Semi Auto Pressure Signs

[kdog70]

I am taking the plunge into reloading i been lurking on here and a few other boards for a while and feel confident. But i realized today how do i know there is too much pressure with a semi auto besides looking at the primer. There is no sticky bolt lift on an AR-10 just wondering.

[IllinoisCoyoteHunter]

just follow the manuals and their recommendations. always start with the starting load (or a little less) and work your way up. you will probably find the most accurate load will be somewhere below the maximun load....so you should have no worries.

[Gazzmann]

Remember, NEVER, NEVER, exceed maximum loads listed from your data sheet.

John

[rwt101]

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[steve4102]

Remember, NEVER, NEVER, exceed maximum loads listed from your data sheet.

How do you do this when all of the "data sheets" differ? As a matter of fact in many instences the "Start" load in one "data sheet" may be the "Max" load in another. Just to declare "do not go above Max" in many cases is impossible!

I think kdog has a good point! Every manual clearly states to "Start Low and Work Up, Looking for Signs of High Pressure" OK, great advice, what are these signs of high pressure in an auto-loader?

If the only answer is to not exceed Max, then why start low? Might as well start at the Max right. After all the only sign we have to go by is the written word.

[DaveInPA]

I've found that bullet manufacturers, especially Hornady are very, very conservative in their load data. I usually trust the powder manufacturer's data first.

[rwt101]

I have the same problem. I reload 9x18 Mak and there is not a lot of data available. Since I am new also I am afraid to load too high. I also find the same thing that the max on one book is the start on another. I don't want my gun to blow up in my face. I just found that link to read the primers. But I am at a loss also.
Bob T

[IllinoisCoyoteHunter]

As a matter of fact in many instences the "Start" load in one "data sheet" may be the "Max" load in another. Just to declare "do not go above Max" in many cases is impossible!I would start as low as possible and work up. Start with the lowest starting load, and work up. It is better to be safe than sorry. But I would definately NOT start with the max load!

[IllinoisCoyoteHunter]

sorry, the first 2 sentences above are suppose to be a quote!

[steve4102]

Start with the lowest starting load, and work up. It is better to be safe than sorry. But I would definately NOT start with the max load!

Work up to what and look for what? As kdog asked, what are we to look for in an auto-loader where pressure signs are concerned. If there is nothing to physically see or hear than why start low? You will be working up to what? A number, a sign, what?

He has asked a very good question and so far there has been no real answer given.

[IllinoisCoyoteHunter]

flatened primers, split brass, ejecting shells a lot farther than factory ammo due to rifle cycling at higher pressure???, brass not lasting as long as normal...I don't know.... but....where have you seen starting loads the same as max loads??? what caliber???

[IllinoisCoyoteHunter]

and why would you NOT start low?????? only hot shots start off with max loads.

[kdog70]

I have a load that is well i think is pretty mild for my AR-10 just a basic mid range 160 ish grain bullet.....but if i wanted to try and shoot palma 155's to near speeds out of it for giggles then how do i know too much is too much thats all i want to know

[steve4102]

and why would you NOT start low?????? only hot shots start off with max loads.

I always start low. I am being sarcastic. I am being sarcastic to the people that have but one answer to pressure concerns, "Follow The Manual". Which can be very confusing and contradicting at best.

If you have several manuals you can find all kinds of data where the Start in one book is a Max in another. If you really want me to I can take some time and post several for you.

[PCJim]

Kdog, anytime you change your reloading components, you should begin with a powder charge of 10% less than maximum for the bullet design/weight listed for the powder you are using. That being said, do not use less than the minimum powder charge as sometimes going less actually creates more pressure.

Working up from that 10% reduced load, you can load all the way up to the maximum listed charge provided that you do not see any of the common pressure signs resulting from that particular firearm. For rifle cartridges, most reloaders will make 5-10 rounds at each 0.5gr increment within the given powder charge range. This allows enough rounds at each load for testing accuracy as well as checking for pressure signs to give you assurance your load is good. If you are using two or more data sources and they list differing min/max charges for the SAME BULLET, I'd suggest you use the overlapping data. Ie., if one manual states 24 - 27gr and another states 24.5-28.5 gr, then use 24.5 - 27 as you have two sources confirming the data. I'm sure you'll find a charge level within the range to suit your needs.

Common pressure signs - flattened primers, split cases, bright ring at the base of the case wall, etc. These are all listed, as well as other signs, in every good reloading manual. Just keep in mind that if you are using your reloads in several firearms, one may not exhibit high pressure signs while another may. This due to very slight manufacturing differences between chambers.

One more comment - never exceed the listed maximum charges even if you have not seen high pressure indications. Charges over maximum can have significantly violent and unpredictible non-linear pressure curves which can be very detrimental to both your firearm and you.

Personally, I have never settled on a load that was maximum for any caliber I reload. I've always found accurate recipes below maximum and figure that I'm extending the life of the firearm by not pushing hot loads thru it. Just my two cents...

[IllinoisCoyoteHunter]

steve....tell us more about the contradicting data you have found. I am curious. I only reload for four common caliber and there is extensive load data on each (9mm, .45acp, .223, .243). I have never come across conflicting load data where a max load in one manual was a start load in another. Are you sure you are comparing the correct bullets and powder combinations??? Thanks!

