Semi-auto Precision

Gas guns will never shoot as well as a bolt gun at long range, simply because of the nature of using gas pressure to cycle the bolt.

That gas pressure applies side force to the barrel and that causes off axis displacement... and that is variable depending on force variations as needed to cycle the action.

You might get good 100 yard groups but don't expect your velocity spreads to be as consistent as a bolt gun.

Feel free to chase semi auto accuracy if you like, but don't be disappointed if you cant match bolt gun performance at extended range.
 
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I think the reason the last shot is low is because when there is still gas pressure leaving the barrel and with the bolt staying open not all the gasses have exited the barrel pushing the bullet - if the bolt can stay close for a fraction of a second longer this problem may be eliminated
 
Cpt.Flan said:
Yes. Non free float AR (C8/C7 ) I tested had a shift of POI of 6 inches at 100m putting a bipod up front vs rest on the mag.
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Resting a C1 on its magazine while shooting used to be frowned apon - there was the general view that this was a) bad for accuracy b) bad for the mag and c) caused misfeeds

What is the thinking with ‘AR’ type rifles?
 
IvoB said:
I think the reason the last shot is low is because when there is still gas pressure leaving the barrel and with the bolt staying open not all the gasses have exited the barrel pushing the bullet - if the bolt can stay close for a fraction of a second longer this problem may be eliminated
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Can also be lack of a round pressing on the bottom of the carrier
 
There is certainly more going on with a semi-auto than a bolt gun, and not all semi-autos offer the same ability to produce comparable levels of precision when compared against one another.

There are and have been a great many ‘assumptions’ on their performance or supposed lack thereof based on here say.
If you are talking “ARtype” rifles, the general consensus from those in the know is that they leave nothing to bolt guns in terms of accuracy potential. Look at all of the work the USAMU have done with ARs. They and others that have actually competed with them are the leading authority on what works and to what level as they have poured hundreds of thousands of rounds down range and thousands of hours researching what works and what doesn’t with them.
There is some good reading by authors such as David TUBB and Glen ZEDIKER who have some excellent published works on the matter.

As to actual reality comparing apples to apples as much as possible:
- Bolt guns are cheaper to built to the same level of quality.
- Bolt guns will handle pressures better, and therefore are likely to give more consistent and more forgiving performance over the variances that can be found in ammunition.
 
AP said:
Resting a C1 on its magazine while shooting used to be frowned apon - there was the general view that this was a) bad for accuracy b) bad for the mag and c) caused misfeeds

What is the thinking with ‘AR’ type rifles?
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Unlike C1/FALs or M14s, there is no issue with shooting an AR resting on its mag as it neither affects accuracy or feeding.
 
AP said:
Resting a C1 on its magazine while shooting used to be frowned apon - there was the general view that this was a) bad for accuracy b) bad for the mag and c) caused misfeeds

What is the thinking with ‘AR’ type rifles?
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There is absolutely no problem to rest on the mag.
 
Cpt.Flan said:
There is absolutely no problem to rest on the mag.
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Actually...

Resting on the mag can cause upward pressure on the bolt if the mag doesn't fit correctly. You can test for it by resting the rifle on an EMPTY mag and try cycling the bolt.

If you feel resistance, then you have a problem. If you cannot detect a difference in the force required to cycle the bolt whether its resting on the mag or not, then you don't have a problem with that particular mag, but you might with some other mag, so test all of them.

I have personally noticed problems in particular with plastic mags that have plastic feed lips, since the feed lips are thicker than metal mags.

Here's a link to a video on YouTube where I demonstrated this occurrence.

Its at 5 minutes into the video if you want to jump to it.

https://youtu.be/iE97ARgxul0?t=291

 
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Maple57 said:
Actually...

Resting on the mag can cause upward pressure on the bolt if the mag doesn't fit correctly. You can test for it by resting the rifle on an EMPTY mag and try cycling the bolt.
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Actually.... I shot over 200000 rounds with a C7/C8 over the years... And I NEVER had a stoppage (FTF) because of that.

In CAF shooting team we actually encourage people to rest on the mag.

But I guess my experience means ####...
 
Cpt.Flan said:
Actually.... I shot over 200000 rounds with a C7/C8 over the years... And I NEVER had a stoppage (FTF) because of that.

In CAF shooting team we actually encourage people to rest on the mag.

But I guess my experience means ####...
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More likely it means the taxpayer was buying you better gear than some of them were buying for themselves.
 
old303 said:
More likely it means the taxpayer was buying you better gear than some of them were buying for themselves.
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No, not really. This is SOP in all Canadian service condition matches when shooting prone. Civies shoot their AR15's and soldiers their C7/C8s in this manner. I've never heard of any failures due to resting the mag on the ground.

 
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All hairy chested ego aside, the ACR video posted speaks for itself.... Resting on the mag can cause the bolt to bind.

I have no reason to believe it's necessarily a better or worse rifle... More likely fat feed lips on plastic mags that is causing the issue.

Better to check and confirm that you are in the clear before assuming it will work without testing.
 
trigger'06 said:
Naw man, they are Canadian soldiers and they train to excell with sometimes mediocre equipment. They do it well, have done forever.

Fortunately.
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Still, the retail market has the Colt Canada rifles at quite a premium over the cheapest ARs, and there will be a lot of ways to cut costs that might fool some kid buying his first restricted rifle that won't even begin to pull the wool over the eyes of CF procurement. Well-worn and overdue for replacement too often, but hardly lacking quality.
 
Depends on the mags,pretty sure magpul modified their magazines with a notch to prevent over insertion. may have something to do with it. or a combination of the rifle and mag type used.
 
Quick update... higher pressure loads showed last shot zinger quite often. Load tuning didn't resolve and since I was seeing more pressure signs then desired, worked down to the lower node.

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190yds in light to no wind... around 0C. Lower node looks very promising.

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Load B 'out' was shot #2... not sure what happened there but the other 4 shots were nice and tight. Load A looks quite consistent with last shot going into the group. Pressure signs are way down at this charge level. So will play around more around Load A and B.

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No problem setting up for barricade work. I see no issue with any receiver flex as set up, shooting off a bipod or off barricades. Quite like the goofy forend install on the BCL's.

Will update as I get more groups shot and can see some consistency in results.

So far, so good.

Jerry
 

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I found that a slight neck crimp with a Lee factory crimp die and .050" deeper seating cut my horizontal in half. This on both Jury and IBI barrels when feeding from the mag.
 
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