Velocity WAY over book values, what causes this?

[Texas10]

Developing a load for shooting buddy in his 243 Savage model 11BL with 22 inch, 9 1/4" twist stock barrel. He wants a hunting load so used the Hornaday 87 grain V-Max, new Winchester brass, CCI250, and 43.5 grains of IMR 4831. Various manuals put this load at around 2900 fps and it shoots a very nice .6 MOA when loaded to touching the lands. Trouble is, it's making 3250 to 3300 fps according to my Magnetospeed, and starting to show pressure signs. BTW, this gun has experienced a mild overpressure event before, blown primer, lost extractor, jammed ejector, etc. Bolt got a lot of new parts and trip to the Smith for a thorough check out.

Load development has been a problem for him and me also with this rifle. Seems the throat is very tight, one might say a bit too tight. A lot of scrubbing and cleaning of the chamber and throat, and verifying with my endoscope that it is carbon free, but still a bullet placed onto the lands shows a lot of scraping along the Ogive from the throat, and takes a fairly hard push to get there when using my Hornaday OAL gage.

An OCW load development shows rounds gradually tightening up from 3 moa to under 1 as bullet is moved closer to the lands in .005 increments once we settled on a powder charge, but at touch, the group suddenly jumps up 1 moa and tightens considerably. I suspect a jump in pressure is being seen.

What do you guys think? Is that kind of jump in apparent pressure typical when loading onto the lands, or do we have a dangerously tight throat?

Any thoughts or suggestions from the vast brain trust here would be appreciated!

[ttexastom]

Would say that you are way over pressure. When you reach reloading book max velocity, time to stop. Some chambers may be somewhat oversize and allow this but, sometimes pressure can be deceptive. Better safe than sorry.

[Texas10]

It's at the mid to low end of the loading chart, no where near the max load for this powder and bullet. That's why the question.

[geargrinder]

It's time to forget what the book is telling you and listend to what your rifle is telling you.

Any time you load at or into the lands you will start to gain pressure and velocity.

You need to back off the powder and/back off the lands. You're approaching dangerous territory (again).

[Slowpoke Slim]

Op,

Please, please STOP!

Time to "read and heed", your load is MUCH hotter than you think. From the Hornady 7th Ed Reloading Manual, pg 239:

87 gr bullet, IMR 4831, STARTING LOAD = 40.8 grs, MAX LOAD = 43.8 grs.

This is with a STANDARD Fed 210 primer.

You are using a MAGNUM primer, and you're jamming your bullets into the lands, AND you are right up near a max charge of powder.

Please, Dear God, tell me you are not also crimping your loaded ammo.

You are playing with lightning in a bottle, and you're going to get a rifle destroyed, or worse, get people injured.

[bearcatrp]

Look at the reload manual and see what they used to test. Chances are not the same barrel length or twist. If identical, Then your chrono is off.

[Slowpoke Slim]

You're load "sounded" hot to me, but I don't load that powder combo in my 87 gr 243 loads, so I grabbed my Hornady manual to be sure.

Please be careful. I would pull all those loads down and start over. And for God's sake, stop using magnum primers in that load. Especially if you're going to jam bullets into the lands.

[darkker]

1) used the Hornaday 87 grain V-Max, new Winchester brass, CCI250, and 43.5 grains of IMR 4831.
2) Various manuals put this load at around 2900 fps and it shoots a very nice .6 MOA when loaded to touching the lands. Trouble is, it's making 3250 to 3300 fps according to my Magnetospeed, and starting to show pressure signs.
3) Load development has been a problem for him and me also with this rifle. Seems the throat is very tight, one might say a bit too tight. A lot of scrubbing and cleaning of the chamber and throat, and verifying with my endoscope that it is carbon free, but still a bullet placed onto the lands shows a lot of scraping along the Ogive from the throat, and takes a fairly hard push to get there when using my Hornaday OAL gage.


