Technical question re: bullets and PRESSURE

[7mm08]

1. Given the same weight bullet..... do you load the same amount of powder for a monolithic ( Barnes TSX or TTSX) vs say a Nosler Accubond? And why?

2. How do you measure PSI as it regards to reloading?

Thanks

 

[280longshot]

I always refer to load data from the bullet manufacture then compare the two and most of the time refer to powder manufacture data also . They have done their homework on pressure so I don't load over the recommended charge but realize it's on the conservative side. I have read where this data is a guideline and always load up and watch for pressure signs when you get to the max recommended charge.
With that being said, I load my Nosler BT and Barnes TSX, TTSX with the same charge in my .280. , cause both bullets produce good accuracy and have the same point of impact over 300 yds.
People that load over recommended charge are looking for speed and know how to look for excessive pressure signs way before it becomes dangerous.
I don't load for speed, I load for accuracy.
Bullets of the same weight from different manufactures will result in different pressures due to different bearing surface.

 

[Omega]

I concur, with my ladders I have never experiences a max round being the most accurate. Most bullets have data, but if not, I've used the data to a like bullet, always starting low and working up till I see good results or see pressure signs.

 

[infoman jr.]

You should not assume powder charges will be the same between copper and lead bullets because copper bullets are less dense therefore larger for a given weight. You should always start low and work up. I will load above the recommended weight, but I'll stop when the gun tells me to and pick the accuracy node with the highest velocity to continue load development. I'm looking for speed AND accuracy.

I use the brass, primer, and bolt to measure pressure. If I start to get really flat primers or a heavy bolt lift, I'll stop.

 

[7mm08]

Example of PSI for .325 WSM 200g
BTW- Hodgdon says 67.0 g MAX for ?bullet I don't know
- Nosler qoutes 64.5 g MAX for NAB

- ALL with Hodgdon H4350?????
What's a OCD , paranoid, newby reloader( I used to and learned with an experienced reloader for my 7-08 but he has since moved) to do.

BTW. BORROWED ( my never give it back) my don's MagnetoSpeed Chrono.... oh my! So easy!!!

 

[Jcalder]

All the data is collected by various sources. Some may use a universal receiver while others use various production guns. Basically the manuals and data are what they found, and what their lawyers would let them publish. So Sierra may have found that 45 grains of powder X is acceptable while Nosler found 48 grains of powder X was acceptable. There's also the fact that bullet makeup varies a bit between manufactures and it may show in in their findings. Another component is brass and case compactly. When I loaded for 308 I used Winchester cases. I tried to switch to Hornady and I had to drop my charge over 2 grains to get the same results. So in theory I would have issues faster with Hornady brass than the Winchester.


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[DaveB]

Monolithic bullets are longer than cup and core-more bearing surface. The longer bearing surface means more friction inside the barrel.

More friction means more resistance to the powder pushing it out the barrel. SO, you get higher pressure, in general, for monolithic bullets than cup and core for the same bullet weight and powder charge.

You will see cautions in the manuals to start low and watch for pressure signs for the monolithic bullets. The reason for the grooves in the bullets is to reduce friction which has a resultant reduction in pressure.

Many of my rounds are at max load and one or two are over max. Our 06, 280, 243, 22-250. & 7mm08 all get their very best accuracy at max+ loads. Our 308 does not.

The equipment to measure chamber pressure is quite expensive and complicated. I do it this way: a flattened primer is close to max pressure. Is the primer cratered(you can feel a ridge around the edge of the firing pin indent): okay, you are at max load. ANY resistance to bolt lift and ejection is your serious prime indicator you are over pressure. Do not fire any more rounds with that powder charge.

If you jam a round into the lands (Mr. Big does because he cannot accept the 'jump' of bullet from case mouth to rifling engagement) you may or may not get overpressure--Barnes use to recommend this I believe? Some mono manufacturer did. You lower the powder charge, go to a slower burning powder, use other tricks to extend the pressure curve (such as a LONG barrel).

I note my Savage rifles have tight chambers and I am stuck with SAAMI max length bullets. To find the best accuracy I use different powders and charge weights.
My Brownings & Remington's are all long throat rifles and I find that by minuscule adjustments to COL I can zero in to the sub MOA objective.

 

[Jcalder]

Something else to consider is your powder. Some powders are very temperature sensitive while others have little effect. So say now that deer season is over you work up a load near max charge. Temps are fairly low this time of year. Fast forward to July and August and you wanna make sure your rifles are ready to go. Depending on the powder you may have issues. As stated already. It's best to work up when changing components.


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[Omega]

Looked it up, that's an old Barnes bullet, replaced by the TSX (Not same load data), I think the old one was moly coated. What bullet do you actually have? Looks like you have data for at least 4 different ones, so if you don't have any, they should be easy to get. I'm particular to the partitions, changed from the grand slams when I ran out.

 

[7mm08]

Looked it up, that's an old Barnes bullet, replaced by the TSX (Not same load data), I think the old one was moly coated. What bullet do you actually have? Looks like you have data for at least 4 different ones, so if you don't have any, they should be easy to get. I'm particular to the partitions, changed from the grand slams when I ran out.

