Max OAL and powder charge

rstorrie · November 8, 2014, 05:32 PM

I have been reloading for 20 years and always followed manuals. I have now progressed to fine tuning ammo for my rifles. I used the Hornady OAL gauge and I know the Barnes TTSX's in my 7mm Rem Mag recommend 0.030 - 0.070" off the lands, but I have a thousand Federal Fusion 150 grains for my .270 Winchester and there is NO such bullets listed in manuals or powder manufacturers.

My question(s) are, since I am seating the bullets further out closer to the lands, the case has more space, but it is closer to the lands and as such where do start off in regards to powder charge? Is max potentially dangerous or is it safe since the pressure is less in the case?

Anyone happen to know what other major bullet manufacturer that the Federal Fusion mimics in regards to the bullet comparison and design for reloading purposes?

Lastly, does anyone know what the recommended distance from the lands would be for a Federal Fusion? 0.20" etc?

Thanks all.............

GJSchulze · November 9, 2014, 03:53 AM

For pistol a longer OAL results in lower pressure. For rifle a longer OAL at first will result in lower pressure, but as the bullet approaches the lands the pressure will increase. Therefore, I think that a max charge with a longer OAL in a rifle can be unsafe.

There, I've just exhausted my knowledge of loading for rifles. I'm sure someone with more knowledge can explain further.

Pond, James Pond · November 9, 2014, 05:40 AM

I had a similar question a while back and the issue of pressure in relation to OAL came up. You can read posts #5 (my query) and Brian Pfleuger's response in post#6 on the issue.

I hope that helps.

GJSchulze · November 9, 2014, 04:04 PM

I read that one and must give Brian credit for what I said above. I don't shoot rifle, but I thought it important to correct the OPs statement.

steve4102 · November 10, 2014, 09:13 AM

There is no cut and dried answer to your OAL question. The most accurate OAL in my rifle may not be the most accurate in yours.

As already states above, the longer the OAL the higher the pressure.

Here is what I would do, YMMV.

Select your desired distance from the lands, say .020 off.

Gather you load data and begin your load work-up starting at the Minimum(do not go below) charge and gradually increase the charge.

Once you have found your "accurate" load you can adjust your OAL shorter if you need to fine tune for accuracy.

By starting with your longest OAL, you will not run into an increased pressure situation when reducing OAL.

Bart B. · November 10, 2014, 12:19 PM

Quote:

By starting with your longest OAL, you will not run into an increased pressure situation when reducing OAL.

I think seating bullets too deep can cause pressure to start going higher. See post 14 in the following:

http://thefiringline.com/forums/showthread.php?t=553830

**Unclenick** · November 10, 2014, 04:50 PM

I'll add that the graph I put up in that post Bart linked to came from a round nose bullet. Pointed ones appear to change pressure faster with seating depth. With permission from Jim Ristow at RSI, the following pressure plots show about 20% pressure difference came with a pointed bullet going from contact with the lands to 0.030" off the lands. I added the labels to make it clear:

If you use QuickLOAD, deeper seating always raises pressure. It does not try to account for throat position and gas bypass.

Clark · November 10, 2014, 06:43 PM

I have done some testing around the threshold of trouble for pressure.
The longer the bullet is seated, the lower the pressure, until it hits the lands. Then the pressure starts to go back up. The lands seat the bullet, so no difference as it gets longer. So pressure vs OAL is a V shaped curve that flattens out on the right.

I have killed ~ 20 deer with the 270 and 7mmRM, mostly ~ 400 yards with a bi pod.

I have settled on Nos Ballistic tips bullets seated at 3.34", adjust the elevation turret and aim for the lungs.
If I were in a shooting match, I might seat longer and touch the lands, but I am hunting.
3.34" is what the magazines were made for, and it works well enough for hunting.

I went through a lot of TSX bullets before I gave up on them. Too much Copper fouling.

obiwannabe · November 10, 2014, 09:47 PM

When working up a load for anything you need to try to control as many variables as possible and manipulate only one at a time. So, pick a charge and vary the seating depth or pick a seating depth and vary the charge. Don't try and do both at the same time.

Here's my approach for match ammo. This is the way is makes the most sense to me.

The highest pressure load for any given powder charge is going to be with a seating depth that jams into the lands. Use your OAL gauge to determine a seating depth that jams 0.010" and START there using the lowest powder charge in your favorite manual and work up in 0.5gr increments watching for pressure signs as usual. Use caution if you end up approaching the book max charge with a jammed bullet. I usually quit a half grain shy of the listed max until I see how the loads behave. Very often I end up not shooting the top rung or two. When you find an accuracy node, load a CBTO (or COAL) test ladder using that charge with seating depths every 0.020"-0.030" until you reach the minimum COAL listed in your manual for your cartridge. The longer your freebore the more rungs in the ladder but it's usually 4-5 groups.