Texas10,
These things tie together and will try not to blur for the sake of clairty.
1 & 2) Don't know what books you are using(how old), but this is a classic case of misunderstanding the oft understated warnings. ALL powders come with a warning, stating to "Drop loads 10% when switching lots". If you double check the only one who lists nominal variations(Western), you will see that lot variations of 10% between powders is completely reasonable. Hodgdon's current data shows you to already be over max by charge, and matching book max velocity. So here is the why: No one lists lot numbers tested, or if they themselves tested or merely re-printed the data. All good data comes from SAAMI minimum spec universal receivers and minimum spec bore and groove barrels. You are working with a mass produced animal, which will have some amount of larger tollerances. Meaning you will bleed more gas, and have lower velocities. So as was stated, whenever you match book velocities, you beat book pressures. So compared to current Hodgy data, your lot is burning faster. The next fly in the ointment is the cartridge and powder. The 243 is imfamous for having wild unexplained pressure excursions when using slow powders. It is usually more troublesome with heavier bullets, but remains in any case. So that could be playing into this as well.
As for the Mag primer comment. Remember that magnum primers came from a request of Roy Weatherby. He himself didn't like shooting his 300 case to full load pressures. After using that case in the Rockies with substantially downloaded capacity, he found ignition issues. Many will claim that it is for ball powders, which is only sort-of half correct. It is true that ball powders will have more air gap between particles, and with a substantially reduced case fill; some very old tech ball powders could actually run-out of air production to sustain ignition if the flame front wasn't aggressive enough. Speer was a leader in that "change", but that didn't happen until 1989-ish. Aluminum was one of the additives to have more "Sparklers" if you like, to aggressively ignite things. However total output isn't substantially increased. No doubt, they are different, but not massively so. All things depend of course, but in my 308 & Creedmoor, swapping magnum primers with standard produced no significant differences detected by the Pressure Trace. Not to say that ALL primers are the same, nor that all powders and loads will be the same. But don't take a sky is falling claim as gospel. Simply remember that when you switch any component, things change.
3) The throat is up to you to determine. I honestly haven't used a books OAL in so long, I can't tell you what any of my rifles are. I always load them for themselves. So take an un-primed, sized case and just barely seat a bullet. Then drop it in the chamber and slam the bolt home. Carefully extract it and measure, this tells you your jam length. Back-off as appropriate for your own desire, or mag length. Personally I like 1/32" of jump, unless a mag length issue arises. While velocity suffers when seated more deeply, I personally think that far too much is made of the importance of jump length for accuracy. There are shooters out there that perhaps it matters for, but not the masses. In my rifles even when chasing my mile targets, ALL bullets get seated to the 32nd jump. Any lack of accuracy, assuming proper powder charge work was done, isn't from bullet jump; it's me missing the wind calls.

Cheers

[Slowpoke Slim]

darkker,

1. The OP has already had one "overpressure event" with this rifle.

2. The OP thought he was "no where near" max with his load.

3. The OP substituted magnum primers for standard primers while jamming bullets into the lands with a max powder charge.

The sky is indeed falling.

[gbflyer]

Back it off a couple grains and try it again with the same seating depth.

I've got a "fast" .308 from PacNor. I too have chased bolt parts out of this rifle. Wakes a guy right up. Sure is a good shooter!

[darkker]

I agree that he's over pressure, I further explained how to understand that. Further I was merely clarifying the history of mag primers, and potential (not absolute) differences. Taken only at face value, your statement would imply anyone jamming bullets couldn't use a mag primer; or that it positively does raise pressures, which isn't the case absolutely.
So, to repeat what i said, when things are different, they are different.

Explaining why he is off is helpful to the cause of him wanting to know what's going on. Telling him he's going to blow himself up especially if using a mag primer, isn't, even if a correct warning of his current pressure situation.
The sky isn't falling, the clouds are merely at a lower altitude.

[Texas10]

Thanks, Darkker. Believe it or not, I do pay attention to what's printed here, especially those i know and are quite knowledgable and helpful. The OP has not had an overpressure event....EVER! But the subject gun has experienced such and event, and that is why I am helping with the load development. Trying to keep my friend healthy and alive, but there's something strange with this barrel, and THAT is what I am trying to sort out.

