Accuracy penalty for semi-auto feed?

Keebler750

Keebler750

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I was just wondering if there was a major problem with bullet tips slamming into the feed ramps etc and causing accuracy problems due to seat depth or concentricity. What about crimping to help with this? Many popular bullets don't have a cannelure.

I will be reloading for my AR and I was wondering how much I should worry about details (other than powder measurement and basic case prep) if the gun will have a tendency to undo your hard work!!

Any thoughts?
 
Keebler750 said:
I was just wondering if there was a major problem with bullet tips slamming into the feed ramps etc and causing accuracy problems due to seat depth or concentricity. What about crimping to help with this? Many popular bullets don't have a cannelure.

I will be reloading for my AR and I was wondering how much I should worry about details (other than powder measurement and basic case prep) if the gun will have a tendency to undo your hard work!!

Any thoughts?
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I always full size and crimp my rounds for the AR15, especially the shorter barreled varieties :D You can get away with neck sizing and no crimping if you shoot a 20" or greater barreled AR15 and are just fooling around at the range. At least this is my experience. If you compete with your AR, always full size and crimp :)
 
I crimp Sierra Match Kings and Hornady hpbt match bullets for my AR with no loss in accuracy. I use a Lee factory crimp die. I wouldn't recommend mucking about with neck sizing for ARs at all. ymmv.
 
I did a test on some rounds once upon a time.

I loaded up 50 dummy bullets (no powder or primer), crimped half, and not the other half. I numbered and measured the length of each shell, and then put my AR on the bench to test things out.

Loaded up the mags (5 at a time dammit) and proceeded to cycle all 50 rounds through the rifle, one at a time.

I then picked up each shell, and re-measured it for length, to see if the round had been pushed back into the case at all.

I repeated this twice, so each shell had been cycled 3 times through the rifle.

Measuring each time the rounds were cycled, and building a table of data.

In the end, I had only 3 out of the 50 rounds that showed a change in OAL (overall Length), and this was from the 3rd cycle in the rifle.

All three rounds were from the "non-crimped" lot.

None of the crimped rounds showed any change, and 22 of the 25 non-crimped rounds showed no change, and those that did, only had a .001" (one thou!) change in length.

So, the result of this was that I no longer worry about crimping .223 ammo.

When I was running single stage, this saved me a LOT of time, but since my Dillong 550B has a spare "crimp" station, I use it now.

So, I suppose that the true test of this would be to find someone with a seated bullet rounout gauge and re-do the test and measure the runout before and after cycling, AND the length.

Over to you guys....feel free to snipe back on this.

NS
 
My question wasn't necessarily just about crimping though....but whether slamming the feed ramp affects accuracy.

Thanks for the above info...that's ALREADY helpful to me. :)
 
Keebler750 said:
My question wasn't necessarily just about crimping though....but whether slamming the feed ramp affects accuracy.

Thanks for the above info...that's ALREADY helpful to me. :)
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No. I cant' tell the difference in accuracy when I single load directly into the chamber or fire semi-auto from the magazine :)
 
I don't think the accuracy issue is as much ammunition effects, but vibration and harmonics on the moving parts. English language gun writers tend to be published in the US and UK. The British authorities reluctantly let shooters have firearms, and their NRA is allergic to any militarist appearances. So between the effects on gun ownership thanks to The Troubles in Northern Ireland and negative public opinion to murders, there are few opportunities for British gun writers to build much momentum. That leaves American writers.

The first semi-auto rifle most Americans of a certain generation was the Garand. Although it was eventually turned into a rugged battle rifle, a rack grade Garand is not much more than a 2MOA rifle. As any bullseye shooter will attest, accurizing a Garand is not for the faint of heart. There are lots of parts flying in formation and even the slightest of pressures on some little part will shift the group quite a bit. The M14 was better and ruled NRA highpower competition for years. It can be a very good sniper rifle, but suffers from many design features that help the soldier but confound the shooter. When they NRA changed the rules, the fancy spaceguns and super accurized AR15s outclass everything else for consistency.

Nope, in my opinion the notion that all semi-autos are incapable of accurate shots is false.
 
The comment about hand feed vs. semi-auto feed is interesting because I suspect that's how you could tell.

I guess a side point to this is: If slamming the ramps and scratching or denting the bullet and tip DOESN'T hurt accuracy, then alot of the worry of making up perfect rounds would appear to be moot.......?
 
The rounds don't really "Slam" into the ramp....the slide up the ramp.

If you've got a stock of HPBT bullets around, have a look at the meplat. (The tip where the hollowpoint is) and see just how uniform it is....or is not.

As accurate as the rounds are, a non-uniform meplat doesn't seem to affect them much.

For Serive rifle, your bullseye is 3 MOA (minimum) so you don't need perfect accuracy, or even a 1MOA gun to shoot.

Rounds that are "good enough" will often do.

