load data for 7mm LRM

[AZShooter]

While my chambering is not a true 7 LRM the 7/375 has finally shown what it likes. I have chambered a total of three different rifles all with 7 Rem mag takeoffs learning this chambering's likes and dislikes.

I had established a OAL with the first rifle I tried, a Mark X, and didn't bother to change it for the Rem action. I had mentioned that the jump to the rifling was .156". I was looking into buying a Wyatt's mag box so I could get the 180 closer to the rifling. When reading the specs I realized that I wasn't using the full space in the the Remington! I was able to adjust the OAL significantly!!! I was actually able to have the bullet engage the lands.


Yesterday I shot several groups with starting with the bullet touching the lands and other loads with the bullet seated deeper in .005" increments. The bullet performed its best .015" from lands. I still need to test a few more times. Here is the load:

180 Berger match target hybrid .015 off lands, fed 215 match, 88 gr of US 869, vel 3090 fps

When I consider Alliant's and Hodgdon's load data for the 7 RUM shooting a 175 gr bullet with top velocities of 3059 fps (alliant) or 3075 fps (Hodgdon) I feel pretty good with the velocities obtained with the 7/375.

I will be interested in any loads that 7 LRM owners end up using with their rifles.

Ross
Hope this information will help any 7 LRM owners.

 

[speeders]

Anyone have any updates with load data for the 7 LRM?

Anyone try anything in 168 gr?

 

[tdean]

im out shooting now

70 retumbo .020 off 2944,2952,2957 = 1 moa
71 retumbo .020 off 3028, 3047, 3034, 3037 = .75 moa
no pressure signs

 

[speeders]

let us know how you make out. Thanks.

 

[tdean]

dont see the point in showing you guys any more pictures of 2" groups

 

[speeders]

Have you tried any other bullets?

 

[tdean]

yea 175 lrab same results

 

[speeders]

Hmmmm, I have the same, 175 LRAB and 180 Vld's sitting on the shelf with a stockpile of H1000 as I wait for rifle to be finished. Hopefully I different results??

 

[tdean]

Im going to say this and then i will shut up about my experiences with LRM.

I went out Friday and shot a group at 450 yards right at dusk no wind, groupmeasured 9". I had previously shot .8 moa 4 shot group with this sameload.

I am convinced that part of the issue is hornady brass. The brass is toosoft and very inconsistent. If i look at 50 once fired brass at least 40 will haveheavy ejector marks and I can load 10 rounds and at least half will have heavybolt lift and the other half will not. This is loaded at 70 grains of h-1000and .040 off to not get any pressure. 2 grains less than Gunwerks loads. If iwanted to get this velocity performance I would have got a 7MM mag. Gunwerksalso told me that i should anneal the brass necks after every 2 firings forwhatever that's worth. I'm sure they wish they could get better brass. Most ofthe primer pockets are loose after just 1 firing. The only other thing it couldbe is the barrel. I will know in a fewmonths when its re-chambered to a 7mm RUM. Another possible issue regarding pressure maybe that the Krieger barrelsare not overbore like the rock creek and bartlien barrels gunwerks uses? But imnot sure about that. I did get contacted by another member who has a krieger and is having the same issues i am having.

 

[AZShooter]

tdean,

I would call both Gunwerks and Hornady and tell them you are having primer pockets enlarge in one firing. You could have a bad lot. Certainly worth a try.


You are experiencing pressure that is certain. Heavy ejector marks, heavy bolt lift and loose primer pockets point to too much pressure! If you have any virgin brass left try a mild powder charge of perhaps 66 gr of H-1000 and see how the brass performs. If those pockets become loose then the brass would have to be soft.

I started a post in the reloading section regarding wall thickness of the 7 LRM. Can you measure a loaded round's neck OD for me and post it here or if you are through posting about the LRM, could you PM me instead? Thanks

Ross

 

[tdean]

I got a call from Gunwerks, they have offered me a refund for some of the work and the dies and brass i bought. I would like to say that i appreciate their integrity and that they now believe me after others have had similar issued with the brass.

 

[bamadawg2009]

Funny you should say that GW called you, I got a PM from Aaron the other day asking if he could help in anyway. I gave him a list of things but have yet to hear back from him. I'm getting an ace in the hole ready in case this project doesn't work out, I'm starting to get a little impatient with my gunsmith saying mine should be ready in a couple weeks every time I ask him a couple weeks has been several months now.

I'm getting parts together for a 7mm-300 win mag if I'm not happy with the LRM. I haven't heard anything bad about that cartridge, kinda wish I had gone this way originally instead.

 

[mustang58]

I have been watching this thread with interest. I don't have a 7mm LRM but a 7mm built on a 6.5x68S. It is similar to the LRM but has a little more case capacity. I use RWS brass and it can be hard to find but good brass. It shoots really well with Berger 168 VLDs. I haven't tried 180s but will. I think these cartridges are just right as far as case capacity and performance go. I will keep watching. Hope your endeavors are successful.

 

[AZShooter]

Thought I'd revive this thread.

A friend just had his gunsmith make him a 7 LRM. He was damaging the 175 LR Accubond when he seated them.

I asked him to get some measurements:

The brass and dies were supplied by Gunwerks. The Hornady die is a FL/bushing die and came with a .316" bushing (I suggested to him he get a .317" bushing as well)

His reamer has a .321" neck dimension

The first few pieces of brass he measured had a neck ODs of .3175" - .318" This translates into necks slightly less than or exactly .017" thick

IF all the brass is no more than .017" thick the bullet release per side in the chamber neck is .002"
That is approaching clearances that are used in BR shooting. Quite frankly it is cutting the clearance too close for brass that isn't neck turned. I would bet that some brass would come with neck wall thicknesses greater than .017".

Sure enough my friend measured one case that he ran through his .317" bushing that had an ID of .277"! That computes to neck wall thickness of .020" WOW! If he were to seat a bullet and try to put it into the chamber it wouldn't fit. OD would be .324"

He is going to use the supplied sizer ball and size a bunch of brass. He will then seat bullets for measurement. (he doesn't have a ball mike) He will then carefully measure all neck ODs. I think he will find quite a few that are thicker. I told him he really should turn all his necks to ensure he doesn't have any pressure issues. Heck even some variance would ruin LR groups.

He says he believes the gunsmith borrowed the reamer from Gunwerks. Will report on that when I know for sure.

Perhaps I have discovered the reason why some cannot duplicate Gunwerk's pet load without excessive pressure. TDean appears to be correct, the Hornady brass is varying in its dimensions.

Another poster made a 7mm-375 Ruger just as I have. We have been comparing information. He noticed that the latest lot of 375 Ruger brass has neck wall thickness varying from .015 to .018" That is quite a variance. I think I will weight all my brass to see if the lots I have had in my possession for well over a year also vary in thicknesses.

Seems like there IS a problem here. Would love to hear from other owners of 7 LRMs and their loaded round neck ODs.

Ross