Acceptable projectile weight range for load data?

[ViperTwoSix]

Is there an acceptable safe guideline regarding how many grains plus or minus in bullet weights you can range from for a given set of load data and feel comfortable you are not risking any safety issues?
So for example:

If I have load data for a 100gr Barnes TTSX projectile, could I potentially use that same load data to use a different monolithic copper projectile in 105gr or 95gr? What about 85gr/110gr? What would be the safe range of bullet weights if any (assuming I would be using the lowest published powder charge and building up a safe load, NOT just taking an existing recipe and substituting a new projectile)?
I see that load data from Hornady, Nosler, and Sierra, for example will often lists multiple projectile types and weights with the same load data for a set of powders. As long as the projectiles are relatively similar, can this concept be safely applied to some of the more custom projectile that don’t generally publish specific load data?

 

[OkieMike]

Hornady and Sierra often show load data on bullets over a 5 grain spread... 150-155, 190-195, etc... I have even used data from one manufacturer's manual for a given bullet weight to load bullets (of the same weight or close) from a different manufacturer.

BUT!!!

I start at the lowest charge and work my way up and look carefully for issues along the way. Always a good practice even if you're following the recipe to a T.

Another thing that has worked well has been to use the data for a heavier bullet (within 5 grains) as the starting info for a lighter one. Example: Using 180 gr load data to load 175's when there is no data for that powder/bullet combo in 175. As always, start at the bottom and work up.

You can PROBABLY use 100 gr load data to start loading 105's, but I bet you'll see pressure signs sooner than you would with 100's.

This is all based on my own experience and CAREFUL experimentation. Your mileage may vary.

Mike

 

[AllenOne1]

If you are going to do this or if you have to do this because of lack of data I would recommend consulting as many sources as possible to arrive at a safe "zone" to start your load development from, sometimes just looking at one source isn't enough.

 

[memtb]

It’s not just the bullet weight. There are many factors that can come into play...differences in bullet alloy, bullet bearing surface in the bore, and even the bullet ogive. All of these can have an effect on chamber pressures! memtb

 

[Evintos]

Another thing that has worked well has been to use the data for a heavier bullet (within 5 grains) as the starting info for a lighter one. Example: Using 180 gr load data to load 175's when there is no data for that powder/bullet combo in 175. As always, start at the bottom and work up.

This is what I also recommend if there is a lack of loading data for the combo.

Something to keep in mind though is bullet profile, bullet length, etc. matters. There is a difference in bullet length for polymer tipped bullets like the Barnes TTSX, Sierra TMK, Hornady ELD, AMAX, compared to their non tipped BTHP counterparts (TSX, SMK, BTHP), that just looking at bullet grain weight may not take into consideration how that length affects case fill percentage. A polymer tipped bullet (say 70gr) would have a max load closer to a heavier grain non-polymer tipped bullet (say 75-77gr).

Even though component costs have gone up, it is always a good idea to work your way up from a risk mitigation perspective.

 

[OkieMike]

This is what I also recommend if there is a lack of loading data for the combo.

Something to keep in mind though is bullet profile, bullet length, etc. matters. There is a difference in bullet length for polymer tipped bullets like the Barnes TTSX, Sierra TMK, Hornady ELD, AMAX, compared to their non tipped BTHP counterparts (TSX, SMK, BTHP), that just looking at bullet grain weight may not take into consideration how that length affects case fill percentage. A polymer tipped bullet (say 70gr) would have a max load closer to a heavier grain non-polymer tipped bullet (say 75-77gr).

Even though component costs have gone up, it is always a good idea to work your way up from a risk mitigation perspective.

It’s not just the bullet weight. There are many factors that can come into play...differences in bullet alloy, bullet bearing surface in the bore, and even the bullet ogive. All of these can have an effect on chamber pressures! memtb

Both of these fellas are correct... I've had to build loads for powder/bullet combos that there was just no published data for. And I would consult as many manuals as I could for bullets in the same weight class or 5 grains heavier to get a general Min/Max range for my powder... And I would start low and work up looking for pressure along the way.

Just be very deliberate and pay very careful attention and you'll usually be fine... Just make sure you know what pressure signs look like and actually inspect your brass for them... I popped a primer once because I got complacent on my inspection... Had I actually looked carefully I would have seen what was coming.

Mike

 

[Bradv86]

Another thing to consider is that 5gr in a .223 may be significant vs 5gr in a .30 cal magnum.

If you are comparing like-designed bullets it may be more wise to go by a percentage of weight, not just a predetermined +/- XX grains.

You always have to use good practices and judgement like has been mentioned, bullet construction, bearing surface, boat tail or not, seating depth, short throat of the rifle itself all plays a factor.

 

[Dead Eye Dick]

The one constant in reloading is “there are no constants”

Everything is a variable. Not only all the differences in bullets that @Mentb mentioned, but differences in barrels. Ever noticing someone mentioning they have a “slow” barrel or a “fast” barrel. These are not fallacies. Freebore, minute difference in internal diameter, ability of the barrel to cool itself, number and deepness of the lands and groves and of course that old climatic battle we all fight, temperature. Of course, lot numbers of brass, powders, bullets and primers.

 

[ViperTwoSix]

Thank you everyone for the info and advice. Much appreciated!