Your first load that backs off the lands 0.010-0.020" will give you a small drop in pressure and velocity but it's usually not that impressive. The above graph looks impressive, but practically I haven't seen anything that dramatic yet in the cartridges I load for. From then on each successively shorter load will increase in pressure ever so slightly but I've never seen it significant enough to cause a detectable change in velocity. Bare in mind that at this point you are again working from low pressure loads toward higher pressure loads.

As long as you stay within your manual's charge range and go no shorter than the listed minimum COAL, pressure won't be a problem. 0.5gr powder changes and 0.030" seating changes are pretty gross adjustments intended to get you "in the ball park" without burning a whole pound of powder and 200 bullets. Any time you find an accuracy node you can fine tune by making smaller adjustments either to charge or seating depth.

Lastly, a couple of caveats. First, jamming a hunting bullet is not always a good idea. A 0.010" jam with the usual ~0.004" of neck tension applied by most standard dies is not likely to leave a bullet stuck in the lands when you unload your rifle BUT you can never say never. If you're only interested in hunting loads it's perfectly fine to start your longest (starting) load at 0.010" jump. Second, being a tangent ogive design, it's very likely that those 150gr Fusions will like some jump. Maybe a lot of jump. Don't be surprised if your most accurate loads are 0.060-0.080" off the lands.

obiwannabe · November 10, 2014, 10:42 PM

BTW, Federal Fusions may be the Speer Deep Curl with a boat tail. I've never heard that officially confirmed, but that's the chatter.

steve4102 · November 11, 2014, 09:20 PM

http://thefiringline.com/forums/show...&highlight=oal

Post #3.

November 8, 2014, 05:32 PM	#1
rstorrie Junior Member Join Date: November 8, 2014 Posts: 1	Max OAL and powder charge I have been reloading for 20 years and always followed manuals. I have now progressed to fine tuning ammo for my rifles. I used the Hornady OAL gauge and I know the Barnes TTSX's in my 7mm Rem Mag recommend 0.030 - 0.070" off the lands, but I have a thousand Federal Fusion 150 grains for my .270 Winchester and there is NO such bullets listed in manuals or powder manufacturers. My question(s) are, since I am seating the bullets further out closer to the lands, the case has more space, but it is closer to the lands and as such where do start off in regards to powder charge? Is max potentially dangerous or is it safe since the pressure is less in the case? Anyone happen to know what other major bullet manufacturer that the Federal Fusion mimics in regards to the bullet comparison and design for reloading purposes? Lastly, does anyone know what the recommended distance from the lands would be for a Federal Fusion? 0.20" etc? Thanks all.............

November 10, 2014, 04:50 PM	#7
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,061	I'll add that the graph I put up in that post Bart linked to came from a round nose bullet. Pointed ones appear to change pressure faster with seating depth. With permission from Jim Ristow at RSI, the following pressure plots show about 20% pressure difference came with a pointed bullet going from contact with the lands to 0.030" off the lands. I added the labels to make it clear: If you use QuickLOAD, deeper seating always raises pressure. It does not try to account for throat position and gas bypass. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

November 10, 2014, 06:43 PM	#8
Clark Senior Member Join Date: December 4, 1999 Location: WA, the ever blue state Posts: 4,678	I have done some testing around the threshold of trouble for pressure. The longer the bullet is seated, the lower the pressure, until it hits the lands. Then the pressure starts to go back up. The lands seat the bullet, so no difference as it gets longer. So pressure vs OAL is a V shaped curve that flattens out on the right. I have killed ~ 20 deer with the 270 and 7mmRM, mostly ~ 400 yards with a bi pod. I have settled on Nos Ballistic tips bullets seated at 3.34", adjust the elevation turret and aim for the lungs. If I were in a shooting match, I might seat longer and touch the lands, but I am hunting. 3.34" is what the magazines were made for, and it works well enough for hunting. I went through a lot of TSX bullets before I gave up on them. Too much Copper fouling. __________________ The word 'forum" does not mean "not criticizing books." "Ad hominem fallacy" is not the same as point by point criticism of books. If you bought the book, and believe it all, it may FEEL like an ad hominem attack, but you might strive to accept other points of view may exist. Are we a nation of competing ideas, or a nation of forced conformity of thought?

