Can I use these 9mm reloads?

[k9cougar]

My quality control slipped a bit and I ended up loading montana gold 124 gr FMJ with 4.5 gr of 231 to a oal of 1.084. I was aiming for 1.1 which works great for both my HK P7 and Browning HP. I loaded several hundred to this lower oal before I caught it.

Think these are usable? The thought of taking these apart kind of sucks. I use them for plinking so accuracy isn't a big deal. Occasional FTF I can handle. Blowing up my gun would put a crimp in my day.

[Fire_Moose]

What's the Max charge? You should be fine as ling as yer .5gr lower then Max.

[Miata Mike]

How close to max were you at 1.1"? I don't care to look up the data, but fire moose's thoughts might be good enough for me to try in my cheapest 9mm.

I lied about not wanting to look it up.

http://data.hodgdon.com/cartridge_load.asp

will show a 4.4 grain to 4.8 grain powder spread for an OAL of 1.090".

125 GR. SIE FMJ Winchester 231 .355" 1.090" 4.4 1009 24,600 CUP 4.8 1088

[AllenJ]

Max charge should be about 4.8 grains, you should be alright.

[Misssissippi Dave]

.020" short on a non max load should be fine. If you are worried about it, just use your hammer type puller to move the bullet out enough to reseat them to the length you wanted to have. If you loaded a lot this could be a pain to do. You don't have to pull them all the way out.

[SL1]

I agree that shortening your COL by 0.016" is probably not a dangerous problem with your charge weight of 4.5 grains, assuming that you have already shot the same load with the intended 1.100" COL and found that they were not hot loads to begin with.

However, relying on data for ANOTHER BULLET of the same weight in 9mm requires a lot of caution, because bullet length, and thus seating depth, has a big effect on peak pressure in this cartridge. So, if you don't have any experience with this particular load at your intended COL of 1.100", then you might be getting into dangerous territory by going shorter with an untested load.

I don't have Montana Gold 124 grain FMJ bullets in my QuickLOAD database, so I can't do the proper calc, without knowing the bullet length. Because 9mm bullets vary so much in shape, and thus in length, it is not really possible to know whether your 1.084" COL is near maximum or not without having its length to use in the calc. If you can measure the bullet's length and post it for us, one of us with QuickLOAD can see what difference in peak pressure your 0.016" change in COL would make.

However, I suggest that you do NOT try to lengthen them with a kinetic type bullet puller. The reason is that the process of lengthening them to more than 1.100" and then shortening them all uniformly to 1.100" will loosen the bullet in the case to some degree. In an autoloader, that could allow the bullet to be set-back into the case when the bullet slams into the feed ramp during the feed cycle. So, when the cartridge actually gets into the chamber, your bullet may have been set back to the original 1.084" COL or even less. So, you could actually end-up with even more peak pressure than just leaving the COL alone.

SL1

[DarthNul]

nevermind...

[Silver00LT]

Interesting topic...How does one calculate any increased pressures? Be good to know for future reference in case something happens I'd like to have something to be able to do calculations with.

[wpsdlrg]

It would be nice to be able to calculate the pressure increase, due to deeper bullet seating. But, it isn't that easy. You can make a computation of ESTIMATED pressure increase, but you first need to know the exact pressure of the particular load in question, at the specified COL. This number is only valid for YOUR load IF the charge weight is identical, the bullet used is virtually the same (not just weight, but design, bearing area and lube (if a cast bullet), etc.) Then, you would have a baseline. However, if this baseline number is off from the ACTUAL value, by only a few percentage points - then the resulting calculation will be mostly meaningless.

Note that the numbers published in load manuals, in and of themselves, are ONLY rough guidelines, at best. The only way to ensure a truly comparable number, as a baseline, is to duplicate the load, conditions and barrel/ gun used for the published number , to the detail. That's kind of difficult.

But, if you have obtained a trustworthy baseline, a simple calculation would seem to give an acceptable ESTIMATE. IF all other factors are held equal, a decrease in volume should produce an linear increase in pressure, with inverse proportionality. In other words, 1/2 the volume would double the pressure. So, if you calculate the percentage decrease in free volume left inside the case, caused by seating the bullet deeper, then you will have a multiplier that can be used to estimate the pressure increase.

For example: A 10% decrease in free case volume should equate to a 10% increase in pressure.

Only, it probably WON'T. The kicker is that not all powders react the same way to such changes in volume. Reduce free case volume by 10% in one load....and you MIGHT get a corresponding 10% increase in pressure. Or, you MIGHT get a 25% spike in pressure. Another powder will react differently - and you MIGHT get a 50% increase in pressure, for the same 10% decrease in volume.

The long an short of it is, there is NO really valid way to mathematically work out such pressure changes. To get valid numbers, you'd have to MEASURE actual pressures directly. So, the best any of us can do is follow some basic rules of thumb.

A) Published pressure numbers are rough guidelines - they should be respected and attention should be paid to them - but they are NOT gospel.

B) Published COL numbers are GUIDELINES. Not absolutes. If you can get reliable feeding, etc., by using the published COL, then do so. If not, then seat deeper, but pay attention to exactly HOW MUCH.

C) The closer you get to maximum loads, the MORE likely that a decrease in COL (increased seating depth) will produce excessive pressures. So, if you have to seat a load for a particular gun abnormally short - it might be best to NOT use maximum loads.

D) As is always the rule, start LOW and CAREFULLY work up. If you find that you must seat a particular load more than a few thousandths shorter than published COL to ensure function, then it would be wise to START at no more than 65 - 70 % of a max. charge....and slowly work up.

E) Use COMMON SENSE. Obviously, loading to the maximum, but seating a bullet 0.015" shorter than the published COL, for example....is a recipe for TROUBLE ! Common sense would dictate backing WAY off on the charge weight - and testing the result.