NS
 
The tip is the least important part of the bullet as far as accuracy is concerned--it is more of a problem if your bullet is not seated snugly in the neck and the feeding cycle "tips" the bullet in the neck so that it is no longer concentric with the bore.

44Bore
 
I've noticed that spitzer softpoints deform badly, but there is no reason to choose this type of bullet for service rifle anyways. FMJ and HPBTs are the way to go.

As Navyshooter said, you have a 3moa bull to work with, and even if you drift outside on a shot or two, you will only loose a point or two. Its the misses and the shots not fired that will ruin your score. If you are clearing a stoppage and a bullet comes loose and spills powder in your action and possibly gets lodged in the throat it can blow your entire match and send 50 points down the drain from your agg. There are no re-shoots allowed for mechanical malfunctions.
I always use a Lee Factory Crimp die on all my service rifle loads to ensure reliability, even at the cost of some accuracy, but they do well enough in that regard anyways.
 
44Bore said:
The tip is the least important part of the bullet as far as accuracy is concerned--it is more of a problem if your bullet is not seated snugly in the neck and the feeding cycle "tips" the bullet in the neck so that it is no longer concentric with the bore.

44Bore
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Interesting, I had never thought that the bullet could tip out of centre like that. Does this happen to your knowledge? What effects would it have on the accuracy and the firearm?
 
Maple Leaf Pilgrim said:
Interesting, I had never thought that the bullet could tip out of centre like that. Does this happen to your knowledge? What effects would it have on the accuracy and the firearm?
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.005" or more is generally considered to be detrimental to accuracy. The type of brass used can be an issue too. I've only had this problem develop using freshly annealed .30-06 brass in a Garand. Of course if you are using IVI 7.62 ammo you don't have to worry, because it already comes loaded crooked from the factory. :rolleyes:
 
Quiet said:
.005" or more is generally considered to be detrimental to accuracy. The type of brass used can be an issue too. I've only had this problem develop using freshly annealed .30-06 brass in a Garand. Of course if you are using IVI 7.62 ammo you don't have to worry, because it already comes loaded crooked from the factory. :rolleyes:
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Has anybody bothered to try and map what the effects are when a bullet is out of centre? I was wondering if there was any possible way to determine the changes to a ballistic path based on the out of centre variation? Does the number of grains of powder change this effect?>

Sorry, I am looking (long term) at doing some long range shooting and this kind of stuff interests me.
 
Maple Leaf Pilgrim said:
Has anybody bothered to try and map what the effects are when a bullet is out of centre? I was wondering if there was any possible way to determine the changes to a ballistic path based on the out of centre variation? Does the number of grains of powder change this effect?>

Sorry, I am looking (long term) at doing some long range shooting and this kind of stuff interests me.
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You will probably find better answers to your question for the Precision Rifle forum. There are other factors that have much more effect on your service rifle scores than small differences in your bullet tips.
 
Yes but this thread relates accuracy to the difference between hand feeding, and semi-auto "slam feed" .....!

I doubt the precision guys have ever dealt with that much variance because of the amount of side force on the bullet, although I bet they have SOME data.
 
"...the difference between..." Feeding has little or nothing to do with accuracy. The worst that can happen is to have the bullet hit the back of the chamber and get pushed into the case. No big deal unless you're shooting an M-1. Crimping might prevent this, but crimping is detrimental to accuracy. There's no need to crimp just because it's a semi-auto. Never have for any of my semi's. No fuss.
The important part of match grade ammo for a semi is carefully working up the load by weighing each charge, using a match grade bullet and full length resizing. If you don't full length resize, sooner or later, you will have feeding issues. If the bullet goes off centre, your sizing die or brass need replacing.
 
Keebler750 said:
I was just wondering if there was a major problem with bullet tips slamming into the feed ramps etc and causing accuracy problems due to seat depth or concentricity. What about crimping to help with this? Many popular bullets don't have a cannelure.

I will be reloading for my AR and I was wondering how much I should worry about details (other than powder measurement and basic case prep) if the gun will have a tendency to undo your hard work!!

Any thoughts?
Click to expand...

This question has been raised many times over the decades I've competed in shooting competitions. The best answer was to be found in an excellent Guns and Ammo article several years (decades?) ago when they proved that the base of the bullet was the steering end. In the report they mashed, filed and otherwise damaged the nose of several bullets, loaded them and fired them against a control batch of undamaged bullets. Then they did the same to the base of the bullets. There was very little change in accuracy or POI at short to medium ranges with the bullets with the damaged noses. There was a HUGE loss in accuracy with the bullets with the damaged bases. I was always careful to protect the base of my bullets when reloading after reading that article. If you shoot long range, which I doubt as you are shooting 5.56 NATO (correct?) then the poorer B.C. of the damaged nose would come into play. The only AR15 I ever used in competition was an SP1 I used in IPSC Three Gun matches, and never over 200 m. If you are shooting at greater ranges and still concerned about damage to the nose then I'd recommend something along the lines of a Nosler Ballistic Tip bullet. Hope this info helps, Derek.
 
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