This is my first attempt at loading to a semi auto. I have a lee factory crimp die. How do I know if I am crimping the correct amount? How much does the crimp effect accuracy?
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Re: Loading for AR-10 How much to crimp?
I have never loaded for an AR-10, but I have loaded for an M1A and AR-15. I use the same Lee crimp die. I just put a slight crimp on the rounds. Basically to keep from shoving the bullet back into the case.
Measurement wise, not even 1/2 the case thickness. If you measure the neck diameter of a loaded round, I would be suprised if the crimped area was .010" smaller than the neck. Does that make sense? or just confuse you? I tend to confuse myself from time to time so.....
I have never loaded for an AR-10, but I have loaded for an M1A and AR-15. I use the same Lee crimp die. I just put a slight crimp on the rounds. Basically to keep from shoving the bullet back into the case.
Measurement wise, not even 1/2 the case thickness. If you measure the neck diameter of a loaded round, I would be suprised if the crimped area was .010" smaller than the neck. Does that make sense? or just confuse you? I tend to confuse myself from time to time so.....
Re: Loading for AR-10 How much to crimp?
I have a LFCD and planned on crimping for my AR10 by keeping it extremely light so as not to deform the bullet and reduce accuracy. In the end the "crimping" was so light it was really doing nothing so now I just use a bushing that gives me .003" neck tension and don't crimp.
I have a LFCD and planned on crimping for my AR10 by keeping it extremely light so as not to deform the bullet and reduce accuracy. In the end the "crimping" was so light it was really doing nothing so now I just use a bushing that gives me .003" neck tension and don't crimp.
Re: Loading for AR-10 How much to crimp?
shot the crimped rounds yesterday. They shot like crap. Even in my bolt gun the groups were three times normal size. What now. I want to hunt with the ar-10 so I need rounds that feed from mag.
shot the crimped rounds yesterday. They shot like crap. Even in my bolt gun the groups were three times normal size. What now. I want to hunt with the ar-10 so I need rounds that feed from mag.
Re: Loading for AR-10 How much to crimp?
I don't crimp for my LR-308. If the brass is resized to the proper diameter there is no need. Of course, I can get by with neck-sizing my brass too which is something I'm not supposed to be able to do either.
All the crimp should be doing is making sure that the bullet doesn't get moved back while feeding from the magazine. Proper neck tension of around .003" does the trick for me.
I usually get .3" groups using 175 or 168gr SMKs.
Good luck!
I don't crimp for my LR-308. If the brass is resized to the proper diameter there is no need. Of course, I can get by with neck-sizing my brass too which is something I'm not supposed to be able to do either.
All the crimp should be doing is making sure that the bullet doesn't get moved back while feeding from the magazine. Proper neck tension of around .003" does the trick for me.
I usually get .3" groups using 175 or 168gr SMKs.
Good luck!
Re: Loading for AR-10 How much to crimp?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jeffm</div><div class="ubbcode-body">sht the crimped rounds yesterday. They shot like crap. Even in my bolt gun the groups were three time normal. What now. I want to hunt with the ar-10 so I need rounds that feed from mag. </div></div>
You are going to want 0.003 in neck tension. This is just enough to hold the bullet (prevent setback) as it gets rammed into the feed ramp and enough to hold the bullet (prevent ram forward) at seated depth as the cartrige rams against the chamber sholder. It is little enough tension for crisp release as the pressure cycle builds.
How do you get this? A) measure the dies and lap them to size in a lathe, B) Use bushing dies.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jeffm</div><div class="ubbcode-body">sht the crimped rounds yesterday. They shot like crap. Even in my bolt gun the groups were three time normal. What now. I want to hunt with the ar-10 so I need rounds that feed from mag. </div></div>
You are going to want 0.003 in neck tension. This is just enough to hold the bullet (prevent setback) as it gets rammed into the feed ramp and enough to hold the bullet (prevent ram forward) at seated depth as the cartrige rams against the chamber sholder. It is little enough tension for crisp release as the pressure cycle builds.
How do you get this? A) measure the dies and lap them to size in a lathe, B) Use bushing dies.
Re: Loading for AR-10 How much to crimp?
+1 for Mitch.. No crimp .003 and you are good to go... Ive done pre and post measures of these rounds going into battery from lockback and had no decrease in OAL.
+1 for Mitch.. No crimp .003 and you are good to go... Ive done pre and post measures of these rounds going into battery from lockback and had no decrease in OAL.
Re: Loading for AR-10 How much to crimp?
One thing to always be cognisant of: When crimping, it's a good idea to watch for loaded round concentricity. Continue to increase crimp until you see a loss in concentricity. At that point, drop back just a little and you'll have a good, "accurate" crimp. Note: This technique requires that you trim brass to one standard size.
I've used this trick on my .223, .308, .44 mag and other "crimpers". Works very well from an accuracy standpoint. Likewise, it will work well for both the Lee collet crimp and standard "RCBS" type crimpers (inside the seating die).
One thing to always be cognisant of: When crimping, it's a good idea to watch for loaded round concentricity. Continue to increase crimp until you see a loss in concentricity. At that point, drop back just a little and you'll have a good, "accurate" crimp. Note: This technique requires that you trim brass to one standard size.
I've used this trick on my .223, .308, .44 mag and other "crimpers". Works very well from an accuracy standpoint. Likewise, it will work well for both the Lee collet crimp and standard "RCBS" type crimpers (inside the seating die).
I am just now noticing the finer points of precision loading and have annealing and neck turning gear en route. I have 2 semi and 2 bolts that I am feeding and am hoping to nail a load all stay tight with. All 16" barrels. FWIW.
You method is the most stable that I have come across yet.
I've never crimped or had a need to. I neck turn to .013 and bullets never move. As stated before .003 is plenty of tension. If I was going into combat , yes I would neck crimp just because. Until critters shoot back, no.
I would feel better with some kind of crimp.
I have not been able to find any information as to the effect of crimping a cartridge that has been turned and sized with .003 neck tension. Am I just canceling the tension out finishing with a crimp or does the surface area (basically, the entire neck) for the most part, not become effected by the crimp?
Think of it as this way, no crimp with .003 neck tension you have bearing on depending upon your bullet up to .200 of bullet shank. When you crimp you have tension on about .005 of bullet shank. The only time crimping make any sense is IF your bullet has a crimping groove and the crimp actually is applied in that groove. And then your accuracy will never be as good. If crimping helps your accuracy, you have an issue with your reloading regiment.
If you want to check your bullet tension measure an OAL set the bullet nose down and push as hard as you can, then measure again. As long as you didn't deform the nose it didn't move. It certainly isn't moving in recoil.
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