Bullet Question....


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Ch4rg3rF4n
January 3, 2008, 04:35 PM
Happy New Year all.....

I have the Lyman manual as well as the speer but
I'm still a little new to this ....
I figured I'd better ask instead of blowing my pistol up-

Is it okay to substitute a FMJ projectile of the same grain weight for a load that calls for a JHP? (load calls for using a 165gr jhp bullet- is it okay to use a 165 fmj instead)....

From what I have been reading- the bullet shape affects pressure levels.....so I have a feeling that this is a no no...but I am still too new to this and cannot find anything in the load manuals that lead me to believe this is true or not....

Thanks in advance for the help.......:)

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cougar1717
January 3, 2008, 04:52 PM
as long as they are the same caliber, they are interchangable. As always, work up from starting loads whenever any component changes.

rcmodel
January 3, 2008, 05:48 PM
No their not!
As long as they are the same caliber, the same shape, and the same construction, they are pretty interchangeable.

But if they aren't all three, they aren't!

For instance, a Secant Ogive bullet would have a much shorter bearing surface then a RN of the same weight. So less bore friction.

A Barnes solid copper X-bullet would require a different charge then a Hornady jacketed bullet of the same weight & shape.

Generally, it is O.K. to substitute a FMJ for a JSP of the same weight & shape.

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rcmodel

38 Super Auto
January 3, 2008, 06:44 PM
I think you can change the bullet and get similar performance, but I'd take Cougar's advice and reestablish your load starting 10% down on powder charge and working up.

Anytime you change bullets, even the same bullet / same vendor / different lot, you should reverify your loads at lower pressures. If a bullet shape changes, you may end up adjusting the seating die and affecting the depth of the seated bullet/OAL.

The reason you need to do this is small changes in bullet weight, sized diameter, bullet hardness, etc. can effect pressure quite a bit. I don't think it's good to run your loads up to the very limit: there are always factors that you don't take into consideration when you're reloading.

When I work up a load, I increment the powder charge up 0.2 to 0.3 grains per step and look for signs of pressure. When I see signs of high pressure, I back off the propellant charge a safe amount and verify the accuracy of the load.

You can load up 6-8 rounds in incrementally increasing powder charge. Proceed slowly: when you see signs of excess pressure. Stop and take your remaining loads home and pull the bullets.

I always proceed cautiously. I don't get into a hurry to establish a final load.

Have fun. Be safe.

steve4102
January 3, 2008, 07:10 PM
I guess that depends on what you mean by "interchangeable". If you mean can you substitute one type of bullet with another type of the same weigh in an Existing load, then the answer is No. Any time you change a component you must back off the powder charge and work back up. This includes, bullets, primer, lot numbers and of course firearm.

If you mean can you substitute one type of bullet with another of same weight, starting low and working up in small increments looking for signs of pressure, then yes, of course. Load data is not a recipe and should not be treated as such. It is only a set of guidelines. After all, every component you will be using in your loads will be different than the ones used to develop said data, especially your firearm. Start low and work up, it's the only way.

Walkalong
January 4, 2008, 08:12 AM
Similar types of the same caliber bullet of the same weight can generally be substituted with no problems if you are not running max loads. If you are you need to back off say 5% and work back up.

I routinely use different brand bullets of the same weight with the same load in several calibers, but they are NOT max loads.

Any max/hot load absolutely needs to be worked back up if you change components. You don't necessarily need to back of a full 10%, but you need to back off. Use common sense on how far. How big of a change it is will determine this. Change two things? Back off the full 10%.

Mal H
January 4, 2008, 09:23 AM
All good advice above, but one thing that has not been mentioned is OAL. You cannot substitute one bullet type for another without adjusting or at least considering the OAL.

One bullet may have a much shorter OAL than a same-weight bullet with a longer profile. If you simply substitute bullet for bullet and load according to data for the shorter one, you might end up with a high pressure problem.

[Correction]
I see 38 Super Auto did caution about adjusting the OAL.

<SLV>
January 4, 2008, 09:56 AM
This is probably common knowledge, but you can get the right OAL for your chamber by LIGHTLY crimping a bullet into an empty un-primed case and slowly chambering it. The lands (rifling) will push the bullet back into the case. Take your caliper and measure the OAL, subtract a reasonable amount, and then set your press to give an appropriate bullet jump.

What this doesn't tell you is the change in case volume from one bullet to the next (but you can get a rough idea by comparing bullet lengths and the rear profile).

I've found most bullet manufacturers to be very accomodating in recommending a charge. Maybe a good place to start.

moxie
January 4, 2008, 10:51 AM
Good advice above. Remember that JHPs are generally a bit longer than FMJs of the same weight so OAL is going to be different and the seating depth may be different as well, which can affect pressure. So, for reasonable loads, as noted above, back off to begin with to ensure safety.

Kimber1911_06238
January 4, 2008, 10:52 AM
use the jhp data as a starting point, start on the low end and work your way up if you like

rcmodel
January 4, 2008, 12:20 PM
Walkalong said:
Similar types of the same caliber bullet of the same weight can generally be substituted with no problems if you are not running max loads. If you are you need to back off say 5% and work back up. This is exactly right.
If you look at the loading data from Winchester for instance, they don't even tell you what brand of bullet they tested.
Just what type & weight it was, and the OAL seating length for each type of bullet..

Their published data only shows one load.
No Starting load, no Maximum load, just THE load they recommend.

They also don't recommend reducing THE load and working up with any of their ball rifle powders.

Now, if you go to another source of data like Speer or Hornady, you may find a heavier max load with their brand of bullet.
But THE load listed by Winchester is safe with any bullet of the same shape, weight, & construction.

Just like Walkalong said.
Unless you are already at or near a maximum load, there is no need to back off 10% and start over,
because you are already backed off!

http://i81.photobucket.com/albums/j219/rcmodel/KTOG/1224.gif
rcmodel

cougar1717
January 4, 2008, 12:35 PM
A lot of great information has been posted here by a lot of knowledgeable people. Just to clarify - interchangeable by definition means "permitting mutual substitution" from Merriam Webster. An object does not have to be identical to be interchangeable.

Without rehashing everything written, use your manuals to determine a starting load and OAL for the new set of components. It is best (but not ablsolutely necessary) to have a reloading manual for every bullet you reload. Check for signs of pressure as you slowly and incrementally increase the loads and use caution when approching maximum loads. If you haven't read the section in your manuals about how to reload, I would urge you to do so before you begin.

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