[totaldla]

Shoot them and have fun.

[Silver00LT]

It would be nice to be able to calculate the pressure increase, due to deeper bullet seating. But, it isn't that easy. You can make a computation of ESTIMATED pressure increase, but you first need to know the exact pressure of the particular load in question, at the specified COL. This number is only valid for YOUR load IF the charge weight is identical, the bullet used is virtually the same (not just weight, but design, bearing area and lube (if a cast bullet), etc.) Then, you would have a baseline. However, if this baseline number is off from the ACTUAL value, by only a few percentage points - then the resulting calculation will be mostly meaningless.

Note that the numbers published in load manuals, in and of themselves, are ONLY rough guidelines, at best. The only way to ensure a truly comparable number, as a baseline, is to duplicate the load, conditions and barrel/ gun used for the published number , to the detail. That's kind of difficult.

But, if you have obtained a trustworthy baseline, a simple calculation would seem to give an acceptable ESTIMATE. IF all other factors are held equal, a decrease in volume should produce an linear increase in pressure, with inverse proportionality. In other words, 1/2 the volume would double the pressure. So, if you calculate the percentage decrease in free volume left inside the case, caused by seating the bullet deeper, then you will have a multiplier that can be used to estimate the pressure increase.

For example: A 10% decrease in free case volume should equate to a 10% increase in pressure.

Only, it probably WON'T. The kicker is that not all powders react the same way to such changes in volume. Reduce free case volume by 10% in one load....and you MIGHT get a corresponding 10% increase in pressure. Or, you MIGHT get a 25% spike in pressure. Another powder will react differently - and you MIGHT get a 50% increase in pressure, for the same 10% decrease in volume.

The long an short of it is, there is NO really valid way to mathematically work out such pressure changes. To get valid numbers, you'd have to MEASURE actual pressures directly. So, the best any of us can do is follow some basic rules of thumb.

A) Published pressure numbers are rough guidelines - they should be respected and attention should be paid to them - but they are NOT gospel.

B) Published COL numbers are GUIDELINES. Not absolutes. If you can get reliable feeding, etc., by using the published COL, then do so. If not, then seat deeper, but pay attention to exactly HOW MUCH.

C) The closer you get to maximum loads, the MORE likely that a decrease in COL (increased seating depth) will produce excessive pressures. So, if you have to seat a load for a particular gun abnormally short - it might be best to NOT use maximum loads.

D) As is always the rule, start LOW and CAREFULLY work up. If you find that you must seat a particular load more than a few thousandths shorter than published COL to ensure function, then it would be wise to START at no more than 65 - 70 % of a max. charge....and slowly work up.

E) Use COMMON SENSE. Obviously, loading to the maximum, but seating a bullet 0.015" shorter than the published COL, for example....is a recipe for TROUBLE ! Common sense would dictate backing WAY off on the charge weight - and testing the result.

Thanks for the good post.

[SL1]

I am going to have to disagree with wpsdlrg.

First, the concept that the change in PEAK pressure will change in inverse proportion to the volume left in the case for the powder is dangerously wrong. Cutting the powder space in half will NOT just double the pressure, it can make a bomb. The problem is that powder burns faster at higher pressure. It is a dynamic process that does not follow the perfect gas laws, because the rate at which gas is being CREATED is a non-linear function of the pressure at each point in time. Halving the powder space in a .38 Special load that produces about 18,500 psi is calculated to produce 42,300psi in an example that I was just working with and used for a test for this post. Halving the powder space in a load such as K9cougar is using might take the pressure from about 25,000 psi to about 78,000 psi (if you could compress the powder enough). Speer found a 9mm load that changed pressure from about 30,000 psi to about 60,000 psi due to a change in COL of just 0.03", which they discuss in their Manual No. 10. (And, that was actual pressure testing, not a calculation. I have not been able to find a load that will produce that result as a calculation, but I would not use that to argue with results of pressure tests done by professionals.)

There IS a computer program available to handloaders that can do a pretty good job of calculating the pressure effects of things like changes in seating depth. It is QuickLOAD, and there are a lot of members that have it and will do some simple calcs for you. Please make use of that. There are also some rules-of-thumb that can allow you to adjust the charge weight appropriately when you need to adjust the seating depth for a bullet, so that you maintain about the same pressure. Those rules work OK so long as you are not making large COL changes.

Pressure in the 9mm cartridge is particularly sensitive to changes in bullet shape and seating depth, so it is a good thing to learn to understand if that is what you are loading.

Edit: After sleeping on it, I realized that I was limiting my examples to target-type loads that use fast powders, and don't show how bad the problem can get. So, here is an example of a major peak pressure increase, using a slower powder in the 9mm cartridge. The QuickLOAD parameters were set to give the SAAMI pressure limit for 9mm (NOT "+P") of 35,000 psi with a 124 grain Speer bullet and AA #7 powder, using the default COL of 1.169". Then, the COL was reduced to 1.075", which reduced the powder space by 25%, giving a new peak pressure of 67,000 psi. So, the peak pressure went up by 91%, rather than increasing by a factor equal to the reciprocal of the powder spaces, 100/75 - 1 = 33%.

This example decreases the COL by 0.094", which is a lot compared to the OP's question about a 0.016" reduction in COL. But, the resulting COL is not really that different from the COL that the OP ended-up with. IF he has ALREADY substituted a bullet compared to his pressure-tested data, and THEN decided to accept a decrease in his COL due to a loading error, he might ALREADy be working with higher pressures than he realizes. And, with fast powders, he may not get the ejection-related indicators of unexpectedly high pressure, because resulting bullet velocities may still not be as high as full-power factory ammo.

SL1