November 10, 2014, 09:47 PM	#9
obiwannabe Member Join Date: February 14, 2014 Posts: 40	When working up a load for anything you need to try to control as many variables as possible and manipulate only one at a time. So, pick a charge and vary the seating depth or pick a seating depth and vary the charge. Don't try and do both at the same time. Here's my approach for match ammo. This is the way is makes the most sense to me. The highest pressure load for any given powder charge is going to be with a seating depth that jams into the lands. Use your OAL gauge to determine a seating depth that jams 0.010" and START there using the lowest powder charge in your favorite manual and work up in 0.5gr increments watching for pressure signs as usual. Use caution if you end up approaching the book max charge with a jammed bullet. I usually quit a half grain shy of the listed max until I see how the loads behave. Very often I end up not shooting the top rung or two. When you find an accuracy node, load a CBTO (or COAL) test ladder using that charge with seating depths every 0.020"-0.030" until you reach the minimum COAL listed in your manual for your cartridge. The longer your freebore the more rungs in the ladder but it's usually 4-5 groups. Your first load that backs off the lands 0.010-0.020" will give you a small drop in pressure and velocity but it's usually not that impressive. The above graph looks impressive, but practically I haven't seen anything that dramatic yet in the cartridges I load for. From then on each successively shorter load will increase in pressure ever so slightly but I've never seen it significant enough to cause a detectable change in velocity. Bare in mind that at this point you are again working from low pressure loads toward higher pressure loads. As long as you stay within your manual's charge range and go no shorter than the listed minimum COAL, pressure won't be a problem. 0.5gr powder changes and 0.030" seating changes are pretty gross adjustments intended to get you "in the ball park" without burning a whole pound of powder and 200 bullets. Any time you find an accuracy node you can fine tune by making smaller adjustments either to charge or seating depth. Lastly, a couple of caveats. First, jamming a hunting bullet is not always a good idea. A 0.010" jam with the usual ~0.004" of neck tension applied by most standard dies is not likely to leave a bullet stuck in the lands when you unload your rifle BUT you can never say never. If you're only interested in hunting loads it's perfectly fine to start your longest (starting) load at 0.010" jump. Second, being a tangent ogive design, it's very likely that those 150gr Fusions will like some jump. Maybe a lot of jump. Don't be surprised if your most accurate loads are 0.060-0.080" off the lands. Last edited by obiwannabe; November 10, 2014 at 10:37 PM.

November 9, 2014, 03:53 AM	#2
GJSchulze Senior Member Join Date: May 3, 2013 Location: Western New York Posts: 454	For pistol a longer OAL results in lower pressure. For rifle a longer OAL at first will result in lower pressure, but as the bullet approaches the lands the pressure will increase. Therefore, I think that a max charge with a longer OAL in a rifle can be unsafe. There, I've just exhausted my knowledge of loading for rifles. I'm sure someone with more knowledge can explain further.

November 9, 2014, 05:40 AM	#3
Pond, James Pond Senior Member Join Date: July 12, 2011 Location: Top of the Baltic stack Posts: 6,079	I had a similar question a while back and the issue of pressure in relation to OAL came up. You can read posts #5 (my query) and Brian Pfleuger's response in post#6 on the issue. I hope that helps. __________________ When the right to effective self-defence is denied, that right to self-defence which remains is essentially symbolic. Freedom: Please enjoy responsibly. Last edited by Pond, James Pond; November 9, 2014 at 04:40 PM.

November 9, 2014, 04:04 PM	#4
GJSchulze Senior Member Join Date: May 3, 2013 Location: Western New York Posts: 454	I read that one and must give Brian credit for what I said above. I don't shoot rifle, but I thought it important to correct the OPs statement.

November 10, 2014, 09:13 AM	#5
steve4102 Senior Member Join Date: December 23, 2005 Location: Minnesota Posts: 2,952	There is no cut and dried answer to your OAL question. The most accurate OAL in my rifle may not be the most accurate in yours. As already states above, the longer the OAL the higher the pressure. Here is what I would do, YMMV. Select your desired distance from the lands, say .020 off. Gather you load data and begin your load work-up starting at the Minimum(do not go below) charge and gradually increase the charge. Once you have found your "accurate" load you can adjust your OAL shorter if you need to fine tune for accuracy. By starting with your longest OAL, you will not run into an increased pressure situation when reducing OAL.

November 10, 2014, 10:42 PM	#10
obiwannabe Member Join Date: February 14, 2014 Posts: 40	BTW, Federal Fusions may be the Speer Deep Curl with a boat tail. I've never heard that officially confirmed, but that's the chatter.

November 11, 2014, 09:20 PM	#11
steve4102 Senior Member Join Date: December 23, 2005 Location: Minnesota Posts: 2,952	http://thefiringline.com/forums/show...&highlight=oal Post #3.