Does Crimping Change P.O.I.

Z

Zen Archery

New member
Found 500 rounds of 100gr Amax for my 6.5CM
Accuracy node is to load long.
After my first hunt I pulled my charge handle back and out spills the brass with all the powder.
Bullet lodged into the chamber! Ooooops!!!!

Dislodged the jammed bullet.
Cleaned the rifle.
Crimped the remaining 19 rounds.
Here's the results.

Click Here For Video.

jp1sNc9l.jpg
 
It can increase start pressure a little where there is bullet jump, but if you are already jamming the lands, I doubt you'll see a difference. It depends how carefully you do the crimping. If you distort the bullet, you will likely see at least a little added dispersion at very long ranges. On the other hand, you may lower your velocity SD's from achieving more consistent ignition. Though again, if you are already in the lands, you've probably achieved those things before now, and you are just making your live rounds extractable.
 
I don't think you will see any difference, I never have I have a 7mm.08 I sighted in and then decided to crimp POI was the same, but my groups were better !!!
 
Like Unclenick I too believe since you are already jammed into the lands, you will see little or no difference from applying a crimp. My bigger concern would be 'am I jamming too far into the lands?" ", "do I have proper neck tension?" or "am I leaving too much lube on the inside of my case necks?". With any of the above, crimping may not help in extraction. Still any change in a load, many times, is also dependent on the individual gun and the load/techniques used in the prior loads. One can only try and see.
 
For hunting I would look for a load that would operate in your magazine. Are you using bushing dies for sizing ? I would think you have a hard jam for a powder spill to happen . Some benchrest shooters soft seat their bullets with .001 neck tension. I wouldn't crimp on a 6.5 bolt action . Work with the recommended OAL and find a load that works . I would think when closing your bolt down you must feel resistance if not your neck tension must be as light as to seat a bullet with finger pressure.
Looking back at your post you mentioned charge handle , even if it's for an auto I would go with recommended OAL an find a charge that is as accurate. I had a stock barrel on my Rem. 700 that had so much free bore I couldn't come close to jamming my rounds . On a 308 the OAL for my listing was 2.800. I seated the bullet to that length , measured the ogive setting an that's what I used for OAL ,worked up a accurate load . That's with only shooting benchrest only loading one round at a time. A-Max in 6.5 great round for benchrest. I've used A-Max in my 308 168 gr. Just as good as Sierra 168MK . Hope I helped in some way.

Chris
 
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Jamming into the lands is a pretty uncommon practice with a gasgun. One of the downsides of doing it (besides going off the edge of the map as far as being able to rely on published load data safely) is that you're going to spill powder if you need to extract the live round.
 
"...out spills the brass with all the powder..." That has nothing to do with crimping. The OAL is simply too long.
 
I only reload handgun rounds and its only to save cost to plink so excuse my ignorance but i have a question. It seems "jamming the lands" would also cause the bullet to be pushed into the brass. Wouldnt that change pressures a cause inconsistency leading to reduced accuracy?
 
I have a different take having hand-loaded for both 6.5 and 6 mm creedmoor AR builds for a few years on what might be happening.

Looking at both your picture and your video you cartridges look to be well under the max COAL--I find it highly unlikely you are jamming the bullet into the lands--at least not simply as a result of your cartridge configuration. I would verify this by getting an actual measurement of where your bullet engages the lands/throat--but again I doubt your bullet is seated long enough to do that in an AR and still be well under the magazine max. While it's possible your bullets are creaping forward upon chambering--again I find that unlikely unless your bolt is slamming hard and you have a pretty loose neck tension to begin with.

What I think might be another explanation to consider--chambering that cartridge can be a tricky affair because of the bullet getting the necessary lift and "geometry approach" into the chamber--that long narrow bullet generally isn't getting good lift until the shoulder engages the feed ramp. Anything that isn't "just right" in the process of the feeding can result in a slight asymmetry of the bullet upon going into battery--that alone can cause a jam--at least in my experience. I could be wrong though--just a suggestion of another possibility : )
 
Some rifle barrel like a jam with a certain bullet some shoot better with a jump. If your jump is too long you bolt may not close , both jump & jams are moved in .010 settings then fine tune one way or the other.Not to the point where it drives the bullet into the case. Only in soft seating does that work , with very little neck tension .001 seating your rounds long an when chambered the bullet stops at the rifling. When opening the bolt with a loaded round the bullet will stick in the rifling an powder will dump in your rifle .
 
It sound like you have a semi auto.

What you ran into was Ogive variation where most are probably below the stick point, some are past it.

Move em back .010 and check accuracy. As you look to be loading to maximum mag length allowed, a bit shorter is not likely to change things.

I believe its possible to have a firing without a fully locked bolt on a semi auto.
 
I've built several of these--if the alignment of the mag, extension and bolt lugs isn't "just right" your going to run into all kinds of cycling and jamming issues.

I know this because...
 
No need to crimp for a cartridge in a bolt action.
Click to expand...
True, oh so true. I've never found crimping helped accuracy in a bolt gun, quite the opposite in fact.

On lever guns, especially with cast bullets and small charges of medium burning rate powders, crimping does seem to give more consistent ignition, though it may or may not be necessary to prevent bullet set-back in a tubular magazine.

Lastly, on my Colt HBAR AR-15, I have never needed to crimp bullets to keep from setting them back and always got better accuracy without the crimp. To my knowledge, neither has my son in his match grade M1A...(what say you 30Cal?) Rod
 
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