to avoid any pressure
problems. So I seated my bullets at 2.312" / 2.311". I'm using Hornady 178gr. A-MAX
bullets.

Loading with Varget powder at various amounts to determine what amount gives me the
best grouping at 100 yds.

I have been shooting Federal GM 175gr. BTHP which I measured to be 2.208".
There is a difference of 0.104".

Will this be an issue or not? Any insight would be appreciated.

Thanks.

MDslammer

 

[Perk]

I have a Rem 700 with krieger barrel oal with 175 is 2.820 to lands for rounds to fit in mag. My Savage barrel the bullets set 3.01 to the lands. ALL depends on the chamber reamer used. Perk

 

[243winxb]

When working up a load, .010" off the lands would be better IMO. This allows for differences in the ogive & slop in the press linkage. With most cartridges, i like to start with the bullets base (full dia., not boatail) at the neck/shoulder junction, if possible.

 

[Erik Cortina]

No issue. Work up to load, if you see pressure signs, stop.

Once you find a powder charge that shoots good, test seating depth by seating bullets .003" deeper into case until you find the best load.

243winxb, you need a new press.

 

[BoydAllen]

Since you should always do your own load workup, seating into the lands, a precise amount, should never be a problem. I would set my length so that I was about .010 longer than touching, and drop back and work up. You will have more pressure with a given amount of powder, but by starting low and working up with that length you can be into the lands and still be at a safe pressure level. FYI the usual increase quoted for touching or being into the lands, as opposed to jumping the bullet is something on the order of 5-6,000 PSI.

Another thing to keep in mind is that reloading manual loads are not worked up with the bullets in the rifling, so don't say to yourself that it must be OK because it is in a manual. It may not be. Always do your own testing. Don't take some hot load off the internet and just use it.

 

[amlevin]

Hi Guys,

I'm very new to reloading so please excuse the newbie question(s).

I used a Hornady O.A.L. gauge on my Remington 700 5R Milspec .308 and the measurement came in at 2.317" to the lands.

I was told I should seat my bullet at least .003" to .005" shorter to avoid any pressure
problems. So I seated my bullets at 2.312" / 2.311". I'm using Hornady 178gr. A-MAX
bullets.

Loading with Varget powder at various amounts to determine what amount gives me the
best grouping at 100 yds.

I have been shooting Federal GM 175gr. BTHP which I measured to be 2.208".
There is a difference of 0.104".

Will this be an issue or not? Any insight would be appreciated.

Thanks.

MDslammer

I'm shooting the "same" rifle. Mine likes 2.800" to 2.820" for accuracy which by most standards is a large jump. When I go out in length it seems like my groups open up drastically. I have had several groups under .200" using the following load:

43.5 gr Varget
Lapua Brass
BR-2 Primer
Nosler Custom Competition 175 gr. BTHP.

Several weeks ago on a calm day I shot a .191" group. Considering that this rifle has a factory 5-R barrel, lots of rounds through it, and small groups like this are repeatable makes me think that I'm better off shooting a round that will fit in the magazine should I want to load more than one at a time.

According to all the papers floating around on this barrel/rifling design, it's been optimized for a 173 gr bullet at approximately 2600 fps. That's why the "odd" twist rate. The long freebore doesn't seem to harm it's accuracy, at least by factory barrel standards.

I guess it's a little like the story of the Bumble Bee. According to aeronautical engineers, it's not supposed to be able to fly but someone forgot to tell the Bee.

 

[Shynloco]

I'm shooting the "same" rifle.

No offense meant to anyone, but I hate to see those words in any question such as was originally posted in this thread. IMHO, that tends to promote an ASSUMPTION that what works in that rifle, will work equally well and will not cause any issues...WRONG! Each rifle is different no matter if the same make, model and caliber. So do like Boyd suggests and run tests for your particular rifle. Never ASSUME anything in reloading. I've seen too many rifles blown up by poor and unintended ASSUMPTIONS.

Now amlevin has made an excellent observation that his rifle loves the jump and hates the jam using the 175 gr bullets. My .308 was the same and the closer I got to the jam, the bigger the groups. Ultimately, 2.800 was the best OAL at 100 yds. BTW, I'll pass along a small piece of info that may or might not help you. I shoot pretty much Sierra bullets. Last year I spoke to one of the wizards at Sierra who informed me that if I was going to shoot my .308 using their HPBT bullets, I was better off in terms of accuracy, using the 168 gr bullet for distances of 100 - 300 and then after that, the 175 gr bullet would perform better and more accurately. But do note, if I was going to move out beyond 300 yds, I redo my ladder tests using the 175 gr probably at 500 -600 yds before settling in the the exact load. Again don't assume what works for best accuracy at one distances, is the best load for that particular rifle at 600yd - 1K.

Just my thoughts and AGAIN, no offense mean to anyone one's comments or their thinking.

 

[amlevin]

I'm shooting the "same" rifle.

No offense meant to anyone, but I hate to see those words in any question such as was originally posted in this thread. IMHO, that tends to promote an ASSUMPTION that what works in that rifle, will work equally well and will not cause any issues...WRONG!

A bit of an oversight on my part. My use of the word "same" was merely in the context of Make, Model, caliber. Absolutely agree that even rifles with consecutive serial numbers and the same "proof marks" can perform differently.

