the more info i get the more questions i have

mdd · February 12, 2012, 07:47 PM

A few weeks ago I made a post about the hornady overall length gauge. I bought it along with a handful of modified cases and the necessary bullet comparators. Finally had time this afternoon to use the new tools and the o.a.l. gauge is very easy to use and the comparators work nicely as designed to attach to caliper blades.
I started with my old standby 223 because I shoot it the most. It is a ruger m77 mkii (787 prefix serial - made approximately 1995) Let me preface any information and measurements by stating I am at least the third owner of this rifle and have absolutely no idea of the round count. Please do not use any of the following measurements as reference points for your own reloads. I have owned it since 2003 and have put an estimated 800 to 900 rounds through it.
It is a 1:12 twist barrel and I shoot 40 grain bullets through it. I used a sierra blitzking in the modified case to measure seating depth. I followed the directions to the letter and recorded my measurement then repeated the process to double check.
My questions are about the measurements. My overall bullet length is 2.296" but both my nosler and hornady manuals show a maximum c.o.l. of 2.260. My first thought is that overall length is due to the dimensional restrictions of AR-15 magazines and may not apply to my bolt gun. My other thought is "damn....is this throat eroded that badly?"
Secondly, I loaded three test rounds with the aforementioned sierras and checked all of them with the comparator and all three are within .001" of length as measured at the ogive. I backed them off the lands .008" thinking it would be a place to start. When I checked a round in my rifle the bolt requires a bit more effort to close and lock in battery. A very small amount more effort mind you but increased from before. I chambered a round and then removed it to inspect it. I cannot see any markings on the bullet that would indicate contact with the lands so I repeated the process and got identical results. Mildly increased resistance but no markings to indicate any contact. Any ideas?
Sorry for the long-winded post but the details are important to determine if and what may be incorrect here. Thanks,
Michael

Brian Pfleuger · February 12, 2012, 07:53 PM

1st--- Book OAL is irrelevant. It's only purpose is to make rounds that fit in SAAMI spec magazines. Your OAL measurement is not surprising. They may not fit in the magazine of your M77 either, but that's up to you if you care or not. I load mine singly.

2nd--- Do your case chamber without resistance with no bullet? That would be the first thing to check. If they do, I'd guess your measurement might be a little off on the OAL. Make sure your pushing the bullet forward very gently. You want it JUUUUSSSTTTT touching the rifling, not jammed into it.

savagelover · February 12, 2012, 08:20 PM

When I check my OAL I mark the end of the bullets with a majic marker..Then you can see the marks from the rifleing..Works greak for all my loading test..Have you tried just the case alone? I may very well be the case...who knows...Try it and post back so I know what you found out...John

mdd · February 12, 2012, 08:37 PM

Good stuff guys. The cases are the issue. Not even an issue but just a bit different. I tried a prepped case with no bullet and it felt the same. I just purchased a new rcbs die set and it is obviously very minutely different in dimension from my old one. Still have several hundred rounds out of the other die set so I compared cases out of the new die vs the old and that is the reason for the change.
As for pushing the bullet forward to the lands, I was very gentle with the forward motion and then rechecked the results to be sure. I'm excited to see how the new stuff works out of this rifle.

February 12, 2012, 07:47 PM	#1
mdd Senior Member Join Date: January 27, 2010 Posts: 626	the more info i get the more questions i have A few weeks ago I made a post about the hornady overall length gauge. I bought it along with a handful of modified cases and the necessary bullet comparators. Finally had time this afternoon to use the new tools and the o.a.l. gauge is very easy to use and the comparators work nicely as designed to attach to caliper blades. I started with my old standby 223 because I shoot it the most. It is a ruger m77 mkii (787 prefix serial - made approximately 1995) Let me preface any information and measurements by stating I am at least the third owner of this rifle and have absolutely no idea of the round count. Please do not use any of the following measurements as reference points for your own reloads. I have owned it since 2003 and have put an estimated 800 to 900 rounds through it. It is a 1:12 twist barrel and I shoot 40 grain bullets through it. I used a sierra blitzking in the modified case to measure seating depth. I followed the directions to the letter and recorded my measurement then repeated the process to double check. My questions are about the measurements. My overall bullet length is 2.296" but both my nosler and hornady manuals show a maximum c.o.l. of 2.260. My first thought is that overall length is due to the dimensional restrictions of AR-15 magazines and may not apply to my bolt gun. My other thought is "damn....is this throat eroded that badly?" Secondly, I loaded three test rounds with the aforementioned sierras and checked all of them with the comparator and all three are within .001" of length as measured at the ogive. I backed them off the lands .008" thinking it would be a place to start. When I checked a round in my rifle the bolt requires a bit more effort to close and lock in battery. A very small amount more effort mind you but increased from before. I chambered a round and then removed it to inspect it. I cannot see any markings on the bullet that would indicate contact with the lands so I repeated the process and got identical results. Mildly increased resistance but no markings to indicate any contact. Any ideas? Sorry for the long-winded post but the details are important to determine if and what may be incorrect here. Thanks, Michael __________________ So many coyotes....so little time....

February 12, 2012, 07:53 PM	#2
Brian Pfleuger Moderator Emeritus Join Date: June 25, 2008 Location: Austin, CO Posts: 19,578	1st--- Book OAL is irrelevant. It's only purpose is to make rounds that fit in SAAMI spec magazines. Your OAL measurement is not surprising. They may not fit in the magazine of your M77 either, but that's up to you if you care or not. I load mine singly. 2nd--- Do your case chamber without resistance with no bullet? That would be the first thing to check. If they do, I'd guess your measurement might be a little off on the OAL. Make sure your pushing the bullet forward very gently. You want it JUUUUSSSTTTT touching the rifling, not jammed into it. __________________ Nobody plans to screw up their lives... ...they just don't plan not to. -Andy Stanley

February 12, 2012, 08:37 PM	#4
mdd Senior Member Join Date: January 27, 2010 Posts: 626	Good stuff guys. The cases are the issue. Not even an issue but just a bit different. I tried a prepped case with no bullet and it felt the same. I just purchased a new rcbs die set and it is obviously very minutely different in dimension from my old one. Still have several hundred rounds out of the other die set so I compared cases out of the new die vs the old and that is the reason for the change. As for pushing the bullet forward to the lands, I was very gentle with the forward motion and then rechecked the results to be sure. I'm excited to see how the new stuff works out of this rifle. __________________ So many coyotes....so little time....

February 12, 2012, 08:20 PM	#3
savagelover Senior Member Join Date: March 5, 2011 Location: Alpine,,NY Posts: 254	When I check my OAL I mark the end of the bullets with a majic marker..Then you can see the marks from the rifleing..Works greak for all my loading test..Have you tried just the case alone? I may very well be the case...who knows...Try it and post back so I know what you found out...John