The Hornaday max load is at 2900 fps. I have checked LEE, Nosler, and Sierra, in addition to Hogdon website. All current additions, and this is the lightest load listed.

Loads were started low, and worked up. Magnum primers were added when we saw large elevation changes in all loads. My take was ignition issues. That change by itself made the desired difference in group shapes, from minimum load to near max all groups formed circles instead of vertical lines.

Nothing was out of the ordinary, no signs of pressure (sorry Darkker, no strain gages on this action) until touch. Then BIG boost in velocity, with only the beginnings of primer cratering.

Nowhere have I read that switching to a magnum primer will result in a 400 fps gain! I suspect that if that were typical, all the long range guys would shoot nothing but magnum primers. I am certainly no expert, but I don't think that's the case.

So what I am asking here, and BTW I am reading about a similar issue regarding a Stealth that might have a short chamber, is this: Would a tight throat cause a significant increase in muzzle velocity such as we are seeing? I know it can raise starting pressures, but 400 FPS?

IF SO....what is the correct course of action? Replace the barrel? Have it re-throated? This gun has been a problem child since new, 25 some years ago and I'd like to identify the problem and fix it, if possible.

Thanks for all your help, guys. Looking forward to your responses

[Slowpoke Slim]

Tex,

I'm glad you clarified the "overpressure event" in your follow up. What concerned me the most in your original post was your assertion (an incorrect one) that your listed load was no where near a max load. I don't know where that info came from, but if you're extrapolating data from other sources, this is quite a bit off from the Hornady manual. 43.8 grs is listed as a max load, and you're 0.3 grs under that, and thinking that you're at a low to mid scale load (your follow up post). This is a huge red flag that something is quite seriously wrong, and a FULL STOP is in order.

As far as velocities go, there are many possibilities why your velocity is "off" from the book. Firstly, the Hornady manual lists that max load as having a 3100 fps muzzle velocity. These test loads in the manual were fired from a Winchester M70 with a 24" bbl. First, there are differences in rifles, chambers, barrel lengths, and even how "fast" a barrel is. Second, there are differences in measuring equipment, aka chronographs. If you took 3 or 4 different rifles, all chambered in the same cartridge, with the same barrel lengths, you would see differences in muzzle velocity when shooting the exact same load over the same test chronograph. Similarly, if you took one rifle, with identical loads, and fired them over multiple chronographs, brands, styles, etc, you will also see a difference in measured muzzle velocity. I have seen rifles that were a couple hundred fps off from each other when shooting the same load. I have also seen chronographs that were several hundred fps different from each other when clocking the exact same rifle and load. That is just The Way of Things.

Darkker,

Reading into my words that the use of magnum primers will bring the end of the world is a huge disservice. That is not what I said, nor what I meant. You are correct that each rifle is it's own individual animal, and needs to be treated as such. Just because you (or I) have a rifle that switching to magnum primers in makes "little difference" is irrelevant. Some barrels, chambers, throats will take the switch with no problem, and some can be a big problem. But for a loader (any loader) to take a max load, with the bullet jammed into the lands, and proceed to use a magnum primer where the load recipe called for a standard primer, should only be done with caution, and only done while slowly working the load up from scratch. Doing so invites an initial pressure spike, as the increased ignition wave due to the bullet not moving sooner in the wave cycle. It can be done, but must be done carefully, and with purpose. Not just swapped in to see what happens (not saying that is the case with the OP). But switching to a magnum primer in a max load, where the bullet is already jammed into the rifling gives the chamber (in this case actually it's the cartridge case that's the "chamber") no where to go. The bullet will sit motionless for a longer period of time, until pressure builds up behind it enough to force it to move down the rifling. Where as if you are jumping bullets, the bullet starts moving almost immediately, as soon as pressure builds enough to overcome the neck tension on the bullet. So the initial ramp up in the pressure wave changes when you jam bullets. The initial pressure wave also changes when you use a magnum primer. More of the powder charge is ignited in the initial instant of ignition, so the pressure wave starts off sharper. When you stack those two occurrences, jammed bullets, and magnum primers, you can have an initial pressure spike in some barrels/chambers that you will not see in others.