I have both 200g Nosler Accubonds and Barnes TSX.

Problem is there is data ALL over the place on loads for these bullets and even with this slightly odd caliber.
Seems a lot of folks load a bit past MAX for H4350 and Reloader 17 which I obtained both. I have only loaded NAB & H4350 so far.

Thanks for the input

 

[jlanecr500]

Since I started using Quick Load and a barrel time chart developed by The Long Family, I haven't used a reloading manual. Reloading manuals do not take into account your specific seating depth off the lands. Therefore, listed chamber pressures cannot be reliably accurate. Distance off the lands, volume of brass, and solid vs jacketed bullets are the biggest causes of pressure changes as compared to book loads. My equipment measures pressure in PSI via a strain gage. Some reloading books list pressures in CUP which is measured by the amount of metal movement of a copper test strip that is exposed to chamber pressure via a hole drilled in the barrel. There is a formula for converting back and forth but it is not very accurate except in straight wall cartridges where CUP and PSI are near equal. I start by measuring case capacity in water grains of fire formed brass. Set the bullet .020 off the lands to start, and run loads in Quick Load with those parameters. With a particular weight projectile and powder combination, there can sometimes be more than one attainable accuracy node before running into pressure. This is where I've used my Pressure Tracing equipment to back up my findings. Take a 308 for instance. A 165 gr projectile with Varget will likely have an accuracy node near max, around 44 to 47gr depending on barrel length. As barrel length increases, the charge needed to obtain the accuracy node decreases. At some point, it is feasible to obtain the next higher node without running into pressure. The following are loads calculated for a smokeless muzzleloader shooting a 310gr bullet and H322 as the powder in barrel lengths from 24 to 30 inches with pressures the shooter chose not to exceed 50kpsi. As you can see, the powder charge decreases as the barrel gets longer and the 29/30 inch barrels are able to obtain a 3rd higher node than the others before hitting the pre-defined pressure ceiling of 50kpsi. Also, you can see that the 24-28" barrels can obtain 2 accuracy nodes and the longer barrels can obtain 3. Of course, there may be some lower nodes than listed but they would be pressure starved. As viewed, the 30" barrel has a node at 62gr, 77gr, and 87gr. Obviously, there will be more velocity gained as the charge is increased in the same length barrel. Most cartridges couldn't stand a 25gr difference in charges but SML's can. I showed this for demonstration purposes. In a 308, the charge difference between nodes could be as little as 2.5gr.

24" BBL 86gr h322 310gr bullet --------- next lower node 70gr

25" BBL 85gr h322 310gr bullet --------- next lower node 69gr

26" BBL 84gr h322 310gr bullet --------- next lower node 67gr

27" BBL 82gr h322 310gr bullet --------- next lower node 66gr

28" BBL 80gr h322 310gr bullet --------- next lower node 64gr

29" BBL 78gr h322 310gr bullet ----------next lower node 63gr ---------- UPPER NODE 90GR NEAR 50KPSI

30" BBL 77gr h322 310gr bullet --------- next lower node 62gr ---------- UPPER NODE 87GR NEAR 50KPSI

 

[DaveB]

Jlane-
You have charts for the 308 example with say 16 18 20 22 and 24 inch barrels? Or just 20 and 22? With 150 cup and core?

 

[jlanecr500]

Jlane-
You have charts for the 308 example with say 16 18 20 22 and 24 inch barrels? Or just 20 and 22? With 150 cup and core?

Basically, the chart is barrel time only in regards to barrel length but not caliber specific. It must be used in combination with Quick Load to calculate the load. I can do a real world example if you can weigh a piece of fire formed brass with primer installed, then fill it with water and weigh again, give me the difference which is water weight. Need to know the exact bullet with part number if possible. Need distance off lands and cartridge overall length. Let me know the barrel length overall from bolt face to muzzle minus brake if it has one. This method is surprisingly accurate and has save me a lot of components by getting the load really close to start. Below is a link to Chris Long's OBT page. Lots of good info. The pdf barrel time list on this page is what I use with Quick Load.

http://www.the-long-family.com/optimal% ... 20time.htm

http://www.the-long-family.com/OBT%20Table.pdf

http://www.the-long-family.com/

 

[Tiny]

A Lot of Good n Sound Advice Above ..

Since the Monlethic all Cooper all Building Bullets came avaiable some loads have n were changed..
However Nolser n I would have to recheck Horndays manual the Loads are the same for there's Same Caliber n Weight Bullet.

I have found a few times the Most Accurate Load to be the Max Listed in the Data but not always..

While I didn't n haven't as yet.. 3006 Nolser 150 he bullets ABs Partition,E-Tip Have all been fired in several of my Uncles 06s with same results Most Accurate across the board load every found.. RL 19 Nolser Manual..

Now I would back off n work up to it if ever Changeing any thing Brass Primer etc n yes a different bullet.. despite the fact he has used it with different Brass without any signs of pressure..

One good way to check pressure is have access to n use a chrnoygraph..
If your load is over a good bit bit vel wise it's a sign of pressure.



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