[Shane Tuttle]

The following information given is a quick research. DO NOT take my posting for a reliable reference to reload This is used as an example ONLY

Take into consideration that this is a VERY common powder used. It isn't some latest and greatest wonder powder. Yet, there's still conflicting information on a given load....

.45ACP 230gr. Win231:

MidwayUSA LoadMAP guide: 1.275 OAL, average loads found--4.5-6.5gr.

Hodgdon's Site: 1.200" OAL, 4.2-5.3gr

Speer Manual #13: 1.260" OAL, 5.6-6.2gr.

Hornady 7th ed.: 1.230" OAL on 3 of the 4 bullets suggested, 5.0-5.7gr.
This is just ONE example of many that I've found that observes loads that are claimed as max when it isn't even the minumum on the other yet. Granted, OAL suggestions are different and this does skew what's considered. However, this is a huge scale of difference on a very common powder.

So, I stand by Steve's claim of finding minimum charges being maximum charges in others. There's plenty of data available, yes. However, there's so many different variables that are induced into data that it still takes prudent research and careful calculations to find a safe load for one's self.

[mkl]

A couple of other ways to check "pressure signs."

#1 If you are shooting a high intensity cartridge that normally develops pressures in the 50,000+ psi range, web expansion is an indication. Web expansion measured with a good micrometer should be zero. If you get any expansion back off six percent and call that maximum. Speer Manual #8 used this method before pressure transducers were available to them.

#2 Use a chronograph. Your velocity should never exceed the maximum load velocity listed in your reloading manual. If you hit the maximum velocity with less than a maximum load, you have just hit the maximum pressure allowable. Pressure equals velocity.

[Shane Tuttle]

Pressure equals velocity.

That's not always true.

[mkl]

That's not always true.

Example please. (Using reasonable loads as found in a loading manual).

[NuJudge]

Pick any reasonably fast powder for a given caliber, plus a heavier bullet, and maximum pressure. Compare its ballistics with that of a slow powder, given the same caliber, bullet and maximum pressure. The area under the time-pressure curve will be much different. The velocity difference should be quite noticeable.

All kinds of anomalies happen in firearms, but with a 180gr .30-'06 using 3031 one would be doing well to achieve 2700 fps. With the same bullet, using N205, published data gives me 2900 fps.

Years ago I burned a lot of 4198 for loading .223 using 50 or 55gr bullets, because that was what was suggested to me. Today I typically shoot 69gr bullets and something in the area of Varget/4895/VV N540, and comparing 69gr published data velocites for maximum loads of 4198 and the slower powders shows a difference of 175fps or so.

CDD

[mkl]

Pick any reasonably fast powder for a given caliber, plus a heavier bullet, and maximum pressure. Compare its ballistics with that of a slow powder, given the same caliber, bullet and maximum pressure. The area under the time-pressure curve will be much different. The velocity difference should be quite noticeable.

Okay, I'll revise my comment to velocity = pressure + time.

What I was thinking when I made the comment regarding using a chronograph was that the shooter was going to be working with one powder and one bullet at a time per the reloading manual. The only variable I was proposing to be changed was the powder charge, not the powder type itself.

This is normally the way I work up handloads -- select a powder, bullet, primer, case combination and then vary the powder charge weight. Given those constraints, e.g. all constant except the powder charge weight, I believe that pressure = velocity and to exceed the velocity listed in the manual would be to exceed the maximum pressure allowable for that specific powder type and bullet weight.

Please let me know it the above is incorrect. I've been reloading for 40+ years and have found that there is always something still to learn.

[Shane Tuttle]

Example please. (Using reasonable loads as found in a loading manual).

Now that you gave a parameter that limits your statement, you're not getting an example that would necessarily meet your criteria.

In rare but true instances, you can load 10% below a max value given on certain cartidge/powder combinations and cause higher chamber pressure and eventual lower velocity. Actually, it sometimes ends up with damage to the gun, owner, or both.

[mkl]

Tuttle8: Okay, perhaps we are in agreement.

My original post (#18) was an attempt to answer the OP's question which was this:

how do i know there is too much pressure with a semi auto besides looking at the primer.

I did assume that he knew something of the fundamentals of reloading and was looking for methods that would indicate excessive pressure other than "primer signs."

I tried to give that information to him when I mentioned chronograph velocities as a way to gage excessive pressure for a given load as suggested in a loading handbook.

My thinking is that all of the major reloading manual publishers now have access to lab grade equipment that will measure pressure very accurately in the test barrels that they are using. I also believe that they will not knowingly exceed SAAMI maximum pressure recommendations in their published loads. That is why I advised that when your chronograph hits the maximum published velocity for a given bullet/powder you stop there even if the powder charge weight is still below the maximum listed.

It is simply another "safety stop" to consider when reloading. And when dealing with lower pressure cartridges is one to keep in mind since primer "signs" will not occur even if the load is over SAAMI maximum for that cartridge.

Best wishes

mkl

[Shane Tuttle]

I think you were giving good general information. I was only nit-picking just in case the OP thought maybe to go well below the charge range.

Didn't mean to be a nag. Just wanted to make sure all the bases of safety were covered...