So when a loader/shooter is having issues with pressure coming on "early", or velocity that seems too high, AND he is jamming bullets with magnum primers, then caution and load reevaluation is in order. But when a loader/shooter states he is shooting a load that is no where near max, but in fact, he is right at book maximum for that load, then EXTREME caution is in order, and a full stop is necessary to evaluate what the heck is going on.

[Slowpoke Slim]

Tex,

Look man, I'm not trying to beat you up here, I'm just trying to keep you safe.

As far as your barrel goes, I don't really see anything that makes me think you should swap the barrel. Maybe get it bore scoped if you want. Have you tried lapping the barrel? Maybe try a full clean to get it down to bare steel and start over with break in (either a foam cleaner multiple times, or a plug in the chamber and stand the rifle up and literally fill it with bore cleaner like Butch's Bore Shine), and let it stand there and soak for a couple days.

Purely as a side note, a tale of 2 rifles,

My brother has an old flat back Savage chambered in 30-06. He's had that gun probably 30 years. He hardly ever shot it, or went hunting with me, just wasn't really his "thing". One day he asked me to load some ammo for him for this rifle. Upon load development, not only does his rifle HATE every load that my Win 70 30-06 LOVES, but I found his rifle chamber was throated a full tenth of an inch shorter than my Win. That is not a typo, it really is 0.100" shorter throated than my Win. He had always complained about hard chambering in the factory ammo he bought for it, but he shot it so infrequently that a single 20 round box lasted him for many years. It wasn't until I "discovered" his short chamber, and developed a load specifically for his rifle, that he could chamber live ammo easily. I'm not sure what his chamber pressure was with that factory ammo he was jamming into that gun, but he did tell me that my handloads "kicked less" than the factory loads he had been using.

Point of all this? Maybe just that some rifles can vary wildly from each other. The safe loads that I shoot from my Win will not even chamber is his rifle.

[Zero333]

Whatever the rifle is telling you is what matters. Regardless of what the manuals claim.

I've worked up a few loads in the same rifle with 87gr vmax and never reached pressure signs all the way up to 3,250 fps.

Keep that load around 3,200 fps max and you'll be safe.

A good gunsmith should be able to re-throat the barrel with a throater for very little money. You can purchase a throater for around $125 form PTG and re-throat it yourself. No need for a lathe either.

I gain about 50 fps when slightly going into the rifling (but not jamming). Once the projectile gets jammed into the rifling (as in the bullet is stuck and can't extract a live round) the pressure goes up drastically.

[Texas10]

Ok, since the conversation seems to focus on the load, I'll share the result of my research when starting out on this load.

First of all, i screwed the pooch in my first post when I wrote 2900 fps. That's a starting load, not the max. Brain does funny things sometimes.

These are all based upon using IMR 4831 and 87 grain V-Max and use current publications.

Hornaday manual (groups 85 and 87 grain bullets together) lists 43.8 grains @ 3100 fps. Their info is derived from actual tests using Rem 700, 24" bbl
Lee manual (85 grain) lists 48.5 grains @ 3183 fps. Their info comes from published data, not actual tests.
Hogdon website (90 grain) lists 43.9 grains @ 3050 fps. Source unknown, probably published data.
Sierra Manual (85 grain) lists 44.5 grain @ 3000 fps as tested in Rem 700, 24" bbl.
Nosler manual (85/90 grain) lists 44.5 grains @ 3240 fps and this is their accuracy load, tested in 24" lija bbl, and Rem 9 1/2 primer.

So based upon all this information, I felt that a 43.5 grain load should be producing about 2900 to 2950 out of a 22 inch bbl (adjusting for 25 fps loss per inch of bbl.)