I will however add, that this particular Make, Model, and Caliber, when reported on by others, seems to respond well to the load I presented and for safety purposes, it's well within the accepted parameters as published.

 

[MDslammer]

All good information and advice. Agreed, no matter what rifle you're loading for, though
there maybe similarities, no too are alike. Load for your own rifle. Start with light loads and work up from there. Start further off the lands and work in.

Thanks to all for helping me out.

Best.

MDslammer

 

[BoydAllen]

One more thing that I think needs to be mentioned, is that shooters will make a move in seating depth and see an increase in group size, and say to themselves that their rifle does not like that. What they do not know is that seating depth and powder charge have sweet spots that are spaced out, with areas of poorer accuracy in between, so when a small move is made, it may simply have taken the rifle out of tune. In reality, with continued adjustment in the same direction, better grouping may have been found. I have fallen into this trap myself. The reason that I like to work up loads with the bullet into the lands is that just about all the rifles that I have owned "liked" a seating depth in the range that I mentioned, and if one starts his workup there, and then reduces seating depth for subsequent tests, pressures will generally be less as the bullets are seated shorter, unless there becomes a case capacity issue at the extremes of jump, with one of the smaller cases. My first CF rifle was a .308 that preferred 168 and 190 gr. SMKs. This was a long time before the 175s came out. If you start your workup off the lands, and end up with a warm load that is not touching, moving the seating depth to touch, or into the lands can increase pressure beyond what is desirable. Working the other way, this will not be the case. Pressure, powder charge constant, will decrease as you come off , or out of the lands.

 

[amlevin]

If you start your workup off the lands, and end up with a warm load that is not touching, moving the seating depth to touch, or into the lands can increase pressure beyond what is desirable. Working the other way, this will not be the case. Pressure, powder charge constant, will decrease as you come off , or out of the lands.

Help me understand this a little. Are you saying that leaving the powder charge the same, but increasing the jump, will not increase pressure? It seems contrary to my understanding of powder charge vs case volume "internal ballistics". I agree that increasing the distance to the lands could reduce pressure but inserting the bullet farther into the case could also increase the pressure-----or do I have this all muddled up in my mind?

For my rifle, I have approached both charge and "jump" perhaps a little different than some. I kind of work it like one might tune an old "Ham Radio". First the frequency knob (charge) then the antenna loading (length), working back and forth until the rig is perfectly tuned. When I have a load that performs well in a given length, I then work with powder charges. If I find any improvement I might then repeat the length adjustment. All with the goal of finding the best possible combination.

 

[BoydAllen]

I have been told by my friend that runs this site, that it has been his experience with bullets typical of a fast twist 6 BR, that if one goes from into the lands to a small amount of jump, that he sees a decrease in pressure, and that if he continues to gradually increase jump, a point will be reached where pressure increases due to the reduction in case volume. I have not worked with this particular combination. What I said was that if you start from a point where you are into the lands, by some amount, when you come just off of the lands, pressure will decrease. I haven not found that I see a noticeable increase in pressure, with the combinations that I work with, as I have increased jump. The reason that peak pressure increases when you go from jumping to touching is that the force that it takes to engrave the bullet is added to the force that it takes to overcome the bullets inertia, because both events are happening at the same time. With a jump the inertia is overcome and then the bullet has a "run" at the rifling. I have read in reloading manuals that the difference in peak pressure between jump and touching or into the rifling is somewhere around 5-6,000 PSI. Accurate loads may be arrived at using more than one procedure. I prefer to identify the largest charge that I can use with the bullet seated so as to produce the greatest pressure, which will be well into the lands. If I were working with a magazine length that severely restricted how long I could seat bullets, I would take another approach. None of my rifles have this problem, and when I help friends order reamers for hunting rifle projects, I try to make sure that the magazine length is not a limiting factor, either by selection of action length, or by the throat length that is built into the reamer. To repeat what I said in my earlier post, if you have a hot load jumping, and change the seating depth so that the bullet is touching or into the rifling, you may see a pressure increase that puts the load at a higher pressure than you would like.

 

[Shynloco]

Ok Guys,
Great discussion! Your comments help remind me of something I perhaps SCREWED UP when I was testing my depth seating with my .308. And that is to decrease my load some as I approach or get into the lands. My .308 was really putting together nice group with an OAL of 2.800 shooting Sierra 168 gr HPBT's. Now I have a new barrel (not yet installed as I'm waiting for a new stock to arrive as well) but here's what I'm REALLY weak on. I've been starting at the stated OAL and then increasing my depth by .010 at a time and testing for group patterns. What I am not sure on, is if I INCREASE my OAL by the stated amount, how much should I DECREASE my powder load by? Now I understand the concept of an increase in pressure as I enter the lands, but I'm sure of the amount of pressure increase before in get to the lands. And keep in my for this educational lession, I like shooting strictly 168 gr HPBT because my distance of shooting is 100 yds as these eyes have gotten tired over the year and I don't see nearly as well as I once did. But thanks to all for my continuing education.

Alex

 

[BoydAllen]

If you start some distance into the lands, and do a pressure test, starting low, one shot per load, .4 gr per increase, you will find the maximum powder charge that can use with the seating depth that makes the most pressure. Once you have your maximum, note the temperature, and look at your target to see if it seems to suggest a powder charge that is below that. From there, pretty much wherever you go, you will know that you are safe for pressure. If you need to load for a throat that is too long for your magazine, then the workup would be different.