So, based upon all this load experience, it looks to me like we're making awfully fast headway for the load we're using, and hence my question. What's causing it?

I really don't think we're about to produce a mushroom cloud with this load, but I am curious about the greatly increased velocity. My magneto speed has been right on the money when testing factory loads with published velocities, so I am confident about its numbers.

If i back off the throat just a couple of thou, groups start to go wild.

BTW: Just before Christmas my son took his first deer ( a beautiful buck) at 220 yds with a heart shot using this gun/load. It was fortunate to have the accuracy for that shot. Deer took two steps and collapsed.

[Texas10]

Whatever the rifle is telling you is what matters. Regardless of what the manuals claim.

I've worked up a few loads in the same rifle with 87gr vmax and never reached pressure signs all the way up to 3,250 fps.

Keep that load around 3,200 fps max and you'll be safe.


A good gunsmith should be able to re-throat the barrel with a throater for very little money. You can purchase a throater for around $125 form PTG and re-throat it yourself. No need for a lathe either.

I gain about 50 fps when slightly going into the rifling (but not jamming). Once the projectile gets jammed into the rifling (as in the bullet is stuck and can't extract a live round) the pressure goes up drastically.


Thanks, Zero. That's some very useful information based upon actual experience.

No, I am not jamming the bullet. Closest we tested was touching, but again, finding the lands is difficult in this particular gun what with it's tight throat. I using the Hornaday OAL gage with modified cartridge, I can push the bullet past the throat to touch the lands, but the chamber/throat has to be free of carbon. So I cleaned very thoroughly before starting to set up this load.

To re-iterate. This gun has been difficult to load for since new, and I am looking for a good course of action to fix it. Don't want to sell a dangerous problem child to some poor un-suspecting soul. If it has a too tight throat, and that is the thrust of my query, reaming or replacing it seems to be the thing to do.

[Texas10]

Back it off a couple grains and try it again with the same seating depth.

I've got a "fast" .308 from PacNor. I too have chased bolt parts out of this rifle. Wakes a guy right up. Sure is a good shooter!

Thanks, GB flyer (is that a Gee Bee, if so, you've got some really BIG ones:cool:), glad to read you weren't hurt while disassembling your gun while using kenetics.

My plan was to do just that, now that we've identified what jump to go with. But the larger issue is how safe the gun is. Is it defective, or within limits?

[darkker]

Well I guess I want to be clear on your terms, then reiterate my powder point.
You keep saying "tight throat". What that says to me is diameter. If you had a tight throat and large brass you could feel the interference/see it. If you actually mean short, then you should know that from a dummy cartridge and simply seat for the rifle, not book OAL.

Either way, short or tight, that should have been caught/noticed already in basic reloading, yes?

Take it back to powder and the warning people ignore/don't understand:
Powder can vary from lot to lot, by 10%. Say that out loud 5 times. Extruded powder has burning rates controlled by geometry mostly, coatings for temp stabilized. So if you load by weight, you ignore burning rate, which (say it with me) can vary by 10%.

Simply extrapolating what you want a speed to be, ignores all warnings about powder. No manual lists when, or by whom anything was tested. Was it calculated? Was it when that IMR plant was original, or now that it was gutted and rebuilt completely by GD? Test for what you have, not what the books prove can vary by 10%. :D

When I started pressure tracing the Creedmoor, Superformance loaded "slightly over mid-range" produced beenobviously well under start. Did I have a bad barrel? No, I had a very slow lot of powder. Well you have a faster lot. And remember that powder doesn't always just play nice, which is why a small increase/change can spike things dramatically.

[darkker]

Slowpoke,
Claim a disservice for repeating and unexplained caution you gave, all you want. I was explaining to the man, you were bemoaning him. I corrected your info, and you took offense. Suddenly you have time to explain how things work?
If you stick around a while you'll see that I regularly post actual Pressure Traced data. Meaning I can see exactly what is happening in my rifle.
Details are important.

If you jam bullets into the lands, do pressures always spike? Are you sure? Have you played with some of General Dynamics progressive burning powders?

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